Feeding Ecology of Sympatric Barn Owls and Long-Eared Owls in Idaho

Abstract

The diets of Barn Owls and Long-eared Owls were compared during two consecutive nesting seasons in the Snake River Birds of Prey Area in southwestern Idaho, U.S.A. Over 12800 prey items were identified. Both species fed almost exclusively on small mammals. Microtus were the most important Barn Owl prey, while Long-eared Owls fed primarily on Peromyscus and heteromyid rodents. Nesting Barn Owls were more closely associated with irrigated agriculture than were Long-eared Owls. The feeding niche of Barn Owls was narrower than that of Long-eared Owls the first year but wider the next. Dietary overlap was 48.4% the first year and 60.9% the next. In comparison with other North American studies of sympatric Barn Owls and Longeared Owls, the owls in our study had wider feeding niches and a reduced dietary overlap. Mean weights of Barn Owl prey were significantly heavier than those of Long-eared Owl prey thus Barn Owl prey weight distributions were shifted towards heavier prey than were those of Long-eared Owls. Differences in habitat use, food niche breadth and prey size are potentially important coexistence mechanisms.