Effects of an extensive wildfire on birds in far eastern Victoria

Abstract

A major wildfire burned 228 400 ha of forest in East Gippsland (Victoria, Australia) in February and March 1983, including Cooaggalah forest block where flora and fauna studies had just commenced. Bird abundance was assessed on 13 sites immediately before and after the fire, and annually for three years to 1986. The sites represented a range of habitats including rainforest, heaths and eucalypt forest, all of which burned. Total bird abundance was reduced to 60% of initial levels by the fire, but recovered within three years. These changes differed significantly between habitats. Initial decreases were greatest and subsequent recovery least in heaths where most above-ground vegetation had been killed. Post-fire increases were greatest in rainforest and on granite ridges, and in each case bird abundance rose to levels substantially higher than before fire. Some changes may have involved recovery from drought as well as fire. Changes over time were highly significant for many groups of birds (e.g., honeyeaters), while others showed little change (e.g., bark-foragers and insectivores that inhabit dense understorey or damp ground below shrubs). Honeyeaters and seed-eaters suffered the greatest initial declines, and some species in these groups were slow to recover (e.g., New Holland and Crescent Honeyeaters and Beautiful Firetail). Some species that feed from open ground increased quickly to levels greater than before fire (Flame and Scarlet Robins, Buff-rumped Thornbill and Superb Fairy-wren), but all except the latter then declined as shrubs regenerated. The main loss of birds immediately after the fire was of highly mobile species, and the composition of the remaining bird fauna appeared to depend on resource availability rather than the capacity of species to survive the fire front. Initial responses of species to fire were poor predictors of their responses after three years. Hence, the effects of fire should be considered in terms of habitat changes over several years. Many forest types including rainforest can provide continuing habitat even when they burn, but populations of mobile birds such as honeyeaters depend on access to alternative habitats on a broad regional scale.