Foraging behaviour of songbirds in woodlands and forests in eastern Australia: resource partitioning and guild structure

One of the major questions in ecology is how species share their ecological space and what enables them to coexist. Partitioning of foraging niches should facilitate local coexistence. Thus, detailed data on foraging ecology are needed to provide insight into the assembly of communities. To this end, we quantified foraging behaviour of songbirds (Passeriformes) on 21 sites in woodlands and open forests of eastern Australia along a 3000 km long latitudinal transect spanning from the tropics to southern temperate regions. We obtained 5894 prey attacks by 2624 individuals from 112 species. Birds foraged mostly by gleaning (53.4% of attacks) on leaves (51.3%) in the outer part of crown (41.4%) and in medium foliage density (40.8%). Birds foraged along the whole vertical extent of vegetation, but individual species concentrated their foraging into particular strata. In the 41 best sampled species (minimum of 30 attacks recorded), we identified foraging guilds defined first by the foraging substrate and then by the foraging method. Specialisation on foraging substrate was positively correlated with specialisation on method. The organisation of guilds, patterns of substrate and method used across species, and species specialisation were similar to previous local-scale studies from eucalypt woodlands and forests, and from forests in northern temperate regions in Europe and North America. Thus, using our own data and comparisons with previous studies, we confirm a general pattern of foraging guild organisation of woodland and forest songbirds outside the tropics.