| Summary: | Climate change around Antarctica is coincident with shifts in the distribution and abundance of Pygoscelid penguins, understanding this link between penguins and climate is the motivation behind this dissertation. I conducted two studies at Palmer Station, located along the rapidly warming West Antarctic Peninsula (WAP). First, I examined foraging behaviors of tagged Adélie and gentoo penguins while an autonomous underwater vehicle simultaneously measured Antarctic krill (penguins’ main prey) distributions. We detected krill aggregations within the horizontal and vertical foraging ranges of both species. Adélie and gentoo penguins had spatially and vertically segregated foraging habitats, a strategy that may limit competition for food. This reveals that these recently sympatric penguin species were unlikely competing for food, which agrees with recent studies showing that krill biomass is not in decline. This is a notable finding because past studies hypothesized that WAP penguin population declines are mainly driven by increased competition and decreased krill biomass, related to large-scale changes in sea ice concentration (SIC) and sea surface temperature (SST). Second, I found that interannual variability in Adélie penguin chick fledging mass was related to large-scale climate and local weather; chicks weighed less in cold, wet and windy years, suggesting there could be increased thermoregulatory costs for wet chicks. The mass of a chick before fledging the colony is thought to be an important indicator because heavier chicks are more likely to recruit into the breeding population. This direct impact of climate on chicks illustrates that climate change may affect penguins through pathways that are unrelated to sea-ice influenced food webs. I also conducted two continent-wide studies to understand spatiotemporal changes in Adélie, gentoo and chinstrap penguin breeding habitats throughout each species entire geographic range using SIC and SST from past satellite observations (1981-2010), and for Adélie ...
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