Joshua S Lee, Corey Thomas Callaghan, William K Cornwell

Large and severe fires (“mega-fires”) are increasing in frequency across the globe, often pushing into ecosystems that have previously had very long fire return intervals. The 2019-20 Australian bushfire season was one of the most catastrophic fire events on record. Almost 19 million hectares were burnt across the continent displacing and killing unprecedented numbers of native fauna, including bird species. Some bird species are known to thrive in post-fire environments, while others may be absent for an extended period from the firegrounds until there is sufficient ecosystem recovery. To test for systematic patterns in species use of the post-fire environment, we combined citizen science data from eBird with data on sedentism, body size, and the specialisation of diet and habitat. Using generalised additive models, we modelled the response of 76 bird species in SE Australia to the 2019-20 mega-fires. Twenty-two species decreased in occurrence after the fire; thirty species increased; and no significant effect was found for the remaining twenty-four species. Furthermore, diet specialism was associated with reduced recolonisation after fire, with diet specialists less likely to be found in burned areas after the fire event compared to before, a result which generates testable hypotheses for recovery from other mega-fires across the globe. Being displaced from the firegrounds for an event of this geographic magnitude may have severe consequences for population dynamics and thus warrant considerable conservation attention in pre-fire planning and in the post-fire aftermath.