Population Dynamics Of Spectacled Eiders On The Yukon- Kuskokwim Delta, Alaska

Author(s): 
Grand, J. Barry
Flint, Paul L.
Rockwell, Robert F.
Petersen, Margaret R.
Moran, Tina L.
U.S. Fish and Wildlife Service
U.S. Geological Survey

Spectacled Eider (Somateria fischeri) populations in western Alaska have declined precipitously since the late 1970's. Subsequently, the species was listed as threatened in 1993. To investigate the potential causes of the decline, we developed a deterministic model of Spectacled Eider population dynamics based on demographic data we collected on the Yukon-Kuskokwim Delta, Alaska, from 1991-1996. The model incorporated estimates of nest success, clutch size at hatch, duckling survival, age of first reproduction, and adult female survival collected at a two locations. We assumed that survival of immature females during their first year was 85% of adult female survival, because immature survival was unknown. In the sensitivity analysis, adult female survival was the most important parameter affecting the rate of population growth. We demonstrated the requirements for nest success, duckling survival, and adult female survival to achieve a stable population. We compared the expected rates of population growth at the two sites, demonstrate the potential importance of lead poisoning to population recovery, and identified research needs to improve the population model.

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