The distribution of three nocturnal bird species across a suburban forest gradient

On a global scale, urbanisation has a profound effect on the distribution of wildlife. Here we seek to test the effects of urban encroachment on the distribution of three key members of the Australian nocturnal bird community: the Tawny Frogmouth (Podargus strigoides), Australian Owlet-nightjar (Aegotheles cristatus) and Southern Boobook (Ninox novaeseelandiae). The distribution of the species was recorded in three landscape types-suburban, urban-fringe and forest with the level of urbanisation classified according to attributes at both landscape level and site level. The effects of urbanisation on individual species were determined by a comparison of broad landscape attributes and species distributions. Site-level attributes were modelled to determine their influence on the presence of species. Although all three species occurred in the urban-fringe landscape (50-64% of sites), the presence of the Tawny Frogmouth, a species with more generalist habitat requirements, increased in response to increasing levels of urbanisation. The Australian Owlet-nightjar and Southern Boobook, which have more specialised habitat requirements than the Frogmouth, showed a corresponding decrease in presence to increasing levels of urbanisation. Although all three species appear to tolerate the level of disturbance in urban-fringe environments, these areas are also at risk of further degradation. It is critical that continued research focuses on urban-fringe environments to investigate species-specific demographic responses to urban gradients.