An intraspecific and interspecific comparison of raptor diets in the south-west of the Northern Territory, Australia

Abstract

Dietary information, collected during 1995-97 in the south-west of the Northern Territory, is presented for 11 raptor species. Unlike better-studied populations of these species in south-eastern and eastern Australia, most of the raptors in the arid inland were found to depend heavily on reptiles and birds, the budgerigar (Melopsittacus undulatus) being a particularly important food for many species during those periods when it was plentiful. Between-territory, between-year and seasonal differences in diet are quantified for most species.The raptor assemblages in central Australia included specialists on medium-sized to large mammals, small to medium-sized birds, and small reptiles/invertebrates, as well as several generalists. Indices of prey diversity and evenness were calculated for each species, and diet overlap between them was used to investigate aspects of interspecific competition for food. Overall, diet overlap was greatest among the bird specialists and between some of the generalists. It increased in 1997, a year of comparative plenty, possibly because several species exploited an abundance of some prey taxa and competitive pressure eased. R a p t o r d i e t s i n t h e No r t h e r n T e r r i t o r y T . A u m a n n

Trophic relationships between neighbouring White-bellied Sea-Eagles (Haliaeetus leucogaster) and Wedge-tailed Eagles (Aquila audax) breeding on rivers and dams near Canberra

“…In general, the diet of riparian Wedge-tailed Eagles in this study was similar to that of riparian and nonriparian Wedge-tailed Eagles previously studied (Leopold and Wolfe 1970;Brooker and Ridpath 1980;Marchant and Higgins 1993;Aumann 2001;Fuentes et al 2003), with mammals dominating the diet (mostly Rabbits and macropods), and ground-feeding birds also being important. There are few data with which to compare the diet of the Sea-Eagles.…”

“…Mammals accounted for 78% of the diet of Wedge-tailed Eagles near Mildura, Victoria, with all but 3% of this Rabbit (Baker-Gabb 1984). In Western Australia, 52-95% of the items in the diet were mammals (Brooker and Ridpath 1980), similar to observations in central Australia (79%; Aumann 2001), and on the Northern Tablelands of NSW (76%; Debus and Rose 1999).…”

“…There is, however, competition for nest-sites (Wiersma 1996). Shephard et al (2005) suggested that European Rabbits may have assisted the increase of inland populations of Whitebellied Sea-Eagles, and Rabbits have been reported as the main prey item for Wedge-tailed Eagles in different locations of Australia (Brooker and Ridpath 1980;Baker-Gabb 1984;Hull 1986;Aumann 2001 (Fuentes et al 2005). Two taxonomically close species in Europe, the White-tailed Sea-Eagle (Haliaeetus albicilla) and Golden Eagle (Aquila chrysaetos), compete directly with each other for lago-morphs, deer calves and sheep carrion (Ferguson-Lees and Christie 2001).…”

Territory fidelity, reproductive success and prey choice in the brown falcon, Falco berigora: a flexible bet-hedger?

“…Most prey items were recorded during the breeding season, which may explain the comparatively high geometric prey weights of this study, as small invertebrate prey have been recorded more frequently outside the breeding season in other studies (Baker-Gabb 1984a, 1984bMarchant and Higgins 1993;Aumann 2001b). No effort was made to separate prey captured by the different sexes.…”

“…By comparison, most falcons have a relatively narrow diet breadth (Marti et al 1993;Marchant and Higgins 1993), with many concentrating on one size class of bird or mammal (Hector 1985;Steenhof and Kochert 1988;Sergio and Bogliani 1999;Aumann 2001b). Brown falcons did prey heavily upon rabbit kittens, and the importance of this introduced mammal in the diet of brown falcons (Baker-Gabb 1984b) and other Australian raptors (Marchant and Higgins 1993) has been noted previously.…”