Food, flows and feathers: Riparian bird assemblages of Australia’s wet-dry tropics

The wet-dry tropics of northern Australia support a diverse avifauna; endemism is high and vastareas of relatively intact landscape provide significant habitat. The aquatic environments of the region are internationally recognised and are critical for the survival of several rare and threatened bird species. While species richness is known to be higher in riparian vegetation zones than neighbouring landscapes, the bird assemblages of these systems are still poorly characterised. Riparian zones are vulnerable to human-induced environmental change, yet they provide important habitat and resources for bird communities. Furthermore, birds are an integral part of river ecology, occupying high trophic levels in relatively short aquatic food chains. Determining aquatic subsidies from feeding activities would provide a better understanding of the importance and role of birds in northern Australian riparian zones. The riparian bird assemblages at various main stream and tributary sites of the Daly River (Northern Territory) and the Fitzroy River (Western Australia) were surveyed and characterised. Eighty-four bird species were recorded during riparian surveys, including globally threatened taxa (i.e. Gouldian Finch and race coronatus of Purple-crowned Fairy-wren) and migratory species listed on the Environment Protection and Biodiversity Conservation Act (i.e. scolopacid shorebirds). Average diversity was higher in the Daly River catchment, although the difference between catchments was not significant. The role of stream order, vegetation community, food web dynamics and disturbance in defining riparian bird assemblages is discussed.