Birds of Mansel Island, northern Hudson Bay

A recent review of bird distributions in Nunavut demonstrated that Mansel Island, in northeastern Hudson Bay, is one of the least known areas in the territory. Here, current information on the birds of Mansel Island is summarized. A list published in 1932 included 24 species. Subsequent visits by ornithologists since 1980 have added a further 17 species to the island’s avifauna. The list includes 17 species for which breeding has been confirmed and 10 for which breeding is considered probable. The island seems to support particularly large populations of King Eiders (Somateria spectabilis) and Tundra Swans (Cygnus columbianus) and the most southerly breeding population of Sabine’s Gull (Xema sabini) and Red Knot (Calidiris canuta; probably).

Correlating tropical climate with survival of an Arctic-breeding, trans-equatorial migrant seabird

Extreme climate can negatively affect survival through increased physiological demands or by reducing prey availability. This can have significant population-level consequences for organisms with low reproductive rates, such as seabirds. As an Arctic-breeding trans-equatorial migrant, Sabine’s gull (Xema sabini) is exposed to a profound variety of climate regimes during the year. Therefore, its annual survival may be affected by broad-scale teleconnection patterns that influence regional climate variability. We used Program MARK to estimate apparent survival and resighting probabilities from 2007 to 2013 for adult Sabine’s gulls breeding at a High Arctic colony. We then combined capture–mark–recapture data for the High Arctic colony with those previously published from a Low Arctic colony (1998–2002) to examine influences of climate variability on survival. Mean ± standard error apparent survival estimated for the High Arctic colony was 0.90 ± 0.03, similar to that previously reported for the Low Arctic colony. We found a negative relationship between survival and the Tropical/Northern Hemisphere pattern, an atmospheric mode that is associated with the Pacific jet stream. Our study suggests that although Sabine’s gull survival was generally high and relatively constant over time, adult mortality may increase during years of extreme climate events in regions far beyond their Arctic breeding grounds.

Diet dichotomy between two migrant seabirds breeding near a high Arctic polynya

High Arctic polynyas are predictable areas of open water, which offer long-distance migrant seabirds a reliable source of food during a period when they have to replenish and accumulate energy for reproduction. Investigating the interaction between species nesting sympatrically in the vicinity of polynyas should provide insights into the role that such oceanographic features play for pre-breeding seabirds. We used stable isotopes (δ 13 C and δ 15 N) to compare the diet of two ground-nesting seabirds, Sabine's gull ( Xema sabini ) and Arctic tern ( Sterna paradisaea ), nesting on an island adjacent to a recurring polynya in the Canadian high Arctic in 2008 and 2009. We show that, unlike Arctic terns, the diet of Sabine's gulls appears to include a non-negligible amount of terrestrially derived prey during early incubation, and that overall both species segregate their dietary niche during pre-laying and early incubation.