Changes in bird assemblages during succession following disturbance in secondary wet forests in south-eastern Australia

Abstract

After a successional forest is severely disturbed by wildfire and subsequent salvage logging or by clearfell timber harvesting and slash burning, if conditions are suitable, the forest will regenerate. It then passes through a series of stages of varying floristic composition and structure until further severe disturbance occurs. The characteristics of a forest-bird assemblage vary with both the successional stage of the forest (time period since the most recent severe disturbance event) and the long-term disturbance history of the forest. To determine how the bird assemblage changes during succession in a south-eastern Australian forest type that is fire-sensitive and also subject to regular timber harvesting, we surveyed birds in five age-classes of wet forest (from 2 to >100 years post-disturbance). Bird-assemblage composition altered sequentially; the pattern and rate of change reflected those of the vegetation. Bird abundance and species richness varied little during succession. No species of bird was abundant only in early successional forest. Some species, such as Brown Thornbill (Acanthiza pusilla), Golden Whistler (Pachycephala pectoralis) and Grey Fantail (Rhipidura albiscapa), were common in all successional stages. Other species, such as White-throated Treecreeper (Cormobates leucophaea) and Striated Pardalote (Pardalotus striatus), were consistently abundant in mid-to late successional stages only; this highlighted the importance of older forests for avian biodiversity. Any increase in the frequency of severe disturbance in these forests would tend to favour only those bird species that are already common. This has implications for management programs in forests that are habitat for wildlife, but are also used by humans for timber harvesting and other commercial or recreational purposes.