Ecology of Brown and Striated Thornbills in Forests of South-eastern New South Wales, with Comments on Forest Management

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Abstract
Brown and Striated Thornbills Acanthiza pusilla and A. lineata are abundant and widespread in forests of south-eastern Australia. The two species are similar in appearance and often occur together. However, the Striated Thornbill forages mainly in the subcanopy and canopy (> 75% of foraging observations) where it specialises in taking food from the foliage of eucalypts (> 90% of observations). The Brown Thornbill forages mainly in the shrub layer (> 70% of observations) and takes prey from bark, debris and the leaves of a large variety of plants including eucalypts. Both thornbills forage mainly by gleaning but the Striated Thornbill commonly hang-gleans (> 20% of observations), a behaviour rarely used by Brown Thornbills (< 5% of observations). Because of their ecological differences, the two thornbills respond differently to forest management. Striated Thornbills are disadvantaged by logging, which reduces the amount of canopy and subcanopy vegetation, but Brown Thornbills benefit from the increased amount of shrub and ground vegetation that results. Conversely, Brown Thornbills are adversely affected by fires that reduce the amount of debris and low vegetation. In the absence of eucalypts, Striated Thornbills are absent from pine (Pinus) plantations, but Brown Thornbills may be abundant. The abundance of thornbills, their wide distribution and different responses to forest management suggests that they could be useful in monitoring the health of forest ecosystems and for developing plans of management that take into account the differing requirements of forest wildlife.