Who wins when the competition heats up? Effects of climate change on interactions among three Antarctic penguin species

• Main Author: Clewlow, Harriet Lucy
• Format: Text
• Language: English
• Published: 2019
• Subjects: Antarctic; Antarctic Peninsula; Scotia Sea; South Shetland Islands; South Orkney Islands; Antarc*; Sea ice
• Online Access: http://nora.nerc.ac.uk/id/eprint/525983/; https://nora.nerc.ac.uk/id/eprint/525983/1/ClewlowH%202019%20PhD.pdf

This thesis sought to elucidate the mechanisms driving the large-scale population changes observed in Pygoscelis penguins in the Western Antarctic Peninsula (WAP)/Scotia Sea region since the 1970s, with particular focus on the interactions between the species. During this period the climate in this region has changed dramatically, with rapid warming and sea ice declines occurring until the late 20th century to be followed by a pause in the warming. These changes have altered biotic and abiotic conditions in the penguins’ ecosystem and researchers widely agree that this is driving their population changes. In order to elucidate the exact mechanisms of population change, we attempted to fill crucial knowledge gaps, including foraging ecology, migration and breeding success, throughout their annual cycle and all with particular focus on the interactions between the three Pygoscelis species. Direct tracking and isotope analysis provided novel insights into foraging behaviour and the role of niche partitioning between the species throughout the annual cycle, and its importance for reducing interspecific competition. During the breeding season, allochrony between Adélie and chinstrap penguins was found to reduce competitive overlap in foraging areas by 54%, compared to synchronous breeding, and to be resilient to climate change. The migration routes and over-winter sites of chinstrap penguins from the South Orkney Islands were identified for the first time and were found to be segregated from birds from the neighbouring South Shetland Islands archipelago. The environmental conditions at the two over-winter sites differed but the population trends at the two archipelagos were similar, suggesting that winter conditions are not likely to be a major driver. Developing on our findings of contrasting environmental conditions across the chinstrap over-wintering sites, we investigated the effect of multiple environmental variables on population trends in the final two thesis chapters. Sea ice has been shown to be a major ...