Burning questions for black cockatoos

Carnaby’s cockatoos feed on the seeds of a variety of native and introduced plant species and on insect larvae. Plants include kwongan heath plants such as banksias, dryandra, hakea, grevillea and also marri seeds. New research suggests fire management may make an important contribution to sustaining the cockatoo’s food sources. (Photo by Leonie Valentine)

Carnaby’s cockatoos feed on the seeds of a variety of native and introduced plant species and on insect larvae. Plants include kwongan heath plants such as banksias, dryandra, hakea, grevillea and also marri seeds. New research suggests fire management may make an important contribution to sustaining the cockatoo’s food sources. (Photo by Leonie Valentine)

The gregarious Carnaby’s cockatoo are such a common sight in Perth that it is easy to forget they are endangered, and that the urban and agricultural expansion of south-western Australia has removed the bulk of their habitat. How we manage their remaining habitat will have important consequences for the species’ survival.

To understand how fire influences food availability in the banksia woodlands the cockatoos depend upon, Leonie Valentine and Richard Hobbs examined how time-since-fire influences plant and cone densities of the two dominant native woodland food species (Banksia attenuata and Banksia menziesii). They then estimated the number of Carnaby’s cockatoo that would be supported in different post-fire aged banksia woodlands (Valentine et al 2014).

They compared tree density and cone productivity of dominant banksias across 44 sites of varying post-fire aged vegetation. The number of Carnaby’s cockatoos that could be supported in banksia woodlands was estimated using the bird’s energetic requirements and seed energy content, and accounting for some aspects of their foraging ecology.

Banksia attenuata produced more cones at sites aged 10–30 years since fire in both survey years, while cone productivity for B. menziesii was highest in very old sites (>35 years since fire) in one year only. The researchers predicted that higher numbers of Carnaby’s cockatoos would be supported in vegetation aged between 14-30 years since fire, peaking in vegetation aged 20–25 years.

The current distribution of post-fire aged vegetation within this area (>60% burnt within the last 7 years) is predicted to support around 2,725 Carnaby’s cockatoos, representing 25–35% of the estimated birds reliant on the area. Their results indicate that food resources are influenced by time since fire. Therefore, if optimising food resources was an objective, the availability of food may be manipulated by altering burning patterns. Importantly, this would involve retaining greater areas of woodland burned with less frequency.

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Reference

Valentine LE, R Fisher, BA Wilson, T Sonneman, WD Stock, PA Fleming & RJ Hobbs (2014). Time since fire influences food resources for an endangered species, Carnaby’s cockatoo, in a fire-prone landscape. Biological Conservation 175: 1–9.

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