Population Status of Sympatrically Breeding Skuas (Catharacta spp.) at Admiralty Bay, King George Island, Antarctica: A Case Report for 2020–2024

The present study sets out to examine the status of sympatric populations of south polar (<i>Catharacta maccormicki</i>) (SPSs) and brown skuas (<i>Catharacta antarctica</i>) (BSs) at two sites on King George Island, Antarctica. The study sites were designated as Important Bird and Biodiversity Areas (IBAs) and were monitored for three (for Point Hennequin (PH)) and four (for West Admiralty Bay (WAB)) consecutive breeding seasons, concluding with the 2023/24 season. The most recently reported data from these areas are from the 2004/05 season, and the data presented herein allow both areas to be assessed in the context of their IBA and Antarctic Specially Protected Area values. The mean number of total pairs for the investigated seasons for WAB was 67 ± 7, while for PH, it was 157 ± 18. The number of pairs of SPSs at PH and WAB justifies the positive evaluation of the areas as IBAs based on global designation criterion A4 proposed jointly by BirdLife International and the Scientific Committee on Antarctic Research (SCAR). PH is of particular interest, as it has been determined that at least 2.3% of the global population of SPSs, estimated by BirdLife International to be between 6000 and 15,000 adult individuals, breeds at this site. The expansion of both IBA boundaries is also recommended based on this study.