Foraging Ecology of a Mulga Bird Community

Abstract

Mulga is a distinctive woodland or shrub community with a wide distribution across the semi-arid zone of southern and central Australia. Mulga (Acacia aneura) is the dominant shrub and small tree, but other species of Acacia are common. Typical of Australian habitats in the arid zone, mulga has a core of resident bird species that is augmented by nomadic (opportunistic) species when conditions are favourable. This paper describes the foraging behaviour and habitat use of a mulga avifauna in the vicinity of Alice Springs during late winter, when many opportunistic species were present. Data were obtained for 24 species, of which 16 were confirmed as nesting. Many birds, regardless of their normal foraging habits, converged on a common food resource: a geometrid moth (Geometridae) that was abundant on mulga plants. Despite their use of a common food resource, species differed in their foraging behaviour, proportions of different substrates used, and foraging heights. Ground-foraging species dominated the avifauna, but in most respects the guild structure of the community was a scaled-down version of Eucalyptus forest avifaunas. Differences in guild structure between mulga and eucalypt forest are best explained by differences between the two habitats in the kinds of resources (e.g. foraging substrates, types of food) that are available.