Ecology and conservation of Australian urban and exurban avifauna

We review the literature on the ecology and conservation of Australian urban birds and report the results of the first Australian study on the relationship between avifauna and habitat variation in exurbia, which is the low-density zone of development on the outer margins of a city. The Australian urban avifauna has synanthropes found widely elsewhere. It also has a large number of native species, some of which are globally threatened. The distribution of species in Australian urban areas relates better to their niche characteristics than their nativity or exoticness and better to very local variations in habitat type than to environmental variation at the landscape scale, which is often masked by the vegetation thickening associated with suburbanisation. In two exurban regions of Hobart, Tasmania, we sampled birds in unmodified wildland forest (native forests away from development), unmodified exurban forest (native forest on exurban properties), modified exurban forest (native forest on exurban properties and with the understorey removed), exurban gardens and exurban paddocks (cleared land). We tested the hypotheses that exurban habitats were different in bird species compositions from wildlands, that similarity in avifaunal assemblages within habitats increased with the degree of human interference and that, within dry open forests, the perforation (small clearances) and fragmentation associated with exurbanisation would be associated with populations of an aggressive small-bird-excluding edge species, the noisy miner Manorina melanocephala. The noisy miner occurred on old land clearance boundaries and not at all in recent forest perforations. In the absence of noisy miners, exurban bird species assemblages were organised by habitat, with the greatest internal consistency being within gardens. In both regions, paddocks had more heterogeneous bird assemblages than expected, and wildlands had identical species assemblages to unmodified exurban forests, but not to other habitat types. The mixture of habitats characteristic of exurbia may not necessarily be detrimental for avifaunal conservation as long as it includes substantial areas of undisturbed native vegetation, even though exurban development may be undesirable for other reasons. We conclude that it is the distinctiveness and high beta diversity of urban and exurban habitats that create opportunities for a wide variety of native and exotic bird species, that local manipulations and creations of urban and exurban habitat can substantially affect avifaunal conservation outcomes and that urban bird management should be a major component of many species recovery plans.