Comparative diets of sympatric nesting raptors in the eastern deciduous forest biome

Abstract

Diets and food-niche metrics of nesting raptors were studied in the eastern deciduous forest biome of northern New Jersey, southeastern New York, and northwestern Connecticut. Raptor diets were determined from 2506 prey individuals recovered from prey remains and pellets collected from nest sites of a community consisting of five hawk and four owl species. Food-niche overlaps were higher on average in the hawk guild (0.422) than in the owl guild (0.342), correlating with increased species packing and decreased body size differences in the hawk guild. Differences in activity times (diurnal versus nocturnal) did not result in reduced food-niche overlap between diurnal and nocturnal raptors. The lack of interference-type competition probably allowed greater exploitative-type competition but was offset by nearly exclusive use of certain prey types by several raptor species. Thus, temporal niche differences ultimately did aid in the resource partitioning of food between hawks and owls. Overall, the forest raptor community displayed significant food-niche overdispersion, with 35 of 36 food-niche overlap values below the 0.6 "competition" threshold. This result would be expected in a community structured by competition.