Migration of King and Common Eiders Past Point Barrow, Alaska, During Summer/Fall 2002 through Spring 2004: Population Trends and Effects of Wind

摘要

We surveyed King (Somateria spectabilis) and Common Eiders (S. mollissima v-nigra) at Point Barrow, Alaska, during the summer/fall migrations of 2002 and 2003 and during the spring migrations of 2003 and 2004. King Eiders comprised approximately 85% of the identified eiders during all migrations and Common Eiders comprised most of the rest; only 86 Spectacled (S. fischeri) and 20 Steller's Eiders (Polysticta stelleri) were identified. In spring, King Eiders migrated past Point Barrow before Common Eiders. During summer/fall migrations, most male and many female King Eiders had migrated out of the Beaufort Sea by early September before they molted, whereas most of the Common Eiders molted flight feathers before they migrated out of the Beaufort Sea in September and October. We suggest that future surveys should investigate combining visual and radar methods for assessing population size of eiders passing Point Barrow. Preliminary analyses of passage rates and wind conditions indicate that King and Common Eiders may respond to wind slightly differently.