Response of birds to a wildfire in the Great Western Woodlands, Western Australia.

Abstract

In December 2005, a wildfire burnt a large area of semi-arid eucalypt woodland along ~10 km of the Norseman- Coolgardie Road north of Norseman in the Great Western Woodlands (GWW), Western Australia. Few birds used the burnt area in the first year after the fire and these were mainly ground and shrub foraging insectivores. There was no influx of seed-eaters or open-country species as reported for post-fire habitats elsewhere in southern Australia. The greatest number of individuals and species of birds occurred in the second year post-fire when ground and shrub vegetation was floristically most diverse. Canopy foragers were attracted to the burnt area in the second year by an outbreak of psyllid insects on seedling eucalypts. At the same time, bark dwelling arthropods associated with the standing stems of fire-killed eucalypts attracted bark-foragers. From the third year, small insectivorous ground, shrub, and canopy foragers dominated the avifauna on the burnt area. These foraged on fire-killed shrubs, as well as living vegetation, including the lignotuberous regrowth of eucalypts. Bark foragers were uncommon after the second year. Throughout the study, the burnt area had fewer species and individuals than adjacent unburnt habitats. Compared with unburnt woodlands there were few differences in how species foraged on the burnt plots, but most species foraged lower reflecting the stature of the vegetation in the burnt woodland. Nectar-feeders, fruit-eaters, large insectivores, raptors, and parrots, although common in the unburnt woodland, were absent or rare in the burnt area. This reflected the limited regrowth of vegetation on the burnt area, which lacked the structural and floristic complexity of nearby unburnt woodlands. Ground foragers probably commenced nesting on the burnt area in the first year, with shrub and canopy foragers nesting from the second year. However, after five years, there was no evidence of large insectivores, nectar-feeders, raptors, seed-eaters, or foliage-eaters (i.e., parrots) nesting despite their abundance in adjacent unburnt woodland. Some of the unburnt woodlands monitored in this study were even-aged regeneration estimated to be 30–50 years post-fire or logging. Regardless of origin, these even-aged plots lacked the diverse avifauna associated with mature woodlands and suggest that post-fire recovery of birds and vegetation in these woodlands is likely to take decades and probably more than 100 years. If so, human activities that increase fire frequency in the GWW, including climate change and fuel-reduction burns, will have long-term adverse impacts on regional biodiversity exceeding those associated with wildfires in less arid forests and woodlands where rates of recovery are more rapid.