Bird diversity within and among Australian heathlands

Abstract

Regional bird diversity is higher in northeastern than in southwestern Australia, owing to the larger area of forests in the northeast and its proximity to New Guinea, a source of speciation via repeated invasions. In protead heathlands bird species are autochthonously produced, and the habitat is more common in southwestern and southern Australia than in the northeast. Bird α-diversity (within-habitats) is the same in southwestern and northeastern heathlands, but β-diversity (among habitats) is higher in the southwest, and γ-diversity (between sites) is higher over shorter distances in the southwest. There are more peripheral species in the northeastern heathlands, and these are drawn primarily from adjacent woodlands, although rainforest and sclerophyll forest species also invade opportunistically. In the southwest, α-diversity increases from protead heathlands through mallee and acacia-scrub to mulga, corresponding to a gradient of increasing productivity largely under edaphic control. The densities of nectarivores decline and those of insectivores increase along this gradient. The core species in the bird community become more predictable from protead heaths to mulga. Soil nutrient status among sites is correlated to leaf specific weight in Acacia, which is negatively correlated to overall bird density.