Prescribed burn severity has minimal effect on common bird species in a fire-prone forest ecosystem

Abstract

Prescribed burning is widely used to mitigate the effects of severe fires across the landscape and to maintain biodiversity. Just like wildfires, the severity of prescribed burns can vary; this study was an opportunistic investigation. In one fortnight during autumn months of 2012, several prescribed burns were carried out in heathy-dry forests of central Victoria, Australia. We used measurements of canopy scorch, bark burn and ground cover burn to calculate a severity score for each site. The severity scores across sites ranged from low (2.5) to high (10). A before-after control-impact (BACI) design was utilised to model the potential impacts of fire and fire severity on birds. We used generalised linear mixed models (GLMM’s), and incorporated first- and second-year post-fire spring/summer observations from 2012 to 2014, against bird data from observations carried out in 2010. The total combined abundances of individual species showed that broadly, bird abundance rebounded to pre-burn levels by the second spring post-fire. There was little response detected in either species richness or turnover. The muted turnover result aligns to other studies that indicate a scarcity of early-successional-stage species in eucalyptus forests and woodlands that rapidly regenerate post-fire. Ten individual species were also examined, and only one species, the White-throated Treecreeper (Cormobates leucophaea), responded to both fire and its severity. The BACI design was informative in illustrating that while the forest birds were resilient to small-scale prescribed burns of any severity, abundances in general may have been in decline, a result aligning with the years of reduced rainfall in the region.