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.