Habitat use and reproductive success of Pacific eiders Somateria mollissima v-nigra during a period of industrial activity

Abstract

This study documents the effect of industrial activities on nesting Pacific eiders on Thetis and Spy islands in the central Alaskan Beaufort Sea during 1983. Eider nests were more numerous on Thetis and Spy island in 1983 (112 and 30 nests for the two islands, respectively) than had been recorded in any previous year. Censuses of other important eider nesting islands along the central Alaskan Beaufort coast suggested that the increase was widespread. Nesting eiders showed a stronger affinity for high-density driftwood nesting habitat, than for medium-or low-density habitats. The density of driftwood at the nest site (within 0·5 m) was a better indicator of habitat preference than was density of drittwood in island segments. Industrial activities and associated disturbance on Thetis Island during 1983 did not have the expected extreme negative effects on the number of eiders nesting in the area. The success of eider nests on Thetis Island was remarkably high compared with almost all other investigations of this species. The mitigation programme which precluded most low-level aircraft overflights and other human intrusions, probably was at least partly responsible for this high success.