Breeding seabirds are central place foragers, and, as such, variability of feeding re- sources around breeding colonies can affect feeding behaviour. Using tracking data from Chinstrap Penguin (Pygoscelis antarcticus) individuals breeding in Nelson Island (Maritime Antarctic Peninsula) combined with acoustic NASC krill densities, we were able to demonstrate that individuals changed their foraging behaviour during foraging trips un- der two years of contrasting krill availability. The results of this study show that foraging trips were longer, deeper, and further in distance during the 2021-22 season, which was a year characterised by warmer sea surface temperature, lower chlorophyll-a concentration, lower winter sea ice cover and considerably lower krill density, having likely negative ef- fects on breeding success. From this results it is inferred that the cascade effect of this krill availability decline on Chinstrap penguin foraging behaviour could be explained by; 1) an increase in patchiness of krill stocks; (2) deepening of the krill abundance peak or; (3) prey-switching to forage myctophid fish.
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