Trends in Duck Breeding Populations 1955–2012

Author(s): 
Zimpfer, Nathan L.
Rhodes, Walter E.
Silverman, Emily D.
Zimmerman, Guthrie S.
Richkus, Ken D.
U.S. Fish and Wildlife Service
Publication Date: 
2012

This report summarizes information about the status of duck populations and wetland habitats during spring 2012, focusing on areas encompassed by the U.S. Fish & Wildlife (USFWS) and Canadian Wildlife Services’ (CWS) Waterfowl Breeding Population and Habitat Survey. We do not include information from surveys conducted by state or provincial agencies. In the traditional survey area, which includes strata 1–18, 20–50, and 75–77 (Figure 1), the total duck population estimate (excluding scoters [Melanitta spp.], eiders [Somateria spp. and Polysticta stelleri ], long- tailed ducks [Clangula hyemalis ], mergansers [Mergus spp. and Lophodytes cucullatus ], and wood ducks [Aix sponsa ]) was 48.6 ± 0.8 [SE] million birds (Figure 3, Appendix A). This represents a 7% increase over last year’s estimate of 45.6 ± 0.8 million, and is 43% higher than the long-term averagea (1955–2011; Table 1). Estimated mallard (Anas platyrhynchos ) abundance was 10.6 ± 0.3 million, which was 15% above the 2011 estimate of 9.2 ± 0.3 million, and 40% above the long-term average of 7.6 ± 0.04 million (Table 2). Estimated abundance of gadwall (A. strepera ; 3.6 ± 0.2 million) was similar to the 2011 estimate and 96% above the long-term average (1.8 ± 0.02 million; Table 3). The estimate for American wigeon (A. americana ; 2.1 ± 0.1 million) was similar to the 2011 estimate and 17% below the long-term average of 2.6 ± 0.02 million (Table 4). The estimated abundance of green-winged teal (A. crecca ) was 3.5 ± 0.2 million, which was 20% above the 2011 estimate and 74% above the long-term average (2.0 ± 0.02 million; Table 5). The estimates of blue-winged teal (A. discors ; 9.2 ± 0.4 million) and northern shoveler (A. clypeata ; 5.0 ± 0.3 million) were similar to their 2011 estimates and 94% and 111% above the long-term averages of 4.8 ± 0.04 million (Table 6) and 2.4 ± 0.02 million (Table 7), respectively. The estimate for northern pintails (A. acuta ; 3.5 ± 0.2 million) was 22% below the 2011 estimate of 4.4 ± 0.3 million and 14% below the long-term average of 4.0 ± 0.04 million (Table 8). The estimated abundance for redheads (Aythya americana ; 1.3 ± 0.1 million) and canvasbacks (Aythya valisineria ; 0.8 ± 0.07 million) were similar to their 2011 estimates and were 89% and 33% above their long- term averages of 0.7 ± 0.01 million (Table 9) and 0.6 ± 0.01 million (Table 10), respectively. Estimated abundance of scaup (A. affinis and A. marila combined; 5.2 ± 0.3 million) was 21% above the 2011 estimate and similar to the long-term average of 5.0 ± 0.05 million (Table 11). Habitat conditions during the 2012 Waterfowl Breeding Population and Habitat Survey were characterized by average to below-average moisture, a mild winter, and an early spring across the southern portion of the traditional and eastern survey areas. Northern habitats of the traditional and eastern surveys areas generally received average moisture and temperatures. The total pond estimate (Prairie Canada and U.S. combined) was 5.5 ± 0.2 million (Table 12, Figure 2). This was 32% below the 2011 estimate of 8.1 ± 0.2 million ponds, and 9% above the long-term average of 5.1 ± 0.03 million ponds. Conditions across the Canadian prairies declined relative to 2011 (Figure 4). Residual moisture from prior years benefitted more permanent wetlands of the coteau in Saskatchewan and near the Saskatchewan and Manitoba border, but temporary wetlands retained little moisture owing to a shallow frost seal and below-average precipitation. The 2012 estimate of ponds in Prairie Canada was 3.9 ± 0.1 million. This was 21% below last year’s estimate (4.9 ± 0.2 million) and 13% above the 1961–2011 average (3.4 ± 0.03 million). Much of the parkland was classified as good; however, habitat conditions declined westward toward Alberta. Following the completion of the survey, the Canadian prairies received above-average precipitation, which may improve habitat conditions for late-nesting waterfowl, re-nesting attempts and brood rearing. Significant declines in wetland numbers and conditions occurred in the U.S. prairies during 2012. The 2012 pond estimate for the north-central U.S. was 1.7 ± 0.1 million, which was 49% below last year’s estimate (3.2 ± 0.1 million) and similar to the 1974–2011 average. Nearly all of the north-central U.S. was rated as good to excellent in 2011; however, only the coteau of North and South Dakota was rated as good in 2012, and no areas were rated as excellent this year. Drastic wetland declines in western South Dakota and Montana resulted in mostly poor to fair habitat conditions. In the bush regions of the traditional survey area (Alaska, Yukon, Northwest Territories, north- ern Alberta, northern Manitoba, northern Saskatchewan, and western Ontario), spring breakup was slightly early in 2012. Average to above-average annual precipitation over much of the bush and ice-free habitats benefited arriving waterfowl. Drier conditions were observed in northern Alberta and Saskatchewan and habitat was classified as fair. A similar trend was noted in western Ontario where habitat conditions declined from excellent in 2011 to good in 2012. Most of the eastern survey area had mild winter temperatures with below-average precipitation, although northern survey areas in Labrador, Newfoundland and eastern Quebec experienced more normal conditions, with some areas receiving heavy snowfall. While habitat quality declined overall relative to 2011, good conditions persisted over the majority of the eastern survey area. Exceptions were northwestern Quebec, northern Maine, and New Brunswick, where, despite an early spring, inadequate precipitation caused wetland conditions to deteriorate. In 2005, the USFWS and CWS began to integrate data from two previously independent water- fowl surveys conducted in eastern North America into a single composite estimate using hierarchical models. Consequently, total indicated bird definitions for American black ducks (Anas rubripes ) were modified to provide a common index across surveys, and adjustments were made to the ge- ographic stratification of the eastern survey area. Additional refinements to analytical methods are incorporated in the estimates presented in this report. For these reasons, population estimates presented in this report for the eastern survey area (strata 51–72; Table 13) are not directly compa- rable with estimates presented in reports issued prior to 2006. Specifically, estimates are presented for only a portion of the eastern survey area and include data from strata 51, 52, 63, 64, 66–68, and 70–72. These 10 strata were chosen for presentation because at least one survey (i.e., either the CWS or USFWS survey) was conducted for each of these strata for the full period of record of the eastern survey (1990–2012). In cases where the USFWS has traditionally not recorded obser- vations to the species level, composite estimates are provided only for multiple-species groupings (i.e., mergansers and goldeneyes [Bucephala clangula and B. islandica ]). The CWS and USFWS agreed to use a hierarchical modeling approach for all species in the east. Currently, the models perform well for the six most common species. In previous years, we used design-based estimates and an overall mean across the two surveys, weighted by their precision, to derive integrated annual population indices for the less common American wigeon, scaup, bufflehead, and scoters until the hierarchical models could adequately analyze the data for these species. These estimates have been discontinued because of concerns about (1) the appropriateness of weighting estimates from these surveys by precision, and (2) whether estimates for some species should be integrated given the data quality and coverage in the eastern survey. Nonetheless, the USFWS will continue to explore methods for deriving integrated estimates for some of the less common species in the eastern sur- vey area. Analytical methods applied to eastern survey area data and results will be presented in greater detail in the 2012 Waterfowl Status Report. Estimated abundance of American black ducks in the eastern survey area was 0.6 ± 0.04 million, which was 11% higher than the 2011 estimate and similar to the long-term average. The 2012 es- timate for mallards was 0.4 ± 0.1 million, which was similar to the 2011 estimate and long-term average. Abundance estimates for goldeneyes, green-winged teal, ring-necked ducks, and mer- gansers were similar to last year’s estimates and their 1990–2011 averages (Table 13, Figure 6, Appendix B).

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