Population and reproductive ecology of ducks in western Alaska. Waterfowl populations breeding on the Yukon-Kuskokwim Delta (YKD) have undergone dramatic fluctuations in population size over the last 20 years. While goose populations have stabilized or are increasing, many populations of ducks are still declining. Of particular interest are spectacled eiders (Somateria fischeri) which have declined to the point of being listed as Threatened under the Endangered Species Act. Additionally, common eiders (Somateria mollisima) and oldsquaw ducks (Clangula hyemalis) are listed as species of special concern by Region 7 of the U. S. Fish and Wildlife Service because of their continued downward trend in numbers. Little is known about the breeding biology, annual survival, or wintering ecology of ducks breeding on the Yukon-Kuskokwim Delta. We consider the main components of basic population models to be survival and productivity. We split productivity into two main areas: nesting productivity and juvenile survival until fledging. Our primary goal in this study is to produce reliable estimates of annual survival, nesting productivity, and juvenile survival. Further, we are examining factors influencing variation in these parameters. These estimates are critical for understanding population trends and defining management options.