Sea ice concentration decline in an important Adélie penguin molt area

Unlike in many polar regions, the spatial extent and duration of the sea ice season have increased in the Ross Sea sector of the Southern Ocean during the satellite era. Simultaneously, populations of Adélie penguins, a sea ice obligate, have been stable or increasing in the region. Relationships be...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2023-11, Vol.120 (46), p.e2306840120-e2306840120
Main Authors: Schmidt, Annie E, Lescroël, Amélie, Lisovski, Simeon, Elrod, Megan, Jongsomjit, Dennis, Dugger, Katie M, Ballard, Grant
Format: Article
Language:English
Subjects:
Animals
Antarctic Regions
Biological Sciences
Breeding
Breeding seasons
Colonies
Ecosystem
Ice Cover
Molting
Polar environments
Population growth
Remote sensing
Sea ice
Seasons
Spheniscidae
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Summary:Unlike in many polar regions, the spatial extent and duration of the sea ice season have increased in the Ross Sea sector of the Southern Ocean during the satellite era. Simultaneously, populations of Adélie penguins, a sea ice obligate, have been stable or increasing in the region. Relationships between Adélie penguin population growth and sea ice concentration (SIC) are complex, with sea ice driving different, sometimes contrasting, demographic patterns. Adélie penguins undergo a complete molt annually, replacing all their feathers while fasting shortly after the breeding season. Unlike most penguin species, a majority of Adélies are thought to molt on sea ice, away from the breeding colonies, which makes this period particularly difficult to study. Here, we evaluate the hypothesis that persistent areas of high SIC provide an important molting habitat for Adélie penguins. We analyzed data from geolocating dive recorders deployed year-round on 195 adult penguins at two colonies in the Ross Sea from 2017 to 2019. We identified molt by detecting extended gaps in postbreeding diving activity and used associated locations to define two key molting areas. Remotely sensed data indicated that SIC during molt was anomalously low during the study and has declined in the primary molt area since 1980. Further, annual return rates of penguins to breeding colonies were positively correlated with SIC in the molt areas over 20 y. Together these results suggest that sea ice conditions during Adélie penguin molt may represent a previously underappreciated annual bottleneck for adult survival.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.2306840120