Niche Partitioning by Two Sympatric Goshawks in the Australian Wet Tropics: Breeding-season Diet

Abstract

In general, coexisting accipiters show low dietary overlap and clear morphological separation. However, most studies have been conducted in the Northern Hemisphere. In Australia, the two accipitrid goshawks, the grey goshawk, Accipiter novaehollandiae, and brown goshawk, A. fasciatus, are relatively similar in size. The diets of the two goshawks were studied in an area of sympatry, at Abergowrie State Forest, Queensland, in the wet tropics, during the breeding season. The diet of the brown goshawk contained more birds than did that of the grey goshawk, which preyed more on medium-sized mammals and reptiles. The proportion of insects in the diet was similar in the two species. Grey goshawks preferred terrestrial and arboreal prey to the brown goshawks' more aerial prey. The grey goshawk took heavier prey on average and had a slightly more diverse diet. Nevertheless, at 93%, dietary overlap between the goshawks was high. Such high overlap may be possible because of the high diversity and abundance of prey in the tropics, easing interspecific competition.