Reproductive Performance of Seabirds and Seals at South Georgia and Signy Island, South Orkney Islands, 1976–1987: Implications for Southern Ocean Monitoring Studies

Abstract

Aspects of the reproductive performance over the last decade of Black-Browed, Grey-Headed and Wandering Albatrosses, Gentoo and Macaroni Penguins and Antarctic Fur Seals, at Bird Island, South Georgia and for Adelie and Chinstrap Penguins at Signy Island, South Orkney Islands, are summarized and reviewed. Breeding success of the Wandering Albatross, which breeds in winter and eats fish and squid, has remained constant, while population size has declined gradually but significantly. The other species at South Georgia, which breed in summer and feed extensively on krill, have shown major fluctuations in some or all of: breeding population size, breeding success, foraging trip duration and offspring growth rate. 1977–78 and 1983–84 were summers of particularly poor reproductive performance by almost all species; circumstantial evidence relating this to reduced availability of krill is discussed. The fluctuations in reproductive performance of the krill-eating, summer-breeding penguins at Signy Island are not synchronized with those at South Georgia; they correlate best (especially for Chinstraps, which suffered badly in 1980–81 and 1982–83) with the date of ice break-out in late spring. Numerous parameters of albatross, penguin and fur seal biology are reviewed in terms of their sensitivity and suitability for detecting changes in the marine environment.