A simulation model coupling the behaviour and energetics of a breeding central place forager to assess the impact of environmental changes

During the breeding season, seabirds are obligate central place foragers, and this may make them vulnerable to impacts of environmental change. An individual based model of a pair of central place foragers and their offspring has been developed for the common guillemot (Uria aalge). The behavioural decisions of each adult depend on the state of themselves, their partner and their chick. The behaviour of the adults and the body masses of all three are followed over the chick rearing period. The model was used to investigate how chick fledging mass, proportion of time the chick was left unattended by its parents and change in adult mass are impacted by different foraging ranges, prey abundance and calorific content. Adults in the model typically declined in mass during the chick rearing period, although none died of starvation. Provisioning parents can, to some extent, increase foraging distance from the colony without a reduction in the proportion of chicks reaching a suitable fledging mass or increasing the time they are left unattended. The foraging range at which a decline in fledging success and colony attendance occurs is influenced by changes in either one or both of, prey abundance and prey quality. Patterns produced by the model are consistent with field observations and biological knowledge. As the model outputs can give an indication of the fitness consequences of environmental changes it can be used to address theoretical ecological questions as well as to inform marine spatial management.