A population model for migratory vertebrates is developed by combining game theory models of foraging behaviour with population biology. Models of foraging behaviour which incorporate interference and resource depletion are developed to determine the density-dependent mortality occurring within sites. Population size can then be related to the strength of interference, the variance in competitive ability and the rate at which resources are depleted. The model is extended to predict evolutionarily stable migration strategies. This novel framework is then used to predict the population decline resulting from habitat loss.