Rapid bird species recovery following high-severity wildfire but in the absence of early successional specialists

Aim: The distribution and abundance of forest biodiversity can be shaped by multiple drivers, including disturbances like wildfires. We quantified the influence of wildfire severity and bird life history attributes on temporal patterns of bird site occupancy. 

Location: Wet eucalypt forests of Victoria, Australia. 

Methods: We employed a Before, After, Control, Impact experimental design, gathering occupancy data on birds 5 years before, and for 10 years after, a wildfire in 2009. We quantified post-fire decline and then recovery on sites subject to high-severity fire, comparing these temporal patterns with those for birds at sites that were unburnt or burnt at moderate severity. We also tested the influence of life history attributes on bird responses to wildfire. Data were analysed using joint species distribution modelling, accounting for imperfect detection. 

Results: We found a two-way interaction between fire severity and time period for overall bird site occupancy. The largest change between time periods was on sites burnt at high severity where bird occupancy declined immediately after fire followed by a strong recovery. Occupancy patterns remained largely unchanged on unburnt sites. For many individual species, interactions between fire severity and time period were similar to overall species occupancy. On sites subject to high-severity fire, most species recovered to pre-fire levels within 6 years. We found no evidence of a three-way interaction between fire severity, time period, and life history attributes, with all trait groups of birds examined largely recovered to pre-fire site occupancy levels 10 years post-fire.

Main conclusions: The Victorian 2009 wildfires were severe, but their impacts on common bird species were relatively short-lived, with immediate post-fire declines mostly reversed within ~10 years. Rapid post-fire stand regeneration appears a likely driver of these responses and may account for the relatively limited influence of life history attributes on bird species recovery. However, diet influenced bird species occupancy after fire, with nectivores recovering slower than insectivores on sites subject to high severity fire. Our findings may be relevant to other forests types globally where there can be rapid post-fire vegetation growth and stand regeneration.