Sibling aggression between Black-legged Kittiwake (Rissa tridacyla) chicks

Siblicidal aggression has been documented in Black-legged Kittiwakes (Rissa tridactyla) by many researchers. First hatched (alpha) chicks attack and evict beta chicks, leading to the death of the younger bird. The infrequent nature of siblicide makes collecting consistent data difficult, but aggressive interactions between chicks are more readily captured. It is possible that patterns in aggressive behaviour will provide insight into the antecedents of siblicide. In this study, we used film footage collected during the breeding seasons from 2018-2021 to analyse aggressive interactions. First, we explored frequency differences in key behaviours between alpha and beta chicks. We then looked at the behavioural sequences within nests to describe aggressive interactions. Alpha chicks were consistently the aggressor in all samples, and beta chicks acted defensively. We comment on these findings and their relation to siblicidal aggression.