Factors affecting nest-site selection of Sabine’s Gulls in the eastern Canadian Arctic

Abstract: The selection of breeding habitat is of prime importance for individual fitness. Among birds, natural selec-tion should favour the ability to recognize and select habitat suitable for nesting and rearing chicks. This study com-pares the characteristics of Sabine’s Gull, Xema sabini (Sabine, 1819), nest sites with random points across a coastal tundra environment on Southampton Island, Nunavut, Canada. The availability of terrestrial invertebrate prey was also examined among habitats. Sabine’s Gull nests were nonrandomly distributed in relation to vegetation, substrate, and proximity to water. Gulls nested within approximately 1 km of the coastline and selected sites with the greatest propor-tions of moss and standing water (i.e., they nested close to the edge of small freshwater ponds near shore). However, there were no detectable differences in characteristics between successful and unsuccessful nests within preferred habi-tat. The dynamics of terrestrial invertebrate prey communities varied between years, but the volume of invertebrates in Sabine’s Gull nesting habitat was intermediate between the most productive habitats and the least productive habitats in both years. However, nest-site selection in Sabine’s Gulls may also be influenced by the availability of aquatic inverte-brates (not examined in this study) and their proximity to the marine coastline, where chicks are taken to be reared. Résumé: La sélection de l’habitat de reproduction est d’importance primordiale pour la fitness individuelle. Chez les oiseaux, la sélection naturelle devrait favoriser la capacité à reconnaître et à choisir un habitat adéquat pour la nidifica-tion et l’élevage des poussins. Notre étude compare les caractéristiques des sites de nidification de la mouette de Sa