Spatial and isotopic niche partitioning during winter in chinstrap and Adélie penguins from the South Shetland Islands

• Published in: Ecosphere
• Main Authors: Hinke, Jefferson T., Polito, Michael J., Goebel, Michael E., Jarvis, Sharon, Reiss, Christian S., Thorrold, Simon R., Trivelpiece, Wayne Z., Watters, George M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2015
• Subjects: Austral; Scotia Sea; South Shetland Islands; Southern Ocean; Weddell; Weddell Sea; Antarc*; Antarctica; Pygoscelis antarctica
• Online Access: http://dx.doi.org/10.1890/es14-00287.1; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1890%2FES14-00287.1; https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.1890/ES14-00287.1

Closely related species with similar ecological requirements should exhibit segregation along spatial, temporal, or trophic niche axes to limit the degree of competitive overlap. For migratory marine organisms like seabirds, assessing such overlap during the non‐breeding period is difficult because of long‐distance dispersal to potentially diffuse foraging habitats. Miniaturization of geolocation devices and advances in stable isotope analysis (SIA), however, provide a robust toolset to quantitatively track the movements and foraging niches of wide ranging marine animals throughout much of their annual cycle. We used light‐based geolocation tags and analyzed stable carbon and nitrogen isotopes from tail feathers to simultaneously characterize winter movements, habitat utilization, and overlap of spatial and isotopic niches of migratory chinstrap ( Pygoscelis antarctica ) and Adélie ( P. adeliae ) penguins during the austral winter of 2012. Chinstrap penguins exhibited a higher diversity of movements and occupied portions of the Southern Ocean from 138° W to 30° W within a narrow latitudinal band centered on 60° S. In contrast, all tracked Adélie penguins exhibited smaller‐scale movements into the Weddell Sea and then generally along a counter‐clockwise path as winter advanced. Inter‐specific overlap during the non‐breeding season was low except during the months immediately adjacent to the summer breeding season. Intra‐specific overlap by chinstraps from adjacent breeding colonies was higher throughout the winter. Spatial segregation appears to be the primary mechanism to maintain inter‐ and intra‐specific niche separation during the non‐breeding season for chinstrap and Adélie penguins. Despite low spatial overlap, however, the data do suggest that a narrow pelagic corridor in the southern Scotia Sea hosted both chinstrap and Adélie penguins for most months of the year. Shared occupancy and similar isotopic signatures of the penguins in that region suggests that the potential for inter‐specific competition ...