| Summary: | The realized niches of closely related species must differ if these species are to co-exist stably. The Gentoo (Pygoscelis papua) and Chinstrap Penguins (P. antarctica) breed concurrently in the Scotia Sea and Antarctic Peninsula regions. To identify species- and site-specific foraging niches, we compared the two species' foraging niches, including diet and foraging locations, at two sites in the South Shetland Islands with contrasting marine habitats. Both species fed primarily on Antarctic krill (Euphausia superba), though fish was also a component of the Gentoo Penguin's diet. Gentoo Penguins foraged closer to shore than did Chinstrap Penguins. Gentoo Penguins foraged during the day, while Chinstrap Penguins foraged throughout the diel cycle, sometimes traveling farther from shore on overnight foraging trips. In most cases, these species-specific foraging patterns were consistent with trends seen elsewhere in the region. However, within each species, site-specific differences in foraging niches were still evident. Overall, we observed that Gentoo Penguins traveled within consistent and limited distances from their colonies, but their diets varied by site in both meal mass and content. Chinstrap Penguins, in contrast, had a uniform diet of krill at both sites but varied the distance from shore and times at which they foraged.
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