Foraging niches of three Diomedea albatrosses

Abstract

Three species of biennial breeding southern hemisphere albatrosses - Diomedea sanfordi from the Chatham Islands, D. antipodensis from Antipodes Island and D. exulans from South Georgia - were tracked using CLS-Argos satellite system during the 1990s. Harness attachment and duty cycling of transmitters enabled long-term deployments covering both the breeding and non-breeding ranges. The feeding ranges for breeding birds of each species were different. D. sanfordi foraged over continental shelves to the shelf edge, whereas D. antipodensis and D. exulans ranged widely over deep water to the shelf edge. Mapping of satellite-determined locations for D. sanfordi and D. antipodensis showed that the demarcation was between the 1000 and 2000 m undersea contour. Non-breeding D. sanfordi wintered over the Patagonian shelf or over the Chilean shelf. There they were virtually confined to seas over the continental shelves of <200 m depth, occasionally out to <1000 m depth. Breeding D. exulans from South Georgia feeding chicks over the same period foraged pelagically and along steep continental slopes up to depths >1000 m, and on less steep slopes to 200 m depth. These data provide the best evidence yet of habitat preference and segregation consistent across breeding and non-breeding seasons for closely related seabirds.