Impacts of picnic areas on bird assemblages and nest predation activity within Australian eucalypt forests

Abstract

We assessed the impacts of picnic areas on birds within adjacent eucalypt forests in the Brisbane region, Australia. Within the picnic areas there was an assemblage of relatively large, aggressive birds, including several generalist predators (Torresian crow, grey and pied butcherbirds, Australian magpie) as well as the noisy miner, resembling that found in suburban areas within the study region. Eight transects abutting picnic areas ("picnic area edges") were compared with two types of matched control transect within forest about 150 m away: "forest interiors", which were also distant from any other edge; and, "context references", which were similar to the picnic area edges in their proximity to the access roads and forest external edges. Bird assemblages at picnic area edges, which were dominated by the noisy miner and Australian magpie, clearly differed from those of forest interiors, which were characterised by a number of smaller-bodied insectivorous species. Levels of artificial nest predation were several-fold greater adjacent to the picnic areas. Context reference transects were more often similar to forest interiors than to picnic area edges. We conclude that picnic areas exert strong localised edge effects on forest bird assemblages, and are likely to cause reduced reproductive success for small-bodied forest bird species which attempt to nest nearby.