Livestock grazing reinforces the competitive exclusion of small-bodied birds by large aggressive birds

1.Grazing by domestic livestock is sometimes promoted as a management tool to benefit biodiversity. In many situations, however, it can produce negative outcomes.

2.Here we examine the impacts of recent and historic livestock grazing on bird communities in the semi-arid woodlands in eastern Australia, testing the notion that grazing removes the suppressive effect of structurally complex vegetation on miners, thereby reducing the richness and abundance of small birds.

3.We used time- and area-limited searches of 108 sites varying in livestock grazing history and intensity, to explore the direct and indirect effects of grazing, habitat complexity and the abundance of aggressive, large-bodied birds on smaller-bodied birds using two-way analysis of variance and structural equation modelling.

4.Small birds were less abundant and had lower richness in the presence of miners. Our structural equation models indicated that recent grazing had direct suppressive effects on the abundance o...