Survival and nesting success of the Pacific Eider (Somateria mollissima v-nigrum) near Bathurst Inlet, Nunavut

We used resighting data from 242 individually marked females to estimate apparent survival of Pacific Eiders ( Somateria mollissima v-nigrum Bonaparte, 1855) at a nesting colony in central arctic Canada from 2001 to 2007. In addition, we used data from nest searches conducted on islands at a freshwater lake and an adjacent marine environment to estimate annual breeding success. Annual survival rate estimates ranged from 0.84 ± 0.04 (mean ± SE) to 0.86 ± 0.05. Mayfield estimates of nest success ranged from 48.8% to 68.1% at the freshwater colony, and from 13.9% to 43.5% at the marine nesting colonies. The overwhelming cause of nest failure at both nesting areas was predation by grizzly bear ( Ursus arctos horribilis Ord, 1815), arctic fox ( Vulpes lagopus (L., 1758)), and wolverine ( Gulo gulo (L., 1758)). The majority of nests were initiated prior to ocean ice breakup in mid-July, thus mammalian predators had access to the islands well into incubation. Our results suggest that during the period from 2001 to 2007, the population of Pacific Eiders was likely not in decline. Therefore, the marked decline observed for eiders migrating past Point Barrow, Alaska, from 1976 to 1996 was more likely attributable to a stochastic event, such as unfavourable ice conditions, than to a chronic factor.