Penetration of remnant edges by noisy miners (Manorina melanocephala) and implications for habitat restoration

Abstract

The noisy miner (Manorina melanocephala) is a large, communally breeding colonial native honeyeater renowned for aggressively excluding virtually all other bird species from areas they occupy. In the woodlands of southern and eastern Australia, numerous studies have identified the domination of remnants by noisy miners as having a profound negative effect on woodland bird communities. Despite this, very little is known about the habitat characteristics that make domination of a site by noisy miners more likely. This study investigated the depth from edges that noisy miners penetrated into large woodland remnants (>48 ha) within Victoria and attempted to identify habitat characteristics that influenced the depth to which they penetrated. Penetration depth differed significantly across four broad habitat types but commonly ranged from 150 m to more than 300 m from the remnant edge. If noisy miners colonise a site, their capacity to penetrate in from a remnant edge has implications for the size that remnants need to be (>36 ha) to contain any core ‘noisy-miner-free’ habitat and the width that habitat corridors need to be to avoid domination by noisy miners (>600 m). Broad differences in habitat type and the abundance of noisy miners at a site were the most powerful predictors of penetration distance. The density of canopy trees on a site was the only other habitat variable contributing to the most parsimonious model of penetration depth. Decreasing density of trees was associated with increasing penetration depth by noisy miners.