Discovery of Antarctic moulting sites in satellite imagery reveals new threat to emperor penguins

Abstract Moult is a critical period in the life cycle of emperor penguin. Like other stages of their life history they depend upon Antarctic sea-ice as a platform to moult. Our knowledge of where the birds moult is limited to a small number of tracking studies and incidental observations, showing most adult emperor penguins moult in small groups on sea ice between January and March. Sea ice extent and duration has reduced dramatically over the last decade, and understanding how these declining ice conditions are impacting emperor penguins is crucial to model future population trajectories. We show that groups of moulting emperor penguins can be seen in medium and very-high-resolution satellite imagery. The study concentrates on a specific the area of West Antarctica, identifying the distribution and number of moulting groups over a seven-year period (2019-2025). Between 2022 to 2024, reduced fast ice extent resulted in a concentrated distribution of moulting groups and early break-up of the moulting platform before the end of the season.