Ardea
Official journal of the Netherlands Ornithologists' Union

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Simmons R. (1986) Ecological segregation of the Red-breasted Sparrowhawk Accipiter rufiventris and six coexisting Accipitrine raptors in southern Africa. ARDEA 74 (2): 137-149
Of seven small to medium (100-900 g) accipitrine hawks in southern Africa, the Red-breasted Sparrowhawk (RBS) is among the poorest known. Two pairs studied intensively in the Drakensberg mountains of South Africa, fed almost exclusively (98%) on small (10-90 g) birds. A diurnal rhythm in prey delivery was evident for one nest, peaking between 09.00 and 12.00. Also evident were a fast low pursuit mode of hunting (in contrast to previous opinions), over the species' grassland habitat, and a difference in prey selection between the sexes. In a comparison of diet, biome, hunting rhythm, hunting mode and foraged habitat of the RBS with six coexisting species, the Ovambo Sparrowhawk showed 60% similarity, and the Little Sparrowhawk 38% ecological similarity with the RBS. None of the five species with a predominantly small bird diet shared both hunting habitat and biome in common. Ecological overlap between species was thus clear-cut and minimal. Of the raptors studied, those closest in body mass to the RBS overlapped least in geographic range, while those much heavier or lighter were the most sympatric. I hypothesis that this may have resulted from interspecific interactions during the speciation of some species or as a post-speciation phenomenon. Although the majority of studies of coexisting congeneric raptors reflect the results outlined here, it is recommended that future studies cover periods when food resources may be limiting.


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