Acoustic cues to development of African Penguins (Spheniscus demersus) begging calls

Avian begging calls mediate parent–offspring conflict and direct parental care to genetically related progeny. We found that the fundamental frequency of begging calls of African Penguins Spheniscus demersus decreases as the penguins age and gain mass, before reaching a lower plateau when the chick reaches about 1 kg. Our results suggest that the food solicitation signals of this species may inform parents of the offspring's body mass. Our results may also lead to the development of non-invasive tools for facilitating censusing chick growth in wild colonies.