Abstract
Birds show enormous variation in their social organization. Many empirical studies of variation in social behavior within-populations or between related species have revealed associations between ecological factors and such variation. Recently, a new notion that life history factors have played an important role in the evolution of social organization in birds has been put forward. The phylogenetic comparative method has been widely applied as a powerful tool for solving the relationships between variation in social behaviour, and ecological, life history and environmental factors. Here, I review studies that have investigated the link between life history traits and variation in avian social organization, particularly mating systems, extra-pair paternity, intraspecific brood parasitism, cooperative breeding systems, and family formation. A hierarchical view is useful for understanding the evolution of social organization and suggests that interspecific variation of social organization is due to a combination of life history predisposition and ecological facilitation.
