Influence of the Increasing Fur Seal Population on Wandering Albatrosses Diomedea exulans Breeding on Bird Island, South Georgia

Abstract

Since 1961, the wandering albatross breeding population at Bird Island, South Georgia has decreased by 22% (1% per annum). Since 1960 Antarctic fur seals at South Georgia have increased by 17% per annum; Bird Island was the main focus of this increase. The seals have destroyed large areas of tussock grassland (the albatrosses breeding habitat) and frequent interactions with albatrosses are observed. We investigated the potential adverse effect of fur seals on wandering albatrosses by comparing breeding numbers, success and other aspects of population dynamics in areas with different abundances (including absence) of seals. Albatross breeding numbers have decreased more rapidly in areas with most seals. In contrast, albatross breeding success has increased over the last decade and is highest in areas with most seals. There is no evidence that seals have any adverse effect on established breeding albatrosses but juvenile recruits to the breeding population tend to avoid areas with abundant seals. Because young birds have lower reproductive success than older birds, this movement may create the increase in average breeding success of the (older) birds remaining in areas with numerous seals.