Key winter habitat of the ivory gull Pagophila eburnea in the Canadian Arctic

摘要

ABSTRACT: The ivory gull Pagophila eburnea is a rare Arctic seabird that breeds in remote locations; little is known of its winter distribution and behaviour. It is listed under Canadian legislation as ‘endangered’, and as ‘near threatened’ by the International Union for the Conservation of Nature. A 70% population decline in the past 3 decades in Canada prompted research on ivory gulls to better understand their year-round movements and habitat requirements. Additionally, the identification of critical habitat is a research priority in the Recovery Strategy for the ivory gull in Canada. We used data from gulls tracked by satellite telemetry from the Canadian Arctic and Svalbard, Norway, as well as data from ship observations collected between 1969 and 2010. We determined that the area of highest use by these gulls in the winter was in Davis Strait, where 90% of their time was spent over sea ice. Agreement of findings among datasets through time and from different breeding regions suggests that the edge of the pack ice in Davis Strait is an annual, key habitat for ivory gulls in winter. Given the proximity of the core wintering area to known hooded seal Crystophora cristata whelping patches, we speculate that remains from seal breeding, as well as polar bear Ursus maritimus kills and pagophilic (ice-loving) fish accessed in the vicinity of pack ice have provided spatially and temporally predictable, and valuable, food resources for ivory gulls in the winter.