Avifaunal responses to single and recurrent wildfires in Amazonian forests

Although forest wildfires threaten to impoverish vast expanses of once fire-resistant humid tropical forest, their effects on the vertebrate fauna remain poorly understood. We report results from a study in central Brazilian Amazonia examining a large area of terra firma (unflooded) forest that had been affected by fires during the 1997-1998 El Nino-mediated dry season. By sampling 0.25-ha forest plots both one and three years after fire disturbance, we noted that over time the bird community became increasingly dissimilar from that in unburned control plots. The influences of burn severity and recurrent fires were then examined across 28 plots that were all sampled three years after the fires. Foraging guilds differed in their responses to the gradient of increasing burn severity; most guilds declined, although arboreal granivores, frugivores, and nectarivores showed unimodal responses and arboreal gleaning insectivores increased. These responses were strongly correlated with associated changes in the habitat structure and reflected differences in resource abundance where this was quantified. Rates of species turnover were high, and there was virtually no species overlap between unburned forest plots and those that had burned in more than one El Nino dry season. Our results indicate that, unless conservation strategies can prevent a recurrent fire regime from becoming established in seasonally dry tropical forests, only nonforest and second-growth bird species, which are of minimal conservation importance, will be able to persist in fire-prone landscapes of the future.