Abundance and breeding of the Antarctic Tern Sterna vittata at the James Ross and Seymour Islands, NE Antarctic Peninsula

Abstract

The Antarctic Peninsula (AP) is experiencing rapid environmental change associated with warming and sea ice retreat, which is likely to affect locally breeding birds. Yet, contrary to the knowledge of bird biology along the maritime West coasts of the AP, there is a remarkable lack of data from the more continental East coast. We report on the distribution, abundance, and breeding of the Antarctic Tern at the James Ross and Seymour islands, the two largest snow-free areas in the NE part of the AP, where this species breeds under harsh climate conditions probably close to its limits. Terns were found breeding in most ice- free areas, with nests located up to 2.9 km from coastlines at altitudes up to 180 m a.s.l. While the large-scale density was relatively low (c. 450 pairs per 127 km 2 of surveyed ice-free area), the local density (total colony area: 3 nests per ha; nest clusters: 100-140 nests per ha) was as high as elsewhere. Mean clutch size (1.21, n = 196) was smaller than in the west AP or in the maritime Antarctic. Daily nest survival rate during incubation varied between years and locations (mean = 0.977; 95 % CI: 0.966-0.985). While both predation and weather-caused mortality were locally important, the impact of skua predation might be lower in areas with alternative prey (penguin colonies). We suggest that the Antarctic Tern deserves attention as a species potentially suitable for monitoring of environmental impacts upon bird populations around the AP.