Diet and Feeding Behavior of the South Polar Skuas Stercorarius maccormicki in the Haswell Islands, East Antarctica.

Simple Summary: This work focuses on the diet and feeding ecology of the South Polar Skua, a large gull-like seabird that breeds around Antarctica and winters in the Indian Ocean and Northern Hemisphere. This study presents information from the Haswell Islands off the Antarctic coast in the Davis Sea, where skuas breed near colonies of other seabird species. The composition of the diet of South Polar Skuas included animal (vertebrate and invertebrate organisms), plant, mineral, and anthropogenic components. The diet during the pre-breeding and breeding periods was based on eggs and chicks found in Emperor and Adélie penguin colonies. During the post-breeding period, skuas have been observed feeding at sea. In general, they obtained food by scavenging, but they could also prey on the eggs and chicks of Adélie Penguins and other seabirds. In recent decades, kitchen waste became an additional food resource that supported the skua population. It was found that South Polar Skuas did not influence the breeding success of Emperor Penguins but could potentially influence the breeding success of Adélie Penguins and other seabirds. The diet and feeding behavior of South Polar Skuas (Stercorarius maccormicki) are well studied within the species' breeding range but are poorly understood on the Haswell Islands. The aim of this study was to determine how South Polar Skuas use available resources during the pre-breeding and breeding periods at the Haswell Archipelago (66°31′ S, 93°01′ E, Davis Sea, Southern Ocean) under conditions of prolonged human activity. I studied pellets, spontaneous regurgitation, and stomach contents of feathered birds to study the diet of skuas and used direct observations of their feeding behavior. South Polar Skuas at the Haswell Islands fed primarily on the Emperor Penguin (Aptenodytes forsteri) colony and on terrestrial resources in the Adélie Penguin (Pygoscelis adeliae) and fulmarine petrel colonies. The dominant prey of skuas were breeding Antarctic penguins. Emperor Penguins and Adélie Penguins make up the bulk of the skuas' diet in the pre-breeding and breeding periods. Surface feeding at sea was observed in the post-breeding period. In recent decades, kitchen waste supported the skua population. Scavenging (placenta and feces of Weddell seals [Leptonychotes weddellii], frozen eggs, chicks and adults of breeding bird species, kitchen refuse) is the dominant strategy for obtaining food. Adélie Penguin eggs and chicks were the main food items of the South Polar Skuas in the Haswell Archipelago. Skua predation could potentially influence the breeding success of Adélie Penguins and fulmarine petrels, but the extent of the impact is unknown. The impact of the South Polar Skua on Emperor Penguins is negligible because skuas feed mainly on frozen chicks and eggs of the species. [ABSTRACT FROM AUTHOR]