WETLANDS, Vol. 25, No. 3, September 2005, pp. 667–674
q 2005, The Society of Wetland Scientists
SHORT-TERM RESPONSE OF WETLAND BIRDS TO PRESCRIBED BURNING IN
RAINWATER BASIN WETLANDS
Elisabeth K. Brennan1, Loren M. Smith1, David A. Haukos2, and Theodore G. LaGrange3
1
Wildlife and Fisheries Management Institute
MS 2125
Texas Tech University
Lubbock, Texas, USA 79409-2125
E-mail: e.brennan@ttu.edu
U.S. Fish and Wildlife Service
MS 2125
Texas Tech University
Lubbock, Texas, USA 79409-2125
2
Nebraska Game and Parks Commission
P.O. Box 30370
Lincoln, NE, USA 68503-0370
3
Abstract: Prescribed burning is often used in wetlands to remove plant litter, decrease woody or invasive
species, and increase use by wetland birds. However, little is known about the within-season, short-term
response of wetland birds to prescribed burning, especially during spring migration. We surveyed use of 19
burned and 19 unburned (reference) wetlands by migratory birds in the Rainwater Basin region of Nebraska,
USA during three spring migrations, 2002–2004. We calculated the change in avian abundance and species
richness, as well as generating the Sørenson’s similarity index for burned and reference wetlands in the
weeks immediately before and after burning. We compared Sørenson’s index values and percent change in
abundance and species richness between burned and reference wetlands using an analysis of covariance with
week and wetland area as covariates to account for migration chronology and differences in the area of
experimental units. Following removal of effects due to wetland area and week, burning had no effect on
the percent change in avian abundance and species richness. Sørenson’s index also did not differ between
burned and reference wetlands. Prescribed burning did not improve use of wetlands by migratory birds in
the short term. Understanding the immediate and long-term effects of prescribed burning on migratory avian
abundance, species richness, and community composition is imperative for management decisions.
Key Words:
avian community, burning, management, migration, Rainwater Basin
INTRODUCTION
stopovers often function as geographic bottlenecks; entire populations within a flyway can be affected by the
quality and quantity of available wetland habitat at
stopover sites (Myers 1983). Therefore, it is essential
to evaluate the effects of prescribed burning on avian
habitat use of wetlands during migration.
Rainwater Basin (RWB) wetlands in Nebraska,
USA provide essential spring stopover sites to migratory wetland birds in the Central Flyway and have
been identified as containing waterfowl habitat of major concern by the North American Waterfowl Management Plan (NAWMP; Gersib et al. 1992). Five to
seven million waterfowl pass through the RWB region
each spring, including virtually all of the 250,000 midcontinent greater white-fronted geese (Anser albifrons)
(Krapu et al. 1995, Haukos 2003), 500,000 Canada
Prescribed burning is a commonly used management technique to remove plant litter, decrease woody
or invasive species, facilitate prescribed grazing (intentional use of grazing to modify vegetative communities), and alter plant species composition in wetlands, with the ultimate goal of improving wildlife
habitat (Singleton 1951, Schlichtemeier 1967, Smith
and Kadlec 1986, Kirby et al. 1988). Burning in wetlands has been shown to influence avian community
composition, as well as relative avian abundance in
breeding and wintering areas (Kantrud 1986, Herkert
1994, Gabrey et al. 1999). However, little is known
about the effects of prescribed burning in wetlands on
birds during migration (Kirby et al. 1988). Migratory
667
668
and cackling geese (Branta canadensis L. and B.
hutchinsii Richardson), 50% of the mid-continental
mallard population (Anas platyrhynchos), and 30% of
the continental northern pintail (A. acuta) population
(Gersib et al. 1992). Although less is known about use
of RWB wetlands by non-waterfowl species, the wetlands provide habitat for 38 shorebird species (Jorgensen 2004) and the endangered whooping crane (Grus
Americana L.) (Farrar 1986). This common dependence among migratory birds on wetlands within the
RWB region has hemispheric implications for migratory bird conservation and management (Myers 1983,
Skagen and Knopf 1993). The United States Fish and
Wildlife Service (USFWS) RWB Management District
manages Waterfowl Production Areas in south-central
Nebraska with the goal of providing resting, feeding,
and staging habitat for waterfowl and other migratory
wetland birds during spring migration. The USFWS
conducts prescribed burns in wetlands to reduce the
occurrence of late successional and non-native (introduced) vegetation and provide optimal feeding and
loafing habitats for migratory waterfowl, whooping
cranes, and shorebirds (Drahota 2004). The USFWS
typically conducts prescribed burning on approximately 25 wetlands each spring (Drahota 2004). Therefore,
it is important to understand the effects that various
management strategies, particularly prescribed burning, have on avian habitat use in the RWB region.
Studies investigating the effects of burning on wetland birds have produced varied and contradictory results. One study that examined the long-term (.1 year)
effects of prescribed burning on breeding birds found
burned shrub/scrub wetlands had lower abundance and
species richness than unburned wetlands (Hanowski et
al. 1999). Gabrey et al. (1999) reported that prescribed
burning in coastal marshes had no effect on the overall
abundance of wintering birds but did alter relative
abundance within specific groups, such as blackbirds
(Icteridae), wrens (Troglodytidae), and sparrows (Emberizidae). Moreover, the effects of prescribed burning
can depend on marsh type. For example, burning had
no effect on wintering bird abundance in wetlands
dominated by rushes (Juncus spp.) but did reduce bird
abundance in cordgrass (Spartina spp.) dominated
wetlands (Issach et al. 2004). Studies examining the
effects of prescribed burning on habitat use have focused on wintering and breeding grounds, but little
work has occurred on migration areas.
Our objective was to determine the immediate effects of prescribed burning on abundance, species richness, and community composition of wetland birds
during spring migration in the RWB region. We hypothesized that burned wetlands would have a greater
positive percent change in abundance, greater positive
percent change in species richness, and less similar
WETLANDS, Volume 25, No. 3, 2005
bird communities following burning than unburned
wetlands. We compared changes in avian abundance,
species richness, and community similarity between
burned and unburned (reference) wetlands of similar
area and vegetation structure during spring migration.
METHODS
Study Area
Wetlands in the RWB region are distributed among
17 counties in south-central Nebraska, USA (Figure
1). The area is characterized by flat to gently rolling
loess plains, with elevations ranging from 455 m to
758 m (Gersib et al. 1989). Precipitation increases on
a west-to-east gradient across the region, with far western and eastern counties receiving an average of 43
and 74 cm annual precipitation, respectively (Gilbert
1989). Most wetlands range in size from ,1 to 16 ha,
although several wetlands are .400 ha. Located primarily on silt loam and silty clay loam soils, RWB
wetlands are classified as playas and believed to have
been originally formed by scouring due to wind
(LaGrange 1997, Smith 2003). Most RWB wetlands
are classified into one of three palustrine emergent
wetland categories (following Cowardin et al. 1979);
temporarily flooded, seasonally flooded, or semi-permanently flooded (Gersib et al. 1989). RWB wetlands
are not naturally connected to ground water; thus, accumulation of water in the basins depends primarily
on runoff from snowmelt and rainfall. However, irrigation runoff from crop fields and pumping by natural
resource agencies contributes to flooding of some basins (Schildman and Hurt 1984).
Most wetland vegetation in the RWB can be characterized as herbaceous, hydrophytic species, persisting throughout the majority of the growing season
(Gersib et al. 1990). Surrounding uplands contain tall
grass and mixed grass prairie ecosystems. Wetland
plant communities consist primarily of species adapted
to alternating wet and dry conditions (Weaver and
Bruner 1954). Gilbert (1989) identified five major vegetation zones in RWB wetlands: an upland zone that
includes pasture and planted prairie stands; a transition
zone consisting of mesic and wet-mesic stands of
grasses, sedges, and forbs; an outer marsh zone consisting of spikerush (Eleocharis spp.) and hydrophytic
grasses and forbs; a persistent emergent zone; and an
inner marsh zone comprised of drawdown and aquatic
bed species.
Prescribed Burning
All prescribed burns evaluated in this study were
conducted by the RWB Management District of the
Brennan et al., AVIAN RESPONSE TO BURNING
669
Figure 1. Rainwater Basin wetlands are located in 17 counties in south-central Nebraska, where short-term effects of prescribed burning on avian abundance, species richness, and community similarity were evaluated during springs 2002–2004.
USFWS (Drahota 2004). In an average year, 1,800 ha
are burned in 25 different units by the USFWS. The
Nebraska Game & Parks Commission also conducts
prescribed burns on their Wildlife Management Areas;
however, none of the state owned wetlands contained
water at the time of burning, and therefore, none were
evaluated in this study. Our study examined 19 wetlands burned in spring 2002–2004; 10 in 2002, two in
2003, and seven in 2004. Burn dates ranged from 12
March to 2 May. Conditions for burning were subjective, depending on wind direction and proximity of the
wetland to a dwelling or a major road (T. Koerner,
USFWS, pers. comm.). Prescribed burns were performed when wind speeds ranged from 5 to 20 km/
hour. The USFWS used a GIS (Geographic Information System) hydric soil boundary layer to estimate
size of each burn within a wetland (T. Koerner,
USFWS, pers. comm.). In most cases, hydric vegetation was burned to the water’s edge; however, in a few
wetlands, a narrow band of vegetation surrounding the
perimeter of the water was left unburned. The prominent vegetation types targeted in prescribed burning
were cattail (Typha spp.), river bulrush (Schoenplectus
fluviatilis Torr.), and common reed (Phragmites australis (Cav.) Trin. ex Steud.), although reed canary
grass (Phalaris arundinacea L.) was also included
(Drahota 2004). All burned wetlands contained water,
although none were 100% full relative to the extent of
hydric soils. Emergent vegetation in the water was not
altered by prescribed burning.
Bird Surveys
We surveyed birds in each burned wetland within
seven days prior to and following burning to estimate
avian species richness and abundance. In addition, a
matching reference wetland was surveyed during the
same weeks and paired with a burned wetland to form
an experimental block. We selected reference wetlands
as similar in area and vegetation cover to burned wetlands as possible. Vegetation cover was based on the
ratio of open water to emergent vegetation, as well as
the percent of wetland vegetation consisting of perennial emergents. Week of survey was recorded to account for differential migration chronology among potential avian communities of burned wetlands. We divided daylight hours into four time intervals (sunrise0800, 0800–1200, 1200–1600, and 1600-sunset), and
wetlands were surveyed during a randomly assigned
time period. We surveyed wetlands by first observing
the wetland from a vantage point and then visiting a
set of pre-established points within the wetland. We
combined point counts (within the wetland) and observations from a vantage point to obtain a better estimate of the total number of birds and species in the
wetland. In some cases, birds were only visible from
670
WETLANDS, Volume 25, No. 3, 2005
the vantage point and visiting the survey points did
not alter our initial counts. However, in more densely
vegetated wetlands, birds were often not visible from
the vantage point and could only be detected from survey points within the wetland. Survey points within
the wetland also increased detectability of secretive
species, such as American bittern (Botaurus lentiginosus) that could not be seen from the vantage point.
To ensure consistent sampling effort, the number of
points visited per wetland varied with wetland area:
one point in wetlands #5 ha; two points in wetlands
5.1–25 ha; three points in 25.1–100 ha wetlands, and
four points in wetlands .100 ha (Naugle et al. 2001).
We visually estimated the total number of wetland
birds within the wetland boundary, recorded all species
present, and estimated number of each species. Any
birds we observed while walking between observation
points within a wetland were included in the overall
count for the wetland. However, if previously counted
birds flew to another part of the wetland, they were
not counted again.
Percent change in species richness and abundance
was calculated for counts recorded prior to and following burning for each burned and associated reference
wetland. Percent change was calculated by subtracting
the abundance or species richness observed post-burn
from the pre-burn abundance or species richness in the
same wetland and dividing by pre-burn abundance or
species richness. We also calculated Sørenson’s similarity index (Krebs 1999) for species occurrence recorded prior to and following burning for each burned
and associated reference wetland. Sørenson’s index
(Ss) was calculated
Ss 5
2a
2a 1 b 1 c
where
a 5 number of species in both pre-burned and postburned wetlands
b 5 number of species in pre-burned wetlands but not
in post-burned wetlands
c 5 number of species in post-burned wetlands but
not in pre-burned wetlands.
Data Analyses
We tested for differences in wetland area between
burned and reference wetlands using a student’s t-test.
We used a simple linear regression to test for relationships between percent of wetland burned and percent
change in abundance and percent change in species
richness. We used an analysis of covariance (ANCOVA) to test prescribed burning effects on avian abundance, species richness, and community similarity.
Week and wetland area were entered as the covariates
to account for migration chronology and the speciesarea relationship (Brown and Dinsmore 1986), respectively. Burned and reference wetlands were paired as
blocks, and the burning treatment was the independent
variable. Dependent variables were percent change of
species richness and abundance and Sørenson’s similarity index. We did not test for between year differences in percent change in abundance, species richness, and Sørenson’s index because of sample-size
limitations.
Data were variable and did not meet ANCOVA assumptions for normality. Therefore, we rank-transformed percent change variables (Zar 1996), and analyses were conducted on transformed variables. All
analyses were conducted using SAS (SAS Institute
1990), with a 5 0.10 to evaluate all hypotheses.
RESULTS
Burned areas in wetlands ranged from 6.5 to 259
ha. Areas of burned and reference wetlands, based on
hydric soils, ranged from 4 to 348 ha. However, actual
wetted areas were much smaller, ranging from 0.5 to
209 ha. Area did not differ between burned (x̄ 5 26.76
ha, SE 5 10.59) and reference (x̄ 5 25.03 ha, SE 5
7.83) wetlands (t19 5 0.13, P 5 0.90). Over 50% of
wetland area was burned in 17 of the 19 burned wetlands (USFWS, unpublished data, Kearney, NE).
There were no relationships between percent of the
wetland burned and percent difference in abundance (r
5 0.10; F1,16 5 0.17, P 5 0.69) or percent difference
in species richness (r 5 0.11; F1,16 5 0.20, P 5 0.66).
We observed 36 bird species in 76 total surveys
from 17 March to 5 May 2002, 18 April to 26 April
2003, and 9 March to 2 April 2004. Mallards were the
most abundant, as well as the most frequently observed species, occurring in 59 of 76 surveys (Table
1). Mallards, northern pintails, and green-winged teal
(Anas crecca) were the most abundant species in
burned and reference wetlands (Table 1). For both
burned and reference wetlands, three species were present during initial surveys that were absent from postburn surveys (Table 1). There were six species present
in burned wetlands post-burn that were not observed
in initial surveys. In reference wetlands, four species
were present in post-burn surveys that were not recorded in initial surveys (Table 1).
Following removal of the influence of week and
wetland area, percent change in relative abundance did
not differ (F1,32 5 2.06, P 5 0.16) between burned and
reference wetlands (Table 2). Following removal of
the influence of week and wetland area, percent change
in richness did not differ (F1,32 , 0.01, P 5 0.95) between burned and reference wetlands (Table 2). Mean
Brennan et al., AVIAN RESPONSE TO BURNING
671
Table 1. Frequency and percent abundance of birds species in 19 burned and 19 reference wetlands for the weeks immediately prior to
(initial) and following (ending) prescribed burning in wetlands in the Rainwater Basin region of south-central Nebraska, springs 20022004.
Reference
Burned
Ending
Initial
Freq
Anser albifrons Greater white-fronted goose (Scopoli)
Chen caerulescens Snow goose (L.)
Branta sp. Canada goose conplex (L.)
Aix sponsa Wood duck (L.)
Anas stepera Gadwall (L.)
Anas americana American wigeon (Gmelin)
Anas platyrhynchos Mallard (L.)
Anas discors Blue-winged teal (L.)
Anas clypeata Northern shoveler (L.)
Anas acuta Northern pintail (L.)
Anas crecca Green-winged teal (L.)
Aythya americana Redhead (Eyton)
Aythya collaris Ring-necked duck (Donovan)
Aythya affinis Lesser scaup (Eyton)
Bucephala albeola Bufflehead (L.)
Lophodytes cucullatus Hooded merganser (L.)
Oxyura jamaicensis Ruddy duck (Gmelin)
Podilymbus podiceps Pied-billed greb (L.)
Podiceps nigricollis Eared grebe (Brehm)
Pelecanus erythrorhynchos American white pelican (Gmelin)
Phalacrocorax auritus Double-crested cormorant (Lesson)
Botaurus lentiginosus American bittern (Rackett)
Ardea herodias Great blue heron (L.)
Fulica americana American coot (Gmelin)
Grus canadensis Sandhill crane (L.)
Pluvialis dominica American golden-plover (Muller)
Charadrius vociferus Killdeer (L.)
Recurviostra americana American avocet (Gmelin)
Tringa melanoleuca Greater yellowlegs (Gmelin)
Tringa flavipes Lesser yellowlegs
Calidris pusilla Semipalmated sandpiper (L.)
Calidris bairdii Baird’s sandpiper (Coues)
Calidris melanotos Pectoral sandpiper (Vieillot)
Limnodromus sp. Dowitcher (Gmelin)
Gallinago delicta Wilson’s snipe (Ord)
Phalaropus tricolor Wilson’s phalarope (Vieillot)
Total species
percent change in abundance and species richness for
burned and reference wetlands represented an overall
increase in abundance and species richness between
initial and ending surveys in the RWB region.
Sørenson’s similarity index did not differ (F1,34 , 0.01,
P 5 0.99) between burned and reference wetlands (Table 2).
DISCUSSION
In contradiction to our hypothesis, we found that
prescribed burning had little short-term effect on rel-
2
5
1
0
5
11
15
8
9
13
13
3
2
1
1
0
0
2
0
2
0
0
1
4
1
0
9
0
3
4
1
3
0
2
2
1
27
%
0.1
0.4
0.0
0.0
0.4
8.8
33.7
1.0
11.3
24.6
17.5
0.3
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.2
0.0
0.0
0.0
0.5
0.0
0.0
0.3
0.0
0.1
0.1
0.1
0.2
0.0
0.1
0.0
0.0
Freq
2
3
1
2
8
9
15
11
8
10
15
1
1
1
1
0
0
0
1
0
1
1
2
6
2
0
12
0
4
5
0
3
1
3
8
1
29
%
1.4
3.4
0.6
0.1
12.9
15.3
10.4
10.9
12.5
4.6
16.8
4.6
0.9
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.2
0.7
0.0
0.7
0.0
0.5
0.3
0.0
0.7
0.4
0.1
0.7
0.0
Ending
Initial
Freq
2
1
1
2
7
12
14
11
12
6
10
3
3
2
2
1
1
2
0
0
0
0
0
5
0
0
8
1
3
3
1
4
0
2
0
2
27
%
0.6
0.4
0.2
0.1
2.3
5.9
18.7
9.1
6.2
37.8
12.5
0.2
0.8
0.1
0.2
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
2.3
0.0
0.0
0.4
0.4
0.6
0.1
0.1
0.3
0.0
0.1
0.0
0.4
Freq
4
3
3
1
6
7
15
12
11
6
12
1
2
2
0
1
1
0
0
0
0
1
0
3
0
1
8
0
2
4
1
4
0
3
1
2
27
%
3.4
10.1
1.2
0.1
5.6
10.8
8.2
10.7
7.3
22.8
11.7
0.0
0.8
0.1
0.0
0.0
0.1
0.0
0.0
0.0
0.0
0.0
0.0
3.3
0.0
0.1
0.4
0.0
0.5
0.3
0.4
1.3
0.0
0.4
0.1
0.4
ative abundance, species richness, or community composition of migratory wetland birds. We chose to examine avian abundance, species richness, and community composition because they are commonly used
measures of wetland quality (Gersib et al. 1990, Gabrey et al 1999, Hanowski et al 1999). However, different measures of habitat quality, such as avian behavior, could also be used to evaluate the effects of
prescribed burning on wetland habitat quality. Although not a strict measure of habitat quality, behavior
is often used to analyze the functional role of wetland
habitats and the benefits they provide (Reinecke 1981).
672
WETLANDS, Volume 25, No. 3, 2005
Table 2. Mean avian abundance, species richness, and Sorenson’s similarity index in burned wetlands (n 5 19) and paired reference
wetlands (n 5 19) prior to (initial) and following (ending) burning during springs 2002-2004 in the Rainwater Basin region of Nebraska.
Reference Wetland
Burned Wetland
Initial
x̄ Abundance
SE
x̄ % Change in Abundance
SE
x̄ Species Richness
SE
x̄ % Change in Species Richness
SE
x̄ Sorenson’s index
SE
1680
806
554.3
545.9
6.6
0.9
48.7
45.7
0.55
0.03
For example, Smith and Kadlec (1985) reported increased herbivory in burned portions of an inland wetland and hypothesized that preferential grazing might
be the result of increased protein and nutritive quality
of wetland plants after burning.
We do not believe that detectability while conducting avian surveys differed between burned and reference wetlands. Given that only dry parts of the wetlands were burned and we conducted avian surveys in
inundated parts of the wetland, we do not believe that
detectability changed appreciably following burning in
those areas of wetlands where birds were counted. In
addition, if detectability varied between burned and
reference wetlands or between pre- and post-burned
wetlands during avian surveys, we would expect to
observe more birds in a wetland post-burn (when visual obstruction was decreased) than pre-burn. This
would provide a positive bias for burning treatments.
However, similarity in the percent change in abundance and species richness in burned wetlands compared to reference wetlands is strong, conservative,
supporting evidence that prescribed burning had little
influence on avian community measures during spring
migration.
The lack of change in avian abundance, species
richness, and community composition in wetlands immediately following prescribed burning could be the
result of being in an ecosystem that has evolved in the
presence of fire (Wright and Bailey 1982). Historically, fires were essential in preventing encroachment of
woody plant species and maintaining the prairie grasslands that surround wetlands in the Great Plains
(Wright and Bailey 1982). However, historical fires
and current management practices differ in the season
of burning. Lightning fires typically occurred from
June to August (Wright and Bailey 1982), whereas
current prescribed burns are conducted from March to
May (Drahota 2004). Spring burns often fail to pro-
Ending
343
178
7.8
0.9
Initial
285
138
525.9
464.9
6.4
1.0
48.9
45.3
0.52
0.09
Ending
294
99
6.5
0.8
duce sufficient heat to alter rhizome efficiency and
shoot viability (Smith and Kadlec 1985, Kostecke et
al. 2004) and, therefore, rarely change long-term vegetation patterns of persistent emergents (Laubhan
1995). Hydrology is the main factor influencing vegetation in wetlands (Smith 1990). Given the results of
our study and the possibility that spring burns will not
permanently change vegetation communities, we believe that prescribed burning alone does not improve
wetland habitat quality for birds during spring migration within the RWB.
Another potential reason that prescribed burning did
not influence avian use in the short term could be that
overall vegetation structure was unaltered in parts of
the wetland typically used by birds (flooded portions
of the wetland). Changes in avian abundance and community composition following prescribed burning are
generally attributed to changes in vegetation structure
(Gabrey et al. 1999, Hanowski et al. 1999, Issach et
al. 2004). During avian surveys, wetland-dependent
birds were typically observed in the water and emergent vegetation in the water or in a narrow vegetation
band surrounding the water, all of which were littleaffected by prescribed burning. Apparently, the changes in the surrounding vegetation also did not alter the
microclimate in the wetland to cause a change in wetland use by birds or that habitat is so limited in the
RWB that birds had little choice but to use the only
available habitat.
Despite the overall similarity in relative abundance
and species richness between burned and reference
wetlands, a few species increased use of burned wetlands following burning. For example, we observed an
increase in frequency and abundance of Wilson’s snipe
(Gallinago delicta) following prescribed burning in
wetlands. Wilson’s snipe and other species typically
observed along the edge of water are most likely to be
influenced by immediate changes in vegetation caused
Brennan et al., AVIAN RESPONSE TO BURNING
by prescribed burning. Future studies of prescribed
burning in wetlands should take into account those
species commonly found in unflooded parts of the wetland and associated upland habitat, as well as those
observed in flooded parts of the wetland.
Snow geese (Chen caerulescens) are attracted to
burned areas and are often found in higher concentrations following burning on the wintering grounds (Gabrey et al. 1999). During our study, burning occurred
after peak snow goose migration. Snow geese occurred
in fewer post-burned wetlands (three) than pre-burned
wetlands (five) but were more abundant in post-burned
wetlands (221 vs. 118 geese per wetland). Given the
millions of snow geese that migrate through central
Nebraska in spring (Gersib et al. 1990), these numbers
represent only a small percentage of that number. If
prescribed burns were conducted earlier during peak
snow goose migration (mid February–mid-March), an
increase in snow geese on burned wetlands could have
conservation implications in the RWB wetlands where
avian cholera (Pasteurella multocida (Lehmann and
Nuemann 1899) Rosenbusch and Merchant 1939) is of
major concern and reduction of this population is an
objective (Johnson 1997). Since 1975, several hundred
thousand waterfowl have died in Nebraska because of
avian cholera (Stutheit 1988). Although little is known
about the factors that influence outbreaks of avian
cholera, Smith and Higgins (1990) found cholera outbreaks to be inversely proportional to semi-permanent
wetland densities in the RWB, suggesting that high
densities of waterfowl on the few remaining semi-permanent wetlands increase the probability of an epizootic outbreak.
MANAGEMENT CONSIDERATIONS
There is little evidence that prescribed burning
meets the objectives of increasing avian species richness or relative abundance during the season of burning. Fire without hydrologic change often has little influence on emergent plant community composition,
and its effects on habitat structure are frequently temporary (Smith 1989). In prairie wetlands, hydrology is
likely the main factor influencing plant community
composition (Smith 1990). The USFWS spends approximately US $15,500 a year on prescribed burning
in RWB wetlands (Drahota 2004). Given the lack of
short-term avian response to prescribed burning and
uncertainty of the effectiveness of prescribed burning
in the long term, management agencies should evaluate effectiveness of prescribed burning over the long
term. Prescribed burning may prove to be an important
tool in other long-term management goals, such as facilitating prescribed grazing and woody plant control,
especially given that it does not seem to have a neg-
673
ative impact on avian use of wetlands during spring
migration. Therefore, we urge wetland managers to
consider incorporating evaluation of prescribed burning, in conjunction with other management practices,
into their long-term management strategies. We also
recommend using funds to restore wetlands to their
original hydrologic regime as a means of improving
vegetation structure and communities for migratory
wetland birds. Understanding the role that prescribed
burning plays in influencing avian abundance, species
richness, and community composition is an essential
component of effective management of wetland birds
during migration.
ACKNOWLEDGMENTS
We thank Tom Koerner and Jeff Drahota of the
RWB Management District (USFWS) for providing
information on prescribed burns. Thanks to Janelle
Jensen and Matthew Gordillo for assisting with avian
surveys. We also thank Craig Davis, Richard Kostecke, and an anonymous reviewer for their thoughtful
reviews and comments that improved this manuscript.
This study was funded by the Rainwater Basin Joint
Venture, the North American Waterfowl Management
Plan through a North American Wetlands Conservation Act Evaluation Grant, the Environmental Protection Agency through a State Wetland Grant, the U.S.
Fish and Wildlife Service, and the Nebraska Game and
Parks Commission. The Nature Conservancy of Nebraska provided partial support of this study through
the Nebraska Chapter’s J. E. Weaver Competitive
Grants Program. L. M. Smith was supported by the
Caesar Kleberg Foundation for Wildlife Conservation.
This is manuscript T-9-1065 of CASNR-TTV.
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