The continental population of scaup (Aythya affinis and A. marila) reached an all time low in 2006, 37% below the 1955-2005 long-term average (U.S. Fish and Wildlife Service 2006), and > 3 million birds below the North American Waterfowl Management Plan (NAWMP) goal of 6.3 million scaup. Two reviews of long-term databases have provided important insights into the continental decline of scaup (Allen et al. 1999, Afton and Anderson 2001). Both reviews noted a decrease in the sex and age ratios (number of females relative to males and number of immatures relative to adults, respectively) of lesser scaup in the U.S. harvest (Allen et al. 1999, Afton and Anderson 2001). These results indicate that recruitment and female survival of lesser scaup have declined during this period. One potential explanation for the observed patterns in continental lesser scaup population is the spring condition hypothesis (Anteau and Afton 2004). This hypothesis suggests that declines in the quantity and quality of winter and spring habitats have resulted in females arriving on breeding areas in poorer body condition than historically, resulting in reduced reproductive success and breeding-season female survival (Anteau and Afton 2004).

Project Details

Scaup use lipid reserves for clutch formation, but rely less on these reserves for incubation than similar-sized waterfowl (Afton and Ankney 1991, Esler et al. 2001). However, because scaup spend long periods at breeding areas prior to laying (Afton 1984), it is unknown if reserves are acquired by females prior to, or while on, breeding areas. If scaup females are arriving on breeding grounds in poorer body condition than historically, they may need to spend more time on the breeding grounds acquiring the reserves necessary to fuel breeding activities. Therefore, reduced spring condition could result in later nest initiation, leading to declines in recruitment (Dawson and Clark 2000). Moreover, if females are unable to overcome nutrient reserve deficits after arrival on the breeding grounds, they may lay fewer eggs or not breed at all.

Literature Cited:

Afton, A..D. 1984. Influence of age and time on reproductive performance of female lesser scaup. Auk 101: 255-265. Afton, A. D., and M. G. Anderson. 2001. Declining scaup populations: a retrospective analysis of long-term population and harvest survey data. Journal of Wildlife Management 65:781-796.

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

Allen, G. T., D. F. Caithamer, and M. Otto. 1999. A review of the status of greater and lesser scaup in North America. U.S. Fish and Wildlife Service, Office of Migratory Bird Management, Arlington, Virginia, USA.

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. Auk 121:917-929.

Esler, D., J. B. Grand, and A. D. Afton. 2001. Intraspecific variation in nutrient reserve use during clutch formation by lesser scaup. Condor 103:810-820.

U.S. Fish and Wildlife Service. 2006. Waterfowl population status, 2006. U.S. Department of the Interior, Washington, D.C., USA

Objectives

We are investigating the link between winter and spring habitat conditions and reproductive success of lesser scaup nesting at Red Rock Lakes National Wildlife Refuge in the Centennial Valley of southwest Montana. Our overall objectives are to identify the relative contribution of resources obtained at wintering and spring staging areas to female condition, reproductive timing, and clutch formation, as well as to determine if female condition on arrival to the breeding area influences reproductive outcome. To help identify major wintering and spring migration stopover areas, we are using satellite telemetry. We marked 9 lesser scaup at the Red Rock Lakes in August 2009 with implant satellite platform terminal transmitters (PTTs) and will track them for approximately one year.

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