Differential sorting of individuals in territorial species affects apparent habitat quality

Territoriality leads to non‐random sorting of individuals into habitats of differing quality. This can affect empirical estimates of population growth rate (λ), a measure of habitat quality, such that habitat‐specific λ varies with population size. I present a simple model of territorial behavior in which territory acquisition depends on age and individual vigor. Under this model, with a low initial population, the λ associated with the best habitat stays constant until all territories are full. At that point, as less competitive individuals move to secondary habitat, the λ value in the better habitat increases. Similarly, as secondary habitat becomes occupied by individuals of successively greater vigor, λ can switch from a sink (λ < 1) to a source (λ > 1). This means that habitat quality is not a fixed quantity but results from an interaction of the characteristics of the habitat with competitive sorting of individuals. If all individuals are in a good habitat, its conservation value will be underestimated and likewise the value of secondary habitat may not be properly assessed. © 2013 The Wildlife Society.