Common Eider and large gull and nesting associations in coastal Labrador

Abstract

Apparent nesting associations between avian egg predators and their prey has received much interest, with gulls and waterfowl receiving considerable attention. We examined the co-occurrence of breeding large gulls (Herring Gull (Larus argentatus Pontoppidan, 1763) and Great Black-backed Gull (L. marinus L., 1758) and Common Eiders (Somateria mollissima L., 1758) along the coast of Labrador from 1998-2003. Nest counts for large gulls and eiders were undertaken by ground crews on 45-109 islands each year, counting 79-283 and 721-3424 nests annually, respectively. Gulls were more likely to nest on an island with nesting eiders (69.4%) than without nesting eiders (38.4%), and the probability and numbers of gulls nesting on an island increased as eider colony size increased. Large gulls were 1.76 times more likely to occupy islands that had nesting eiders in the previous year, while eiders were equally likely to colonize islands that did or did not have nesting gulls in the previous year. Eiders were no more likely to abandon islands that had nesting gulls in the previous year. In sub-arctic coastal landscapes, large gulls appear to preferentially nest in association with nesting eiders, while eiders appear not to avoid nesting islands based on the previous presence of large gulls.