FORAGING ECOLOGY OF A MULGA BIRD COMMUNITY

Mulga is a distinctive woodland or shrub community with a wide distrib ution across the semi-arid zone of southern and central Australia. Mul ga (Acacia aneura) is the dominant shrub and small tree, but other spe cies of Acacia are common. Typical of Australian habitats in the arid zone, mulga has a core of resident bird species that is augmented by n omadic (opportunistic) species when conditions are favourable. This pa per describes the foraging behaviour and habitat use of a mulga avifau na in the vicinity of Alice Springs during late winter, when many oppo rtunistic species were present. Data were obtained for 24 species, of which 16 were confirmed as nesting. Many birds, regardless of their no rmal foraging habits, converged on a common food resource: a geometrid moth (Geometridae) that was abundant on mulga plants. Despite their u se of a common food resource, species differed in their foraging behav iour, proportions of different substrates used, and foraging heights. Ground-foraging species dominated the avifauna, but in most respects t he guild structure of the community was a scaled-down version of Eucal yptus forest avifaunas. Differences in guild structure between mulga a nd eucalypt forest are best explained by differences between the two h abitats in the kinds of resources (e.g. foraging substrates, types of food) that are available.