Evaluating the waterfowl breeding population and habitat survey for scaup

Abstract

Potential bias in breeding population estimates of certain duck species from the Waterfowl Breeding Population and Habitat Survey (WBPHS) has been a concern for decades. The WBPHS does not differentiate between lesser (Aythya affinis) and greater (A. marila) scaup, but lesser scaup comprise 89% of the combined scaup population and their population estimates are suspected to be biased. We marked female lesser scaup (i.e., marked scaup) in the Mississippi and Atlantic Flyways, Canada and United States, with implantable satellite transmitters to track their spring migration through the traditional and eastern survey areas of the WBPHS, 2005–2010. Our goal was to use data independent of the WBPHS to evaluate whether breeding population estimates for scaup were biased and identify variables that might be used in the future to refine population estimates. We found that the WBPHS estimates of breeding scaup are biased because, across years, only 30% of our marked scaup had settled for the breeding period when the strata in which they settled were surveyed, 43% were available to be counted in multiple survey strata as their migration continued during the WBPHS, 32% settled outside the WBPHS area, the number of times a marked scaup was available to be counted by survey crews varied positively with the latitude that a marked scaup settled on breeding areas, the probability of a marked scaup being in a stratum while it was surveyed varied among years, and these probabilities were positively correlated with the traditional and eastern breeding population estimates for scaup. Annual population estimates derived from banding data provide a less biased and preferable method of monitoring scaup population status and trend. Development of models that include metrics such as survey stratum latitude and annual spring environmental conditions might potentially be used to improve scaup breeding population estimates derived from the WBPHS, but independent estimates from banding data would be important to evaluate such models. © 2018 The Wildlife Society.

Monitoring boreal avian populations: how can we estimate trends and trajectories from noisy data?

“…and scoters (Melanitta spp. ); the survey is timed with the nesting phenology of early migrants, such as the Mallard (Anas platyrhynchos), and the timing of the WBPHS has been questioned for late-nesting species such as sea ducks (Naugle et al 2000, Boyd et al 2015, Schummer et al 2018. The visual correction factors that account for observations missed during the surveys have not been updated in the boreal forest since the early 1990s (Smith 1995).…”

Band Wear and Effects on Recovery and Survival Estimates of Diving Ducks

“…Alternatively, there is a more restrictive bag limit for redhead ( A. americana ) than other duck species in most years, but there is not a species‐specific harvest management strategy. Diving ducks may not be appropriately represented by the May Breeding Habitat and Population Survey (Smith 1995, Finger et al 2016, Schummer et al 2018). Inferences about their population dynamics might be improved by using integrated population models that use multiple data streams, including banding data (Péron et al 2012, Arnold et al 2018).…”

“…Lesser scaup ( Aythya affinis ) have had their own harvest management strategy since 2008 (Boomer and Johnson 2007). Management of scaup has been hotly debated during the past 2 decades, and difficulties in understanding lesser scaup population dynamics has pointed to a need for better banding data and population estimates (Arnold et al 2016, 2017; Lindberg et al 2017; Schummer et al 2018). Alternatively, there is a more restrictive bag limit for redhead ( A. americana ) than other duck species in most years, but there is not a species‐specific harvest management strategy.…”

A Demographic model for ring‐necked ducks breeding in Minnesota

“…Fish and Wildlife Service [USFWS] ), which indicates an increasing population trend in the traditional survey area (N. L. Zimpfer, USFWS, unpublished data) and a stable trend in the eastern survey area, neither of which include Minnesota. The May Waterfowl Survey, however, is poorly timed for the late‐nesting ring‐necked duck and other diving ducks (Smith , Naugle et al , Schummer et al ), instead being timed for mallards and other early‐nesting ducks. Diving ducks that are still migrating when the survey is conducted may be counted more than once, and the extent of possible double‐counting may vary among years with weather and water conditions (Naugle et al , Schummer et al ).…”

“…The May Waterfowl Survey, however, is poorly timed for the late‐nesting ring‐necked duck and other diving ducks (Smith , Naugle et al , Schummer et al ), instead being timed for mallards and other early‐nesting ducks. Diving ducks that are still migrating when the survey is conducted may be counted more than once, and the extent of possible double‐counting may vary among years with weather and water conditions (Naugle et al , Schummer et al ). Thus, this index of abundance for late‐nesting diving ducks may be inflated in southern portions of the Prairie Pothole Region (Naugle et al ).…”