Diets of breeding Brown Goshawks Accipiter fasciatus and Collared Sparrowhawks A. cirrocephalus near Canberra, Australia and comparisons with other regions and raptors

Abstract

We examined 80 Brown Goshawk Accipiter fasciatus and 27 Collared Sparrowhawk A. cirrocephalus collections of prey remains and pellets. They were obtained from 2002 to 2010 within 30 km of Canberra (ACT) from 36 Goshawk and nine Sparrowhawk breeding events in 24 and six territories, respectively. For Brown Goshawks, 412 prey individuals and six species not previously found in the species’ diet were recorded; for Collared Sparrowhawks, 301 prey individuals and seven ‘new’ species were recorded. Dietary overlap was 43.5%, including 12 bird species taken by both hawks. In addition to European Rabbits Oryctolagus cuniculus, Brown Goshawks took birds (especially parrots, House Sparrows Passer domesticus and Common Starlings Sturnus vulgaris), reptiles and insects. Collared Sparrowhawks took mostly birds (especially House Sparrows, rosellas Platycercus spp., Crested Pigeons Ocyhaps lophotes and Common Starlings) and insects, but no mammals or reptiles. Sparrowhawks did not consume rabbits, a main prey item of Brown Goshawks and other raptor species in the Canberra area. Standardised Food Niche Breadth and the Shannon Diversity Index were similar for the diets of the two hawks, but Brown Goshawks captured larger prey, which was reflected in the 2.7 times difference in Geometric Mean Prey Weight between the species (Brown Goshawks 18.35 g; Collared Sparrowhawks 6.92 g), which resembled the 2.8 times disparity in mass between males of the two species (Collared Sparrowhawks 126 g; Brown Goshawks 350 g). Surprisingly, Sparrowhawks took seven Australian Magpies Gymnorhina tibicen (albeit probably juveniles), a species as large as the female Sparrowhawk. Both hawks take a much higher proportion of insect prey than do their ecological counterparts in North America, the Cooper’s Hawk Accipiter cooperii and Sharp-shinned Hawk A. striatus, and the Eurasian counterpart of the Collared Sparrowhawk, the Northern Sparrowhawk A. nisus.