foraging habits of spring migrating waterfowl in the upper mississippi

DIETS OF SPRING − MIGRATING WATERFOWL IN THE UPPER MISSISSIPPI

RIVER AND GREAT LAKES REGION by

Arthur Neil Hitchcock, Jr.

B.S., Mississippi State University, 2005

A Thesis

Submitted in Partial Fulfillment of the Requirements for the

Master of Science Degree

Department of Zoology

In the Graduate School

Southern Illinois University Carbondale

December 2008

THESIS APPROVAL

DIETS OF SPRING − MIGRATING WATERFOWL IN THE UPPER MISSISSIPPI

RIVER AND GREAT LAKES REGION

By

Arthur Neil Hitchcock, Jr.

A Thesis Submitted in Partial

Fulfillment of the Requirements for the Degree of

Masters of Science in the field of Zoology

Approved by:

Dr. Michael W. Eichholz, Chair

Dr. Joshua D. Stafford

Dr. Tina Yerkes

Dr. Matt R. Whiles

Graduate School


August 14, 2008

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AN ABSTRACT OF THE THESIS OF

JAY HITCHCOCK, for the Master of Science degree in ZOOLOGY, presented on

AUGUST 14, 2008, at Southern Illinois University Carbondale.

TITLE: DIETS OF SPRING − MIGRATING WATERFOWL IN THE UPPER

MISSISSIPPI RIVER AND GREAT LAKES REGION

MAJOR PROFESSOR: Michael W. Eichholz

I evaluated diet and food selection of 5 species of spring-migrating female waterfowl including 3 dabbling ducks (Blue-winged teal, Anas discors , Mallard, Anas platyrhynchos , Gadwall, Anas strepera ) and 2 diving ducks (Lesser Scaup, Aythya affinis , and Ring-necked duck, Aythya collaris ). Diet was evaluated with regards to the proportion of invertebrates and seeds consumed, and compared to forage availability data collected in habitats available to them at 6 study locations throughout the Upper

Mississippi River and Great Lakes Region. I found latitude (i.e., stage of migration), longitude, food availability, and date all influenced the diet of spring migrating waterfowl, with some factors having a stronger influence than others. I observed differing diet trends with regard to foraging guild (e.g., dabbling and diving ducks), as each foraging guild was represented by 1 species that was heavily dependant on invertebrates (dabbling duck – Blue-winged teal; diving duck – Lesser scaup) and 1 species that was heavily dependant on seeds (dabbling duck – Mallard; diving duck –

Ring-necked duck). The proportion of invertebrate foods in the diet increased throughout spring for all species of waterfowl, suggesting the importance of invertebrate food sources during spring staging. Data from this study provides valuable information to habitat managers and conservationists wishing to improve spring habitat conditions for migrating waterfowl, which likely influences waterfowl productivity. i

ACKNOWLEDGMENTS

Without the financial support of Ducks Unlimited, Inc. and several private donors,

USFWS (Upper Mississippi River and Great Lakes Joint Venture), Ohio Division of

Wildlife, Wisconsin DNR, Illinois DNR, Bruning Foundation, Christel DeHaan Family

Foundation, Saginaw Bay Wetlands Initiative Network, Herbert H. and Grace Dow

Foundation, Rollin M. Gerstacker Foundation, Waterfowl Research Foundation, Southern

Illinois University Carbondale, and The Ohio State University this research would not have been possible.

Although he made it quite clear on several occasions that I was not the ‘sharpest tool in the shed’, I would like to thank my graduate advisor and friend, Dr. Michael

Eichholz for allowing me to conduct this research and for his support, advise, and expertise throughout my years at SIU. I am greatly indebted to Dr. Joshua Stafford for his invaluable statistical expertise and for the hours he committed to editing and replying to thousands of questions and emails. I would also like to thank my other committee members, Dr. Tina Yerkes and Dr. Matt Whiles for taking interest in my research and providing editorial comments and professional advice.

My extensive data set would not have been possible without the countless hours in the field and laboratory of the many technicians that worked for us. Of those, I would like to personally thank Stephanie, Cassie, Zac, Kristopher, Tim, Nick, Brent, Bryan,

Chris, Devan, John Fulcher, Big John, Sara, Adam, Melissa, and Rick for helping with duck collection and laboratory analyses of gut contents. Many thanks are due to collaboraters Rich Schultheis, Jake Straub, Kyle Loper, Dr. Robert Gates, and Dr. John

Colucci for their dedication to the project and timely delivery of data. I have thoroughly ii

enjoyed making new friends and colleagues at SIU, all of which have made my time here more enjoyable.

Thanks to several federal refuges, state wildlife areas, and private landowners for allowing this research to be conducted on their property. Specifically, Cypress Creek

National Wildlife Refuge, Chautauqua National Wildlife Refuge, Horicon National

Wildlife Refuge, Central Gun Club, Winous Point Hunt Club, and Bill and Vivian Young for providing us with housing during our field season. I am greatly appreciative of the logistical and fieldwork help by Aaron Yetter, Chris Hine, Dr. Joshua Stafford, and

Randy Smith of the Illinois Natural History Survey Forbes Biological Station in Havana,

IL.

I am especially indebted to my family for their love and support throughout my life and for supporting me as I follow my dream to be a wildlife/waterfowl biologist. To my wife, Randa, I would have to write another thesis to explain my gratitude and love for you. Your patience and love have upheld me throughout the writing process. No more graduate school – I promise! Just you, me, and Belle. And duck season! iii

TABLE OF CONTENTS

CHAPTER PAGE

ABSTRACT……………………………………………………………………………….i

ACKNOWLEDGMENTS………………………………………………………………...ii

LIST OF TABLES……………………………………………………………………......vi

LIST OF FIGURES…………………………………………………………………...…..x

GENERAL INTRODUCTION ………………………………………………………...…1

CHAPTER 1 – DIET OF MIGRATING WATERFOWL DURING SPRING

IN THE UPPER MISSISSIPPI RIVER AND GREAT LAKES REGION………….…....5

INTRODUCTION……………………………….………………………………………..5

Diet in Relation to Annual Life Cycle of Waterfowl ………...………………….5

STUDY OBJECTIVES …………………………………………………………………...7

METHODS ……………………………………………………………………………….8

Study Site Selection ……………………………………………………………...8

Study Species ………………………………………………………………...…15

Waterfowl Collection ……………………………………………………...……16

Laboratory Analysis …………………………………………………………....17

Statistical Analysis …………………………………………………………..…18

RESULTS ……………………………………………………………………………….20

Summary Statistics ……………………………………………………………..20

MANCOVA results ………………………………………………………….…31

Breeding vs. Non-breeding …………………………………………..…31

Diet ………………………….………………………………………….33

Blue-winged Teal Diets………..………………………………………..33

Mallard Diets …….......…………………………………………………43

Gadwall Diets ……………………….......……………………………....50

Lesser Scaup Diets …….......………………………………………...…55

Ring-necked Duck Diets ………......……………………………………61

DISCUSSION …………………………………………………………………………...65

Temporal and Latitudinal Variation in Spring Diet Within a Species …….....…74

Longitudinal Variation in Spring Diet Within a Species ……………………….76 iv

CHAPTER 2 – FOOD SELECTION BY MIGRATING WATERFOWL

DURING SPRING IN THE UPPER MISSISSIPPI RIVER AND GREAT

LAKES REGION ………………………………………………………………………..80

INTRODUCTION ………………………………………………………………………80

Food Selection ……………………………………………………………….…80

STUDY OBJECTIVES ………………………………………………………………….83

METHODS …………………………………………………………………………..….85

Food Availability ………………………………………………………………85

Laboratory Analysis ……………………………………………………………87

Statistical Analysis ………………………………………………………….….88

RESULTS …………………………………………………………………………...…..89

Availability ……………………………………………….……………………..89

Blue-winged Teal Food Selection ……………………….……………...………89

Mallard Food Selection ………..........…………………………………………..91

Lesser Scaup Food Selection ……………………………………….………..…91

Ring-necked Duck Food Selection ………….....…………………………....….93

DISCUSSION …………………………………………………………………......……93

Food Selection ……………………………………………………………….....93

Blue-winged Teal …………………………………………….………......…94

Mallard ……………………………..………………………….………..…..95

Lesser Scaup ………………….........……………………..…………....…...97

Ring-necked Duck ……………………………………………….……....…99

CHAPTER 3 − IMPLICATIONS FOR WETLAND MANAGEMENT FOR

SPRING − MIGRATING WATERFOWL IN THE UMR/GLR…....……............……101

Management Implications ...............................................................................................101

Managing Wetlands for Invertebrates During Spring Migration ....................................102

Managing Wetlands for Seeds During Spring Migration ...............................................103

Challenges to Providing Habitat for Spring-Migrating Waterfowl ................................104

LITERATURE CITED …………..........……………………………………………….105

APPENDICES

Waterfowl Diets at Different Study Sites........…………...…………………………….114

VITA ……...……..……………………………………………………………………..162 v

LIST OF TABLES

TABLE PAGE

Table 1.1 Number of ducks collected in the Upper MS River and Great Lakes

Region that contained food items during spring 2006 and 2007 (BWTE

= blue-winged teal, MALL = mallard, GADW = gadwall, RNDU = ring-necked duck, LESC = lesser scaup, CA = Cache River, IR =

Illinois River, WI = Wisconsin, SR =Scioto River, LE = Lake Erie,

SB = Saginaw Bay) ...................................................................................21

Table 1.2 Aggregate percent (A) ± standard error and percent occurrence (O) of food items in ducks (BWTE = blue-winged teal, MALL = mallard,

GADW = gadwall, LESC = lesser scaup, RNDU = ring-necked duck) collected in the Upper MS River and Great Lakes Region during spring

2006 and 2007…….……….......................................................................21

Table 1.3 Aggregate percent biomass of animal foods consumed by dabbling ducks collected in the Upper MS River and Great Lakes Region during spring 2006 and 2007. If food items were < 1.0% aggregate mass, they were listed as trace (tr.)......................................................................22

Table 1.4 Aggregate percent biomass of plant foods consumed by dabbling ducks collected in the Upper MS River and Great Lakes Region during spring 2006 and 2007. If food items were < 0.5% aggregate mass, they were listed as trace (tr.)..............................................................................24

Table 1.5 Aggregate percent biomass of vegetation consumed by dabbling ducks collected in the Upper MS River and Great Lakes Region during spring 2006 and 2007. If food items were < 0.1% aggregate mass, they were listed as trace (tr.) .............................................................................26

Table 1.6 Aggregate percent biomass of animal foods consumed by diving ducks collected in the Upper MS River and Great Lakes Region during spring 2006 and 2007. If food items were < 1.0% aggregate mass, they were listed as trace (tr.)..............................................................................27

Table 1.7 Aggregate percent biomass of plant foods consumed by diving ducks collected in the Upper MS River and Great Lakes Region during spring 2006 and 2007. If food items were < 0.5% aggregate mass, they were listed as trace (tr.)..............................................................................29

Table 1.8 Aggregate percent biomass of vegetation consumed by diving ducks collected in the Upper MS River and Great Lakes Region during spring 2006 and 2007.................................................................................32 vi

Table 1.9 Results from the initial MANCOVA model evaluating the effects of site, species (Sp), date (Jul), habitat (Hab), reproductive status (RS) and year (Yr) on proportions of invertebrates and seeds consumed by

5 species of ducks collected in the Upper MS River and Great Lakes

Region during spring 2006 and 2007.........................................................34

Table 1.10 Date of first and last dabbling duck collected at each study site in

2006 and 2007 ...........................................................................................37

Table 1.11 Results from a MANCOVA model evaluating the effects of site, date (Jul), habitat (Hab), reproductive status (RS), and year (Yr) on proportions of invertebrates and seeds consumed by blue-winged teal in the Upper MS River and Great Lakes Region during spring

2006 and 2007............................................................................................38

Table 1.12 Results from a MANCOVA model evaluating the effects of transect

(Tran), date (Jul), habitat (Hab), reproductive status (RS), year (Yr) and transect by year (Tran*Yr) on proportions of invertebrates and seeds consumed by blue-winged teal in the Upper MS River and Great Lakes

Region during spring 2006 and 2007………….........................................40


(Tran), date (Jul), habitat (Hab), and reproductive status (RS) on proportions of invertebrates and seeds consumed by blue-winged teal in the Upper MS River and Great Lakes Region during spring

2006 ………...............................................................................................41


(Tran), date (Jul), habitat (Hab), and reproductive status (RS) on proportions of invertebrates and seeds consumed by blue-winged teal in the Upper MS River and Great Lakes Region during spring

2007 …….....................................................................…..........................42

Table 1.15 Results from a MANCOVA model evaluating the effects of site, date (Jul), habitat (Hab), reproductive status (RS), and year (Yr) on proportions of invertebrates and seeds consumed by mallards in the Upper MS River and Great Lakes Region during spring 2006 and 2007….................................................................................................46


(Tran), date (Jul), habitat (Hab), reproductive status (RS), year (Yr) and transect by year (Tran*Yr) on proportions of invertebrates and seeds consumed by mallards in the Upper MS River and Great Lakes Region during spring 2006 and 2007 ……................……………........................48 vii

Table 1.17 Results from a MANCOVA model evaluating the effects of site, date (Jul), habitat (Hab), and year (Yr) on proportions of invertebrates, seeds, and vegetation consumed by gadwalls in the Upper MS River and Great Lakes Region during spring 2006 and 2007………..................51


(Tran), date (Jul), habitat (Hab), year (Yr) and transect by year

(Tran*Yr) on proportions of invertebrates, seeds, and vegetation consumed by gadwalls in the Upper MS River and Great Lakes Region during spring 2006 and 2007 ...……...........................………………......53


(Tran), date (Jul), and habitat (Hab) on proportions of invertebrates, seeds, and vegetation consumed by gadwalls in the Upper MS River and Great Lakes Region during spring 2006 ………................................54


(Tran), date (Jul), and habitat (Hab) on proportions of invertebrates, seeds, and vegetation consumed by gadwalls in the Upper MS River and Great Lakes Region during spring 2007 ………................................56

Table 1.21 Date of first and last diving duck collected at each study site in

2006 and 2007 ...........................................................................................59

Table 1.22 Results from a MANCOVA model evaluating the effects of site, date (Jul), habitat (Hab), and year (Yr) on proportions of invertebrates and seeds consumed by lesser scaup in the Upper MS River and Great

Lakes Region during spring 2006 and 2007…..........................................60


(Tran), date (Jul), habitat (Hab), and year (Yr) on proportions of invertebrates and seeds consumed by lesser scaup in the Upper MS

River and Great Lakes Region during spring 2006 and 2007 ...................63

Table 1.24 Results from a MANCOVA model evaluating the effects of site, date (Jul), habitat (Hab), and year (Yr) on proportions of invertebrates and seeds consumed by ring-necked ducks in the Upper MS River and Great Lakes Region during spring 2006 and 2007…..........................66


(Tran), date (Jul), habitat (Hab), and year (Yr) on proportions of invertebrates and seeds consumed by ring-necked ducks in the

Upper MS River and Great Lakes Region during spring 2006 and 2007….……........................................................................................68 viii

Table 2.1 Mean food availability (kg/ha) and standard error (SE) of seeds and invertebrates found in shallow (for dabbling ducks) and deep (for diving ducks) habitats during spring 2006………..…………………...…90

Table 2.2 Results of selection analyses for ducks collected at study sites in the Upper MS River and Great Lakes Region (CA = Cache River, IR =

Illinois River, WI = Wisconsin, SR = Scioto River, LE = Lake Erie, and SB = Saginaw Bay) during spring 2006. An “I” indicates selection of invertebrates, “=” indicates consumption in proportion to availability, and “S” indicates selection of seeds ….……………..…...…92

Table 2.3 Mean percentage of food items and standard error (SE) in diet of dabbling ducks at study sites in the Upper MS River and Great Lakes

Region during spring 2006 …….................………………………...……96

Table 2.4 Mean percentage of food items and standard error (SE) in diet of diving ducks at study sites in the Upper MS River and Great Lakes

Region during spring 2006 ……….......……………………..…………...98 ix

LIST OF FIGURES

FIGURE PAGE

Figure 1.1 Location of the Upper MS River and Great Lakes Region with respect to wintering and breeding grounds of ducks migrating through the

Upper MS River and Great Lakes Region (image taken from United

States Fish and Wildlife Service 2008) .... ..................................................9

Figure 1.2 Location of study sites in the Upper MS River and Great Lakes Region

(image provided by Jake Straub, The Ohio State University) ..................10

Figure 1.3 Percent of seeds and invertebrates in the diet of 6 species (BWTE

= blue-winged teal, MALL = mallard, GADW = gadwall, LESC = lesser scaup, RNDU = ring-necked duck) collected in the Upper MS

River and Great Lakes Region during spring 2006 and 2007

(least-squares mean ± standard error). Different letters indicate significantly different means......................................................................35

Figure 1.4 Percent of seeds and invertebrates consumed by blue-winged teal at

6 locations (SR = Scioto River, LE = Lake Erie, SAG = Saginaw Bay,

CA = Cache River, IR = Illinois River, WI = Wisconsin) in the

Upper MS River and Great Lakes Region during spring 2006 and

2007 (least-squares mean ± standard error). Different letters indicate significantly different means ......................……………………..…….....39

Figure 1.5 Percent of seeds and invertebrates consumed by blue-winged teal at western/eastern transect in the Upper MS River and Great Lakes

Region during spring 2006 (least-squares mean ± standard error).

Different letters indicate significantly different means ................………44

Figure 1.6 Percent of seeds and invertebrates consumed by blue-winged teal at western/eastern transect in the Upper MS River and Great Lakes


Different letters indicate significantly different means ....................……45

Figure 1.7 Percent of seeds and invertebrates consumed by mallards at 6 locations (SR = Scioto River, LE = Lake Erie, SAG = Saginaw Bay,


Upper MS River and Great Lakes Region during spring 2006 and 2007

(least-squares mean ± standard error). Different letters indicate significantly different means .............…………………………………....47 x

Figure 1.8 Percent of seeds and invertebrates consumed by mallards at western/eastern transect in the Upper MS River and Great Lakes

Region during spring 2006 and 2007 (least-squares mean ± standard error). Different letters indicate significantly different means ........……49

Figure 1.9 Percent of seeds, vegetation, and invertebrates consumed by gadwalls at 6 locations (SR = Scioto River, LE = Lake Erie, SAG =

Saginaw Bay, CA = Cache River, IR = Illinois River, WI = Wisconsin) in the Upper MS River and Great Lakes Region during spring 2006 and 2007 (least-squares mean ± standard error). Different letters indicate significantly different means ...............………..……………......52

Figure 1.10 Percent of seeds, vegetation, and invertebrates consumed by gadwalls at western/eastern transect in the Upper MS River and Great Lakes



Figure 1.11 Percent of seeds, vegetation, and invertebrates consumed by gadwalls at western/eastern transect in the Upper MS River and Great Lakes



Figure 1.12 Percent of seeds and invertebrates consumed by lesser scaup at 6 locations (SR = Scioto River, LE = Lake Erie, SAG = Saginaw Bay,



2007 (least-squares mean ± standard error). Different letters indicate significantly different means .........................………………………........62

Figure 1.13 Percent of seeds and invertebrates consumed by lesser scaup at western/eastern transect in the Upper MS River and Great Lakes

Region during spring 2006 and 2007 (least-squares mean ± standard error). Different letters indicate significantly different means …....……64

Figure 1.14 Percent of seeds and invertebrates consumed by ring-necked ducks at 6 locations (SR = Scioto River, LE = Lake Erie, SAG = Saginaw

Bay, CA = Cache River, IR = Illinois River, WI = Wisconsin) in the


2007 (least-squares mean ± standard error). Different letters indicate significantly different means .........................………………………..…..67

Figure 1.15 Percent of seeds and invertebrates consumed by ring-necked ducks at western/eastern transect in the Upper MS River and Great Lakes

Region during spring 2006 and 2007 (least-squares mean ± standard error). Different letters indicate significantly different means ....………69 xi

GENERAL INTRODUCTION

Diets of most organisms are primarily determined by what foods are available to them, but also vary among species of closely related organisms, stage of growth, reproductive status, and stage of annual cycle; the latter 3 are likely most influenced by physiological changes in nutritional demand (Sedinger 1992). For example, diets of many animals coincide with changes in forage abundance and quality (Kennish 1996), and small changes in forage quality may influence fitness. Reindeer ( Rangifer tarandus

L.) in Alaska that fed in high-quality habitats (i.e., a diversity of forage) consumed highenergy foods disproportionately to availability, subsequently increasing their bodymass by 14% and were 35% more likely to conceive than reindeer that fed in low-quality habitats (White 1983). Cook et al. (2001) observed reduced pregnancy rates in elk

( Cervis elaphus nelsoni ) fed diets with low digestible energy, indicating reserves acquired during summer and early autumn are important for survival and reproduction later in the year. Results of these studies indicated some animals not only forage to satisfy daily nutritional and energetic requirements, but also to obtain nutrient reserves that influence survival and fitness.

Similarly, migratory waterfowl acquire and depend on a variety of foods throughout their annual cycle but have evolved to exploit unfamiliar feeding sites with variable forage abundance and quality. For example, waterfowl sustain long flights from breeding to staging areas via nutrients acquired from high-energy foods during late summer and early fall (Gruenhagen and Fredrickson 1990). Refueling and maintenance of body condition occurs on staging and wintering grounds by increasing consumption of high-energy foods (Heitmeyer 1985, Delnicki and Reinecke 1986). At the onset of

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spring, waterfowl migrate from wintering areas to their breeding areas. During spring migration, some waterfowl switch from high-energy diets to diets high in protein to prepare for reproduction (Lovvorn 1987, Miller 1987, Manley et al. 1992). It is unclear however, when the switch from a high carbohydrate winter diet to a high protein breeding diet occurs. This is important to understand because knowing when this switch occurs can guide habitat management practices to produce desirable food types depending on stage of migration.

Late-winter and spring are critically important to arctic-nesting geese that depend on fat and protein accumulated before reaching their breeding areas, as these reserves are used to meet nutritional requirements of reproduction (Ankney and MacInnes 1978).

Some duck species also rely on reserves acquired during migration for reproduction

(Krapu 1981, Afton and Ankney 1991, Ankney and Alisauskas 1991), and poor body condition in late-winter may lead to reduced fitness (Dubovsky and Kaminski 1994).

Several field studies have shown that birds are capable of breeding earlier and achieving greater reproductive success if fed high-quality diets prior to nesting (Nager 2006), suggesting there is an endogenous nutrient threshold influencing the initiation of breeding

(Reynolds 1972, Gorman et al. 2008). A female that rapidly exceeds this threshold after arrival should therefore experience greater reproductive success (Reynolds 1972).

Migratory waterfowl are likely limited by the quantity and quality of habitats available for foraging. Wetlands that migratory waterfowl depend on to acquire nutrients for survival and reproduction are being lost at a rate of 47,000 ha/yr (Tiner 1998), with the majority of this loss being anthropogenic (Howe et al. 1989). My study occurred in the Upper Mississippi River and Great Lakes Region (UMR/GLR), located in the middle

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of the Mississippi Flyway and annually used by millions of waterfowl (Bellrose 1980).

The Upper Mississippi River and its nutrient-rich floodplain has been dramatically altered by the expansion of agriculture. Of the six states in North America that have lost

> 80% of their original wetlands, five (Iowa, Missouri, Illinois, Indiana, and Ohio) are located in the UMR/GLR (Dahl 1990). Consequently, populations of waterfowl that breed in and migrate through the UMR/GLR must rely on fewer wetlands (most of which are degraded due to decreased water quality and invasive plant species), than historically available to meet nutritional requirements, potentially having negative impacts on populations (Krapu 1981). Because there is limited information regarding nutritional demands of ducks during spring, an important period for waterfowl populations, my objective in Chapter 1 was to document the diet of spring migrating waterfowl. I emphasized how diet varied among species and attempted to describe how some of the exogenous factors (e.g., latitude, longitude, year, date, foraging habitat, and reproductive status) of individuals may have influenced diet.

If specific nutrients (e.g., protein) are required during specific periods, and those nutrients are limited in the environment, then organisms should exhibit selection for resources high in required nutrients. Thus, researchers should be able to gain insight into nutritional requirements of organisms by determining what food sources are being selected, relative to their availability. Many previous diet studies were inadequate at evaluating resource selection because they did not assess or consider consequences of forage availability. Thus, little information is available regarding nutritional requirements of waterfowl during spring migration; a period of time when nutrient availability likely influences individual fitness. Insight into diet of waterfowl will allow

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habitat managers to manage habitat to provide resources that meet the needs of waterfowl during spring migration, potentially influencing the ability of individuals to successfully reproduce. My objective in Chapter 2 was to document if spring migrating waterfowl were selecting foods (i.e., consuming foods in greater proportion than what was available to them) high in specific nutrients (i.e., proteins or carbohydrates) from representative wetland habitats throughout the UMR/GLR during spring. Hereafter, if I observed a duck consuming a food type in greater proportion than available to them, I considered them to be selecting for that food type. Not only will this information provide a guideline for habitat management for spring migrating ducks but it will allow me to infer nutritional demands of ducks during this time period, as nutritional needs likely change as migration advances and reproduction nears.

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CHAPTER 1: DIET OF MIGRATING WATERFOWL DURING SPRING IN

THE UPPER MISSISSIPPI RIVER AND GREAT LAKES REGION

INTRODUCTION

Diet in Relation to Annual Life Cycle of Waterfowl

Waterfowl have adapted to efficiently use foods in heterogeneous environments to acquire nutrients and energy for life-cycle activities (i.e., migration, courtship, and reproduction) while having limited nutrient-storage capacities (Barlein 2003). Because nutritional and energetic demands and food availability vary throughout the year, duck diets are diverse and variable (Krapu and Reinecke 1992). Assessment of forage availability and diet of ducks during breeding (Krapu 1979) and fall migration (Weller

1988, Stafford et al. 2006, Havens 2007, Kross et al. 2008) has been documented, enabling managers to identify, conserve, and restore habitats that provide critical forage during these seasons. Diet may impact reproductive success, as spring diet has been shown to influence reproductive habits of American black ducks ( Anas rubripes )

(Barboza and Jorde 2002), however little information is available on diet of spring migratory ducks and how it varies among species, with regards to availability, latitude and longitude, years, time within a season, habitat types, and reproductive status.

Abundance of foods that waterfowl depend on varies within and among seasons and often have patchy distributions. Diet throughout the annual cycle is strongly correlated with availability, as invertebrates are most abundant during summer (Kaminski and Prince

1981) and seeds are most abundant during fall and winter (Gruenhagen and Fredrickson

1990). Food availability during spring is largely unknown, but is likely scarce when compared to other seasons of the year, especially considering that most managed

5

wetlands are flooded in early fall for wintering waterfowl and these wetlands are more likely to have fewer seeds due to decomposition (Greer et al. 2006).

Although there is a general trend for duck diets to consist of high protein during breeding and carbohydrates outside of breeding, the proportions of proteinacious and carbohydrate foods consumed varies considerably among taxa (e.g., dabbling ducks vs. diving ducks). Some species such as mallards ( Anas platyrhynchos ) depend almost exclusively on carbohydrates while others such as blue-winged teal ( Anas discors ) consume a more varied diet that consists of both protein and carbohydrates.

Additionally, some waterfowl species exhibit a switch in diet, from predominately seeds to predominately invertebrates, in late winter and early spring (Taylor 1978, Gruenhagen

1987, Lovvorn 1987, Miller 1987, Krapu and Reinecke 1992, Manley et al. 1992). The cause of this switch is not known, but is likely related to a reduction in availability of seeds or changes in nutritional demands, hence selection of proteinacious foods (Lovvorn

1987).

Because poor winter habitats may delay nesting in mallards (Kaminski and

Gluesing 1987, Dubovsky and Kaminski 1994) and American black ducks (Barboza and

Jorde 2002), it is likely that poor-quality spring foraging habitat may also negatively impact nesting waterfowl (Afton and Ankney 1991). Inadequate reserves acquired during spring-staging may decrease nest success through delayed nesting (Harris 1969, McNeil and Leger 1987, Rohwer 1992, Koons and Rotella 2003) or cause some hens to defer reproduction altogether (Newton 2006). Implicit in these findings is that, as spring progresses, diet should reflect reproductive needs. In particular, dietary needs of waterfowl at northern latitudes during spring may differ from waterfowl at southern

6

latitudes during spring. There is strong evidence that late-winter and spring conditions have carryover effects on reproductive success of lesser scaup (Anteau and Afton 2004), however, there is sparse information pertaining to ecology of spring migrating waterfowl in the mid-latitude portions of the Mississippi Flyway, particularly with regards to how diet may change with date or latitude.

Existing information on diet during spring migration is sparse and conflicting

(Newton 2006); some studies found that ducks consumed high-carbohydrate foods (Jorde

1981, LaGrange 1985, Gruenhagen and Fredrickson 1990, Strand et al. 2008), whereas others found ducks consumed high-protein foods (Manley et al. 1992, Badzinski and

Petrie 2006 a ). Two recent studies on feeding ecology of scaup during spring reported high-carbohydrate foods were the main component of their diet (Smith 2007, Strand et al.

2008), but a third indicated high-protein foods as the main dietary component (Badzinski and Petrie 2006 a ).

STUDY OBJECTIVES

Previous spring feeding ecology studies of waterfowl are lacking in that they focused only on 1 or 2 species and usually only at a single location; therefore, my specific objective was to determine if diet during spring varied among selected dabbling

(mallard, gadwall ( Anas strepera ) and blue-winged teal) and diving (lesser scaup ( Aythya affinis ) and ring-necked duck ( Aythya collaris )) ducks. Additionally, I was interested in assessing if diets were influenced by availability of foods (including annual variation), collection date, habitat type, latitude, longitude, and reproductive status during spring.

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METHODS

Study Site Selection

The Upper Mississippi River and Great Lakes Region (UMR/GLR) encompasses ten states and is located between important breeding and wintering areas of North

American waterfowl (Figure 1.1). Study sites within the UMR/GLR were selected based on their presumed importance to migratory waterfowl during the spring (UMR/GLR Joint

Venture 1998) and because they represent typical habitat within the region. The location of the sites exhibited considerable longitudinal and latitudinal variation to enable incorporation of spatial variation in diet as birds migrated northward during spring

(Figure 1.2). The study region was divided into 2 transects, a western transect and an eastern transect, with each transect having three study sites distributed south to north. The western transect included (1) the Cache River region of southern Illinois, (2) the Illinois

River region of central Illinois and, (3) the Horicon Marsh region of southeast Wisconsin, whereas the eastern transect was comprised of (1) the Scioto River region of southern

Ohio, (2) the Lake Erie region of northern Ohio, and (3) the Saginaw Bay region of

Michigan.

The southernmost study site ( 89 o 3’ W, 37 o 18’ N ) of the western transect was located in Southern Illinois and included the Cache River and its floodplain. This region supports a variety of migratory birds, and was deemed an area of international importance by the RAMSAR convention. Bottomland forest habitat, identified as critical habitat for mid-migratory waterfowl (Heitmeyer 1985), represented 70% of available wetland area in the Cache River floodplain. This region also is home to extensive baldcypress and tupelo swamps that are unique to the Upper Mississippi River region. Because of the

8

Figure 1.1.

Location of the Upper MS River and Great Lakes Region with respect to wintering and breeding grounds of ducks migrating through the Upper MS River and

Great Lakes Region (image taken from United States Fish and Wildlife Service 2008).

9

Figure 1.2.

Location of study sites in the Upper MS River and Great Lakes Region

(image provided by Jake Straub, The Ohio State University).

10

uniqueness of this habitat to my area of interest (i.e., the UMR/GLR), it was not included in sampling efforts. Cypress-tupelo swamps did however represent approximately 16% of the wetland habitat in the Cache River floodplain. The Cache River floodplain also contained scrub-shrub (6.3%), open water (3.5%), moist-soil (2.0%), and emergent vegetation (1.3%) wetland habitat types (Havera 1999). The rivers floodplain is expansive and availability of wetland habitat in this region is largely dependant on winter and spring precipitation to produce flooding of riparian habitats. Due to restoration efforts in recent years through the wetlands reserve program (WRP), there are numerous managed wetlands that persist despite altered river conditions. Mean annual temperature is 13.7° C, with average winter temperatures ranging from 3.2 − 8.3° C, and spring temperatures ranging from 8.5 − 18.8° C (Illinois State Water Survey 2008). Mean annual rainfall is 122.7 cm; greatest precipitation occurs in late winter and spring (Illinois

State Water Survey 2008).

The mid-latitude study site ( 90 o 12’ W, 40 o 12’ N

) of the western transect was located along the central region of the Illinois River near Chandlerville, IL. In the early

1900’s, pristine bottomland water areas made the Illinois River one of the most important regions for migratory waterfowl in North America (Bellrose et al. 1983, UMR/GLR Joint

Venture 1998). The Illinois River drains over half of the state, most of which is intensively farmed in row crops (Barrows 1910). Threats to this region include row crop and bank erosion (i.e., increasing nutrient and sediment loads in the river and causing the filling of lateral lakes) and navigation dams that increased low midsummer river levels, resulting in a deepening and extension of all water areas (Steffeck et al. 1980). As a result of the navigation dams, lakes that were previously separated from the river channel

11

by bottomland timber are now connected and mast-producing timber is dead from inundation (Bellrose et al. 1983). Consequently, wetlands of this region (particularly lateral lakes) have been adversely impacted. Similar to some of my other study sites (i.e. the Cache and Scioto Rivers); the wetland area of this region is dictated by winter and spring precipitation and flood events of the river. Fortunately for waterfowl that depend on this region, the greatest precipitation occurs in winter and spring (Illinois State Water

Survey 2008) and coincide with peak waterfowl migration (Havera 1999). Mean annual temperature is 10.8° C, with average winter temperatures ranging from -1.9 − 4.8° C, and spring temperatures ranging from 4.4 − 16.9° C (Illinois State Water Survey 2008).

The northernmost study site ( 88 o 50’ W, 43 o 48’ N

) of the western transect was located in the Upper Rock River watershed in southeast Wisconsin near Horicon Marsh.

This area has been identified as the region of Wisconsin that contains the majority of migratory habitat for waterfowl (UMR/GLR Joint Venture 1998). Representative wetland habitats in this area include riverine wetlands, lacustrine wetlands and a number of kettle ponds and prairie potholes. Agriculture represents 59% of the land use of this watershed and has resulted in substantial drainage of pothole wetlands (Wisconsin

Department of Natural Resources 2002). A number of actively managed wetlands are present in this region with the majority of them being located on Horicon National

Wildlife Refuge and State Wildlife Area and surrounding waterfowl production areas.

One of the largest freshwater wetlands in the United States, Horicon Marsh covers 31,904 acres and is owned and managed by the Fish and Wildlife Service and the Wisconsin

Department of Natural Resources. Soil erosion and siltation, invasion of exotic species

(i.e. carp, purple loosestrife) and high inflow of nutrients from surrounding farms are the

12

biggest threats to this wetland complex (Wisconsin Department of Natural Resources

2002). Mean annual temperature is 7.6° C, with average winter temperatures ranging from -6.3 − 1.9° C, and spring temperatures ranging from 0.2 − 14.3° C (Midwestern

Regional Climate Center 2008). Mean annual rainfall is 83.9 cm; greatest precipitation occurs in late summer and early fall, while the driest periods are mid-late winter

(Midwestern Regional Climate Center 2008).

The southernmost study site ( 82 o 59’ W, 39 o 40’ N ) of the eastern transect was located near Circleville, Ohio and contained the Scioto River and its floodplain. The

Scioto River Valley is recognized as an important area for migrating American black ducks and mallards, despite the fact that the area contains little wetland area (UMR/GLR

Joint Venture 1998). Wetland area in the Scioto River Valley, as defined by the National

Wetlands Inventory (Cowardin et al. 1979), was the least of the six study sites (i.e., 9.5 km

2

). The majority of wetland habitat at this study site was riverine with adjacent forested and scrub-shrub wetlands. Heavy rain and subsequent flooding from the Scioto

River produces many acres of flooded hardwoods and agriculture that attract thousands of ducks (UMR/GLR Joint Venture 1998). Consequently, if the Scioto stays within its banks (i.e., in years of little precipitation), as experienced in the spring of 2006, there is little wetland habitat available to waterfowl. Mean annual temperature is 10.5° C, with average winter temperatures ranging from -3.06 − 5.67° C, and spring temperatures ranging from -1.11 − 15.5° C. Mean annual snowfall is 36.1 cm and mean annual rainfall is 99.1 cm; with highest snowfalls in January and greatest precipitation in summer and late spring (Midwestern Regional Climate Center 2008).

13

The mid-latitude study site ( 82 o

59’ W, 41 o

27’ N ) of the eastern transect was located on Sandusky Bay Lake Erie, approximately 2 km southwest of Port Clinton, OH.

Wetland habitat in this area consists of marshland, which separates the lake from agricultural farmland, and diked wetlands managed for migrating and wintering waterfowl. Agricultural practices have eliminated all but coastal marshes, which are now being impacted by urban encroachment (UMR/GLR Joint Venture 1998). This region still remains important to ducks that migrate through both the Mississippi and Atlantic

Flyways despite the loss of historical Lake Erie marshes. The largest concentrations of staging American black ducks in North America can be found on Lake Erie marshes in this area (UMR/GLR Joint Venture 1998). Water levels in this region of Lake Erie are in constant flux because of varying wind direction and velocity. For example, a strong southwest wind may decrease the water level in this area, while a strong “northeaster” wind may cause water levels to rise (Farney 1975). Mean annual temperature is 9.89° C, with average winter temperatures ranging from -4.2 − 5.17° C, and spring temperatures ranging from -2.56 − 15.28° C. Mean annual snowfall is 55.1 and mean annual rainfall is 91.8 cm; with highest snowfalls in January and the greatest precipitation occurring in late summer (Midwestern Regional Climate Center 2008).

The northernmost study site ( 83 o

25’ W, 43 o

45’ N ) of the eastern transect was located near Sebewaing, MI in Saginaw Bay of Lake Huron. Saginaw Bay is a large, shallow embayment of Lake Huron. Wetland habitat outside of the bay is limited and restricted to hunting clubs and state wildlife areas, which are all used in the spring by thousands of migrant tundra swans, Canada geese and various duck species (J. Straub,

Ohio State University, personal communication). Agriculture is the dominant inland land

14

use. Wetland degradation and loss in this area can be attributed to residential development (UMR/GLR Joint Venture 1998) and invasion of Common Reed

( Phragmites australis ). Mean annual temperature is 7.06° C, with average winter temperatures ranging from -6.11 − 3.11° C, and spring temperatures ranging from -5.33 –

11.5° C. Mean annual snowfall is 85.6 cm and mean annual rainfall is 66 cm with the greatest precipitation occurring in late summer (Midwestern Regional Climate Center

2008).

Study Species

I selected 3 species of dabbling ducks (Anatinae) for my study because of their diversity in body size, migration habits, and timing of reproduction. Dabbling ducks feed in shallow water by submerging their head or tipping up to reach submersed foods, whereas diving ducks feed in deeper water by diving underwater to feed. The mallard is the largest of the selected dabblers, travels the shortest distance to its wintering areas and initiates nesting within days after arriving on breeding areas. The blue-winged teal is the smallest of the selected dabblers, travels the greatest distance to its wintering areas and initiates nesting within days after arrival at breeding areas. The gadwall is a mid-sized dabbling duck, travels intermediate distances to its wintering areas and initiates nests 3 to

4 weeks after arriving on its breeding area (Arzel et al. 2006).

I selected the lesser scaup, hereafter may be referred to as scaup, and ring-necked duck to represent diving ducks (Aythyinae) for my study because they are similar in migratory and reproductive habits, but different with respect to diet and population trends. Scaup populations have experienced a substantial decline relative to the long-

15

term average, while ring-necked duck populations have been stable or increasing during the same period (Wilkins et al. 2006). Additionally, scaup diets have previously been documented to include a large proportion of invertebrates during all stages of the annual cycle (Rogers and Korschgen 1966, Gammonley and Heitmeyer 1990), whereas ringnecked ducks appear to transition from seeds during fall and spring to invertebrates during breeding (Hohman 1985). Scaup and ring-necked ducks are similar in body size, wintering areas, and time between arrival and onset of incubation at breeding sites (Arzel et al. 2006).

Waterfowl Collection

To estimate diet during spring migration, I collected foraging female mallards, gadwall, blue-winged teal, scaup, and ring-necked ducks with a shotgun. Collection began as soon as ice thawed and continued until migrant ducks vacated the study areas

(early May). I attempted to collect only individuals that had fed for ≥ 10 minutes to ensure birds contained ingesta. In some cases, dense vegetation reduced visibility (i.e., forested and emergent wetlands), and I only collected individuals that I knew had been in the habitat for an extended time and were suspected to have been feeding.

I collected foraging females using a layout boat, by stalking, or from camouflaged observation blinds. Layout boats were operated with a trolling motor and camouflaged with sheets of artificial grass. I approached ducks in the layout boat from upwind to encourage them to flush in the direction of the collector.

I recorded locations of collected birds with a global positioning system (GPS) unit and created a shapefile containing the collection data using a handheld personal digital

16

assistant (PDA). Immediately following collection, I injected the esophagi with 10% buffered formalin solution to prevent post-mortem digestion of food items (Swanson and

Bartonek 1970) and placed a zip-tie at the base of the skull to ensure formalin and food items were retained. I assigned ducks an identification number, placed an identification tag on their leg, and refrigerated them until the esophageal tract and proventriculus could be removed. I removed the esophageal tract and proventriculus within 5 days of collection and stored them in vials of 10% buffered formalin solution marked with the unique bird number and species.

Laboratory Analysis

Esophagi of collected ducks were analyzed at Southern Illinois University

Carbondale’s (SIUC) Cooperative Wildlife Research Laboratory Annex. To determine diet, I removed, rinsed, and sorted contents of the esophagus and proventriculus and used a dissecting microscope to separate animal and plant food items. Animal food item identification was conducted at SIUC and seed identification was conducted at The Ohio

State University. Animal foods recovered from esophageal contents were identified to family (Merritt and Cummins 1996), whereas plant material was identified as either milfoil ( Myriophyllum sp.), coontail ( Ceratophyllum demersum ), algae, duckweed

( Lemna sp.), Wolffia sp., sporangia ( Chara sp.), or ‘other vegetation’, and seeds identified to genus. Food items were dried at 60 o

C for ≥ 48 hours before being weighed on a top-loading balance.

17

Statistical Analysis

To reduce the influence of rare occurrences when I encountered a duck that consumed a single food item in a large amount, I summarized diet data using a weighted, aggregate percent mass method explained in Swanson et al. 1974. I also divided the number of birds that consumed a particular food item by the number of birds in the sample to derive percent occurrence of food items. I summarized diet data for 2006 and

2007 for each individual duck species in 3 categories: vegetation, invertebrates, and seeds.

For data to be used in a multivariate analysis of covariance (MANCOVA), I converted aggregate percent dry mass of food items found in the esophagus into proportions of invertebrates and seeds and used those values as dependant variables for 4 of the aforementioned species (mallard, blue-winged teal, scaup, and ring-necked duck).

Because vegetation composed a large portion of gadwall diets, I included proportion of vegetation in diet as a third dependant variable for gadwall. To examine variability in diet composition among species during spring, I used a MANCOVA in which I included the effects of species (blue-winged teal, gadwall, mallard, lesser scaup, and ring-necked duck), study site (Cache River, Illinois River, Wisconsin, Scioto River, Lake Erie, and

Saginaw Bay), collection date, habitat type (agricultural, seasonal emergent, permanent emergent, open-water, and bottomland hardwood), reproductive status (follicle development present or absent), and year (2006, 2007) (PROC GLM, MANOVA option;

SAS Institute, Inc., Cary, NC).

I conducted 2 MANCOVA’s for each species, 1 in which I considered the study site in which the duck was collected and 1 in which I considered the transect in which the

18

duck was collected. Because a study site was not replicated in each of the transects, I had to consider them in separate MANCOVA’s. To determine if spring diet varied by latitude, longitude, or date within each species, I included the effects of study site or transect, date, habitat, reproductive status, and year; including date by site and site by year interactions as additional effects of interest (PROC GLM, MANOVA option; SAS

Institute, Inc., Cary, NC). I only included reproductive status (i.e., hens that had entered rapid follicle development (RFD) vs. hens that had not) as an independent variable in

MANCOVA models for blue-winged teal and mallards, because these were the only species I encountered that had started RFD. When evaluating diet of a particular species,

I reduced initial MANCOVA models using a step-wise procedure by removing the nonsignificant interaction terms ( P > 0.10 based on Type III sums of squares) to obtain a final reduced model that contained all main effects and significant interaction terms

(Badzinski and Petrie 2006 a ). If an interaction term was significant, I conducted separate

MANCOVA’s on year 1 and year 2 data to reduce confounding effects of interaction terms on main effects. Contrasts of the effects in the reduced MANCOVA model were adjusted using the Tukey-Kramer method (PROC GLM; SAS Institute, Inc., Cary, NC).

Because large variances are typically associated with diet data, I considered data to be highly significant at P ≤ 0.05 or marginally significant at P ≤ 0.10 using the Type III sums of squares.

19

RESULTS

Summary Statistics

We collected 919 ducks during the study; 402 in spring 2006 and 517 in spring

2007. Of these, 847 contained sufficient amounts of food to be included in analyses ( n =

203 blue-winged teal, 188 mallards, 116 gadwalls, 135 lesser scaup, and 205 ring-necked ducks) (Table 1.1). Aggregate percent biomass estimates for invertebrates, seeds and vegetation consumed by each species are reported in Table 1.2. A more detailed description of diet at each study site is provided in Appendix A.

Invertebrates that composed the largest portion of diet (i.e., greatest aggregate percent biomass) in dabbling ducks were: gastropods and Chironomidae in blue-winged teal, Chironomidae and microcrustacea (e.g., Cladocera , Copepoda and Ostracoda ) in gadwall, and Chironomidae , macrocrustacea (e.g., Amphipoda and Isopoda), and nondipteran insects in mallards (Table 1.3). The most common seeds were: Polygonum sp.,

Cyperus sp., Scirpus sp., and Leersia sp. in blue-winged teal, Polygonum sp., Cyperus sp. and Scirpus sp. in gadwall, and Polygonum sp., Leersia and Scirpus in mallards (Table

1.4). Lemna was the most commonly consumed vegetation by dabbling ducks, except gadwall, which consumed slightly more algae (Table 1.5).

The most common invertebrates in diving duck diets were Chironomidae and

Gastropods in scaup and Chironomidae and non-dipteran insects in ring-necked ducks

(Table 1.6). The most common seeds found in scaup were Polygonum sp. and

Potamogeton sp. and in ring-necked ducks were Polygonum sp., Potamogeton sp., and

Echinochloa sp. (Table 1.7). Lemna and unidentifiable vegetation were the most

20

Table 1.1.

Number of ducks collected in the Upper MS River and Great Lakes Region that contained food items during spring 2006 and 2007. (BWTE = blue-winged teal,

MALL = mallard, GADW = gadwall, RNDU = ring-necked duck, LESC = lesser scaup,

CA = Cache River, IR = Illinois River, WI = Wisconsin, SR = Scioto River, LE = Lake

Erie, SB = Saginaw Bay)

________________________________________________________________________

2006 2007

SPECIES CA IR WI SR LE SB Total CA IR WI SR LE SB Total TOTAL

________________________________________________________________________________________________

BWTE 22 21 19 2 20 12 96 27 28 17 10 6 19 107 203

MALL 15 15 9 11 26 19 95 17 13 14 20 8 21 93 188

GADW 8 14 0 0 18 2 42 15 8 16 1 17 17 74 116

RNDU 13 11 3 7 37 15 86 24 10 12 26 25 22 119 205

LESC 0 10 2 1 20 16 49 2 25 5 16 9 29 86 135

Total 58 71 33 21 121 64 368 85 84 64 73 65 108 479 847

________________________________________________________________________________________________

Table 1.2. Aggregate percent (A) ± standard error and percent occurrence (O) of food items in ducks (BWTE = blue-winged teal, MALL = mallard, GADW = gadwall, LESC = lesser scaup, RNDU = ring-necked duck) collected in the Upper MS River and Great

Lakes Region during spring 2006 and 2007.

________________________________________________________________________ vegetation invertebrates seeds

A O A O A O

______________________________________________________________________________________

BWTE 4.8 ± 1.8 19.7 41.4 ± 2.5 76.3 53.7 ± 2.8 91.1

MALL 4.3 ± 1.9 17.8 16.4 ± 2.6 48.1 79.2 ± 2.9 91.6

GADW 52.9 ± 2.4

LESC 5.6 ± 2.2

70.6

23.3

8.9 ± 3.3

54.7 ± 3.1

75.8

84.9

38.0 ± 3.7

39.6 ± 3.5

75.8

82.7

RNDU 8.7 ± 1.8 24.1 17.6 ± 2.5 53.7 73.6 ± 2.8 91.1

______________________________________________________________________________________

21

Table 1.3. Aggregate percent biomass of animal foods consumed by dabbling ducks collected in the Upper MS River and Great Lakes Region during spring 2006 and 2007.

If food items were < 1.0% aggregate mass, they were listed as trace (tr.).

______________________________________________________________________________________

Food Item BWTE ( n = 155) GADW ( n = 88)

Agg. % Agg. %

MALL ( n = 92)

Agg. %

______________________________________________________________________________________

Gastropoda

Lymnaeidae

Physidae

37.2

10.9

10.7

2.1

tr.

1.1

12.6

2.2

6.9

Planorbidae 15.5 tr. 3.5

Bivalvia

Sphaeriidae

Chironomidae

1.4

1.4 0.0 0.0

19.1

0.0

31.8

0.0

19.8

Non-Chironomidae Dipterans

Ceratopogonidae

Chaoboridae

Simuliidae

Stratiomyidae

Tabanidae

Tipulidae

Macrocrustacea

6.6

2.7

0.0

0.0

2.1

tr.

tr.

9.7

14.4

4.1

1.1

1.0

2.8

1.0

1.1

3.9

11.7

2.2

0.0

0.0

2.7

1.1

2.2

19.2

Amphipoda

Isopoda

Microcrustacea

Cladocera

Copepoda

Ostracoda

Annelida

Hirudinea

4.5

5.1

7.2

3.9

2.1

1.1

5.0

tr.

2.3

1.6

16.3

5.4

9.6

1.2

4.2 9.4

0.0

6.9

12.2

2.1

tr.

1.0

tr.

1.4

22

Table 1.3 continued.

______________________________________________________________________________________

Food Item BWTE ( n = 155) GADW ( n = 88)

Agg. % Agg. %

MALL ( n = 92)

Agg. %

______________________________________________________________________________________

4.2 3.2 8.0 Oligochaeta

Nematoda tr. 11.2 1.2

10.2 12.1 20.5 Non-Dipteran Insects

Collembola

Caenidae

Coenagrionidae

2.5

tr.

1.6

1.5

2.8

tr.

0.0

tr.

1.9

Cicadellidae tr. 0.0 1.0

Corixidae

Naucoridae

Dytiscidae

Carabidae

Hydrophilidae

Leptoceridae

Limnephilidae

tr.

0.0

1.3

0.0 1.0

1.1 0.0

tr.

tr.

tr.

tr.

0.0

1.4

0.0 2.5

tr. 2.4

0.0 2.0

0.0 1.0

Phryganeidae

Pyralidae

tr.

tr.

Miscellaneous / Unknown Inverts 4.0

Terrestrials 2.6

0.0 2.0

1.8 1.0

4.6 3.9

3.5 2.0

Unknowns 1.4 1.1 1.9

______________________________________________________________________________________

23

Table 1.4.

Aggregate percent biomass of plant foods consumed by dabbling ducks collected in the Upper MS River and Great Lakes Region during spring 2006 and 2007.


______________________________________________________________________________________

Food Item BWTE ( n = 185)

Agg. %

GADW ( n = 88)

Agg. %

MALL( n = 175)

Agg. %

______________________________________________________________________________________

0.0 0.0 0.7 Abutillion sp.

Alisma sp.

Amaranthus sp.

Bidens sp.

Carex sp.

Cephalanthus sp.

Chenopodium sp.

Corn

Cyperaceae sp.

Cyperus sp.

Digitaria sp.

Echinochloa sp.

Eleocharis sp.

Eragrostis sp.

Helenium sp.

Leersia sp.

Ludwigia sp.

Myriophyllum sp.

Najas sp.

Panicum sp.

Poaceae sp.

Polygonum sp.

Potamogeton sp.

1.3

5.3

6.3

3.9

1.9

0.8 tr.

1.0

8.1

1.3

4.8

4.9

1.8

0.0

7.8

4.0

tr. tr.

4.9 tr.

20.4

2.6

2.2

0.7 tr.

6.0

2.2 tr.

0.0

0.0

15.5

2.2

4.3

2.9

2.2

0.0

6.4

1.8

0.7

2.6

2.8

1.1

21.5

2.4

0.7

1.5

0.9

1.2

0.7 tr.

9.4

0.0

2.2

0.5

6.9

0.7

0.8

0.7

12.9 tr. tr.

1.0

1.7 tr.

17.2

4.1

24


______________________________________________________________________________________


Agg. %

GADW ( n = 88)

Agg. %

MALL ( n = 175)

Agg. %

______________________________________________________________________________________

0.5 0.0 0.0 Rhynchospora sp.

Rumex sp.

Sagittaria sp.

0.7 tr. tr.

0.6

1.4

0.5

Scirpus sp.

Setaria sp.

Sparganium sp.

Toxicodendron sp.

Trifolium sp.

8.0 tr.

0.0

0.0 tr.

12.4 tr.

0.0

0.0

0.6

11.8

2.2

0.6

0.5 tr.

Vitis sp.

Unknown Seeds

0.0

5.2

0.0

6.4

0.6

4.2

Tubers tr. tr. 9.3

______________________________________________________________________________________

25

Table 1.5.

Aggregate percent biomass of vegetation consumed by dabbling ducks collected in the Upper MS River and Great Lakes Region during spring 2006 and 2007.


______________________________________________________________________________________


Agg. %

GADW ( n = 82)

Agg. %

MALL ( n = 34)

Agg. %

______________________________________________________________________________________

Algae

Ceratophyllum sp.

0.0

0.2

35.8

1.1

2.9

2.9

Myriophyllum sp.

Lemna sp.

Wolffia sp.

Chara sporangia

Other Vegetation

0.0

77.7

0.0 tr.

22.0

1.2

32.8 52.3

2.8

2.8

23.3

0.0

0.0

0.2

41.4

______________________________________________________________________________________

26

Table 1.6.

Aggregate percent biomass of animal foods consumed by diving ducks collected in the Upper MS River and Great Lakes Region during spring 2006 and 2007.


______________________________________________________________________________________

Food Item LESC ( n = 113)

Agg. %

RNDU ( n = 109)

Agg. %

______________________________________________________________________________________

Gastropoda

Lymnaeidae

Physidae

Planorbidae

Bivalvia

Dreisseniidae

Sphaeriidae

Chironomidae


Ceratopogonidae

Macrocrustacea

Amphipoda

Isopoda

Microcrustacea

Cladocera

Ostracoda

Annelida

Oligochaeta

Nematoda

Non-Dipteran Insects

Coenagrionidae

Libellulidae

Phryganeidae

20.3

4.5

9.8

5.9

4.0

0.0

4.0

41.7

3.2

1.6

9.3

1.9

7.4

4.2

2.4

1.0

3.5

3.5

5.0

6.0

1.3

1.4

0.0

11.8 tr.

8.1

3.0

2.2

1.4 tr.

47.4

2.0 tr.

6.7

2.2

4.5 tr. tr. tr.

4.9

4.9

1.8

18.1

3.4

6.6

1.8

27


______________________________________________________________________________________


Agg. %

RNDU ( n = 109)

Agg. %

______________________________________________________________________________________

Miscellaneous / Unknown Inverts

Bryozoan

Unknowns

3.0

1.9

1.1

4.5

3.6

0.9

______________________________________________________________________________________

28

Table 1.7.

Aggregate percent biomass of plant foods consumed by diving ducks collected in the Upper MS River and Great Lakes Region during spring 2006 and 2007. If food items were < 0.5% aggregate mass, they were listed as trace (tr.).

______________________________________________________________________________________


Agg. %

RNDU ( n = 185)

Agg. %

______________________________________________________________________________________

Amaranthus sp.

Bidens sp.

2.2

0.5

3.6 tr.

Brassica sp.

Carex sp.

Cephalanthus sp.

Ceratophyllum sp.

0.0

1.3

0.9

3.7

0.5 tr. tr.

2.8

Chenopodium sp.

Corn

Cyperus sp.

Echinochloa sp.

Eleocharis sp.

Eragrostis sp.

Impatiens sp.

Ipomea sp.

2.0

3.5

8.9

5.8 tr.

0.8

0.6

0.8 tr.

2.0

5.9

14.2

0.5 tr.

0.0

0.0

Juncus sp.

Leersia sp.

Ludwigia sp.

Myriophyllum sp.

Najas sp.

Panicum sp.

Phalaris sp.

Phragmites sp.

Poaceae sp.

1.1

4.2

1.8

0.7

0.8 tr. tr.

0.9

0.8

0.0

6.4

1.2

1.1

4.5

5.0

0.9 tr.

0.5

29


______________________________________________________________________________________


Agg. %

RNDU ( n = 185)

Agg. %

______________________________________________________________________________________

0.7 0.0 Polygonaceae sp.

Polygonum sp.

Potamogeton sp.

20.4

15.1

20.4

14.7

Sagittaria sp.

Scirpus sp.

Trifolium sp.

0.6

9.2

0.0 tr.

5.7

0.5

Vallisneria sp.

Zannichellia sp.

Unknown Seeds

Tubers

0.0

0.7

8.1 tr.

0.5 tr.

2.2

4.1

______________________________________________________________________________________

30

commonly consumed vegetation by diving ducks, although ring-necked ducks also consumed large amounts of Chara sp. (Table 1.8).

MANCOVA results

I applied an arcsine square-root transformation to the diet data; however this did not eliminate the nonnormality of the proportions in the diet. I therefore concluded that my data was robust to transformation. Additionally, because of a prevalence of zeros in my data, I decided against using compositional analyses to evaluate diet. Even though these assumptions were violated by analyzing my diet data in a MANCOVA, this approach, however, has been utilized in recent waterfowl diet studies and appears to be the most efficient method of evaluating waterfowl diet data (Afton et al. 1991, Badzinski and Petrie 2006).

Breeding vs. Non-Breeding

Thirty-three mallards and 9 blue-winged teal had entered RFD. Interestingly, the diets of both mallards ( F

1,13

= 0.64, P = 0.42 for invertebrates and F

1,13

= 0.14, P = 0.71 for seeds) and blue-winged teal ( F

1,12

= 0.39, P = 0.53 for invertebrates and F

1,12

= 0.41, P

= 0.52 for seeds) in RFD were similar to diets of mallards and blue-winged teal not in

RFD and when I excluded RFD females from analyses, it did not change results; therefore I did not consider them separately in subsequent analyses. Although not statistically significant, there were, however, higher mean proportions of invertebrates in diets of blue-winged teal (58% vs. 42%) and mallards (27.7% vs. 15.7%) that had begun

RFD than those that had not begun RFD.

31

Table 1.8.

Aggregate percent biomass of vegetation consumed by diving ducks collected in the Upper MS River and Great Lakes Region during spring 2006 and 2007.

______________________________________________________________________________________


Agg. %

RNDU ( n = 49)

Agg. %

______________________________________________________________________________________

Algae 3.2 0.0

Ceratophyllum sp.

Myriophyllum sp.

3.2

0.0

46.3

4.0

0.0

24.3 Lemna sp.

Wolffia sp. 0.0 2.0

Chara sporangia

Other Vegetation

3.3

43.7

24.5

44.9

______________________________________________________________________________________

32

Diet

The final MANCOVA model (with non-significant interactions removed) evaluating duck diets considered only main effects of study site, species, date, habitat, reproductive status, and year. Significant effects of the model included study site, species, and date for both the proportions of invertebrates and seeds in the diet (Table

1.9). Blue-winged teal, gadwall, and scaup had similar proportions ( P > 0.10) of invertebrates and seeds in their diets. Likewise, the diet of mallards was similar to ringnecked ducks (Figure 1.3). Invertebrate consumption significantly increased with date, whereas seed consumption decreased.

Blue-winged Teal Diets

Two-hundred and three blue-winged teal ( n = 96 in 2006 and n = 107 in 2007) were included in the analysis evaluating diet at the scale of study site (Table 1.1).

Likewise, 203 blue-winged teal ( n = 69 from eastern transect and n = 134 from western transect) were included in the analysis evaluating diet at the scale of transect ( n = 34 in

2006 and n = 35 in 2007 from the eastern transect and n = 62 in 2006 and n = 72 in 2007 from the western transect). In 2006, the first blue-winged teal was collected on 14 March and the last on 5 May and in 2007, the first was collected on 18 March and the last on 3

May (Table 1.10).

The final reduced MANCOVA model evaluating latitudinal variation in diet

(invertebrates and seeds) of blue-winged teal included only the main effects of site, date, habitat, reproductive status, and year. The percentage of invertebrates in the diet varied

33

Table 1.9.

Results from the initial MANCOVA model evaluating the effects of site, species (Sp), date (Jul), habitat (Hab), reproductive status (RS), and year (Yr) on proportions of invertebrates and seeds consumed by 5 species of ducks collected in the

Upper MS River and Great Lakes Region during spring 2006 and 2007.

________________________________________________________________________

Source DF Type III SS Mean Square F value Pr > F

________________________________________________________________________

Invertebrates

Site 5

Sp 4

Jul

Hab

RS

1

5

1

8.41

9.69

0.74

1.10

0.29

1.68

2.42

0.74

0.22

0.29

12.34 < 0.05

17.78 < 0.05

5.43

1.62

2.18

< 0.05

0.15

0.14

Yr

Seeds

Site

1

5

0.34

9.15

0.34

1.83

2.55

12.98

0.11

< 0.05

Sp

Jul

Hab

RS

4

1

5

10.87

0.87

1.06

2.71

0.87

0.21

19.28

6.20

1.51

< 0.05

0.01

0.18

1 0.21 0.21 1.49 0.22

Yr 1 0.22 0.22 1.55 0.21

________________________________________________________________________

34

50

40

30

20

10

0

100

90

80

70

60 a/b d/e

BWTE c f

MALL a d

GADW

Species

b

e

LESC c

f

RNDU

% seed

% invert

Figure 1.3.

Percent of seeds and invertebrates in the diet of 6 species (BWTE = bluewinged teal, MALL = mallard, GADW = gadwall, LESC = lesser scaup, RNDU = ringnecked duck) collected in the Upper MS River and Great Lakes Region during spring

2006 and 2007 (least-squares means ± standard error). Different letters indicate significantly different means.

35

significantly by date and the percentage of seeds varied significantly among study sites and by date (Table 1.11). Blue-winged teal exhibited a daily increase of 0.79% ± 0.29% in invertebrate consumption ( P = 0.006). Additionally, the proportion of seeds in the diet was moderately lower ( P = 0.065) for blue-winged teal collected at Saginaw Bay than blue-winged teal collected at Wisconsin (Figure 1.4).

The final reduced MANCOVA model evaluating longitudinal variation in diets of blue-winged teal included the main effects of transect, date, habitat, reproductive status, year, and a transect by year interaction (Table 1.12). Because of the significant interaction term, I analyzed data by year (i.e., removed interaction term), and found invertebrate consumption varied significantly with transect in 2006 and date in 2006 and

2007 (Table 1.13 and Table 1.14), whereas seed consumption varied with transect in

2006 (Table 1.13) and only date in 2007 (Table 1.14). Blue-winged teal collected in the eastern transect consumed 30.4% ± 9.1% more invertebrates and 31.3% ± 9.1% less seeds than teal collected in the western transect in 2006 (Figure 1.5). Blue-winged teal collected in 2006 increased invertebrate consumption by 0.81% ± 0.38% daily. In 2007, invertebrate and seed consumption varied only by date (Table 1.14 and Figure 1.6).

Invertebrate consumption increased daily by 0.82% ± 0.37% and seed consumption decreased daily by 0.89% ± 0.37% in 2007.

36

Table 1.10. Date of first and last dabbling duck collected at each study site in 2006 and

2007.

________________________________________________________________________

2006 2007

SPECIES FIRST LAST FIRST LAST

______________________________________________________________________________________

BWTE

Cache River

Illinois River

Wisconsin

23 March

14 March

05 April

19 April

01 May

05 May

18 March

22 March

02 April

26 April

29 April

03 May

MALL

Scioto River

Lake Erie

Saginaw Bay

Cache River

Illinois River

Wisconsin

Scioto River

27 March

16 March

06 April

16 February

12 March

03 April

23 February

30 March

21 April

27 April

01 April

11 April

25 April

10 March

21 March

26 March

25 March

13 March

02 April

09 April

12 April

03 May

22 February 29 March

18 April

04 May


Lake Erie

Saginaw Bay

GADW

Cache River

Illinois River

Wisconsin

Scioto River

Lake Erie

10 March

17 March

03 March

13 March

N/A

N/A

10 March

21 April

20 April

12 April

03 April

N/A

N/A

19 April

13 March

19 March

22 February

13 March

28 March

27 February 27 February

19 March

18 April

23 April

01 April

10 April

03 May

18 April

Saginaw Bay 06 April 12 April 20 March 19 April

______________________________________________________________________________________

37

Table 1.11. Results from a MANCOVA model evaluating the effects of site, date (Jul), habitat (Hab), reproductive status (RS), and year (Yr) on proportions of invertebrates and seeds consumed by blue-winged teal in the Upper MS River and Great Lakes Region during spring 2006 and 2007.

________________________________________________________________________


________________________________________________________________________

Invertebrates

Site 5

Jul 1

4 Hab

RS

Yr

Seeds

1

1

1.44

1.25

0.27

0.06

0.10

0.29

1.25

0.06

0.06

0.10

1.79

7.80

0.42

0.39

0.63

0.11

< 0.05

0.79

0.53

0.42

Site

Jul

5

1

1.92

0.98

0.38

0.98

2.38

6.12

< 0.05

< 0.05

Hab 4 0.27 0.06 0.42 0.79

RS

Yr

1 0.06 0.06 0.41 0.52

1 0.12 0.12 0.79 0.37

________________________________________________________________________

38

70

60

50

40

30

20

10

0

c

c

a/b

c

b

a/b

c

a/b

c

a

c

SR LE

East Transect

SAG CA

Study Site

IR

West Transect

WI

% seed

% invert

Figure 1.4. Percent of seeds and invertebrates consumed by blue-winged teal at 6 locations (SR = Scioto River, LE = Lake Erie, SAG = Saginaw Bay, CA = Cache River,

IR = Illinois River, WI = Wisconsin) in the Upper MS River and Great Lakes Region during spring 2006 and 2007 (least-squares means ± standard error). Different letters indicate significantly different means.

39

Table 1.12. Results from a MANCOVA model evaluating the effects of transect (Tran), date (Jul), habitat (Hab), reproductive status (RS), year (Yr), and transect by year

(Tran*Yr) on proportions of invertebrates and seeds consumed by blue-winged teal in the

Upper MS River and Great Lakes Region during spring 2006 and 2007.

________________________________________________________________________


________________________________________________________________________

Invertebrates

Tran 1

Jul 1

Hab

RS

Yr

4

1

1

1.03

1.58

0.25

0.01

0.002

1.03

1.58

0.06

0.01

0.002

6.59

10.12

0.41

0.06

0.02

< 0.05

< 0.05

0.80

0.81

0.90

Tran*Yr

Seeds

Tran

1

1

0.78

1.36

0.78

1.36

5.01

8.67

< 0.05

< 0.05

Jul

Hab

RS

Yr

1

4

1

1.36

0.23

0.01

1.36

0.05

0.01

8.65

0.37

0.06

< 0.05

0.83

0.80

1 0.002 0.002 0.01 0.91

Tran*Yr 1 0.79 0.79 5.04 < 0.05

________________________________________________________________________

40

Table 1.13. Results from a MANCOVA model evaluating the effects of transect (Tran), date (Jul), habitat (Hab), and reproductive status (RS) on proportions of invertebrates and seeds consumed by blue-winged teal in the Upper MS River and Great Lakes Region during spring 2006.

________________________________________________________________________


________________________________________________________________________

Invertebrates

Tran 1

Jul 1

1.65

0.66

1.65

0.66

11.18

4.51

< 0.05

< 0.05

Hab

RS

Seeds

Tran

4

1

0.75

0.04

0.19

0.04

1.28

0.29

0.28

0.59

1 1.75 1.75 11.65 < 0.05

Jul

Hab

1 0.31 0.31 2.09 0.15

4 0.74 0.18 1.24 0.30

RS 1 0.08 0.08 0.52 0.47

________________________________________________________________________

41

Table 1.14. Results from a MANCOVA model evaluating the effects of transect (Tran), date (Jul), habitat (Hab), and reproductive status (RS) on proportions of invertebrates and seeds consumed by blue-winged teal in the Upper MS River and Great Lakes Region during spring 2007.

________________________________________________________________________


________________________________________________________________________

Invertebrates

Tran 1

Jul 1

0.02

0.79

0.02

0.79

0.15

4.75

0.70

< 0.05

Hab

RS

Seeds

Tran

4

1

0.10

0.01

0.02

0.01

0.16

0.07

0.95

0.79

1 0.11 0.11 0.68 0.41

Jul

Hab

1 0.94 0.94 5.66 < 0.05

4 0.18 0.04 0.28 0.89

RS 1 0.01 0.01 0.08 0.78

________________________________________________________________________

42

Mallard Diets

One-hundred and eighty-eight mallards ( n = 95 in 2006 and n = 93 in 2007) were included in analyses evaluating diet at the scale of study site (Table 1.1). Likewise, 188 mallards ( n = 105 from eastern transect and n = 83 from western transect) were included in the analysis evaluating diet at the scale of transect ( n = 56 in 2006 and n = 49 in 2007 from the eastern transect and n = 39 in 2006 and n = 44 in 2007 from the western transect). In 2006, the first mallard was collected on 16 February and the last on 25 April and in 2007, the first was collected on 22 February and the last on 4 May (Table 1.10).

The final reduced MANCOVA model evaluating latitudinal variation in diets

(invertebrates and seeds) of mallards included the main effects of site, date, habitat, reproductive status, and year; none of which were significant with regard to the proportions of invertebrates or seeds in the diet (Table 1.15 and Figure 1.7).

The final reduced MANCOVA model evaluating longitudinal variation in diet of mallards included the main effects of transect, date, habitat, reproductive status, and year.

The reduced model included only a date effect for the proportions of invertebrates and seeds in the diet (Table 1.16 and Figure 1.8). Mallards exhibited a daily increase of

0.47% ± 0.18% in invertebrate consumption ( P = 0.002) and a daily decrease of 0.55% ±

0.19% in seed consumption ( P = 0.004).

43

100

80

60

40

20

0

a

c

West

Transect

b

d

East

% seed

% invert

Figure 1.5. Percent of seeds and invertebrates consumed by blue-winged teal at western/eastern transect in the Upper MS River and Great Lakes Region during spring

2006 (least-squares means ± standard error). Different letters indicate significantly different means.

44

80

70

60

50

40

30

20

10

0

a

b

West

Transect

a

b

East

% seed

% invert

Figure 1.6. Percent of seeds and invertebrates consumed by blue-winged teal at western/eastern transect in the Upper MS River and Great Lakes Region during spring


45

Table 1.15. Results from a MANCOVA model evaluating the effects of site, date (Jul), habitat (Hab), reproductive status (RS), and year (Yr) on proportions of invertebrates and seeds consumed by mallards in the Upper MS River and Great Lakes Region during spring 2006 and 2007.

________________________________________________________________________


________________________________________________________________________

Invertebrates

Site 5

Jul 1

5 Hab

RS

Yr

Seeds

1

1

0.93

0.16

0.72

0.07

0.02

0.18

0.16

0.14

0.07

0.02

1.71

1.51

1.32

0.64

0.19

0.13

0.22

0.25

0.42

0.66

Site

Jul

5

1

0.71

0.24

0.14

0.24

1.18

2.02

0.32

0.15

Hab 5 0.57 0.11 0.96 0.44

RS

Yr

1 0.01 0.01 0.14 0.71

1 0.02 0.02 0.17 0.68

________________________________________________________________________

46

40

20

0

-20

120

100

80

60

a

b

SR

a

b

a b

LE

East Transect

SAG

a

b

CA

Study Site

a

b

a

b

IR

West Transect

WI

% seed

% invert

Figure 1.7. Percent of seeds and invertebrates consumed by mallards at 6 locations (SR =

Scioto River, LE = Lake Erie, SAG = Saginaw Bay, CA = Cache River, IR = Illinois

River, WI = Wisconsin) in the Upper MS River and Great Lakes Region during spring


47

Table 1.16. Results from a MANCOVA model evaluating the effects of transect (Tran), date (Jul), habitat (Hab), reproductive status (RS), year (Yr), and transect by year

(Tran*yr) on proportions of invertebrates and seeds consumed by mallards in the Upper

MS River and Great Lakes Region during spring 2006 and 2007.

________________________________________________________________________


________________________________________________________________________

Invertebrates

Tran 1

Jul 1

5 Hab

RS

Yr

Seeds

1

1

0.02

0.76

0.33

0.02

0.03

0.02

0.76

0.06

0.02

0.03

0.21

6.81

0.59

0.16

0.30

0.65

< 0.05

0.70

0.68

0.58

Tran

Jul

1

1

0.04

1.02

0.04

1.02

0.38

8.45

0.53

< 0.05

Hab 5 0.39 0.08 0.65 0.66

RS

Yr

1 0.00 0.00 0.00 0.98

1 0.01 0.01 0.08 0.77

________________________________________________________________________

48

120

100

80

60

40

20

0

a

a

West

b

Transect

East

b

% seed

% invert

Figure 1.8. Percent of seeds and invertebrates consumed by mallards at western/eastern transect in the Upper MS River and Great Lakes Region during spring 2006 and 2007

(least-squares means ± standard error). Different letters indicate significantly different means.

49

Gadwall Diets

One-hundred and sixteen gadwalls ( n = 42 in 2006 and n = 74 in 2007) were included in analyses evaluating diet at the scale of study site (Table 1.1). Likewise, 116 gadwalls ( n = 55 from eastern transect and n = 61 from western transect) were included in the analysis evaluating diet at the scale of transect ( n = 20 in 2006 and n = 35 in 2007 from the eastern transect and n = 22 in 2006 and n = 39 in 2007 from the western transect). In 2006, the first gadwall was collected on 3 March and the last on 19 April and in 2007, the first was collected on 22 February and the last on 3 May (Table 1.10).


(vegetation, invertebrates, and seeds) of gadwalls included the main effects of site, date, habitat, and year; sample sizes were insufficient to include date by site and site by year interactions. There was a marginally significant year effect on percentage of invertebrates in gadwall diets (Table 1.17), with invertebrate consumption being greater in year 2 than year 1 ( P = 0.080). Proportions of vegetation, invertebrates, and seeds did not differ among study sites (Figure 1.9).

The final reduced MANCOVA model evaluating longitudinal variation in diet

(vegetation, invertebrates and seeds) of gadwalls included the main effects of transect, date, habitat, year, and a transect by year interaction (Table 1.18). Because of the significant interaction term, I separated data by years (i.e., removed interaction term), and found invertebrate consumption of gadwalls in 2006 was not effected by transect, date, or the habitat they were collected in. However, the proportion of seeds and vegetation consumed by gadwalls in 2006 varied significantly with date and transect (Table 1.19).

Gadwalls collected in the western transect in 2006 consumed 40.8% ± 15.4% more seeds

50

Table 1.17.

Results from a MANCOVA model evaluating the effects of site, date (Jul), habitat (Hab), and year (Yr) on proportions of invertebrates, seeds, and vegetation consumed by gadwalls in the Upper MS River and Great Lakes Region during spring

2006 and 2007.

________________________________________________________________________


________________________________________________________________________

Invertebrates

Site 5

Jul 1

4 Hab

Yr

Seeds

Site

1

5

0.11

0.01

0.06

0.16

1.60

0.02

0.01

0.01

0.16

0.32

0.40

0.23

0.28

3.12

1.80

0.84

0.63

0.88

0.08

0.12

Jul

Hab

1

4

0.29

1.25

0.29

0.31

1.61

1.75

0.20

0.14

Yr

Vegetation

Site

1 0.43 0.43 2.42 0.12

5 1.81 0.36 1.87 0.10

Jul

Hab

1 0.42 0.42 2.16 0.14

4 1.38 0.34 1.77 0.14

Yr 1 0.06 0.06 0.32 0.57

________________________________________________________________________

51

100

50

0

-50

-100

250

200

150

SR LE

East Transect

SAG CA IR

West Transect

WI

Study Site

% seed

% invert

% veg

Figure 1.9. Percent of seeds, vegetation and invertebrates consumed by gadwalls at 6 locations (SR = Scioto River, LE = Lake Erie, SAG = Saginaw Bay, CA = Cache River,


52

Yr

Tran*yr

Vegetation

Tran

Jul

Hab

Yr

Tran*yr

Table 1.18.

Results from a MANCOVA model evaluating the effects of transect (Tran), date (Jul), habitat (Hab), year (yr), and transect by year (Tran*yr) on proportions of invertebrates, seeds, and vegetation consumed by gadwalls in the Upper MS River and

Great Lakes Region during spring 2006 and 2007.

________________________________________________________________________


________________________________________________________________________

Invertebrates

Tran 1

Jul 1

4 Hab

Yr

Tran*yr

Seeds

1

1

Tran

Jul

Hab

1

1

4

0.00

0.09

0.09

0.12

0.00

0.87

0.16

1.15

0.00

0.09

0.02

0.12

0.00

0.87

0.16

0.29

0.01

1.75

0.45

2.25

0.06

5.05

0.94

1.67

0.92

0.19

0.77

0.13

0.80

< 0.05

0.33

0.16

1 0.83 0.83 4.81 < 0.05

1

1

1

4

1

1

1.11

0.83

0.50

1.28

0.32

0.99

1.11

0.83

0.50

0.32

0.32

0.99

6.45

4.36

2.61

1.66

1.68

5.20

< 0.05

< 0.05

0.11

0.16

0.19

< 0.05

________________________________________________________________________

53

Table 1.19.

Results from a MANCOVA model evaluating the effects of transect (Tran), date (Jul), and habitat (Hab) on proportions of invertebrates, seeds, and vegetation consumed by gadwalls in the Upper MS River and Great Lakes Region during spring

2006.

________________________________________________________________________


________________________________________________________________________

Invertebrates

Tran 1

Jul

Hab

1

3

0.00

0.01

0.03

0.00

0.01

0.01

0.08

0.35

0.45

0.78

0.55

0.72

Seeds

Tran

Jul

Hab

Vegetation

Tran

1

1

3

1

1.13

0.98

1.26

1.04

1.13

0.98

0.42

1.04

6.95

6.04

2.59

6.20

< 0.05

< 0.05

0.07

< 0.05

Jul 1 1.16 1.16 6.93 < 0.05

Hab 3 1.26 0.42 2.51 0.07

________________________________________________________________________

54

than gadwalls collected in the eastern transect in 2006 (Figure 1.10). Seed consumption decreased daily by 1.4% ± 0.5% and vegetation consumption increased daily by 1.5% ±

0.6% in gadwalls collected in 2006. Gadwalls collected in the eastern transect in 2006 consumed 39.2% ± 15.7% more vegetation than gadwalls collected in the western transect in 2006 (Figure 1.10). There was no effect of transect, date, or habitat on seeds, invertebrates, and vegetation consumed by gadwalls in 2007 (Table 1.20 and Figure

1.11).

Lesser Scaup Diets

One-hundred and thirty-five lesser scaup ( n = 49 in 2006 and n = 86 in 2007) were included in analyses evaluating diet at the scale of study site (Table 1.1). Likewise,

135 lesser scaup ( n = 91 from eastern transect and n = 44 from western transect) were included in the analysis evaluating diet at the scale of transect ( n = 37 in 2006 and n = 54 in 2007 from the eastern transect and n = 12 in 2006 and n = 32 in 2007 from the western transect). In 2006, the first lesser scaup was collected on 08 March and the last on 29

April and in 2007, the first was collected on 27 February and the last on 2 May (Table

1.21).

The final reduced MANCOVA model evaluating latitudinal variation in diets

(invertebrates and seeds) of scaup included the main effects of site, date, habitat, and year. The percentage of invertebrates and seeds in the diet varied significantly among study sites and habitats (Table 1.22). More invertebrates ( P = 0.006) were consumed by scaup at the Saginaw Bay study site (77.0% ± 9.0%) than all other study sites except the

Scioto River (52.0% ± 12.7%). Moderately fewer seeds (

P = 0.073) were consumed by

55

Table 1.20.

Results from a MANCOVA model evaluating the effects of transect (Tran), date (Jul), and habitat (Hab) on proportions of invertebrates, seeds, and vegetation consumed by gadwalls in the Upper MS River and Great Lakes Region during spring

2007.

________________________________________________________________________


________________________________________________________________________

Invertebrates

Tran 1

Jul

Hab

1

3

0.00

0.08

0.06

0.00

0.08

0.02

0.00

1.19

0.30

0.95

0.28

0.82

Seeds

Tran

Jul

Hab

Vegetation

1

1

3

0.04

0.02

0.69

0.04

0.02

0.23

0.24

0.14

1.36

0.63

0.71

0.26

Tran 1 0.04 0.04 0.23 0.63

Jul

Hab

1 0.02 0.02 0.10 0.75

3 0.80 0.27 1.35 0.26

________________________________________________________________________

56

120

100

80

60

40

20

0

a d

c

West

Transect

b c

East

e

% seed

% invert

% veg

Figure 1.10. Percent of seeds, vegetation and invertebrates consumed by gadwalls at western/eastern transect in the Upper MS River and Great Lakes Region during spring


57

100

80

60

40

20

0 c

a

b

a b

West

Transect

East

c

% seed

% invert

% veg

Figure 1.11. Percent of seeds, vegetation and invertebrates consumed by gadwalls at western/eastern transect in the Upper MS River and Great Lakes Region during spring


58

Table 1.21. Date of first and last diving duck collected at each study site in 2006 and

2007.

________________________________________________________________________

2006 2007

SPECIES FIRST LAST FIRST LAST

______________________________________________________________________________________

LESC

Cache River

Illinois River

Wisconsin

N/A

15 March

06 April

N/A

10 April

11 April

18 March 31 March

03 March

27 March

30 April

09 April

RNDU

Scioto River

Lake Erie

Saginaw Bay

Cache River

Illinois River

Wisconsin

Scioto River

08 March

11 March

19 March

02 March

14 March

05 April

23 February

08 March

21 April

29 April

01 April

04 April

13 April

29 March

27 February

14 March

26 March

25 February

14 March

26 March

04 April

04 April

02 May

18 April

09 April

24 April


Lake Erie

Saginaw Bay

07 March

29 March

20 April

25 April

12 March

19 March

19 April

02 May

______________________________________________________________________________________

59

Table 1.22. Results from a MANCOVA model evaluating the effects of site, date (Jul), habitat (Hab), and year (Yr) on proportions of invertebrates and seeds consumed by lesser scaup in the Upper MS River and Great Lakes Region during spring 2006 and 2007.

________________________________________________________________________


________________________________________________________________________

Invertebrates

Site 5

Jul 1

4.08

0.19

0.81

0.19

5.67

1.37

< 0.05

0.24

Hab

Yr

Seeds

Site

3

1

1.07

0.03

0.35

0.03

2.49

0.24

0.06

0.62

5 5.08 1.01 8.04 < 0.05

Jul

Hab

1 0.03 0.03 0.24 0.62

3 1.34 0.44 3.53 < 0.05

Yr 1 0.12 0.12 0.98 0.32

________________________________________________________________________

60

scaup at the Scioto River study site than at the Wisconsin and Illinois River study sites

(Figure 1.12). Scaup consumed moderately more invertebrates ( P = 0.069) in permanent emergent habitat (73.1% ± 11.1%) than in agricultural habitat (16.4% ± 21.1%) and less seeds ( P = 0.045) in permanent emergent habitat (21.2% ± 10.4%) than agricultural habitat (81.3% ± 19.7%) and open-water habitat (50.1% ± 6.9%).

The final reduced MANCOVA model evaluating longitudinal variation in diets of scaup included the main effects of transect, date, habitat, and year. The percentage of invertebrates in the diet varied significantly among transects, whereas the percentage of seeds in the diet varied significantly among transects and years (Table 1.23). More seeds and, thus, less invertebrates were consumed by scaup in the western transect (Figure

1.13). Scaup consumed 13.78% ± 7.19% more seeds in year 1 than year 2 (

P = 0.058).

Ring-necked Duck Diets

Two-hundred and five ring-necked ducks ( n = 86 in 2006 and n = 119 in 2007) were included in analyses evaluating diet at the scale of study site (Table 1.1). Likewise,

205 ring-necked ducks ( n = 132 from the eastern transect and n = 73 from the western transect) were included in the analysis evaluating diet at the scale of transect ( n = 59 in

2006 and n = 73 in 2007 form the eastern transect and n = 27 in 2006 and n = 46 in 2007 from the western transect). In 2006, the first ring-necked duck was collected on 23

February and the last on 25 April and in 2007, the first was collected on 25 February and the last on 2 May (Table 1.21).

61

100

90

80

70

60

50

40

30

20

10

0

a/c

d/e

a/b

d

SR LE

East Transect

c

e

SAG d/e

a/b/c

CA

Study Site

b

d

IR

b

West Transect

d

WI

% seed

% invert

Figure 1.12. Percent of seeds and invertebrates consumed by lesser scaup at 6 locations

(SR = Scioto River, LE = Lake Erie, SAG = Saginaw Bay, CA = Cache River, IR =

Illinois River, WI = Wisconsin) in the Upper MS River and Great Lakes Region during spring 2006 and 2007 (least-squares means ± standard error). Different letters indicate significantly different means.

62

Table 1.23. Results from a MANCOVA model evaluating the effects of transect (Tran), date (Jul), habitat (Hab), and year (Yr) on proportions of invertebrates and seeds consumed by lesser scaup in the Upper MS River and Great Lakes Region during spring

2006 and 2007.

________________________________________________________________________


________________________________________________________________________

Invertebrates

Tran 1

Jul 1

1.64

0.02

1.64

0.02

10.36

0.17

< 0.05

0.68

Hab

Yr

Seeds

Tran

3

1

0.67

0.21

0.22

0.21

1.42

1.38

0.23

0.24

1 2.70 2.70 19.19 < 0.05

Jul

Hab

1 0.08 0.08 0.58 0.45

3 0.69 0.23 1.63 0.18

Yr 1 0.51 0.51 3.67 0.06

________________________________________________________________________

63

40

30

20

10

0

90

80

70

60

50

West

Transect

East

% seed

% invert

Figure 1.13. Percent of seeds and invertebrates consumed by lesser scaup at western/eastern transect in the Upper MS River and Great Lakes Region during spring


64


(invertebrates and seeds) of ring-necked ducks included the main effects of site, date, habitat, and year. The percentage of invertebrates and seeds in the diet varied significantly among study sites (Table 1.24). Ring-necked ducks collected at the Saginaw

Bay study site contained more invertebrates and fewer seeds than those collected at the other study sites ( P = 0.022). Also, ring-necked ducks collected at the Scioto River study site contained moderately more invertebrates and less seeds than those collected at

Wisconsin ( P = 0.060) (Figure 1.14).

The final reduced MANCOVA model evaluating longitudinal variation in diets of ring-necked ducks included the main effects of transect, date, habitat, and year. The percentage of invertebrates and seeds in the diet varied significantly by transect and date.

The percentage of invertebrates in the diet varied significantly between years (Table

1.25). Ring-necked ducks collected in 2006 consumed less invertebrates than those collected in 2007 ( P = 0.050). Also, ring-necked ducks on the eastern transect consumed significantly more invertebrates than ring-necked ducks collected on the western transect

( P = 0.0001) (Figure 1.15).

DISCUSSION

Many factors influence diet of waterfowl. Some of which may be foraging behaviors, morphological adaptations, time of year, and food availability (Poysa 1983).

An example of a morphological adaptation is bill morphology, with some being narrow

(e.g., favoring grazers such as gadwall) and some being broad (e.g., favoring straining as seen in Northern shovelers and teal sp.

). Although diets tend to be similar during parts of

65

Table 1.24. Results from a MANCOVA model evaluating the effects of site, date (Jul), habitat (Hab), and year (Yr) on proportions of invertebrates and seeds consumed by ringnecked ducks in the Upper MS River and Great Lakes Region during spring 2006 and

2007.

________________________________________________________________________


________________________________________________________________________

Invertebrates

Site 5

1

6.30

0.10

1.26

0.10

12.12

0.98

< 0.05

0.32 Jul

Hab 4 0.30 0.07 0.74 0.56

Yr

Seeds

1 0.18 0.18 1.80 0.18

Site

Jul

5

1

6.98

0.11

1.39

0.11

12.73

1.08

< 0.05

0.30

Hab

Yr

4 0.32 0.08 0.75 0.56

1 0.01 0.01 0.11 0.73

________________________________________________________________________

66

40

20

0

-20

120

100

80

60

b/c

g

SR

a/b

f/g

LE

e h

SAG

East Transect

a/b

Transect f/g

CA

a/b

f/g

IR

West Transect

a/d

f

WI

% seed

% invert

Figure 1.14. Percent of seeds and invertebrates consumed by ring-necked ducks at 6 locations (SR = Scioto River, LE = Lake Erie, SAG = Saginaw Bay, CA = Cache River,


67

Table 1.25. Results from a MANCOVA model evaluating the effects of transect (Tran), date (Jul), habitat (Hab), and year (Yr) on proportions of invertebrates and seeds consumed by ring-necked ducks in the Upper MS River and Great Lakes Region during spring 2006 and 2007.

________________________________________________________________________


________________________________________________________________________

Invertebrates

Tran 1

Jul 1

1.94

0.58

1.94

0.58

15.68

4.67

< 0.05

< 0.05

Hab

Yr

Seeds

Tran

4

1

0.41

0.48

0.10

0.48

0.82

3.89

0.51

0.05

1 2.02 2.02 15.21 < 0.05

Jul

Hab

1 0.72 0.72 5.44 < 0.05

4 0.39 0.09 0.75 0.56

Yr 1 0.12 0.12 0.92 0.33

________________________________________________________________________

68

50

40

30

20

10

0

100

90

80

70

60

a b

West

c

Transect

East

d

% seed

% invert

Figure 1.15. Percent of seeds and invertebrates consumed by ring-necked ducks at western/eastern transect in the Upper MS River and Great Lakes Region during spring


69

the annual life cycle of waterfowl (e.g., reproduction), it is likely that feeding niches reduce competition among species and have a large influence on diet (Nudds 1983), as larger dabbling ducks (e.g., mallards) are able to utilize foods vertically deeper in the water column than smaller dabbling ducks (e.g., blue-winged teal). This niche separation has also been demonstrated in foraging depths of dabbling and diving ducks (Green

1998).

Diets of ducks during clutch formation tend to be less variable than other times during the annual cycle, as ducks must meet protein demands during egg production by taking advantage of abundant invertebrates on wetlands typically utilized during reproduction. Swanson et al. (1985) reported breeding female mallards in North Dakota consumed > 70% animal matter during RFD. Similarly, the diet of female blue-winged teal, scaup, and ring-necked ducks during RFD resemble that of breeding mallards

(Dirschl 1969, Swanson et al. 1974, Hohman 1985). The gadwall, however, is one of the most herbivorous waterfowl species and literature indicates a weaker dependence on invertebrates during RFD, as they may consume as little as 50% animal matter (Ankney and Alisauskas 1991).

The diet of mallards and blue-winged teal I collected that had begun various stages of RFD, varied considerably from the previously mentioned diet studies conducted on traditional breeding areas (e.g., prairie pothole region) during the breeding season.

My sample size of follicle developing blue-winged teal was small (e.g., 9), thus, my inferences are limited; my estimate of the proportion of invertebrates consumed by bluewinged teal in RFD (58% invertebrates) was similar to estimates reported by Dirschl

(1969), but considerably lower than the 95% reported by Swanson et al. (1974).

70

Similarly, I documented mallards in RFD only consumed 27.7% invertebrates in comparison to the 72% previously reported by Swanson et al. (1985). The difference between my study and previous studies is likely a difference in nutrient demand associated with stage of RFD of ducks breeding on my study sites or a difference in food availability. Because I collected females only at the beginning of the nesting season, the females I collected may have been in an earlier stage of egg development, thus having a lower demand for protein than females from other studies. Alternatively, Elmberg et al.

(2000) discovered a relationship between invertebrate abundance and duck-use during the breeding season in Sweden, suggesting the importance of wetlands with high invertebrate densities during RFD. Most wetlands in the breeding range of ducks (e.g., prairie pothole and parkland habitat) are seasonal in nature (e.g., have standing water only through midsummer). Neckles et al. (2006) found seasonal wetlands in Manitoba supported the highest densities of invertebrates. It is likely, therefore, that ducks in my study areas may have had fewer invertebrates available (e.g., compared to breeding ducks in prairie and aspen wetlands) because most wetlands encountered in the UMR/GLR exhibit a longer hydroperiod than seasonal wetlands, thus ducks were supplementing their diet with seeds that are high in carbohydrates, but also provide important amino acids.

In contrast to diets during RFD, diet breadth increases during fall and winter, as most species consume large amounts of carbohydrates (Delnicki and Reinecke 1986,

Thompson et al. 1992) and some species consume large amounts of invertebrates (Rogers and Korschgen 1966). Typically, animal matter comprises only a small portion (< 5%) of a ducks diet during winter (Paulus 1982, Delnicki and Reinecke 1986, Thompson et al.

1992, Peters and Afton 1993). This is likely a consequence of the need for high-energy

71

foods (e.g., seeds and agricultural grains) to fuel migration and endure sub-freezing temperatures. Greater variation exists however during this time as compared to breeding diets, as algae and green vegetation are the main components of gadwall diets (Paulus

1982) during winter. Likewise, Rogers and Korschgen (1966) reported scaup diets during winter to consist of > 50% animal matter.

Despite the wealth of knowledge regarding wintering ducks, little is known about duck diets during spring. Existing literature indicates spring diet is similar to winter diet for some species (e.g., mallards), yet very different for others (e.g., blue-winged teal). I found blue-winged teal consumed ~ 35% invertebrates at southern study sites (e.g., the

Cache and Scioto River) and ~ 40% – 60% at northern study sites (e.g., Wisconsin and

Saginaw Bay). My estimates of invertebrate consumption by blue-winged teal were similar to previous spring diet studies at southern latitudes (e.g., Louisiana) but lower than those reported in North Dakota (Manley et al. 1992, Swanson et al. 1974). The only study, however, that examined blue-winged teal diet at similar latitudes as my study was conducted in Missouri and reported teal consumed 70% animal matter (Taylor 1978).

This study evaluated only 10 teal, however, which were collected in seasonally flooded wetlands (i.e., the same habitat type). My estimates of mallard diet during spring are similar to previous studies (e.g., < 1% animal matter in Nebraska and 12% − 24% in

Illinois) and indicate a heavy reliance on seeds and agricultural grains (Jorde 1981, Smith

2007). Mallard diets in my study ranged from 7% − 27% invertebrates, with mean percentages being the least at southern sites (e.g., 9% at Cache River and 7% at Scioto

River) and highest at northern sites (e.g., 23.7% at Wisconsin and 27% at Saginaw Bay).

Because of the lack of spring diet studies of gadwall, I was unable to contrast my results.

72

My data indicated that gadwall diet during spring in the UMR/GLR was composed of approximately 53% vegetation, 38% seeds, and 9% invertebrates. I did not, however, anticipate gadwall to consume large amounts of invertebrates because of their herbivorous food-habits (Ringelman 1990).

I observed a noticeable difference in the spring diet of the diving ducks (e.g., scaup and ring-necked ducks). At southern and mid-latitude study sites, I detected scaup consuming similar proportions of invertebrates and seeds. At northern sites, however, I detected differing trends, with scaup at Saginaw Bay consuming ~ 80% invertebrates and scaup at Wisconsin consuming ~ 30% invertebrates. Previous spring diet studies of scaup indicated a heavier reliance on invertebrates than I observed (Gammonley and

Heitmeyer 1990, Anteau and Afton 2006, Badzinski and Petrie 2006 a ). I suggest these differences may be related to habitats in which the scaup were collected (i.e., differences in availability) and differences in latitude of collected ducks (i.e., I collected scaup at more southerly latitudes than previous spring studies). Anteau and Afton (2008) only collected scaup in semi-permanent and permanent wetlands, whereas scaup in this study were collected from all wetland types in which they were regularly observed foraging in

(i.e., often seasonal emergent wetlands). More recently, spring diet studies of scaup at southerly latitudes produced similar results, indicating there may be more reliance on plant foods than historically perceived (Smith 2007, Strand et al. 2008).

No diet data existed on spring-migrating ring-necked ducks but Hohman’s (1985) results from pre-laying females in Minnesota may provide an indication of what to expect. He found pre-laying females consumed 36% animal matter (Hohman 1985).

This estimate was higher than my estimate of ring-necked duck invertebrate consumption

73

at all staging sites in the UMR/GLR except for Saginaw Bay, where they consumed 60% invertebrates. Given that none of the ring-necked ducks collected at Saginaw Bay had begun RFD and that their diet was similar to female ring-necked ducks that had initiated egg-laying in Minnesota (Hohman 1985), I speculate invertebrate consumption at

Saginaw Bay was a function of availability.

Temporal and Latitudinal Variation in Spring Diet Within a Species

Some waterfowl rely on endogenous lipid to produce a clutch of eggs, thus as spring progressed, I expected to see an increase in consumption of invertebrates to supplement stored lipids. I detected this pattern in blue-winged teal, and to a lesser extent in mallards and ring-necked ducks, and found some evidence that this increase in invertebrate consumption was influenced by (1) latitude (i.e., diet shift as they moved further north during the spring) and (2) date (i.e., diet shift as spring progressed).

Because blue-winged teal have a late and protracted spring migration when compared with other species in this study, I was able to describe this temporal pattern while controlling for latitude of collection site; whereas these 2 factors (i.e. latitude and time) were confounded with the other species in this study. For example, my data included teal that were collected in late April at both southern and northern study sites, whereas mallards had departed southern study sites by late April, thus were collected only at northern study sites in late April. No significant differences in invertebrate consumption existed among study-sites for blue-winged teal after controlling for date (Figure 1.4).

However, there was a significant increase in invertebrate consumption with time, indicating that diet of blue-winged teal during spring migration is likely more influenced by date rather than latitude. It is possible that this is a consequence of a nutritional

74

demand for more protein as breeding neared or that there were simply more invertebrates available as spring progressed; the latter of which is likely not the case (e.g., see Chapter

2).

There was a temporal trend among transects, with mallards and ring-necked ducks increasing invertebrate consumption throughout the spring; however, this trend was not apparent when controlling for study site in which they were collected (e.g., a nonsignificant effect of date when evaluating diets at the level of study site). This temporal trend was observed in ring-necked ducks collected in the eastern transect and in mallards collected in both the western and eastern transects. These results indicate that mallards and ring-necked ducks appear to be transitioning to diets consisting of more invertebrates as spring progressed.

Diet varied little by latitude among dabbling ducks in my study. Specifically, my data indicated no significant differences in diet composition between study sites for mallards (Figure 1.6) and gadwall (Figure 1.8) when controlling for collection date.

Blue-winged teal collected at Saginaw Bay consumed less seeds than blue-winged teal collected in Wisconsin, but invertebrate consumption did not differ among study sites

(Figure 1.4). These results suggested that latitude did not strongly influence the diet of the dabbling ducks collected in my study.

In contrast to dabbling ducks, some study-site variation existed among diving ducks in my study. These differences, however, occurred with no latitudinal pattern and therefore may exist solely because of differences in availability at these sites. Scaup consumed significantly more invertebrates and fewer seeds at Saginaw Bay than scaup at

Lake Erie, Illinois River, and Wisconsin (Figure 1.10). Ring-necked ducks at Saginaw

75

Bay consumed significantly more invertebrates and fewer seeds than ring-necked ducks at all other sites. I found availability of both invertebrates and seeds to be scarce to diving ducks at Saginaw Bay, whereas seeds were more available to diving ducks at Lake

Erie and the Illinois River (see Chapter 2, Table 2.1). This may explain why fewer seeds were consumed by scaup and ring-necked ducks at Saginaw Bay. Additionally, ringnecked ducks consumed significantly more invertebrates and less seeds at the Scioto

River than the Wisconsin site (Figure 1.12).

Previous work shows photoperiod is one of the most important factors influencing migration patterns (Beason 1978). Because latitude of migration appears to have little impact on diet during spring, yet I found date to influence diet of several species, I speculate that photoperiod (e.g., indirectly date) plays a larger role in diet habits.

Longitudinal Variation in Spring Diet Within a Species

Analyses indicated longitudinal differences in diet for all species in my study except mallards (Figure 1.7). The similarity in the diet of female mallards among transects (i.e., high use of carbohydrate and low use of high-protein foods) likely reflects their preference for high-carbohydrate foods for migration and their efficiency at acquiring their preferred food. Female blue-winged teal (Figure 1.5), scaup (Figure

1.11), and ring-necked ducks (Figure 1.13) consumed a higher percentage of seeds and fewer invertebrates in the western transect than the eastern transect. Invertebrate consumption did not differ among transects for gadwall, but more seeds and less vegetation was consumed by female gadwalls collected in the western transect than those collected in the eastern transect (Figure 1.9).

76

Possible explanations for the differences in diet among transects in blue-winged teal, scaup, and ring-necked ducks include (1) ducks collected on the eastern transect may nest in a different region than ducks collected on the western transect, resulting in different foraging strategies dependant on the distance they are from their breeding areas and the quality of wetlands at respective breeding areas; (2) differences in wintering populations, resulting in body conditions that were dependant on the quality of wetlands in respective wintering areas, and; (3) resource availability (see Chapter 2).

Most blue-winged teal winter in Central and South America and it is possible that teal collected in the western transect wintered along the Gulf Coast of North America and

Central America, whereas teal collected on the eastern transect wintered in South

America (Bellrose 1980). Badzinski and Petrie (2006 b ) found scaup that wintered in the

Atlantic flyway used parts of the lower Great Lakes during spring migration. Scaup collected in the western transect, therefore, likely wintered in Central America or along the Gulf Coast of Louisiana and Mississippi, whereas scaup collected on the eastern transect likely wintered in Florida or along the Atlantic Coast (Bellrose 1980). Ringnecked ducks staging along the western and eastern transects in the UMR/GLR during spring probably wintered in similar areas as scaup (Bellrose 1980). Lastly, according to the migration corridors provided by Bellrose (1980), it appears that the gadwall encountered in the eastern transect spent winters on the east coast of North America, whereas the gadwall encountered in the western transect likely wintered in Louisiana and

Mississippi. Diet of scaup and ring-necked ducks that winter in the Atlantic and

Mississippi Flyways may differ, possibly explaining some of the discrepancy I observed in diet during spring among the western and eastern transects and possibly supporting the

77

notion that I collected different wintering populations of birds in different transects. In support of this idea, I found the variation in diet was slightly higher in ring-necked ducks and scaup collected in the eastern transect than those in the western transect (avg. SE in western transect = 0.075 and avg. SE in eastern transect = 0.086). Scaup staging in coastal South Carolina (i.e., Atlantic Flyway) during winter consumed < 1% animal matter (Kerwin and Webb 1972), whereas scaup staging in coastal Louisiana (i.e.,

Mississippi flyway) during winter consumed 63% animal matter (Rogers and Korschgen

1966). Conversely, ring-necked ducks staging in Louisiana during winter consumed <

1% animal matter (Peters and Afton 1993), whereas ring-necked ducks staging in South

Carolina during winter consumed 58% animal matter (Hoppe et al. 1986). Diet data for gadwall during the winter was only available for the Mississippi Flyway (Paulus 1982,

McKnight and Hepp 1998) as no diet data exists for gadwall wintering along the Atlantic

Flyway. The lack of gadwall diet studies on the wintering grounds in the Atlantic Flyway makes it difficult to hypothesize if I may have encountered different wintering populations of gadwall during the spring in the UMR/GLR based on their diets alone.

Likewise, winter diet data for blue-winged teal is sparse and has only been collected in

Central America (Thompson et al. 1992).

Lastly, if distance to breeding area or wetland productivity at respective breeding areas differed among transects, I may have detected a difference in diet because ducks that were closer to breeding areas may have consumed more invertebrates to increase protein reserves. It has been suggested that ducks nesting in different areas may differ in their reliance on endogenous reserves as a consequence of wetland productivity at breeding areas (Young 1993). For example, migratory mallards breed in both aspen

78

parkland and prairie habitats and the invertebrate food base in prairie wetlands are more likely to exhibit annual variation than aspen parkland wetlands. Existing literature, however, does not allow me to make any predictions regarding where the ducks I am encountering in each transect may breed. In any case, my data indicates that latitude has no affect on diet of spring migrating ducks, so it is likely that distance to breeding areas has little influence on diet.

Although neither of the previously hypothesized explanations can be excluded, I believe the most likely explanation for longitudinal differences in diet was simply a result of differences in availability, as availability varied among the western and eastern transects in 2006 (J. Straub, The Ohio State University, thesis in progress, R. Schultheis,

Southern Illinois University, dissertation in progress). Seed abundance was considerably higher than invertebrate abundance at western transect study sites, whereas seed and invertebrate abundances were more similar at eastern transect study sites.

79

CHAPTER 2: FOOD SELECTION BY MIGRATING WATERFOWL DURING

SPRING IN THE UPPER MISSISSIPPI RIVER AND GREAT LAKES

REGION

INTRODUCTION

In the previous chapter, I identified several factors that may influence diet of spring migrating ducks, including interspecific, temporal, latitudinal (i.e., relative distance from breeding sites) and longitudinal (i.e., variation caused by encountering different wintering populations) variation, and variation in availability of food types.

This information may be used to manage wetlands to produce highly-consumed food types, but it provides little insight regarding nutritional or physiological needs of ducks during spring. By assessing consumption relative to food availability, hence selection for a food type; biologists can gain insight on nutritional demands of ducks.

Food Selection

A number of previous studies established that ducks are capable of selecting specific food types (Pederson and Pederson 1983, Manley et al. 1992, Thompson et al.

1992, McKnight and Hepp 1998, Anderson et al. 2000, Smith 2007). During fall and winter, most ducks consume foods high in carbohydrates; however, the degree to which this selection occurs varies among species and molt intensity (Anderson et al. 2000).

Although high-carbohydrate seeds and grains comprise a large portion of winter diets of dabbling ducks, and diving ducks consume varying amounts of animal matter during winter, few studies have evaluated diet in relation to availability during winter simultaneously (Pederson and Pederson 1983, Thompson et al. 1992, McKnight and

Hepp 1998, Anderson et al. 2000). Alternatively, during breeding, dabbling and diving

80

ducks forage almost exclusively on invertebrates (Swanson et al. 1974, Swanson et al.

1985, Ankney and Alisauskas 1991). Assuming breeding season diet is partially based on a physiological demand for protein, it is unclear when demands shift from high-energy foods during winter to high-protein foods during breeding. A number of factors may influence the timing of this transition in food types consumed (e.g., food availability, digestive physiology, amount of time spent at breeding areas before initiating rapid follicle development (RFD), use of endogenous/exogenous nutrients in clutch formation, proximity to breeding areas, etc.).

Birds that have been habituated to one food type (e.g., high-carbohydrate foods during winter) cannot immediately transition to an alternative digestive physiology that permits them to efficiently use other food types (e.g., high-protein foods during spring and summer); therefore, it is plausible that ducks may increase invertebrate consumption during spring in order to increase efficiency of high-protein diets at breeding areas (Afik and Karasov 1995). This digestive efficiency concept could be especially important to waterfowl that spend little time on their breeding areas before initiating nests (Toft et al.

1982).

Generally, diving ducks spend more time on breeding areas before initiating RFD than dabbling ducks (Alisauskas and Ankney 1992). This is important because waterfowl that immediately initiate RFD upon arrival (e.g., mallards and blue-winged teal) at breeding areas probably depend heavily on existing lipid reserves or somatic protein.

Likewise, a species that spends 3 − 4 weeks at a breeding area before RFD (e.g., gadwall, lesser scaup, ring-necked duck) likely uses that time to acquire nutrients needed for RFD and subsequent incubation.

81

Because some species of waterfowl store nutrients before reaching breeding areas, conditions experienced prior to breeding must be considered when evaluating reproductive success (Raveling 1979). Poor-quality spring habitat and forage may negatively impact productivity of waterfowl (Afton and Ankney 1991, Dubovsky and

Kaminski 1994, Barboza and Jorde 2002). Dubovsky and Kaminski (1994) found poor winter habitat conditions may have delayed nesting in mallards, presumably due to a lower rate of nutrient acquisition. Inadequate reserves acquired during spring-staging may decrease nest success through delayed nesting (Harris 1969, McNeil and Leger

1987, Rohwer 1992, Koons and Rotella 2003), lead to a reduction in clutch size, or cause some hens to defer reproduction altogether (Newton 2006). The degree to which ducks depend on endogenous protein and lipid for breeding differs; some ducks relying more on lipid stores (wood ducks - Drobney 1980, mallards - Krapu 1981, ring-necked ducks -

Hohman 1986), and others more on somatic protein (American wigeon and gadwall -

Alisauskas and Ankney 1992). Understanding food selection during spring can provide insight on how lipid reserves and somatic protein are acquired before breeding. For example, reserves obtained during spring are central to reproduction in Arctic nesting geese (Ankney and MacInnes 1978, Raveling 1979). Despite evidence that late-winter and spring conditions have carryover affects on reproductive efforts of ducks (Kaminski and Gluesing 1987, Dubovsky and Kaminski 1994), little information is available regarding food selection of spring migrating ducks in mid-latitude portions of the

Mississippi Flyway.

Lastly, proximity to nesting areas during spring migration may influence diet.

Food consumption of ducks at northern latitudes during spring may reflect dietary needs

82

for reproduction, whereas diet at southern latitudes during spring may reflect habitat conditions at respective wintering areas. Correspondingly, it is important to consider that

“breeding areas” of blue-winged teal, gadwalls, and some mallards (e.g., Missouri Coteau area of the Prairie Pothole Region) are likely closer to the UMR/GLR than are “breeding areas” of lesser scaup and ring-necked ducks (e.g., Alaska and boreal forest region of

Canada).

I selected the suite of species for this study because they represented a variety of foraging behaviors observed in spring-migrating ducks (i.e., dabbling and diving ducks).

By examining diverse species, I expected to be able to detect differences in diet selection during spring based on different life-history strategies and traits. By determining if and where (i.e., at what latitude) diet transitions from one food type to another occur during spring, I will be able to recommend habitat management practices that maximize the productivity of foods and meet nutritional requirements of a wide variety of ducks.

STUDY OBJECTIVES

The goal of my study was to determine what 2 classes of foods, seeds or invertebrates, were selected by mallards, blue-winged teal, lesser scaup, and ringed-neck ducks during spring migration through the UMR/GLR. I was unable to evaluate food selection in gadwall because the largest component of their diet was vegetation, and I did not evaluate availability of vegetation. My specific objective was to determine if these species transitioned from selecting high-carbohydrate foods to high-protein foods prior to or during spring migration, and if the timing of this potential transition varied in a predictable manner as a function of life-history characteristics.

83

Based on life-history characteristics, I predicted that blue-winged teal and mallards would increase consumption of invertebrates as spring progressed, allowing them to efficiently transition to a high-protein diet and initiate RFD soon after arrival on breeding areas. Because gadwalls are herbivorous, protein-limited (i.e., depend on somatic protein for clutch formation; Ankney and Alisauskas 1991), and spend 3 − 4 weeks at breeding areas prior to nest initiation, I predicted they would increase invertebrate consumption as they migrated north during spring. Because of their herbivorous nature and dependence on green vegetation, however, I expected to see only small increases in invertebrate consumption with latitude. Scaup have been documented to consume > 50% animal matter at both wintering and breeding sites, therefore, I expected to see a heavy dependence on invertebrates by spring migrating scaup relative to other species in the UMR/GLR. I expected seeds to be an important component of scaup diets, however, because: (1) scaup consume a considerably large proportion of invertebrates throughout the annual cycle (Rogers and Korschgen 1966) and (2) scaup spend considerable time at breeding areas before initiating RFD and the habitats scaup depend on during breeding are highly productive for invertebrates, and (3) breeding female scaup do not further accumulate lipid reserves while on breeding areas (Afton and

Ankney 1991). Similarly, I expected the diet of ring-necked ducks to consist largely of seeds, given that their time on breeding areas before initiating RFD is allocated to protein acquisition (Hohman 1985).

84

METHODS

Food Availability

I collected data used in these analyses in 2006 at the same study sites described in the previous chapter. I collected food availability samples during 3 time-periods of spring (early, middle, late) to quantify variation in forage abundance throughout migration. Timing of sampling varied among study sites to account for climatic differences and migratory stages of waterfowl (e.g., the difference in the timing of peak waterfowl abundance between northern and southern sites). For example, the early food sampling period began in early to mid-February at southern sites and mid-March at northern sites. As deemed by the latitude of the study area, early food samples were taken as soon as ice conditions permitted to determine food availability during early stages of migration. Mid-spring food samples were collected during the peak of waterfowl migration, whereas late food samples were taken after the majority of birds had passed through. Samples were collected using stratified random sampling from wetland types to estimate forage availability at each study site and to provide an index of food availability in different wetland types (i.e., palustrine forested, palustrine emergent, and lacustrine open-water/riverine wetlands). I determined sample locations by overlaying a grid of 400m x 400m (16 hectares) cells and excluding cells with < 2 ha of wetland habitat as identified by the national wetlands inventory (NWI) (Cowardin et al.

1979) or < 8 ha of soil that held moisture, as identified by soil moisture index data

(Ducks Unlimited 2005). I categorized remaining cells as forested wetland, non-forested wetland, riverine/lacustrine, or agricultural according to dominant vegetation and wetland types present. I selected agricultural habitats based on soil moisture index data as areas

85

that had wet or very wet soils. Within each selected cell, I identified and sampled each wetland type. For example, if cell 231 at the Cache River study area was identified as forested wetland based on NWI data, but the cell contained palustrine forested and palustrine emergent wetland, I identified and sampled each wetland type.

I sampled 60 wetland cells at each of the 6 study sites, 20 of which were agricultural wetlands and the rest were sampled in proportion to abundance of wetland type. For example, forested wetland represented approximately 80% of wetland area in the Cache River study area; therefore, 32 of the 60 cells selected for sampling were dominated by forested wetland. I did not select blocks proportionally in flooded agricultural habitat due to the high abundance of ephemeral pools in agricultural fields that may have resulted in over-sampling if considered proportionally. Additionally, reliable data were not available to estimate the total proportion of flooded agricultural crops in an area. Because waterfowl use of agricultural land may be substantial

(LaGrange and Dinsmore 1989, Krapu et al. 2004), I allocated 20 cells as flooded agriculture regardless of the estimated proportion of flooded agriculture at a study site.

Within a wetland basin, I collected food samples along randomly selected transects. Once in the center of a wetland basin, I used the time (in seconds) on a handheld PDA to determine the direction in which the transect occurred (00 corresponding to straight north, 15 to straight east, 30 to straight south, 45 to straight west, and so on). Then, I took 2 samples along the transect; a deep sample taken at the first location encountered along the transect that was approximately 45 cm deep and a shallow sample taken at a randomly selected depth provided by the PDA between 45 cm

86

and 1 cm. Deep food samples were used to estimate food availability to diving ducks whereas shallow food samples were used for dabbling ducks.

A wetland sample consisted of a d-frame sweep net sample taken along the length of a drop box for 3 sweeps, (33 cm diameter, 500 µm mesh) and a core sample (7 cm diameter, ~5 cm deep) taken from within the drop box (100 cm x 50 cm x 75 cm, 500 µm mesh side panels). The drop box was used to ensure consistency in sampling area of each sample. I rinsed samples through a 500 µm mesh sieve bucket to remove clay material and unwanted debris, placed core and sweep samples in separate bags, and preserved the sample in 10% buffered formalin solution.

Laboratory Analysis

I washed food availability samples through 1mm, 750 µm and 500 µm sieves to facilitate processing of sample contents by size. All seeds and invertebrates were recovered from samples in the laboratory at Southern Illinois University Carbondale

(SIUC). Animal food items were identified at SIUC (Schultheis, Southern Illinois

University, dissertation in progress; Merrit and Cummins 1996), whereas seed identification was conducted at the Ohio State University (Straub, The Ohio State

University, thesis in progress). Foods recovered from availability samples were identified similarly to esophageal contents, but I did not record plant material (i.e., algae,

Lemna sp.

, etc.). I dried food items for ≥ 48 hours at 60 o

C and then weighed them on a top-loading balance.

87

Statistical Analysis

There was evidence that both invertebrate and seed availability did not significantly increase or decrease throughout spring (Straub 2008, Schultheis, dissertation in progress), therefore I calculated means and standard errors of invertebrates and seeds in both diet and availability samples (PROC UNIVARIATE; SAS Institute, Inc., Cary,

NC) and compared them using a Z-test in program CONTRAST to investigate if the proportion of food items in duck diets differed from the proportion of food items available at the study site in which the ducks were collected (i.e., selecting for a food type) (Hines and Sauer 1989). I assumed that a diet that was significantly different ( P <

0.05) than availability indicated selection of that food item. Additionally, I assumed a diet was moderately significant if 0.05 < P < 0.10. I did not evaluate selection by a species if < 5 ducks of a particular species were collected at a study site. I considered all seeds and invertebrates recorded from shallow and deep samples as available to foraging dabbling and diving ducks, respectively.

I estimated forage availability for diving ducks by including deep availability samples taken in lacustrine open-water and palustrine emergent habitats, but did not include samples from palustrine forested habitats because I considered it unavailable to diving ducks (i.e., diving ducks were never observed using this habitat and I considered it to be inaccessible to diving ducks). Likewise, I estimated forage availability for dabbling ducks by including all shallow availability samples that were collected. Ducks collected in agricultural habitats were not included in these analyses because food sampling methods in these habitats were not replicable among sites in 2006. Additionally, to eliminate possible bias in diet estimates, I removed 5 mallards collected in emergent

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wetlands because corn was the predominant food item in esophageal contents. With regard to gadwall diet and selection analyses, I was unable to assess selection because vegetative items composed the largest proportion of their diet and vegetative items were not sorted from availability samples (i.e., I could not determine availability, hence selection, of vegetative food items).

RESULTS

Availability

Generally, there were more seeds available at each study site than invertebrates

(Table 2.1). Availability estimates were not calculated for diving ducks at Wisconsin because < 5 ring-necked ducks and lesser scaup were collected in 2006. Mean seed availability was highest for dabbling ducks at the Wisconsin site (309.8 ± 51.4 kg/ha) and diving ducks at the Illinois River site (131.1 ± 38.7 kg/ha). Mean invertebrate availability was highest for dabbling ducks at the Saginaw Bay site (116.4 ± 37.6 kg/ha) and diving ducks at the Cache River site (68.7 ± 20.8 kg/ha).

Blue-winged Teal Food Selection

I included data from 94 blue-winged teal collected in spring 2006 in selection analyses. Of these, 22 were collected at the Cache River, 21 at the Illinois River, 19 at

Wisconsin, 20 at Lake Erie, and 12 at Saginaw Bay. Only 2 teal were collected at the

Scioto River, therefore I did not include these in analyses. Using the mean available forage and associated standard error from shallow food samples in program CONTRAST,

I found blue-winged teal consumed a significantly higher percentage of invertebrates than

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Table 2.1. Mean food availability (kg/ha) and standard error (SE) of seeds and invertebrates found in shallow (for dabbling ducks) and deep (for diving ducks) habitats during spring 2006.

________________________________________________________________________

Species Type Site Mean SE

________________________________________________________________________

Dabbling Ducks Seeds Cache River

Invertebrates Cache River

163.1

49.7

44.7

14.3

Dabbling Ducks

Dabbling Ducks

Seeds Illinois River

Invertebrates Illinois River

Seeds Wisconsin

Invertebrates Wisconsin

97.2

33.9

309.8

50.6

19.8

6.8

51.4

16.3

Seeds Scioto River

Invertebrates Scioto River

115.4

12.1

33.9

3.4

Dabbling Ducks

Dabbling Ducks

Dabbling Ducks

Diving Ducks

Seeds

Invertebrates Lake Erie

Seeds

Invertebrates Saginaw Bay

Seeds

Lake Erie

Saginaw Bay

Cache River

Invertebrates Cache River

177.3

31.4

145.5

116.4

124.6

68.7

42.9

9.5

32.5

37.6

37.3

20.8

Diving Ducks

Diving Ducks

Diving Ducks

Seeds

Seeds

Seeds

Illinois River

Invertebrates Illinois River

Wisconsin

Invertebrates Wisconsin

Scioto River

Invertebrates Scioto River

131.1

22.3

N/A

N/A

70.0

58.2

38.7

9.3

N/A

N/A

32.3

35.1

Diving Ducks Seeds Lake Erie

Invertebrates Lake Erie

120.6

12.2

44.3

4.0

Diving Ducks Seeds Saginaw Bay 25.9 12.9

Invertebrates Saginaw Bay 20.5 8.3

_ _______________________________________________________________________

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were available at Wisconsin ( P < 0.001) and Lake Erie ( P < 0.001) (Table 2.2). Bluewinged teal consumed food in proportion to availability at the Cache River, Illinois

River, and Saginaw Bay ( P > 0.05).

Mallard Food Selection

I included data from 84 mallards collected in spring 2006 in selection analyses.

Of these, 13 were collected at the Cache River, 11 at the Illinois River, 8 at Wisconsin,

11 at the Scioto River, 24 at Lake Erie, and 17 at Saginaw Bay. Using the mean available forage and associated standard error from shallow food samples in program CONTRAST,

I found mallards consumed food in proportion to availability at all study sites ( P > 0.05)

(Table 2.2).

Lesser Scaup Food Selection

I included data from 46 scaup collected in spring 2006 in selection analyses. Of these, 10 were collected at the Illinois River, 20 at Lake Erie, and 16 at Saginaw Bay.

Only 2 scaup were collected at Wisconsin and 1 at the Scioto River, therefore I did not include these in analyses. Using the mean available forage and associated standard error from deep food samples in program CONTRAST, I found scaup consumed a significantly higher percentage of invertebrates than were available at Lake Erie ( P <

0.001) (Table 2.2). Scaup consumed food in proportion to availability at Illinois River and Saginaw Bay ( P > 0.05).

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Table 2.2. Results of selection analyses for ducks collected at study sites in the Upper MS

River and Great Lakes Region (CA = Cache River, IR = Illinois River, WI = Wisconsin,

SR = Scioto River, LE = Lake Erie, and SB = Saginaw Bay) during spring 2006. An “I” indicates selection of invertebrates, “=” indicates consumption in proportion to availability, and “S” indicates selection of seeds.

_______________________________________________________________________

CA IR WI SR LE SB

________________________________________________________________________

Blue-winged teal = = I I =

Mallard = = = = = =

Ring-necked duck S = = = =

Lesser scaup = I =

________________________________________________________________________

92

Ring-necked Duck Food Selection

I included data from 83 ring-necked ducks collected in spring 2006 in selection analyses. Of these, 13 were collected at the Cache River, 11 at the Illinois River, 7 at the

Scioto River, 37 at Lake Erie, and 15 at Saginaw Bay. Only 3 ring-necked ducks were collected at Wisconsin, therefore I did not include these in analyses. Using the mean available forage and associated standard error from deep food samples in program

CONTRAST, I found ring-necked ducks consumed a significantly fewer invertebrates than were available at the Cache River ( P = 0.007) (Table 2.2). Ring-necked ducks consumed food in proportion to availability at the Illinois River, Scioto River, Lake Erie, and Saginaw Bay sites ( P > 0.05).

DISCUSSION

Food Selection

For species I observed consuming higher percentages of a food type than was available to them, I interpreted this as selection. Likewise, I considered ducks to be consuming food in proportion to availability if diet was not significantly different than availability (e.g., P > 0.10). I observed all species except mallards, exhibit selection for either invertebrates or seeds (Table 2.2). The mallard was the only species with large enough sample sizes (e.g., ≥ 5) to evaluate selection at all study sites; therefore, my inferences regarding diet trends for some species in spring 2006 were limited. In the previous chapter, I considered southern sites to be the Cache River and Scioto River, the mid-latitude sites to be the Illinois River and Lake Erie, and the northern sites to be

Wisconsin and Saginaw Bay, based on their location within their respective transect (e.g.,

93

western or eastern transect). For purposes of detecting a diet trend according to the latitude in which they were collected, I considered transects jointly and hereafter refer to the Cache River as the southern site ( 37 o 18’ N

), Scioto ( 39 o

40’ N ) and Illinois River ( 40 o

12’ N

) and Lake Erie ( 41 o

27’ N ) as mid-latitude sites, and Saginaw Bay ( 43 o

45’ N ) and

Wisconsin ( 43 o 48’ N

) as northern sites. It is important to consider, however, that this is only for conceptual purposes, as both the Saginaw Bay and Wisconsin site would be

“southern sites” to ducks breeding in Alaska.

Blue-winged teal.- Previous spring studies of blue-winged teal indicated selection of invertebrates (Swanson et al. 1974, Manley et al. 1992). Another diet study of bluewinged teal also demonstrated a heavy reliance on invertebrates during spring, but availability data was not collected (Taylor 1978). Interestingly, breeding blue-winged teal rely heavily on somatic lipid, whereas somatic protein remains relatively constant through clutch formation, suggesting exogenous resources are used to meet protein demands (Rohwer, unpublished data). Considering this, and the fact that teal initiate nesting shortly after arrival at breeding areas (Toft et al. 1982), I expected lipid acquisition (i.e., consumption of high-lipid seeds) to be relatively important to spring migrating blue-winged teal.

Contrary to my expectation, blue-winged teal appeared to rely more on invertebrates than seeds during spring as teal exhibited selection for invertebrates at both

Wisconsin and Lake Erie study sites (Table 2.2). My results are similar to previous spring studies of blue-winged teal, indicating selection of invertebrates (Swanson et al.

1974, Manley et al. 1992).

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Mallard. - Mallard diet studies during spring provided mixed results, with one reporting selection for Chironomidae larvae (Pederson and Pederson 1983) and others documenting a heavy reliance on seeds and agricultural grains (Jorde 1981, Heitmeyer 1985, LaGrange

1985). Only one of these studies, however, collected data on food availability to assess diet selection (Pederson and Pederson 1983). Breeding mallards rely heavily on somatic lipids acquired prior to arrival on breeding grounds (Krapu 1981) and initiate nesting shortly after arriving at breeding area (Toft et al. 1982); therefore I expected mallards staging in the UMR/GLR to consume large amounts of seeds. Because digestive physiology of ducks, however, restricts them from making abrupt changes in diet composition (i.e., from seeds to invertebrates), I expected to see a heavier reliance on animal foods as they approached reproduction in late spring (Barlein 2003).

Although I was unable to detect selection of food items, seeds seemed to be most important to spring migrating mallards in the UMR/GLR in 2006, as mallards consumed

> 78% seeds at all study sites in 2006 (e.g., a diet would have to be exclusively seeds to indicate any kind of seed selection because invertebrate availability was so low at these sites) (Table 2.3). A recent food selection study conducted at one site during spring in the UMR/GLR found similar results with mallards selecting moist-soil seeds (Smith

2007).

I was unable to detect a diet transition, as I observed mallards consuming food in proportion to availability at all sites (i.e., latitudes) (Table 2.2). I did, however, observe the highest proportions of invertebrates in the diet of mallards collected at Saginaw Bay and Wisconsin (i.e., northern sites) (Table 2.3). Young (1993) suggested that somatic protein is not used by mallards during egg laying; rather, protein was obtained from

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Table 2.3. Mean percentage of food items and standard error (SE) in diet of dabbling ducks at study sites in the Upper MS River and Great Lakes Region during spring 2006.

________________________________________________________________________

Food Type Site Mean % SE

________________________________________________________________________

Mallard Seeds

Invertebrates

Cache River

Cache River

91

9

7

7

Mallard Seeds

Invertebrates

Illinois River

Illinois River

80

20

11

11

Mallard

Mallard

Seeds

Invertebrates

Seeds

Invertebrates

Mallard Seeds

Invertebrates

Mallard Seeds

Invertebrates

Blue-winged teal Seeds

Invertebrates

Scioto River

Scioto River

Lake Erie

Lake Erie

Wisconsin

Wisconsin

Saginaw Bay

Saginaw Bay

Cache River

Cache River

90

10

86

14

78

22

78

22

67

33

9

9

6

6

15

15

7

7

8

8


Invertebrates


Invertebrates

Illinois River

Illinois River

Lake Erie

Lake Erie

72

28

46

54

8

8

9

9


Invertebrates


Invertebrates

Wisconsin

Wisconsin

Saginaw Bay

Saginaw Bay

33

67

30

70

10

10

12

12

________________________________________________________________________

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exogenous sources. This, along with the fact I found mallards consuming large amounts of seeds, emphasizes the importance of spring-staging areas for lipid acquisition.

Lesser scaup. - It has been suggested that decreased body condition of breeding scaup, resulting from poor spring-habitat conditions, may be partly responsible for declines in scaup breeding populations (Anteau and Afton 2006, Anteau and Afton 2008). Current spring-staging populations of scaup encounter habitats that do not provide historically preferred foods and may therefore be unable to acquire nutrients that were available previously (Anteau and Afton 2006). I found scaup in the UMR/GLR either consumed more invertebrates than were available or in proportion to availability (Table 2.2). These invertebrates, however, were not the “historically preferred” invertebrates (e.g., amphipods) consumed by scaup during spring, but primarily Gastropoda and

Chironomidae larvae (see previous chapter). Despite the selection of invertebrates I observed in staging scaup, their diets consisted of higher proportions of seeds (Table 2.4) than reported in another recent scaup spring-diet study (Anteau and Afton 2008). Other previous studies indicated scaup fed primarily on invertebrates during spring (Rogers and

Korschgen 1966, Gammonley and Heitmeyer 1990, Afton et al. 1991, Anteau and Afton

2006, Badzinski and Petrie 2006 a , Anteau and Afton 2008); however, 2 recent studies reported scaup spring-diet consisted primarily of moist-soil plant seeds (Smith 2007,

Strand et al. 2007), and 1 suggested scaup selected this food type (Smith 2007). I believe the contradictory result of food selection by spring-migrating scaup in recent studies is likely a result of geographic location. For example, the most southern sites of Anteau and Afton (2006) were at an equivalent latitude to my northern sites. Additionally,

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Table 2.4. Mean percentage of food items and standard error (SE) in diet of diving ducks at study sites in the Upper MS River and Great Lakes Region during spring 2006.

________________________________________________________________________

Food Type Site Mean % SE

________________________________________________________________________

Lesser Scaup Seeds

Invertebrates

Illinois River

Illinois River

77.0

23.0

13.0

13.0

Lesser Scaup Seeds

Invertebrates

Lake Erie

Lake Erie

42.0

58.0

8.0

8.0

Lesser Scaup Seeds

Invertebrates

Ring-necked Duck Seeds

Invertebrates


Invertebrates

Saginaw Bay

Saginaw Bay

Cache River

Cache River

Illinois River

Illinois River

26.0

74.0

99.5

0.5

91.0

9.0

10.0

10.0

0.4

0.4

9.0

9.0


Invertebrates


Invertebrates

Scioto River

Scioto River

Lake Erie

Lake Erie

88.0

12.0

88.0

12.0

7.0

7.0

5.0

5.0

Ring-necked Duck Seeds Saginaw Bay 36.0 13.0

Invertebrates Saginaw Bay 64.0 13.0

________________________________________________________________________

98

Anteau and Afton (2006) examined scaup diets at breeding sites (Anteau and Afton

2006), whereas no scaup bred at any sites in my study (i.e., macroscopic examination of internal reproductive organs did not indicate follicle development in any of the collected scaup).

I did not collect scaup at the southern study site in 2006 and was unable to determine scaup diet at southern latitudes; however, I did detect selection of invertebrates at a mid-latitude site (e.g., Lake Erie). Interestingly, scaup consumed foods in proportion to availability at the Illinois River site, yet selected for invertebrates at Lake Erie, even though invertebrate and seed availability was similar at these sites (Table 2.1). Also unique to the Illinois River site, I regularly observed large concentrations of scaup foraging in unharvested cornfields soon after inundation. Considering scaup spend 3 − 4 weeks on breeding areas to acquire and maintain fat reserves before initiating RFD, and their diets during this time consist of high-protein foods that are inefficient for building somatic lipid (Afton and Hier 1991), the pattern I observed in scaup diet staging on the

Illinois River is what I expected to observe in spring migrating scaup (i.e., consuming high-carbohydrate seeds to lessen their dependence on high-carbohydrate foods at breeding areas).

Ring-necked duck. - To my knowledge, this study was the only food-selection study of spring-migrating ring-necked ducks conducted. Previously, feeding ecology of springmigrating ring-necked ducks could only be inferred from pre-laying female ring-necked ducks presumably at their breeding area in Minnesota (Hohman 1985). I found ringnecked ducks staging in the UMR/GLR in spring 2006 consumed substantially less

99

animal matter than pre-laying female ring-necked ducks in Minnesota (Hohman 1985) at all sites except Saginaw Bay, and either selected for seeds or consumed foods in proportion to availability.

My data indicated spring-migrating female ring-necked ducks were heavily dependant on seeds but may have transitioned to a diet consisting mostly of invertebrates at northern latitudes (e.g., Saginaw Bay). Because of small sample sizes at the Wisconsin site in 2006, however, I was unable to test these results at an additional northern latitude site. Female ring-necked ducks typically acquire lipid reserves that are used to meet reproductive requirements before reaching nesting areas (Hohman 1986). Therefore, it is not surprising that I found ring-necked ducks selecting seeds at the Cache River site during spring, as these high-carbohydrate foods are likely used to accumulate or restore somatic lipid. Because the proportions of invertebrates and seeds available for ringnecked ducks collected at Saginaw Bay was similar to Scioto River (approximately 50% seeds and 50% invertebrates available; see Table 2.1), yet ring-necked ducks at the Scioto

River consumed approximately twice the amount of seeds as ring-necked ducks at

Saginaw Bay, I suggest that ring-necked ducks at Saginaw Bay were in a different physiological state. It is possible that ring-necked ducks staging at Saginaw Bay during spring were in close proximity to breeding areas, perhaps explaining why I observed an increase in invertebrate consumption at this site.

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CHAPTER 3: IMPLICATIONS FOR WETLAND MANAGEMENT FOR

SPRING-MIGRATING WATERFOWL IN THE UMR/GLR

Management Implications

Unlike the diet of ducks during breeding, when all ducks depend heavily on invertebrates or during fall migration and winter when seeds and agricultural grains compose the majority of the diet of ducks, spring diet is much more variable and differs considerably among species. At least some species appear to transition to invertebrates later in spring migration, leading to intraspecific variation of diet. The variability I discovered in spring diets emphasizes the importance of providing a variety of habitats

(e.g., food types) during spring. Even though ducks are likely capable of searching for, and selecting specific food types from within their environment (see chapter 2), the variability I discovered in diet among sites and transects indicates that the ability of ducks to modify food intake is limited. Thus, food availability still plays a large role in diet, hence nutrient acquisition.

Management of wetland habitats specifically to benefit spring-migrating waterfowl is uncommon. Current wetland management practices typically intend to maximize seed (i.e., moist-soil and agricultural) abundance for fall-migrating and wintering waterfowl. Although this approach likely benefits fall-migrating and wintering waterfowl, it may not yield quality foraging habitat in spring (Greer et al. 2006). My research indicated that wetlands managed for moist-soil plant species provide important foraging habitats for some spring-migrating waterfowl (e.g., mallards, ring-necked ducks), and attract others that consume invertebrates and seeds (e.g., blue-winged teal, gadwall, lesser scaup). Thus, I recommend managers provide shallow and deep water habitats during spring with abundant moist-soil seeds and invertebrates.

101

Managing Wetlands for Invertebrates During Spring Migration

Differing water regimes will affect macroinvertebrate taxa available to foraging waterfowl. For example, Neckles et al. (2006) found that semipermanent flooding

(standing water present through the growing season) in marshes in Manitoba, Canada reduced total invertebrate densities. The taxa that were negatively impacted by semipermanent flooding are very important to foraging waterfowl (e.g., Cladocera,

Ostracoda, and Culicidae). Neckles et al. (2006) suggested that semi-permanent flooding may eliminate cues necessary for oviposition and hatch among dominant taxa. Under seasonally flooded wetlands (standing water present only through mid-summer), however, macroinvertebrate densities were not reduced, regardless of the availability of detritus. A flooding regime that would likely benefit spring-migrating and wintering waterfowl is deep-flooding impoundments that were kept flooded shallowly during winter, as these newly flooded deep wetlands will expand into previously dry habitat as water levels rise, resulting in deep habitat for diving ducks and shallow habitat for dabbling ducks (Fredrickson and Reid 1988). Conversely, wetlands that undergo spring water drawdown, likely concentrate invertebrates as they follow receding water levels and consequently improve foraging conditions for invertebrates. Gray et al. (1999) found moist-soil wetlands that were mowed during winter, rather than disked or tilled, supported diverse invertebrate communities, likely because of detritus that served as substrate for invertebrate production (Kaminski and Prince 1981). Therefore, late-winter flooding of moist-soil wetlands with mowed areas would likely benefit spring-migrating waterfowl by maximizing invertebrate abundance. Invertebrate abundance is also higher on wetlands lacking predators, such as fathead minnows and other fish (Cox et al. 1998,

102

Hornung and Foote 2006); therefore wetlands managed for waterfowl should experience complete annual drawdown and be protected from flood events that can establish such fish populations. Preventing flood events will also likely increase water clarity, hence improving foraging conditions for ducks.

We found invertebrate production was highest in shallow palustrine forested wetlands during spring (Schultheis, dissertation in progress). Although this habitat type

(e.g., forested wetlands) is likely inaccessible to diving ducks, it supported a diversity of foods beneficial to spring-migrating dabbling ducks, particularly blue-winged teal that rely heavily on invertebrate foods. Thus, forested wetland habitat should be maintained throughout spring, particularly wetlands predominated with button-bush ( Cephalanthus sp.) and willow trees ( Salix sp.) because of their high flood tolerance. Water levels in green-tree reservoirs (GTR) (e.g., bottomland hardwood forests intentionally flooded to produce habitat for waterfowl), in particular, should be held as long as possible to provide rich invertebrate sources to late-migrating dabbling ducks. Because the integrity of

GTR’s depends on the survival of early successional mast-producing oak trees and these trees are susceptible to disease when inundated during the growing season, late-winter flooding with a pre-growing season drawdown may be beneficial to both the GTR and spring-migrating waterfowl.

Managing Wetlands for Seeds During Spring Migration

To optimize seed abundance for spring-migrating ducks, I suggest late-winter flooding of moist-soil wetlands at varying depths, as this wetland management practice provides abundant seeds (Greer et al. 2006). Seed loss from depredation and

103

decomposition from inundation is minimized by a delayed flooding regime. By delaying flooding of GTR’s, not only is seed availability maximized, but survival of important mast-producing hardwood species is encouraged.

Challenges to Providing Habitat for Spring-Migrating Waterfowl

As I previously stated, I believe the greatest opportunity to manage wetland habitats for spring-migrating waterfowl is on state and federal refuges. These, however, are often managed to accommodate public waterfowl hunters, and delayed flooding of these areas may meet heavy criticism from the hunting constituency. To avoid this, wetlands could be kept at low pool during winter, still providing habitat for hunters, with water coverage allowed to increase (newly flooding the perimeter) throughout spring.

Minimally, this strategy should be used on non-huntable wetlands that are true ‘refuges’ during winter.

Another challenge to maximizing forage availability for spring-migrating waterfowl, particularly in the Midwest, is convincing private landowners and area managers to provide wetland habitat other than flooded agricultural fields (i.e., moist-soil wetlands). While these habitats may be heavily utilized by spring-migrating waterfowl

(LaGrange and Dinsmore 1989), these food-types are lacking in important amino acids

(Buckley 1989). Additionally, water must be removed from these wetlands in early spring to prepare for planting next years crop, rendering these wetlands useless to many mid- and late-migratory species during spring. In contrast, wetlands managed for native, moist-soil plants can remain flooded without negatively impacting conditions for the subsequent year.

104

LITERATURE CITED

Affik, D., and W. H. Karasov. 1995. The trade-offs between digestion rate and efficiency in warblers and their ecological implications. Ecology 76:2247-2257.

Afton, A. D., and C. D. Ankney. 1991. Nutrient-reserve dynamics of breeding lesser scaup: a test of competing hypotheses. The Condor 93:89-97.

Afton, A. D. and R. H. Hier. 1991. Diets of lesser scaup breeding in Manitoba. Journal of

Field Ornithology 62:325-334.

Afton, A. D., R. H. Hier, and S. L. Paulus. 1991. Lesser scaup diets during migration and winter in the Mississippi flyway. Canadian Journal of Zoology 69:328-333.

Alisauskas, R. T., and C. D. Ankney. 1992. The cost of egg laying and its relationship to nutrient reserves in waterfowl. Pages 30-61 in B. D. J. Batt, A. D. Afton, M. G.

Anderson, C. D. Ankney, D. H. Johnson, J. A. Kadlec, and G. L. Krapu, editors.

Ecology and management of breeding waterfowl.University Minnesota Press,

Minneapolis, Minnesota, USA.

Anderson, J. T., L. M. Smith, and D. A. Haukos. 2000. Food selection and feather molt by non-breeding American green-winged teal in Texas playas. The Journal of

Wildlife Management 64:222-230.

Ankney, C. D., and C. D. MacInnes. 1978. Nutrient reserves and reproductive performance of female lesser snow geese. Auk 95:459-471.

Ankney, C. D., and R. T. Alisauskas. 1991. Nutrient-reserve dynamics and diet of breeding female gadwalls. The Condor 93:799-810.

Anteau, M. J., and A. D. Afton. 2004. Nutrient reserves of lesser scaup ( Aythya affinis ) during spring migration in the Mississippi flyway: a test of the spring condition hypothesis. The Auk 121:917-929.

Anteau, M. J., and A. D. Afton. 2006. Diet shifts of lesser scaup are consistent with the spring condition hypothesis. Canadian Journal of Zoology 84:779-786.

Anteau, M. J. and A. D. Afton. 2008. Diets of lesser scaup during spring migration throughout the upper-midwest are consistent with the spring condition hypothesis.

Waterbirds 31:97-106.

Arzel, C., J. Elmberg, and M. Guillemain. 2006. Ecology of spring-migrating Anatidae: a review. Journal of Ornithology 147:167-184.

Badzinski, S.S., and S. A. Petrie. 2006 a . Diets of lesser and greater scaup during autumn and spring on the lower Great Lakes. Wildlife Society Bulletin 34:664-674.

105

Badzinski, S.S., and S. A. Petrie. 2006 b . Satellite tracking lesser scaup and greater scaup from the lower Great Lakes. Pages 100–101 in Proceedings of the 4 th

North

American Duck Symposium and Workshop. Integrating science and duck management, 23-26 August 2006, Bismarck, North Dakota, USA.

Barboza, P. S., and D. G. Jorde. 2002. Intermittent fasting during winter and spring affects body composition and reproduction of a migratory duck. Journal of

Comparative Physiology B 172:419-434.

Barlein, F. 2003. Nutritional strategies in migratory birds. Pages 321-332 in P. Berthold,

E. Gwinner, and E. Sonnenschein, editors. Avian Migration. Springer-Verlag

Berlin, Heidelberg, New York.

Barrows, H. H. 1910. Geography of the Middle Illinois Valley. Illinois Geological

Survey Bulletin 15.

Beason, R. C. 1978. The influences of weather and topography on water bird migration in the southwestern United States. Oecologia 32:153-169.

Bellrose, F. C. 1980. Ducks, geese, and swans of North America. Third edition.

Stackpole Books. Harrisburg, Pennsylvania, USA.

Bellrose, F. C., S. P. Havera, F. L. Paveglio, Jr., and D. W. Steffeck. 1983. The fate of lakes in the Illinois River Valley. Illinois Natural History Survey Biological Notes

119.

Buckley, C. E. 1989. The nutritional quality of selected row crop and moist-soil seeds for

Canada geese. Thesis, University of Missouri, Columbia, Missouri, USA.

Cook, R. C., D. L. Murray, J. G. Cook, P. Zager, and S. L. Monfort. 2001. Nutritional influences on breeding dynamics in elk. Canadian Journal of Zoology 79:845-

853.

Cowardin, L. M., V. Carter, F. C. Golet, and E. T. LaRoe. 1979. Classification of wetlands and deepwater habitats in the United States. U. S. Dept. Interior, Fish &

Wildlife Service, FWS/OBS-79/31.

Cox, R. R., M. A. Hanson, C. C. Roy, N. H. Euliss, D. H. Johnson, and M. G. Butler.

1998. Mallard duckling growth and survival in relation to aquatic invertebrates.

Journal of Wildlife Management 62:124-133.

Dahl, T. E. 1990. Wetland losses in the United States 1780s to 1980s. U. S. Dept. of

Interior, Fish and Wildlife Service, Washington, D.C.

106

Delnicki, D., and K. J. Reinecke. 1986. Mid-winter food use and body weights of mallards and wood ducks in Mississippi. Journal of Wildlife Management 50:43-

51.

Dirschl, H. J. 1969. Foods of lesser scaup and blue-winged teal in the Saskatchewan

River Delta. Journal of Wildlife Management 33:77-87.

Drobney, R. D. 1980. Reproductive bioenergetics of wood ducks. Auk 97:480-490.

Dubovsky, J. A., and R. M. Kaminski. 1994. Potential reproductive consequences of winter-diet restrictions in mallards. Journal of Wildlife Management 58:780-786.

Ducks Unlimited. 2005. Development of a Potential Wetland Restoration Layer for

Research and Planning in the Great Lakes. <www.ducks.org/media/Conservation/

GLARO/_documents/library/_gis/GLPotentialWetland.pdf> Accessed 1 May

2005.

Elmberg, J., K. Sjoberg, H. Poysa, and P. Nummi. 2000. Abundance-distribution relationships on interacting trophic levels: the case of lake-nesting waterfowl and dytiscid water beetles. Journal of Biogeography 27:821-827.

Farney, R. A. 1975. Fall foods of ducks in Lake Erie marshes during high water years.

Thesis, The Ohio State University, Columbus, Ohio, USA.

Fredrickson, L. H. and F. A. Reed. 1988. Invertebrate response to wetland management.

Fish and Wildlife Leaflet 13.3.1, Waterfowl Management Handbook. U. S. Fish and Wildlife Service, Washington, D.C., USA.

Gammonley, J. H., and M. E. Heitmeyer. 1990. Behavior, body condition, and foods of buffleheads and lesser scaups during spring migration through the Klamath Basin,

California. Wilson Bulletin 102:672-683.

Gorman, K. B., D. Esler, P. L. Flint, and T. D. Williams. 2008. Nutrient-Reserve dynamics during egg production by female greater scaup ( Aythya marila ):

Relationships with timing of reproduction. The Auk 125:384-394.

Gray, M. J., R. M. Kaminski, G. Weerakkody, B. D. Leopold, and K. C. Jensen. 1999.

Aquatic invertebrate and plant responses following mechanical manipulations of moist-soil habitat. Wildlife Society Bulletin 27:770-779.

Green, A. J. 1998. Comparative feeding behaviour and niche organization in a

Mediterranean duck community. Canadian Journal of Zoology 76:500-507.

Greer, A. K., B. D. Dugger, D. A. Graber, and M. J. Petrie. 2006. The effects of seasonal flooding on seed availability for spring migrating waterfowl. Journal of Wildlife

Management 71:1561-1566.

107

Gruenhagen, N. M. 1987. Feeding ecology, behavior and carcass dynamics of migratory female mallards. Thesis, University of Missouri, Columbia, Missouri, USA.

Gruenhagen, N. M., and L. H. Fredrickson. 1990. Food use by migratory female mallards in northwest Missouri. Journal of Wildlife Management 54:622-626.

Harris, M. P. 1969. Effect of laying date on chick production in oystercatchers and herring gulls. Britain Birds 62:70-75.

Havens, J. H. 2007. Winter abundance of waterfowl, waterbirds, and waste rice in managed Arkansas rice fields. Thesis, Mississippi State University, Mississippi

State, Mississippi, USA.

Havera, S. P. 1999. Waterfowl of Illinois: status and management. Illinois Natural

History Survey Special Publication 21.

Heitmeyer, M. E. 1985. Wintering strategies of female mallards related to dynamics of lowland hardwood wetlands in the upper Mississippi delta. Dissertation,

University of Missouri, Columbia, Missouri, USA.

Hines, J. E. and J. R. Sauer. 1989. Program CONTRAST – A general program for the analysis of several survival or recovery rate estimates. US Fish and Wildlife

Service, Fish and Wildlife Technical Report 24, Washington, D.C., USA.

Hohman, W. L. 1985. Feeding ecology of ring-necked ducks in northwestern Minnesota.

Journal of Wildlife Management 49:546-557.

Hohman, W. L. 1986. Changes in body weight and body composition of breeding ring- necked ducks. Auk 103:181-188.

Hoppe, R. T., L. M. Smith, and D. B. Webster. 1986. Foods of wintering diving ducks in

South Carolina. Journal of Field Ornithology 57:126-134.

Hornung, J. P. and A. L. Foote. 2006. Aquatic invertebrate responses to fish presence and vegetation complexity in western boreal wetlands, with implications for waterbird productivity. Wetlands 26:1-12.

Howe, M.A., P. H. Geissler, and B. A. Harrington. 1989. Population trends of North

American shorebirds based on the International Shorebird Survey. Biological

Conservation 49:185-199.

Illinois State Water Survey [ISWS]. 2008. ISWS home page. <http:www.sws.uiuc.edu>.

Accessed 1 April 2008.

Jorde, D. G. 1981. Winter and spring staging ecology of mallards in south central

Nebraska. Thesis, University of North Dakota, Grand Forks, North Dakota, USA.

108

Kaminski, R. M., and H. H. Prince. 1981. Dabbling duck and aquatic macroinvertebrate responses to manipulated wetland habitat. Journal of Wildlife Management 45:1-

15.

Kaminski, R. M. and E. A. Gluesing. 1987. Density- and habitat-related recruitment in mallards. Journal of Wildlife Management 51:141-148.

Kennish. R. 1996. Diet composition influences the fitness of the herbivorous crab

Grapsus albolineatus . Oecologia 105:22-29.

Kerwin, J. A., and L. G. Webb. 1972. Food of ducks wintering in coastal South Carolina,

1956-1957. Pages 223-245 in Proceedings of the 25 th

Annual Conference of the

Southeastern Association of Game & Fish Commissioners, Tallahassee, Florida,

USA.

Koons, D. N., and J. J. Rotella. 2003. Have lesser scaup, Aythya affinis , reproductive rates declined in parkland Manitoba? The Canadian Field-Naturalist 117:582-588.

Krapu, G. L. 1979. Nutrition of female dabbling ducks during reproduction. Pages 59 –

70 in T.A. Bookhout, editor. Waterfowl and wetlands – An integrated review.

Proceedings of the symposium of the North Central Section, The Wildlife

Society, Madison, Wisconsin, USA.

Krapu, G. L. 1981. The role of nutrient reserves in mallard reproduction. Auk 98:29 – 38.

Krapu, G. L., and K. J. Reinecke. 1992. Foraging ecology and nutrition. Pp. 1-29 in B. D.

J. Batt, A. D. Afton, M. G. Anderson, C. D. Ankney, D. H. Johnson, J. A.

Kadlec, and G. L. Krapu, editors. Ecology and management of breeding waterfowl. University Minnesota Press, Minneapolis, Minnesota, USA.

Krapu, G. L., D. A. Brandt, and R. R. Cox, Jr. 2004. Less waste corn, more land in soybeans, and the switch to genetically modified crops: trends with important implications for wildlife management. Wildlife Society Bulletin 32:127-136.

Kross, J., R. M. Kaminski, K. J. Reinecke, E. J. Penny, and A. T. Pearse. 2008. Moist-soil seed abundance in managed wetlands in the Mississippi Alluvial Valley. Journal of Wildlife Management 72:707-714.

LaGrange, T. G. 1985. Habitat use and nutrient reserve dynamics of spring migratory mallards in central Iowa. Thesis, Iowa State University, Ames, Iowa, USA.

LaGrange, T.G., and J. J. Dinsmore. 1989. Habitat use by mallards during spring migration through central Iowa. Journal of Wildlife Management 53:1076-1081.

109

Lovvorn, J. R. 1987. Behavior, energetics, and habitat relations of canvasback ducks during winter and early spring migration. Dissertation, University of

Wisconsin, Madison, Wisconsin, USA.

Manley, S. W., W.L. Hohman, J.L. Moore, and D. Richard. 1992. Food preferences of spring-migrating blue-winged teal in southwest Louisiana. Proceedings of the

Annual Conference of the Southeastern Association of Fish and Wildlife

Agencies, Tallahassee, Florida, USA.

McKnight, S. K., and G. R. Hepp. 1998. Diet selectivity of gadwalls wintering in

Alabama. Journal of Wildlife Management 62:1533-1543.

McNeil, R., and C. Leger. 1987. Nest-site quality and reproductive success of early- and late-nesting double-crested cormorants. Wilson Bulletin 99:262-267.

Merritt, R. W. and K. W. Cummins, editors. 1996. An introduction to the aquatic insects of North America. Kendall/Hunt Publishing Company, Dubuque, Iowa, USA.

Midwestern Regional Climate Center [MRCC]. 2008. MRCC home page. <http://mcc. sws.uiuc.edu/climate_midwest>. Accessed 1 April 2008.

Miller, M. R. 1987. Fall and winter foods of northern pintails in the Sacramento Valley,

California. Journal of Wildlife Management 51:405-414.

Nager, R. G. 2006. The challenges of making eggs. Ardea 94:323-346.

Neckles, H. A., H. R. Murkin, and J. A. Cooper. 2006. Influences of seasonal flooding on macroinvertebrate abundance in wetland habitats. Freshwater Biology 23:311-

322.

Newton, I. 2006. Can conditions experienced during migration limit the population levels of birds? Journal of Ornithology 147:146-166.

Nudds, T. D. 1983. Niche dynamics and organization of waterfowl guilds in variable environments. Ecology 64:319-330.

Paulus, S. L. 1982. Feeding ecology of gadwalls in Louisiana in winter. Journal of

Wildlife Management 46:71-79.

Pederson, G. B., and R. L. Pederson. 1983. Feeding ecology of mallards and pintails in the lower Klamath Marshes. USFWS Final Report Contract # 14-16-0001-79106.

Humboldt State University. Humboldt, California, USA.

Peters, M. S., and A. D. Afton. 1993. Diets of ring-necked ducks wintering on Catahoula

Lake, Louisiana. The Southwestern Naturalist 38:166-168.

110

Poysa, H. 1983. Morphology-mediated niche organization in a guild of dabbling ducks.

Ornis Scandinavica 14:317-326.

Raveling, D. G. 1979. The annual cycle of body composition of Canada geese with special reference to control of reproduction. The Auk 96:234-252.

Reynolds, C. M. 1972. Mute swan weights in relation to breeding. Wildfowl 23:111-118.

Ringelman, J. K. 1990. Life history traits and management of the gadwall. 13.1.2 Fish and Wildlife leaflet 13, Waterfowl management handbook. U. S. Fish and

Wildlife Service, Washington, D.C., USA.

Rohwer, F. C. 1992. The evolution of reproductive patterns in waterfowl. Pages 486-539 in B. D. J. Batt, A. D. Afton, M. G. Anderson, C. D. Ankney, D. H. Johnson, J. A.

Kadlec, and G. L. Krapu, eds. Ecology and management of breeding waterfowl.

University Minnesota Press, Minneapolis, Minnesota, USA.

Rogers, J. P., and L. J. Korschgen. 1966. Foods of lesser scaups on breeding, migration, and wintering areas. Journal of Wildlife Management 30:258-264.

Sedinger, J. S. 1992. Ecology of prefledging waterfowl. Pages 109 − 127 in B. D. J. Batt,

A. D. Afton, M. G. Anderson, C. D. Ankney, D. H. Johnson, J. A. Kadlec, and

G. L. Krapu, editors. Ecology and management of breeding waterfowl. University

Minnesota Press, Minneapolis, Minnesota, USA.

Smith, R. V. 2007. Evaluation of waterfowl habitat and spring food selection by mallard and lesser scaup on the Swan Lake, Illinois Habitat Rehabilitation and

Enhancement Project. Thesis, Southern Illinois University, Carbondale, Illinois,

USA.

Stafford, J. D., R. M. Kaminski, K. J. Reinecke, and S. W. Manley. 2006. Waste rice for waterfowl in the Mississippi Alluvial Valley. Journal of Wildlife Management 70:

61-69.

Steffeck, D. W., F. L. Paveglio, Jr., F. C. Bellrose, and R. E. Sparks. 1980. Effects of decreasing water depths on the sedimentation rate of Illinois River bottomland lakes. Water Resources Bulletin 16:553-555.

Strand, K. A., S. R. Chipps, S. N. Kahara, K. F. Higgins, and S. Vaa. 2008. Patterns of prey use by lesser scaup Aythya affinis (Aves) and diet overlap with fishes during spring migration. Hydrobiologia 598:389-398.

Straub, J. 2008. Contribution of wetland and crop plant foods to meet energy needs of spring-migrating waterfowl in the Upper Mississippi River and Great Lakes

Region. Thesis, The Ohio State University, Columbus, Ohio, USA.

111

Swanson, G. A., and J. C. Bartonek. 1970. Bias associated with food analysis in gizzards of blue-winged teal. Journal of Wildlife Management 34:739-746.

Swanson, G. A., M. I. Meyer, and J. R. Serie. 1974. Feeding ecology of breeding blue- winged teals. Journal of Wildlife Management 38:396-407.

Swanson, G. A., M. I. Meyer, and V. A. Adomaitis. 1985. Foods consumed by breeding mallards on wetlands of south-central North Dakota. Journal of Wildlife

Management 49:197-203.

Taylor, T. S. 1978. Spring foods of migrating blue-winged teals on seasonally flooded impoundments. Journal of Wildlife Management 42:900-903.

Thompson, J. D., B. J. Sheffer, and G. A. Baldassarre. 1992. Food habits of selected dabbling ducks wintering in Yucatan, Mexico. Journal of Wildlife Management

56:740-744.

Tiner, R. W. 1998. In search of swampland: A wetland sourcebook and fieldguide.

Rutgers University Press, New Brunswick, New Jersey, USA.

Toft, C. A., D. L. Trauger, and H. W. Murdy. 1982. Tests for species interactions: breeding phenology and habitat use in subarctic ducks. The American Naturalist

120:586-613.

United States Fish and Wildlife Service. 2008. Division of Conservation Planning

<www.fws.gov/Midwest/Planning/Images/Region3states.jpg> Accessed

1 October 2008.

Upper Mississippi River and Great Lakes Region Joint Venture. 1998. Implementation

Plan. North American Waterfowl Management Plan.

Weller, M. W., editor. 1988. Waterfowl in winter. University Minnesota Press,

Minneapolis, Minnesota, USA.

White, R. G. 1983. Foraging patterns and their multiplier effects on productivity of northern ungulates. Oikos 40:377-384.

Wilkins, K. A., M. C. Otto, and M. D. Koneff. 2006. Trends in duck breeding populations, 1955-2006. United States Fish and Wildlife Service Administrative

Report. Washington, D.C., USA.

Wisconsin Department of Natural Resources. 2002. Upper Rock River Watershed

Management Plan. < www.dnr.state.wi.us/org/gmu/uprock/surfacewaterfiles/ watersheds/12ur_Watershed_011902.doc > Accessed 1 April 2008.

112

Young, A. D. 1993. Intraspecific variation in the use of nutrient reserves by breeding female mallards. The Condor 95:45-56.

113

APPENDICES

1

APPENDIX A

Table A1. Aggregate percent biomass of food items in blue-winged teal collected at the

Cache River study site in spring 2006 (n = 22) and 2007 (n = 27). If food items were

<0.1% they were listed as trace (tr.).

______________________________________________________________________________________

2006 2007

Food Item Agg. % Agg. %

______________________________________________________________________________________

2.9 3.4 Total Vegetation

Total Animal Matter 31.8 38.7

Gastropoda 4.3

Physidae 4.0

Planorbidae

Bivalvia

Spaheriidae

Chironomidae


Ceratopogonidae

Macrocrustacea

0.3

0.0

0.0

9.8

0.2 tr.

6.9

Amphipoda 2.6

Isopoda

Microcrustacea

Cladocera

Copepoda

Ostracoda

Annelida

Baetidae

Caenidae

Total Seed

Alisma sp.


4.3

4.7

3.1

0.1

1.5

4.6

1.5

0.0

0.0

64.9

0.0

17.2

2.2

15.0

2.7

2.7

5.2

3.3

3.2

1.1

0.1

1.0 tr. tr. tr.

0.0

0.1

8.6

3.7

2.5

57.8

1.9

114

Table A1 continued.

______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

Amaranthus sp. 4.9 2.5

Asclepias sp. 0.0 1.2

Bidens sp.

Cyperus sp.

Digitaria sp.

5.2

0.8

4.9

0.0

4.5 tr.

Echinochloa

Eleocharis

Eragrostis

Leersia

Lonicera

Ludwigia

sp.

sp.

sp.

sp.

sp. sp.

5.1

0.7

1.2

3.5

0.0

0.0

2.6

3.1

0.1

2.7

2.1

17.7

Panicum sp. 10.8 3.3

Polygonum sp.

Rhynchospora sp.

11.1

2.8

6.7

0.0

Scirpus sp. 7.4 4.2

Unknown Seeds 8.0 3.1

______________________________________________________________________________________

115


Illinois River study site in spring 2006 (n = 21) and 2007 (n = 28). If food items were


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

Total Vegetation 1.1 0.2

28.3 48.5 Total Animal Matter

Gastropoda

Lymnaeidae

Physidae

Planorbidae

3.2 tr.

3.2

0.0

13.3

6.7

6.2

0.3

Chironomidae


Culicidae

Macrocrustacea

9.7

0.3

0.3

4.7

4.8

2.0

1.7

3.9

3.1 Amphipoda

Isopoda

Microcrustacea

Cladocera

Copepoda

Annelida


Collembola

0.9

3.8

1.9

1.9 tr.

0.0

7.4

4.5

Coenagrionidae

Dytiscidae

Elmidae

0.0

2.8

0.0

Miscellaneous / Unknown

Total Seed

Amaranthus sp.

1.0

70.6

2.8

0.7

7.0

1.3

4.7

6.9

8.6 tr.

3.5 tr.

1.7

1.7

51.2

1.7

116

Table A2 continued.

______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

Bidens sp. 2.7 1.5

Carex sp.

Cephalanthus sp.

0.0

0.3

6.0

4.1

Cyperaceae sp. 4.8 0.0

Cyperus sp.

Digitaria sp.

Echinochloa sp.

22.9

0.0

4.3

1.7

4.0

2.0

Eleocharis

Eragrostis

Impatiens

Leersia

Ludwigia

sp.

sp.

sp. sp.

sp. tr.

5.1

2.0

9.9

0.0

1.7

1.0

0.0

0.8

2.2

Panicum sp. 0.3 3.0

Polygonum sp.

Unknown Seeds

5.7

8.8

15.4

3.0

______________________________________________________________________________________

117


Wisconsin study site in spring 2006 (n = 15) and 2007 (n = 17). If food items were


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________



Gastropoda

Lymnaeidae

Physidae

Planorbidae

11.9

5.4 tr.

6.3

38.0

33.1

1.5

3.2

Chironomidae 6.7 0.5


Stratiomyidae

Tipulidae

Macrocrustacea

Amphipoda

Isopoda

0.1

0.1

0.0

6.7 tr.

6.7

8.6

8.3

0.2

1.4

0.3

1.0

Microcrustacea

Non-Dipteran Insects tr.

0.8


Total Seed

Alisma sp.

4.7

69.0

0.3

Amaranthus sp. 9.4

Bidens sp. 8.9

Carex sp. 0.0

Cyperus sp.

Echinochloa

Leersia sp.

sp.

14.8

0.0

12.7 tr.

0.8 tr.

48.7

4.2

0.5

9.6

4.2

6.2

5.8

1.6

118

Table A3 continued.

______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

Polygonum sp. 17.0 1.0

Potamogeton

Scirpus sp.

sp. 0.0

0.0

2.5

7.2

Solanum sp.

Unknown Seeds

0.0

6.2

4.6

0.0

______________________________________________________________________________________

119


Scioto River study site in spring 2006 (n = 2) and 2007 (n = 10). If food items were


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

6.2 Total Vegetation

Total Animal Matter

Gastropoda

Lymnaeidae

Physidae

Planorbidae

Bivalvia

Spaheriidae

Chironomidae

0.0

52.1

44.6

38.8

5.9

0.0

0.9

0.9 tr.

Non-Chironomidae Dipterans 0.0

Macrocrustacea

Isopoda

Microcrustacea

Cladocera

Annelida

0.0

0.0

0.0

0.0

2.7


Hydrophilidae

Total Seed

Amaranthus sp.

Bidens sp.

Carex sp.

Echinochloa

Eleocharis

Leersia

sp.

sp.

sp.

3.9

3.8

47.9

0.4

47.5

0.0

0.0

0.0

0.0

26.2

2.0

0.6

0.5

0.9

0.0

0.0

8.5

0.2

0.1

0.1

10.9

10.9

4.0

0.1

0.0

67.5 tr.

0.0

1.6

4.1

9.5

9.8

120

Table A4 continued.

______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

Panicum sp. 0.0 3.6

Polygonum sp.

Potamogeton sp.

0.0

0.0

16.7

18.2


______________________________________________________________________________________

121


Lake Erie study site in spring 2006 (n = 20) and 2007 (n = 6). If food items were <0.1% they were listed as trace (tr.).

______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

Total Vegetation


Gastropoda

Lymnaeidae

Physidae

Planorbidae

22.6

41.1

35.4

5.4

16.4

13.6

Chironomidae 1.6

Non-Chironomidae Dipterans tr.

Macrocrustacea

Amphipoda

0.9

0.3

Isopoda

Microcrustacea

Annelida


Aeshnidae

Coenagrionidae

Dytiscidae

Total Seed

Cyperus sp.

Eleocharis sp.

0.6 tr.

1.4

1.6

0.2

0.6

0.4

36.3

0.0

10.1

31.8

14.2

12.3 tr.

0.9

11.3

0.1

0.4

1.0

1.0

0.0

0.2

0.0 tr.

0.0 tr.

0.0

53.9

11.5

0.0

Leersia sp.

Polygonum sp.

5.3

10.6

0.0

30.1

Scirpus sp. 6.3 9.9

______________________________________________________________________________________

122


Saginaw Bay study site in spring 2006 (n = 11) and 2007 (n = 19). If food items were


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________



Gastropoda

Lymnaeidae

Physidae

Planorbidae

Bivalvia

Sphaeriidae

Chironomidae

1.3

65.6

37.8

7.0

3.0

27.8

3.6

3.6

13.8

Non-Chironomidae Dipterans tr.

Macrocrustacea

Amphipoda

Isopoda


7.8

5.0

2.8

2.6

0.4 Caenidae

Coenagrionidae

Dytiscidae

Hydrophilidae

Phyrganeidae

Total Seed

Amaranthus sp.

Carex sp.

Cladium

Cyperus

sp.

sp.

1.2

0.0

0.0

0.6

33.1

11.5

0.0

0.0

0.0

55.1

33.6

12.2

5.7

15.6

2.8

2.8

6.9

0.0

5.1

2.1

2.9

6.5 tr.

1.0

3.7

1.2

0.3

39.2 tr.

3.3

3.8

5.3

123

Table A6 continued.

______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

Eleocharis sp. tr. 4.6

Najas sp.

Polygonum sp.

Potamogeton sp.

0.0

3.0

0.0

1.1

8.4

4.4

Scirpus sp. 8.2 4.8


______________________________________________________________________________________

124

Table A7. Aggregate percent biomass of food items in gadwall collected at the Cache

River study site in spring 2006 (n = 8) and 2007 (n = 15). If food items were <0.1% they were listed as trace (tr.).

______________________________________________________________________________________

2006 2007


______________________________________________________________________________________


Algae

Lemna

Wolffia

Other Vegetation

49.5

6.6

17.3

tr.


Chironomidae


Microcrustacea

5.0

0.7

0.2

tr.

28.7

0.0

0.0

18.1

18.5

11.5

tr.

0.1


Collembola

Terrestrial Invertebrates

Total Seed

Carex sp.

Cyperus sp.


Digitaria sp.

3.9

3.8

tr.

0.0

21.6

4.3

2.7

0.0

tr.

0.0

6.6

6.6

34.5

0.1

3.6

1.5

Echinochloa

Eragrostis

Ludwigia

sp.

sp.

sp.

tr.

2.2

0.0

6.6

6.6

7.2

Panicum sp. 0.0 3.3

Polygonum sp. 4.3 4.0

Trifolium sp. 6.8 0.0

______________________________________________________________________________________

125

Table A8. Aggregate percent biomass of food items in gadwall collected at the Illinois


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________


Algae

3.0

2.2

74.4

42.4

9.0 Lemna

Other Vegetation


Chironomidae

Microcrustacea

Annelida

Oligochaeta

Coenagrionidae

Libellulidae

Corixidae

Total Seed

Amaranthus sp.

Carex sp.


0.0

0.7

6.5

6.1

0.3

tr.

0.0

0.0

0.0

0.0

0.0

90.6

2.1

13.9

Cephalanthus

Cyperus sp.

Echinochloa

Leersia

Najas

sp.

sp.

Panicum sp.

Polygonum

sp.

sp.

sp.

Potamogeton sp.

1.8

40.6

3.8

0.0

3.6

1.0

6.3

3.3

22.9

21.5

10.6

tr.

8.6

8.6

2.1

0.5

0.7

0.4

4.0

tr.

0.0

0.0

tr.

0.1

1.5

0.2

0.0

1.5

0.1

126

Table A8 continued.

______________________________________________________________________________________

2006 2007


______________________________________________________________________________________


______________________________________________________________________________________

127

Table A9. Aggregate percent biomass of food items in gadwall collected at the Wisconsin study site in spring 2007 (n = 16). If food items were <0.1% they were not listed.

______________________________________________________________________________________

2007

Food Item Agg. %

______________________________________________________________________________________


Algae

Lemna

Other Vegetation


Chironomidae

Stratiomyidae

Tipulidae


Pyralidae

Total Seed

Cyperus sp.

Echinochloa sp.


Ceratopogonidae

66.1

11.7

48.0

6.4

2.1

0.2

1.4

0.2

0.2

0.8

0.3

0.1

31.7

2.6

2.8

Panicum sp.

Polygonum

Scirpus sp.

sp.

7.9

9.7

5.9

______________________________________________________________________________________

128

Table A10. Aggregate percent biomass of food items in gadwall collected at the Scioto

River study site in spring 2007 (n = 1). If food items were <0.1% they were not listed.

______________________________________________________________________________________

2007

Food Item Agg. %

______________________________________________________________________________________


Algae


97.6

97.6

2.4

Chironomidae

Total Seed

2.4

0.0

______________________________________________________________________________________

129

Table A11. Aggregate percent biomass of food items in gadwall collected at the Lake

Erie study site in spring 2006 (n = 18) and 2007 (n = 17). If food items were <0.1% they were listed as trace (tr.).

______________________________________________________________________________________

2006 2007


______________________________________________________________________________________


Algae

Ceratophyllum

Chara sporangia

Myriophyllum

Lemna

Wolffia

Other Vegetation

62.9

32.6

4.9

0.0

0.0

24.6

0.6

tr.


Gastropoda

Chironomidae

3.9

0.3

0.5

Non-Chironomidae Dipterans 0.2

Macrocrustacea

Amphipoda

Microcrustacea

0.7

0.7

0.3

Annelida

Oligochaeta

Nematoda


Total Seed

Cyperus sp.

Myriophyllum sp.

Polygonum sp.

Potamogeton sp.

0.4

0.4

0.8

0.6

33.2

7.1

2.9

9.6

0.0

25.5

0.0

2.4

5.8

5.4

3.2

8.8

9.8

tr.

1.0

0.1

1.3

1.3

tr.

tr.

tr.

6.4

tr.

38.7

3.5

0.0

19.8

1.4

130

Table A11 continued.

______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

Scirpus sp. 6.8 11.2


______________________________________________________________________________________

131

Table A12. Aggregate percent biomass of food items in gadwall collected at the Saginaw

Bay study site in spring 2006 (n = 2) and 2007 (n = 17). If food items were <0.1% they were listed as trace (tr.).

______________________________________________________________________________________

2006 2007


______________________________________________________________________________________


Algae 0.0 11.2

45.9 5.8 Lemna

Wolffia

Other Vegetation


0.0

0.0

10.9

1.0

38.3

9.5

Chironomidae


Empididae

Tabanidae

Tipulidae

Macrocrustacea

Amphipoda


Total Seed

Carex sp.

9.2

0.8

0.5

0.0

0.3

0.0

0.0

0.9

43.2

2.4

7.2

0.5

0.0

0.5

0.0

1.6

1.6

tr.

33.9

0.0

Eleocharis

Najas sp.

Polygonum

Scirpus

sp. sp.

sp.

0.0

30.3

10.6

0.0

11.7

0.0

3.1

11.8


______________________________________________________________________________________

132

Table A13. Aggregate percent biomass of food items in mallards collected at the Cache


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

Total Vegetation tr. 0.0


Gastropoda

Bivalvia

8.8

0.4

0.0

9.2

0.1

tr.

Chironomidae


Macrocrustacea

Microcrustacea

Annelida

Nematoda


Naucoridae

Pyralidae

0.3

0.0

0.2

0.0

0.0

6.7

1.3

1.3

0.0

2.5

tr.

0.4

tr.

tr.

0.0

6.1

0.0

5.6

Total Seed

Carex sp.

Cephalanthus sp.

Cornus sp.

Cyperus sp.

Echinochloa

Eleocharis

sp.

sp.

Eragrostis sp.

Helenium

Leersia

Lupinus

sp.

sp.

sp.

91.2

4.5

7.5

1.9

1.7

2.5

0.5

0.0

8.2

14.3

5.5

90.8

2.5

0.5

0.0

0.7

8.0

2.1

1.8

0.0

1.9

0.0

133


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

Myriophyllum sp. 1.6 0.0

Panicum

Rumex

sp.

Polygonum sp.

Potamogeton

sp.

sp.

7.4

12.7

6.2

1.4

tr.

26.8

tr.

5.0

Scirpus sp.

Toxicodendron sp.

Unknown Seeds

7.8

1.1

5.4

tr.

3.9

2.6

Tubers 0.0 33.6

______________________________________________________________________________________

134

Table A14. Aggregate percent biomass of food items in mallards collected at the Illinois


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

tr. 9.7 Total Vegetation

Lemna tr. 0.1

9.6 Other Vegetation


Gastropoda

Physidae

Planorbidae

Chironomidae


0.0

20.1

0.0

0.0

0.0

6.0

tr.

27.5

4.9

4.6

0.2

13.9

tr.

Macrocrustacea 0.0 0.1

Microcrustacea

Annelida

Hirudinea

Oligochaeta

Nematoda


Baetidae

Coenagrionidae

tr.

0.0

0.0

0.0

0.7

6.7

0.0

0.0

0.0

7.5

1.0

6.5

0.0

1.1

0.6

0.3

Dytiscidae

Carabidae


Total Agricultural Seed (Corn)

Total Non-Agricultural Seed

Amaranthus sp.

0.0

6.7

6.7

13.3

66.6

6.7

0.2

0.0

tr.

6.5

56.3

tr.

135


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

Bidens sp. 1.8 0.0

Cephalanthus

Cyperus sp. sp. 0.0

4.5

0.7

tr.

Echinochloa sp. 8.9 0.3

Eragrostis

Leersia

sp.

sp.

Myriophyllum sp.

6.7

3.0

0.0

0.0

12.3

1.0

Polygonum sp.

Potamogeton

Vitis sp.

sp.

Unknown Seeds

28.1

6.7

0.0

0.0

20.4

0.0

1.0

4.1

Tubers 0.0 15.4

______________________________________________________________________________________

136

Table A15. Aggregate percent biomass of food items in mallards collected at the

Wisconsin study site in spring 2006 (n = 9) and 2007 (n = 14). If food items were <0.1% they were listed as trace (tr.).

______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

tr. 5.6 Total Vegetation

Lemna tr. 2.2

0.0 3.4 Other Vegetation


Gastropoda

Chironomidae

22.2

tr.

6.3

24.3

tr.

5.0


Stratiomyidae

Macrocrustacea

Amphipoda

Isopoda

Annelida


Notonectidae

11.0

11.0

4.7

4.7

0.0

tr.

tr.

0.0

0.3

0.3

10.1

0.0

10.1

1.1

7.0

0.1

Leptoceridae


Total Agricultural Seed (Corn)


Alisma sp.

Amaranthus sp.

Bidens sp.

Carex sp.

Echinochloa

Leersia sp.

sp.

0.0

0.0

10.9

66.8

0.0

tr.

0.7

0.0

0.2

26.5

6.9

0.6

0.0

70.0

3.0

1.3

0.1

1.0

tr.

7.8

137


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

Panicum sp. 0.1 0.7

Phalaris sp.

Polygonum sp.

Potamogeton sp.

0.0

17.4

0.0

1.1

20.0

2.3

Scirpus sp. 21.5 14.9

Sparganium sp.

Vitis sp.

Unknown Seeds

Tubers

0.0

0.0

0.0

6.9

1.4

2.9

0.0 5.7

______________________________________________________________________________________

138

Table A16. Aggregate percent biomass of food items in mallards collected at the Scioto


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________


6.0 Total Animal Matter

Gastropoda

Chironomidae


Macrocrustacea

10.9

tr.

2.4

tr.

8.3

tr.

0.0

tr.

tr.

Amphipoda

Isopoda

Microcrustacea

Annelida


Total Agricultural Seed (corn)


Bidens sp.

Convolvulus sp.

Echinochloa

Fabaceae

Leersia

sp.

sp.

sp.

8.3

tr.

tr.

tr.

tr.

0.0

80.4

5.8

0.0

34.7

0.0

34.3

0.0

tr.

0.0

5.6

0.1

42.7

47.7

tr.

1.9

1.9

1.4

9.6

Polygonum

Rumex

Setaria

sp.

sp.

sp. 2.9

tr.

tr.

8.6

1.6

16.3

Unknown Seeds 0.9 tr.

Tubers 0.0 4.8

______________________________________________________________________________________

139

Table A17. Aggregate percent biomass of food items in mallards collected at the Lake


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

12.4 tr. Total Vegetation

Lemna 11.4 tr.



Gastropoda

Lymnaeidae

Physidae

Planorbidae

Chironomidae

7.4

2.8

0.0

2.4

0.4

tr.

12.2

7.7

0.2

5.8

1.7

tr.

0.0 Non-Chironomidae Dipterans

Macrocrustacea

Amphipoda

Isopoda

Microcrustacea

Annelida


Caenidae

Aeshnidae

Coenagrionidae

Elmidae

Hydrophilidae



Abutilion sp.

tr.

2.5

0.9

1.6

tr.

tr.

1.8

0.0

tr.

1.3

0.1

0.2

10.2

69.9

6.6

3.1

3.1

0.0

0.0

0.0

1.4

0.1

0.7

0.5

0.0

0.0

0.0

87.7

0.0

140


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

Alisma sp. tr. 10.8

Cornus sp.

Cyperus sp.

2.1

4.8

0.0

0.7

Digitaria sp. tr. 9.0

Echinochloa

Leersia sp.

Panicum sp.

sp. 9.6

11.7

2.6

12.1

16.6

6.7

Poaceae

Scirpus

sp.

Polygonum sp.

Potamogeton

sp.

sp.

tr.

14.7

4.5

0.5

6.7

14.9

0.5

8.0

Unknown Seeds

Tubers

6.4

3.4

0.0

0.0

______________________________________________________________________________________

141

Table A18. Aggregate percent biomass of food items in mallards collected at the Saginaw

Bay study site in spring 2006 (n = 20) and 2007 (n = 22). If food items were <0.1% they were listed as trace (tr.).

______________________________________________________________________________________

2006 2007


______________________________________________________________________________________


Ceratophyllum 1.2 0.0

tr. tr. Lemna

Other Vegetation


Gastropoda

Lymnaeidae

Physidae

4.9

20.4

1.0

0.1

0.5

4.3

27.0

0.4

tr.

0.0

Planorbidae 0.4 0.4

Chironomidae


Diptera puparium

Macrocrustacea

Amphipoda

Isopoda

2.2

0.3

0.3

10.1

2.2

7.9

6.6

0.1

0.0

10.4

4.6

5.8

Microcrustacea

Ostracoda

Annelida


Caenidae

Coenagrionidae

Libellulidae

0.2

0.2

tr.

6.5

0.4

0.1

1.0

tr.

0.0

4.6

4.7

0.0

0.2

tr.

Gyrinidae 0.6 0.0

Hydrophilidae tr. 3.5

142


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

Limnephilidae 0.0 0.8

Phryganeidae 3.9 tr.



Amaranthus sp.

9.9

63.4

1.3

0.0

68.6

3.2

Carex

Najas

sp.

Chenopodium

Cyperus

Leersia

sp.

Echinochloa

sp.

sp.

Nymphaea

Polygonum

sp.

sp.

sp.

sp.

0.0

0.0

0.3

0.1

0.0

3.8

0.3

6.3

3.4

1.8

0.0

0.1

1.0

2.8

0.0

4.7

Potamogeton

Sagittaria

Scirpus

Setaria

sp.

sp.

sp.

sp. 5.5

3.4

32.9

0.0

3.4

0.3

18.6

1.8

Trifolium sp.

Vallisneria sp.

Unknown Seeds

0.0

0.1

5.4

1.7

tr.

3.5

Tubers 3.6 21.3

______________________________________________________________________________________

143

Table A19. Aggregate percent biomass of food items in lesser scaup collected at the

Cache River study site in spring 2006 (n = 0) and 2007 (n = 2). If food items were <0.1% they were listed as trace (tr.).

______________________________________________________________________________________

2007

Food Item Agg. %

______________________________________________________________________________________

Total Vegetation 0.0


Gastropoda

Planorbidae

Bivalvia

Sphaeriidae

Macrocrustacea

Amphipoda

Isopoda

6.7

6.7

43.1

43.1

21.0

6.1

14.8

Microcrustacea

Total Seed

Amaranthus sp.

Digitaria sp.

Echinochloa sp.

tr.

29.1

0.2

4.5

10.6

Leersia sp.

Ludwigia

Panicum

sp.

sp.

0.8

0.1

4.4

Polygonum sp. 8.2

______________________________________________________________________________________

144


Illinois River study site in spring 2006 (n = 10) and 2007 (n = 25). If food items were


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________



Gastropoda

Lymnaeidae

Physidae

Planorbidae

Bivalvia

Sphaeriidae

Chironomidae

9.6

1.4

8.2

0.0

0.0

0.0

1.2

12.1

2.6

0.3

9.2

8.0

8.0

3.0

tr. Non-Chironomidae Dipterans

Macrocrustacea

Isopoda

Microcrustacea

Cladocera

Annelida





Amaranthus sp.

Ceratophyllum sp.

Cyperus

Echinochloa

Leersia

sp.

sp.

sp.

0.0

1.8

1.8

tr.

tr.

10.0

0.0

0.3

0.0

76.9

13.0

0.0

29.3

3.6

6.9

9.2

9.1

2.5

2.2

1.5

0.3

tr.

15.0

44.3

0.1

2.9

1.6

4.1

13.1

145


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________


Poaceae sp.

Polygonum sp.

5.0

6.7

0.0

14.8

Potamogeton sp. 0.0 3.9


Tubers 0.0 1.2

______________________________________________________________________________________

146


Wisconsin study site in spring 2006 (n = 2) and 2007 (n = 5). If food items were <0.1% they were listed as trace (tr.).

______________________________________________________________________________________

2006 2007


______________________________________________________________________________________



Gastropoda

Chironomidae


Ceratopogonidae

36.0

0.0

0.0

36.0

1.8

1.0

18.8

0.0

0.0

Psychodidae

Total Seed

Ceratophyllum sp.

Polygonum sp.

34.2

64.0

0.0

14.0

0.0

80.1

1.3

0.0

Potamogeton sp. 0.0 78.7

Scirpus sp. 50.0 tr.

______________________________________________________________________________________

147


Scioto River study site in spring 2006 (n = 1) and 2007 (n = 16). If food items were


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________


Lemna

Other Vegetation

0.0

0.0

0.0

18.8

13.9

4.7


Gastropoda

Physidae

Chironomidae


Chaoboridae

100.0

0.0

0.0

0.0

0.0

56.0

1.8

1.8

41.2

2.7

0.0 2.7

0.0 tr. Microcrustacea

Annelida

Libellulidae

Hydrophilidae

Total Seed

Echinochloa sp.


100.0

0.0

0.0

0.0

0.0

0.0

2.5

7.5

2.7

4.7

25.2

6.3

Ipomoea

Scirpus

sp.

Polygonum sp.

Potamogeton

sp.

sp.

0.0

0.0

0.0

0.0

3.0

2.1

6.3

5.7


______________________________________________________________________________________

148

Table A23. Aggregate percent biomass of food items in lesser scaup collected at the Lake


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________


Algae 2.3 0.0



Fish (Gizzard Shad)

Gastropoda

Lymnaeidae

Physidae

48.9

0.0

27.9

tr.

25.2

50.3

11.0

tr.

0.0

tr.

Planorbidae 2.5 0.0

Bivalvia

Sphaeriidae

Chironomidae


Ceratopogonidae

Macrocrustacea

Microcrustacea

Annelida

0.0

0.0

9.9

tr.

tr.

1.5

tr.

1.2

8.4

8.4

21.5

7.4

7.4

0.0

tr.

1.6


Collembola

Coenagrionidae

Libellulidae


Total Seed

Abutilion sp.

5.8

1.4

1.1

2.8

2.9

38.1

2.2

0.0

0.0

0.0

0.0

0.1

49.6

0.0

149


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

Carex sp. tr. 2.5

Cyperus sp.

Ceratophyllum sp.

0.3

2.6

4.3

0.0

Echinochloa sp. 3.0 0.0

Leersia sp.

Polygonaceae

Polygonum

sp.

sp.

tr.

2.1

5.0

1.0

0.0

24.1

Potamogeton

Scirpus sp.

sp. 7.7

3.7

2.2

14.7


______________________________________________________________________________________

150


Saginaw Bay study site in spring 2006 (n = 16) and 2007 (n = 29). If food items were


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________


Lemna

5.6

5.6

0.1

0.1


Fish

Bluegill

Eurasian Round Goby

Gastropoda

Lymnaeidae

0.0

0.0

0.0

6.6

0.4

7.6

0.7

6.9

15.6

6.9

Physidae

Planorbidae

Chironomidae


4.0

2.2

57.1

0.5

1.6

7.0

44.9

0.2

Chaoboridae 0.5 0.0

Macrocrustacea

Amphipoda

Isopoda

Microcrustacea

Cladocera

Annelida


Caenidae

Coenagrionidae

Hydrobiidae


0.6

0.6

0.0

tr.

tr.

1.0

2.5

1.9

0.4

0.0

tr.

6.8

4.0

2.7

3.0

2.9

0.0

3.5

tr.

0.4

2.7

7.5

151


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

Bryozoan 0.0 7.5

Total Seed

Ceratophyllum sp.

Chenopodium sp.

25.9

4.8

0.1

10.5

1.0

2.0

Cyperus sp. 1.8 0.3

Impatiens sp.

Polygonum sp.

Potamogeton sp.

4.3

0.5

7.9

0.0

1.7

2.6

Scirpus sp. tr. 1.5


______________________________________________________________________________________

152

Table A25. Aggregate percent biomass of food items in ring-necked ducks collected at the Cache River study site in spring 2006 (n = 13) and 2007 (n = 24). If food items were


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________


Chara sporangia 0.0 3.7



Gastropoda

Physidae

Planorbidae

Bivalvia

Chironomidae

0.5

0.0

0.0

0.0

0.0

tr.

6.0

4.3

0.2

4.1

0.3

0.4

0.2 Non-Chironomidae Dipterans

Macrocrustacea

Annelida


Libellulidae

Corixidae



Ceratophyllum sp.

Echinochloa sp.

Ludwigia

Panicum

sp.

sp.

Polygonum sp.

Potamogeton

Scirpus sp.

sp.

0.0

0.0

0.0

0.4

0.4

0.0

6.9

92.0

0.0

41.3

0.0

38.3

7.7

0.2

0.0

tr.

tr.

0.7

0.2

0.3

3.9

82.4

5.0

26.0

8.1

3.7

10.3

11.9

2.1

153


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

Setaria sp. 2.4 0.0

Unknown Seeds

Tubers

1.6

0.0

0.0

13.9

______________________________________________________________________________________

154

Table A26. Aggregate percent biomass of food items in ring-necked ducks collected at the Illinois River study site in spring 2006 (n = 11) and 2007 (n = 10). If food items were


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________



Gastropoda

Physidae

Chironomidae

Macrocrustacea

Isopoda

0.0

0.0

0.0

9.4

9.4

5.2

5.2

tr.

tr.

tr.

Annelida


Hydrophilidae



Amaranthus sp.

Bidens sp.

Ceratophyllum sp.

Cyperus

Echinochloa

Leersia

sp.

sp.

sp.

tr.

0.0

0.0

0.0

90.6

28.3

0.0

0.0

30.4

2.7

0.0

0.0

4.3

4.3

9.4

80.4

tr.

1.0

1.1

0.4

4.9

26.9

Panicum sp.

Polygonum sp.

Unknown Seeds

0.0

20.3

1.0

2.0

38.6

4.5

Tubers 7.3 0.0

______________________________________________________________________________________

155

Table A27. Aggregate percent biomass of food items in ring-necked ducks collected at the Wisconsin study site in spring 2006 (n = 3) and 2007 (n = 12). If food items were


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________



Chironomidae

Annelida

Total Seed

Bidens sp.

0.0

0.2

99.8

3.7

0.4

0.0

98.2

1.0

Ceratophyllum

Cyperus

Phalaris

sp.

Eleocharis sp.

sp.

sp. 33.3

6.3

8.4

0.0

0.0

0.0

0.4

5.1

Polygonum sp.

Potamogeton

Scirpus sp.

sp.

23.3

24.8

0.0

9.9

66.8

13.0

Tubers 0.0 1.1

______________________________________________________________________________________

156

Table A28. Aggregate percent biomass of food items in ring-necked ducks collected at the Scioto River study site in spring 2006 (n = 7) and 2007 (n = 26). If food items were


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________


Chara sporangia

Other Vegetation

4.2

3.6

0.6

12.1

11.8

0.0


Gastropoda

Physidae

Planorbidae

Chironomidae


12.4

8.0

7.0

1.0

tr.

0.2

0.1

tr.

tr.

22.3

0.1

tr. 4.7 Annelida

Total Seed

Amaranthus sp.

Cyperus sp.

Echinochloa sp.


Libellulidae

4.1

4.0

83.4

1.6

tr.

0.0

0.7

0.0

60.0

3.6

8.1

6.2

Leersia

Najas

sp.

sp.

Poaceae sp.

Polygonum sp.

0.0

41.5

0.0

14.4

3.2

0.0

3.8

16.2

Potamogeton sp.

Trifolium sp.

11.9

14.0

15.3

0.0

Tubers 0.0 1.0

______________________________________________________________________________________

157

Table A29. Aggregate percent biomass of food items in ring-necked ducks collected at the Lake Erie study site in spring 2006 (n = 36) and 2007 (n = 25). If food items were


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________


Ceratophyllum

Lemna

9.9

4.1

tr.

9.2

0.0

0.4

Chara sporangia 2.7 tr.

3.0 8.7 Other vegetation


Fish

Gizzard Shad

6.1

0.0

0.0

14.7

3.9

3.9

Gastropoda

Lymnaeidae

Physidae

Planorbidae

Chironomidae


Macrocrustacea

Annelida


Coenagrionidae

Phryganeidae



Ceratophyllum sp.

Cyperus sp.

Echinochloa sp.

1.4

tr.

0.7

0.6

1.8

tr.

0.0

tr.

2.9

tr.

2.3

2.7

81.3

0.2

2.7

22.1

0.6

0.0

0.6

0.0

5.3

0.0

tr.

2.1

2.8

1.5

1.2

0.0

76.0

1.3

6.2

9.1

158


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

Leersia sp. 13.3 10.6


Panicum sp. 6.1 2.5

Polygonum sp.

Potamogeton

Scirpus sp.

sp.

21.0

4.6

5.5

27.0

8.0

7.5


______________________________________________________________________________________

159

Table A30. Aggregate percent biomass of food items in ring-necked ducks collected at the Saginaw Bay study site in spring 2006 (n = 15) and 2007 (n = 22). If food items were


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________


Lemna

Wolffia

27.8

1.2

0.0

9.6

tr.

4.2

Other Vegetation 26.6 5.3


Gastropoda

Lymnaeidae

Physidae

5.5

tr.

4.7

4.1

0.2

1.6

Planorbidae 0.5 2.2

Bivalvia

Dreissenidae

Chironomidae


0.0

0.0

35.7

tr.

6.9

6.9

18.5

0.0

Macrocrustacea

Amphipoda

Microcrustacea

Annelida


Ephemeridae

Coenagrionidae


Bryozoan

Total Seed

Amaranthus sp.

0.4

0.4

tr.

tr.

0.4

0.0

tr.

0.0

0.0

30.1

12.1

1.6

1.5

0.0

0.5

6.3

0.7

5.3

20.6

16.0

32.0

tr.

160


______________________________________________________________________________________

2006 2007


______________________________________________________________________________________

Ceratophyllum sp. 8.0 4.5

Myriophyllum

Najas sp.

sp. 4.8

tr.

3.8

6.8

Potamogeton

Scirpus sp.

sp.

Unknown Seeds

4.6

0.0

0.0

0.3

6.9

0.2

Tubers 0.0 8.9

______________________________________________________________________________________

161

VITA

Graduate School

Southern Illinois University

Arthur N. Hitchcock, Jr. Date of Birth: May 20, 1981

1987 Lincolnshire Blvd., Ridgeland, MS 39157

Mississippi State University

Bachelor of Science, Wildlife and Fisheries Science, May 2005


Master of Science, Zoology, December 2008

Thesis Title:

Diets of Spring-Migrating Waterfowl in the Upper Mississippi River and Great Lakes Region

Major Professor: Michael W. Eichholz

162

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