Coexistence of three species of hawks (Buteo spp.) in the prairie–parkland ecotone

We investigated the extent of ecological segregation in the use of the food, space, and habitat resources of three sympatric species of the genus Buteo (red-tailed, ferruginous, and Swainson's hawks) coexisting in the prairie–parkland ecotone of southeastern Alberta. We concluded that food was not a resource for which the hawks were competing because the overlap in diets exceeded 80%, and because ferruginous hawks successfully fledged supernumerary broods and Swainson's hawks, broods of at least average size. Furthermore, there was no evidence that each species hunted prey at different times of the day or concentrated on different-sized prey. Each of the three species exhibited a dispersed distribution of nest sites which suggests competition for space; this pattern was not as evident when the distribution of nests among species was considered. Nevertheless, when pairs of different species nested in close proximity their reproductive success declined significantly, suggesting interspecific competion for space. The three species exhibited differences in nest site characteristics, suggesting that, although sympatric, they tended to segregate on the basis of habitat. Ferruginous hawks appear to inhabit arid and open landscapes, red-tailed hawks woodland habitat, and Swainson's hawks the interface.