Urban fauna communities may be strongly influenced by environmental and socio-economic factors, but the relative importance of these factors is poorly known. Most research on urban fauna has been conducted in large cities and it is unclear if the patterns found in these locations coincide with those from smaller human settlements. We examined the relative importance of environmental and socio-economic factors in explaining variation in urban bird communities across 72 neighbourhoods in 18 regional towns in south-eastern Australia. Native bird species richness varied from 6 to 32 across neighbourhoods and was higher in neighbourhoods with more nectar-rich plants. Variation in bird species diversity across neighbourhoods was also strongly positively related to the density of nectar-rich plants, but was higher also in neighbourhoods with higher socio-economic status (reflecting higher levels of disposal income, education and home ownership). The density of native birds across neighbourhoods per season varied from 1 to 15 birds per hectare and was lower in neighbourhoods with a greater cover of impervious surfaces. The density of exotic birds (introduced to Australia) per season also varied across neighbourhoods (0–13 birds per hectare) and was lower in neighbourhoods with more nectar-rich plants and higher in neighbourhoods with greater impervious surface cover. Our results demonstrated that the vegetation characteristics of household gardens, along streetscapes and in urban parklands had a strong influence on the richness and diversity of urban bird communities. The density of native and exotic birds varied primarily in response to changes in the built environment (measured through impervious surface cover). Socio-economic factors had relatively little direct influence on urban birds, but neighbourhood socio-economics may influence bird communities indirectly through the positive relationship between socio-economic status and vegetation cover recorded in our study area.