Effects of Snow Cover on Nesting and Reproductive Success in Gentoo (Pygoscelis Papua) and Adélie (Pygoscelis Adeliae) Penguins at Lions Rump, King George Island, West Antarctica

This study examines how prolonged snow cover and meltwater affect breeding behavior and success in Gentoo ( Pygoscelis papua ) and Adélie ( Pygoscelis adeliae ) penguins. We monitored nearly 7,000 nests at Lions Rump, King George Island, where both species breed sympatrically, across two seasons with contrasting snow cover: a relatively snow-free 2008/09 season and a snow-heavy 2009/10 season.While penguin population changes and trends have been widely studied, the effects of extreme snow conditions—such as abnormally thick cover during the onset and incubation periods—on the breeding success of Gentoo and Adélie penguins nesting in the same colonies remain poorly understood.These anomalous conditions strongly influenced breeding outcomes by delaying nest initiation and increasing habitat instability during incubation and chick-rearing. In response to extensive snow cover during the 2009/10 season, Gentoo penguins shifted their nest-site distribution, concentrating on elevated, snow-free bedrock and moraine exposures while abandoning snow-covered beach terraces and low-elevation valley sites. In contrast, Adélie penguins largely retained their traditional elevated bedrock nesting areas with minimal spatial adjustment. Despite these behavioral differences, both species experienced delayed breeding, increased nest attrition, and reduced clutch sizes under snow stress. Gentoo penguins exhibited greater sensitivity to these conditions, with more variable breeding success and lower chick survival. Adélie penguins, by comparison, maintained stable chick survival and stronger nest-site fidelity, indicating greater resilience to snow-induced environmental stress. Importantly, Gentoo penguins also demonstrate significant interannual variability in breeding chronology and flexible nest-site selection, which may buffer reproductive success under varying environmental conditions. The pronounced nest loss and spatial reorganization in Gentoo penguins reflect their heightened vulnerability to snow accumulation and meltwater exposure, whereas Adélie penguins, though affected, sustained more consistent nesting patterns and reproductive outcomes.These findings highlight the vulnerability of Antarctic seabirds to shifts in snow dynamics and emphasize the ecological importance of microhabitat resilience and species-specific behavioral strategies in coping with environmental variability.