The importance of fission-fusion social group dynamics in birds

Almost all animal social groups show some form of fission-fusion dynamics, whereby group membership is not spatio-temporally stable. These dynamics have major implications at both population and individual levels, exerting an important influence on patterns of social behaviour, information transfer and epidemiology. However, fission-fusion dynamics in birds have received relatively little attention. We review the existing evidence for fission-fusion sociality in birds alongside a more general explanation of the social and ecological processes that may drive fission-fusion dynamics. Through a combination of recent methodological developments and novel technologies with well-established areas of ornithological research, avian systems offer great potential to further our understanding of fission-fusion social systems and the consequences they have at an individual and population level. In particular, investigating the interaction between social structure and environmental covariates can promote a deeper understanding of the evolution of social behaviour and the adaptive value of group living, as well as having important consequences for applied research.