Refuges for birds in fire-prone landscapes: The influence of fire severity and fire history on the distribution of forest birds

Abstract

Unburnt patches within a fire boundary may act as refuges for fauna, facilitating their survival and persistence within fire-prone landscapes. Unburnt patches can arise due to various processes, including topographic variation, fire behaviour, and fuel reduction from recent burning. However, the value of unburnt patches of differing characteristics to the post-fire persistence of faunal communities has rarely been examined. In this study, we examined the relative importance of fire history and severity in predicting the occurrence of birds in a burnt forest landscape. We conducted surveys in mixed eucalypt forest of south-east Australia, 2–3years after a high intensity, landscape-scale wildfire (>200,000ha). Sites (n=91) were selected to encompass fire severity ranging from unburnt patches to stands of crown-burnt forest. Fire history prior to the wildfire was defined as short (<3years) or long (>20years) time-since-fire. Unburnt patches of long time-since-fire were important avian refuges, harbouring 20–40% more species, up to 56% more individuals and an assemblage that was distinct from that at all sites burnt by the wildfire, including low severity ground fire. No difference in species richness or composition was detected between sites in unburnt patches of short or long time-since-fire; but bird abundance was ∼20% lower in patches of short time-since-fire. Unburnt and ground-burnt patches of short time-since-fire provided habitat for more species and had distinct assemblages from that of severely burnt sites. For sites severely burnt in the wildfire, there was no difference in avifaunal richness, abundance or composition between those burnt twice in rapid succession and those not burnt for >20years. Together, these results highlight: (1) the particular importance of unburnt vegetation remaining within fire-affected areas as faunal refuges, and (2) the potential for recent planned burns to contribute to refuge habitat if it avoids severe burning in a subsequent wildfire.