Rare upside of climate-induced phenological changes: Gentoo penguins (Pygoscelis papua) avoid heat events at Martillo Isl., Tierra del Fuego, Argentina

Heat waves have detrimental effects on most species, and particularly on cold-adapted species such as penguins. In this study we aim to understand what are the responses to heat weather events of Gentoo penguins ( Pygoscelis papua ) at one of their northernmost colonies: Martillo Island in Argentina. This colony was monitored using a time-lapse camera between 2013 and 2024. In this study we observe acute heat-related mortality events such as the death of five penguin chicks within forty-five minutes while recorded temperatures reached 24°C. During the observation period we found Gentoos are advancing their breeding season by 2 days per year, which is concurrently reducing the number of days exposed to high temperatures (≥ 20°C). While future climate change scenarios may increase the frequency and intensity of heat waves, for now, this is a rare example in which a warming-induced phenological change withdraws chicks from potentially deadly hot summer days by fledging sooner.