Surviving Alpha: Using sequential analysis to examine the behaviours of Black-legged Kittiwake chicks during sibling pecking attacks

Kittiwake chicks engage in pecking attacks against their siblings, which can result in brood reduction by facultative siblicide. Attacks are almost exclusively carried out by Alpha (first-hatched) chicks against Beta (second-hatched) chicks. Onset of this behaviour is attributable to food stress brought about by environmental conditions which impact parental foraging success within breeding seasons. Size differences between siblings, due to asynchronous hatching, allow alpha chicks to dominate parental feeds and pecking attacks primarily occur during feeding events in response to beta attempts to gain food from parents. Yet attacks have been observed outside of feeding events and beta chicks can survive to fledging, even delivering retaliatory attacks in some instances. The responses of beta chicks during attacks were examined by Cullen (1957) whereby beak hiding motions by beta chicks such as facing away or tucking in the beak served as appeasement strategies and these were discussed as adaptations to Kittiwakes’ habit of cliff nesting. Use of appeasement by beta chicks suggests that, notwithstanding the environmental and hierarchical factors, beta chicks have some agency in their survival through their behavioural responses to alpha siblings. In this thesis, I use sequential analysis to examine in concatenation, the behavioural sequences of alpha and beta chicks, with particular attention to those immediately preceding and following pecking attacks. In this way I hope to better understand the inter-relationship of alpha and beta chick behaviours during pecking attacks. Observations were made of Kittiwake nests using four years of archival film footage of a Lundy population. Beak grabbing was used as a specific measure of attempts to gain food from parents, as opposed to the more general begging label used in previous studies. Results found that beta chicks were only very rarely pecked when they performed the beak grab behaviour. Beta chicks were also found to use appeasement strategies in combination with food gaining behaviours. Pecking attacks did not follow where these motions were employed. Results of this study are discussed in terms of the functions of the behaviours displayed.