Feeding ecology of the raptor guild of the Canberra Region

We studied the feeding ecology of twelve species of breeding raptors near Canberra, providing the first report of the food habits of a full raptor guild. There was no major dominant prey species for the overall guild. Some raptors had a very specialized diet: Black-shouldered Kites Elanus axillaris (House Mice Mus musculus); Australian Hobbies Falco longipennis (flying prey – birds, insects, and bats); and Peregrine Falcons Falco peregrinus (birds). Whistling Kites Haliastur sphenurus and Brown Falcons Falco berigora had the most diverse diet, with prey from five or more major taxa, including some unusual prey in the falcon’s diet such as molluscs. White-bellied Sea-Eagles Haliaeetus leucogaster captured a variety of prey of aquatic origin but in different proportions from what has previously been reported, with birds as the main food source, followed by fish and reptiles. Wedge-tailed Eagles Aquila audax had a diverse diet based on macropods, large birds, and lagomorphs. Little Eagles Hieraaetus morphnoides preyed mainly on mammals and birds, especially European Rabbits Oryctolagus cuniculus. The role of how large killed prey vs carrion is brought to the nest needs to be studied for Wedge-tailed Eagles and Whistling Kites. Both Accipiter species (Brown Goshawks A. fasciatus and Collared Sparrowhawks A. cirrocephalus) had similar diets to what has been reported previously, with a particularly high number of insects. Nankeen Kestrels Falco cenchroides and Southern Boobooks Ninox boobook (the two hollow-nesters) had similar diets based on insects (by number), birds (by biomass), and reptiles of similar size. Birds were the most important prey group for the overall guild, and geometric mean prey weight suggested a size selection in how the raptors are dividing this resource, with Wedge-tailed Eagles taking the heaviest prey. There were five cases of intraguild predation.

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