Ontogeny of vocalizations in Adelie penguin (Pygoscelis adeliae) chicks

Passive acoustic monitoring (PAM) is an efficient method to monitor dense aggregations of vocal animals but requires understanding the acoustic ecology of the species under examination. Avian vocal development is largely understood from songbirds, limiting its application to non-passerine taxa with different social and environmental pressures. As an example, colonial seabirds such as the Adelie penguin (Pygoscelis adeliae) inhabit acoustically crowded environments and rely on vocal cues, in addition to spatial information, for parent-offspring recognition. While adult penguin vocal communication is well studied, chick vocal development remains poorly characterized. Using the deep learning-based system DeepSqueak, we aimed to characterize the vocal development of wild P. adeliae chicks in the West Antarctic Peninsula. We found that acoustic features of chick calls changed systematically with age, with calls becoming longer and more frequency modulated over time. Characterizing chick vocal development from hatch to fledge provides important information to study phenological communication patterns in vocal-dependent seabirds and supports the application of PAM to assess climate-driven impacts on indicator species.