Models of how people make decisions are central to economic theory. But when cast in a darwinian framework, such models provide insights into animal social behaviour. This is especially true of family-based societies in which the profitability of pursuing different behaviours is strongly influenced by gender, kinship and social position within the group. The potential of this approach is shown by modelling the reproductive decisions facing individuals in a complex bird society, that of the white-fronted bee-eater.