POSSIBLE DRIVERS OF NEST USURPATION IN AFRICAN PENGUINS SPHENISCUS DEMERSUS

Nest usurpation is a relatively common phenomenon in birds but remains poorly documented in penguins. This behaviour may advantage bolder and aggressive individuals and influence population dynamics by affecting breeding success. African Penguins Spheniscus demersus are aggressive towards conspecifics during the breeding season when competing for territory. However, nest usurpation is rarely observed in this species. We describe three records of nest usurpation in African Penguins from Bird Island, Algoa Bay (South Africa) in 2017. After a climate-related massive breeding failure, late breeders in search of a territory attacked occupants of earlier-breeding nests, sometimes leading to the death of their brood. These observations may be the consequence of an extreme weather event, which created a marked asynchrony in breeding stages in this specific year, with many birds tending chicks, while others were just beginning to look for territories. This mismatch provided the opportunity for particularly aggressive individuals to decrease the breeding output of less aggressive birds, thereby possibly influencing the species' population dynamics.