Research Note
Declining Body Condition of Northern Pintails Wintering
in the Playa Lakes Region
JENA A. MOON,1,2 United States Fish and Wildlife Service, Department of Range, Wildlife, and Fisheries Management, Texas Tech University, Lubbock,
TX 79409, USA
DAVID A. HAUKOS, United States Fish and Wildlife Service, Department of Range, Wildlife, and Fisheries Management, Texas Tech University,
Lubbock, TX 79409, USA
LOREN M. SMITH, Wildlife and Fisheries Management Institute, Texas Tech University, Lubbock, TX 79409, USA
ABSTRACT Overwinter body condition (e.g., fat) provides an index to the health of northern pintail (Anas acuta) populations and may be a
factor in the decline of the continental pintail population that has been previously overlooked or understated. We compared body condition
between 1984–1985 and 2002–2003, and found that body condition of pintails arriving during early winter in the Playa Lakes Region (PLR) of
Texas, USA, has declined by an average of 32%. Body fat levels declined at varying levels with juvenile males showing the largest decline of
41%, followed by adult females with 39%, juvenile females with 30%, and adult males with an overall 18% decline. Declines are likely related
to declines in migration and wintering habitat quantity and quality within the PLR and potentially across the Central Flyway. We recommend
further acquisition and management of playas to ensure that these valuable habitats remain available to provide critical habitats for migrating
and wintering pintails and other waterfowl in the Central Flyway. ( JOURNAL OF WILDLIFE MANAGEMENT 71(1):218–221; 2007)
DOI: 10.2193.2005-596
KEY WORDS Anas acuta, body condition, body fat, northern pintail, Playa Lakes Region.
The North American population of northern pintail has
declined since the late 1970s to levels .60% below the goal
of 5.6 million birds established by the North American
Waterfowl Management Plan (U.S. Fish and Wildlife
Service and Canadian Wildlife Service 1998, Miller and
Duncan 1999, U.S. Fish and Wildlife Service 2003). A
number of potentially interrelated factors possibly contribute
to the declining populations including low nest success,
reduced recruitment, poor breeding propensity, disease
(avian cholera [Pasteurella multocida], avian botulism [Clostridium botulinum], lead poisoning), and declining annual
survival (Austin and Miller 1995, Miller and Duncan 1999).
Body condition reflects the amount of lipids or other
endogenous reserves that provide an index to the nutrient
status of a bird or population (Reinecke et al. 1986). Body
condition during migration and winter influences many of
the factors associated with the decline of the pintail
population. Body condition of nonbreeding waterfowl
influences annual survival and future reproductive success
in waterfowl (Heitmeyer and Fredrickson 1981, Whittow
1986, Raveling and Heitmeyer 1989). Specifically, body
condition influences behavior, courtship activities, pair-bond
formation, and habitat use of wintering pintails, thus
affecting the entire life cycle of these birds (Miller 1986,
Smith and Sheeley 1993). Body condition of waterfowl
wintering in the Playa Lakes Region (PLR) of Texas, USA,
is influenced by many factors including habitat conditions,
weather, disturbance, and food availability (Bergan and
Smith 1993, Haukos and Smith 1993, Smith and Sheeley
1993).
The PLR provides important migrating and wintering
1
E-mail: jena_moon@hotmail.com
Present address: Lower Rio Grande National Wildlife Refuge,
Route 2 Box 202A, Alamo, TX 78516, USA
2
218
habitat for several million waterfowl each year (Bellrose
1980, Fedynich et al. 1989). Historically, at least a third of
the pintail population wintering in the Central Flyway used
the PLR, at times numbering over 300,000 birds during
midwinter (Bellrose 1980). However, there has been an
estimated 47% decline in midwinter pintail numbers since
1977 in the PLR (Haukos 2004); this drop is likely due to
declines in the overall continental pintail population and
habitat loss within the PLR (Luo et al. 1997, Moon 2004).
Changing habitat conditions during the past 20 years across
the Central Flyway (e.g., Reynolds et al. 2001, Gleason et al.
2003) could also affect body condition of pintails arriving in
the PLR. Because of the importance of PLR habitats to
midcontinental pintails (Haukos et al. 2006), body condition of birds using these essential wintering and migration
habitats may influence the health of the continental
population of pintails. Further, assessment of the influence
of conservation efforts associated with pintail habitats
requires an investigation of the contemporary body condition levels. We hypothesized that habitat changes since
the mid-1980s in the PLR and Central Flyway have
influenced body condition of the current population of
pintails wintering in the PLR. Our objective was to compare
past (1984–1985) and present (2002–2003) body condition
of pintails arriving and wintering in the PLR to identify
changes in body condition between the reference periods.
STUDY AREA
Our study area encompassed the PLR of northwest Texas,
which included the High Plains (north of the Canadian
River), the Southern High Plains (SHP), and a portion of
the adjacent eastern Rolling Plains ecological region
(Haukos and Smith 1994, Moon 2004). We concentrated
the study in the SHP, which included 130,000 km2 and
contained about 20,000 playa wetlands (Haukos and Smith
The Journal of Wildlife Management
71(1)
Table 1. Average (SE) and associated 90% confidence intervals of grams of fat for after-hatch-year (AHY) and hatch-year (HY) northern pintails captured
on the Southern High Plains of Texas, USA, during 1984–1985 and 2002–2003.
M
F
AHY
Capture date
HY
AHY
x̄
SE
90% CI
n
x̄
SE
90% CI
n
x̄
SE
90% CI
1984
Oct
Nov
112.5
185.7
16.5
14.4
81–143
160–211
8
17
147.7
198.8
22.5
41.2
107–188
123–274
10
9
195.0
195.3
44.0
64.0
113–276
59–331
1985
Oct
Nov
Pooled 1984–1985
223.6
235.7
205.2
12.7
17.4
7.9
202–245
206–265
192–218
22
22
69
210.2
179.9
30.4
19.7
149–271
147–212
5
24
199.4
238.4
212.9
33.6
14.4
17.4
2002
Oct
Nov
174.1
198.2
5.4
12.5
165–183
176–219
153
20
105.2
178.2
8.2
26.4
91–119
131–224
75
14
120.11
170.3
2003
Oct
Nov
Pooled 2002–2003
168.8
149.7
169.3
6.2
8.9
3.6
158–179
135–164
163–175
103
64
340
109.5
74.4
106.2
11.3
7.3
5.6
91–128
62–87
97–115
70
37
196
126.4
139.5
130.4
1994). The SHP had a dry steppe climate with mild winters
(Blackstock 1979), an average growing season of 180–220
days (Gould 1975), and an average annual precipitation of
47–53 cm, depending on region (National Climatic Data
Center 2004). Most precipitation occurred as rainfall, with
54–72% occurring during intense, localized thunderstorms
from May to September (Bolen et al. 1989). Elevations in
the SHP range between 1,000 m and 1,200 m (Haukos and
Smith 1994), with nearly level to gently undulating
topography interrupted by numerous enclosed depressions
lined by a vertisol clay that held playa wetlands (Blackstock
1979).
METHODS
We determined body condition (g lipids) of after-hatch-year
(AHY) and hatch-year (HY) pintails in the PLR during
October and November, which represented pintails that
either had just arrived or had been in the region for a short
period. During 1984 and 1985, we shot pintails on playa
basins (Smith and Sheeley 1993); during fall 2002 and 2003
we captured pintails using baited swim-in traps and rocket
nets (corn and hen scratch). Landowners did not allow
hunting during periods of capture.
We aged (HY and AHY) and sexed collected or captured
birds based on plumage characteristics (Duncan 1985,
Carney 1992). We measured wing chord (mm) and body
mass of each bird. We released birds at their capture site
after we determined age and sex and took structural
measurements. We estimated body fat, as an index to body
condition, based on equations derived by Smith et al. (1992)
using wing chord and body mass values. These equations
accurately estimate body fat of pintails in the PLR, with R2
values of 0.73, 0.69, 0.72, and 0.75 for adult males, adult
females, juvenile males, and juvenile females, respectively.
For each year (1984, 1985, 2002, 2003), month (Oct, Nov),
Moon et al.
Declining Body Condition of Pintails in Texas
HY
x̄
SE
90% CI
8
4
149.5
112.5
29.5
19.4
94–204
71–153
8
4
132–267
213–264
184–241
5
11
28
165.5
246.5
154.4
25.0
23.1
17.0
93–238
179–314
126–182
2
2
16
4.4
8.6
113–127
155–185
69
18
88.9
171.3
5.7
9.3
79–98
155–187
50
27
7.3
9.2
3.7
114–138
124–155
124–136
77
32
196
94.9
99.7
108.5
8.9
11.4
4.1
79–109
79–119
102–115
40
19
136
n
n
and age and sex class, we present the average estimated
grams of body fat as well as associated standard error and
90% confidence intervals. We pooled years (1984–1985 and
2002–2003) for each respective study period because of
small samples sizes in the first reference period and we were
interested in the average overall decline in body condition
between the 2 reference periods. We calculated an average
percentage change in body fat levels from 1984–1985 to
2002–2003 and used a t-test to compare average lipid levels
for each age and sex class between the reference periods. We
set a ¼ 0.05 and used a Bonferroni adjustment to account for
multiple comparisons; final a ¼ 0.0125 (Scheiner and
Gurvitch 1993).
RESULTS
We estimated body lipids for 137 and 868 pintails for the
reference periods of 1984–1985 and 2002–2003, respectively. Body lipids of AHY males declined by 18% from
1984–1985 to 2002–2003 (t407 ¼ 4.11, P , 0.001).
Although we did not collect HY males in 1985, we did
document an overall decline in pooled body condition (1984
vs. 2002–2003) of 41% for HY male body fat (t218 ¼ 4.25, P
, 0.001). For AHY females, body lipids declined by 39%
(t202 ¼ 7.05, P , 0.001) from 1984–1985 to 2002–2003.
Despite the relatively low sample size of HY females (16)
when compared with other age and sex classes during 1984–
1985, we found a 30% decline between the reference
periods (t150 ¼ 3.48, P , 0.001; Table 1).
DISCUSSION
Body condition in ducks is influenced by numerous
environmental and anthropogenic factors (e.g., habitat
conditions, available forage, precipitation, disturbance, and
weather) associated with the wintering period, making it a
highly variable measure (Miller 1986, Smith and Sheeley
219
1993). Pintail body condition in the PLR is principally
related to amount of natural foods in playas (Haukos and
Smith 1993, Smith and Sheeley 1993). The trend of lipid
gains from October to November during both reference
periods (exception of M during 2003 and F during 1984)
demonstrates the importance of available natural foods in
playas for pintails upon arrival in the PLR.
However, body condition of pintails wintering in the PLR
has declined considerably since the mid-1980s. This decline
possibly reflects relatively poorer habitat quality across the
Central Flyway (e.g., drought, cropland conversion [i.e.,
decrease in cereal grains], and grassland conversion) during
fall migration, which may be causing pintails to arrive in the
PLR in poorer condition than 20 years ago (Reynolds et al.
2001, Gleason et al. 2003). These declining body condition
estimates also may indicate that birds are over-flying
traditional stopover areas, experiencing increased levels of
disturbance, or may be migrating from nontraditional
breeding areas. Indeed, before 1975, nesting pintails were
documented to settle at an average of 53836 0 N latitude;
however, since 1985, pintails have increased distances
traveled to settle at an average of 568N latitude (Runge
and Boomer 2005). This increase in overall distance traveled
may have a negative effect on pintail body condition and
consequently may decrease potential reproductive effort.
Although our collection method differed between reference periods, methods likely did not have an impact on our
results. Weatherhead and Ankney (1984) speculated a
sample collected with bait traps would likely result in a
biased sample of birds in lower body condition. However,
tests for a condition bias related to the use of bait traps
either have found no relationship (Reinecke et al. 1988) or
were inconclusive (Dufour et al. 1993a). Weatherhead and
Ankney (1984) also predicted that shooting birds over
decoys would also result in a negative condition bias due to
exploitation of a feeding response, and several studies have
demonstrated that condition was biased low for birds
collected over decoys (Hepp et al. 1986, Reinecke et al.
1988, Dufour et al. 1993b). However, we did not use decoys
to collect birds during 1984–1985 but rather shot birds
flushed from playas. Therefore, we feel confident that
neither sampling effort biased the estimated fat levels of our
sample.
Disparate habitat conditions based on availability of
wetlands between reference periods could have had an effect
on our results. Body condition has been tied to habitat
conditions for wintering pintail populations in the PLR and
California (Miller 1986, Smith and Sheeley 1993). Both
reference periods had a relatively wet year (average habitat:
1985, 2002) and dry year (below-average habitat: 1984,
2003); therefore, we do not feel that body condition
estimates between the 2 reference periods were skewed
based on wetland availability. Data on pintail arrival time in
the PLR respective to capture period were unavailable for
the first reference period, which also may have had an
impact on body condition levels, but should have been
220
similar between periods given pintail migration patterns
(Bellrose 1980).
Similar to pintails, the continental population of lesser
scaup (Aythya affinis) is experiencing an overall decline
(Anteau and Afton 2004). The Spring Condition Hypothesis states that female scaup are arriving on their breeding
grounds in poorer body condition than historically (Afton
and Anderson 2001). Declines in spring lipid reserves for
scaup have been documented to negatively impact reproduction, because hens in poorer body condition are less
likely to breed and have fewer resources to dedicate to
reproduction (Anteau and Afton 2004). However, recent
research has found that fall and winter scaup body mass
tended to be similar or greater than estimates from the
1980s, indicating that fall migration and winter habitats
remain adequate for scaup in the Mississippi Flyway (Vest
2002). The continental pintail population may be experiencing similar trends in body condition. Therefore, we
recommend additional monitoring of body condition levels
of pintails arriving on breeding grounds to assess impacts on
breeding pintails and ultimately, recruitment of young into
the continental population.
MANAGEMENT IMPLICATIONS
Despite acknowledgement of the value of playas to waterfowl through the creation of the Playa Lakes Joint Venture
by the North American Waterfowl Management Plan (U.S.
Fish and Wildlife Service and Canadian Wildlife Service
1998), past management recommendations to improve
wintering habitats for pintails and other waterfowl have
not been implemented across the region. Continued lack of
wetland management and conservation in the SHP, where
the majority of playas occur (Haukos and Smith 2003,
Smith 2003), will continue to have negative impacts to body
condition of pintails. Acquisition and perpetual protection
of playas as suggested by Haukos and Smith (2003) will
ensure availability of high quality wetland habitats for
pintails and other waterfowl wintering in the PLR. If
pintails show decreased body condition across their life
cycle, females arriving on breeding areas in poorer condition
may be less likely to breed, have smaller clutch sizes, and
reduced recruitment rates, which would result in smaller fall
flights. Therefore, further investigation of pintail body
condition and causes for the decline in the PLR is
warranted, in addition to examination of body condition
in other major pintail wintering areas.
ACKNOWLEDGMENTS
We thank Texas Tech University, U.S. Fish and Wildlife
Service Region 2 Migratory Bird Office, Northern Prairie
Wildlife Research Center, and the Playa Lakes Joint
Venture for providing funding. We are grateful to R. Cox,
W. Johnson, B. Davis, L. Gustafson, D. Casida, J. Smith, J.
Bredy, P. Thorpe, and F. Roetker for providing field
assistance during this study. L. Nymeyer provided field
technicians, vehicles, and access to trapping sites. We are
appreciative of G. Filnor, J. Heath, J. Jones, B. Jones, M.
The Journal of Wildlife Management
71(1)
Been, M. Montene, C. Sargent, A. McNeil, and J. Stevens
for providing access to private lands for trapping efforts. We
thank D. Sheeley for collecting and measuring birds during
1984–1985. We also thank R. Cox, J. Fleskes, and 2
anonymous reviewers for thorough reviews of previous
drafts. This is paper T-9-1088 of the College of
Agricultural Sciences and Natural Resources, Texas Tech
University.
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