Wildfire and fire mosaic effects on bird species richness and community composition in south-western Australia

Abstract

Background: A fire management strategy of deliberate patch-mosaic burning (PMB) is postulated to promote biodiversity by providing a range of habitat patches with different fire histories, habitat qualities, and vegetation ages at a given scale. We investigated the response of avian fauna to fire, particularly species richness and community composition, in a landscape composed of a diversity of vegetation ages including long-unburned refuges (age 26 years), compared with a landscape of uniform vegetation ages recovering from an extensive and intense fire. Results: There was no effect of heterogeneity in vegetation age on species richness at whole forest management block (about 6000 ha), or local (2 ha) scales. There were different responses of particular species to vegetation age. Nine species showed responses to vegetation age at local (2 ha) scales, which is presumably a surrogate for availability of key resources and which changes over time. Australian Pipit (Anthus australis Vieillot, 1818) were absent from swamp vegetation <3.5 years old, while Spotted Pardalote (Pardalotus punctatus Shaw & Nodder, 1792) were only found in forest vegetation <3.5 years old. Year-to-year changes in local assemblages were detected after removing the effect of time since fire. There was no difference in effect of the two fire regimes on assemblage composition or feeding-guild structure. Conclusions: Mosaics of different vegetation ages had no net benefit for biodiversity, as measured by species richness and assemblage composition, at the forest block management unit scale. Different responses to vegetation age among bird species did not lead to increased bird richness at the scale of forest management block. A potential advantage of mosaics in conservation of avian biodiversity is through preservation of patches of older vegetation ages in the landscape, compared to the periodic extensive loss of older vegetation ages in wildfires. However, the absence of large-scale effects of vegetation age on bird species richness, the tendency for birds to specialize to fuel ages >5.5 years in the landscape studied, and indications of flexible responses of some species at landscape scales allows some flexibility in fuel management strategies and the scale at which they are applied with respect to avifauna.