Foraging conditions for breeding penguins improve with distance from colony and progression of the breeding season at the South Orkney Islands

• Main Authors: Jessica A. Phillips, Annette L. Fayet, Tim Guilford, Fabrizio Manco, Victoria Warwick-Evans, Philip N. Trathan
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2021
• Subjects: Chinstrap penguin; Seabird; Foraging; Habitat selection; Index of patch quality; Prey availability; Ashmole’s halo; GPS; TDR; South Orkney Islands; Antarc*; antarcticus
• Online Access: https://figshare.com/articles/journal_contribution/Foraging_conditions_for_breeding_penguins_improve_with_distance_from_colony_and_progression_of_the_breeding_season_at_the_South_Orkney_Islands/23780751

Background: According to central place foraging theory, animals will only increase the distance of their foraging trips if more distant prey patches offer better foraging opportunities. Thus, theory predicts that breeding seabirds in large colonies could create a zone of food depletion around the colony, known as “Ashmole’s halo”. However, seabirds’ decisions to forage at a particular distance are likely also complicated by their breeding stage. After chicks hatch, parents must return frequently to feed their offspring, so may be less likely to visit distant foraging patches, even if their quality is higher. However, the interaction between prey availability, intra-specific competition, and breeding stage on the foraging decisions of seabirds is not well understood. The aim of this study was to address this question in chinstrap penguins Pygoscelis antarcticus breeding at a large colony. In particular, we aimed to investigate how breeding stage affects foraging strategy; whether birds foraging far from the colony visit higher quality patches than available locally; and whether there is evidence for intraspecific competition, indicated by prey depletions near the colony increasing over time, and longer foraging trips. Methods: We used GPS and temperature-depth recorders to track the foraging movements of 221 chinstrap penguins from 4 sites at the South Orkney Islands during incubation and brood. We identified foraging dives and calculated the index of patch quality based on time allocation during the dive to assess the quality of the foraging patch. Results: We found that chinstrap penguin foraging distance varied between stages, and that trips became shorter as incubation progressed. Although patch quality was lower near the colony than at more distant foraging patches, patch quality near the colony improved over the breeding season. Conclusions: These results suggest chinstrap penguin foraging strategies are influenced by both breeding stage and prey distribution, and the low patch quality near the colony may ...