The Tasmanian Wedge-tailed Eagle Aquila audax fleayi is listed as Endangered under provisions of the Environment Protection and Biodiversity Conservation Act (1999) for threatened species. The subspecies is distributed across most of Tasmania and some of its offshore islands, but is believed to be in slow decline (Bell and Mooney 1999, Garnett and Crowley 2000). The subspecies range includes a number of recently constructed wind power generation facilities (wind farms) and more facilities are proposed.
Wind farms may pose a risk of collision to the eagle as bird mortalities are known from wind farms in a variety of situations worldwide and a few Wedgetailed Eagles have already been recorded as casualties of collision with turbines in Tasmania and elsewhere in Australia. The present project is specifically aimed at determining the cumulative risks posed by collision of eagles with wind turbines. A variety of associated impacts of wind farm developments may affect bird populations. They include direct loss of habitat due to constructed facilities and roads; alienation of habitat caused by disturbance during construction and on-going operation; and potential for electrocution and collisions with overhead distribution lines. These latter impacts are not addressed as part of the present project.
The project has two essential aims:
1. To predict, based upon the extant population of Tasmanian Wedge-tailed Eagles, the potential cumulative impacts of collision risk posed by a number of wind farms across the range of the species distribution. The project utilises bird collision risk modelling to generate assessments of the cumulative risk to the endangered Tasmanian Wedge-tailed Eagle posed by such collisions.
2. To determine a suitable assessment to provide an estimate of the level at which predicted collision (and hence number of turbines or presented area of turbines) is likely to present concerns for the Tasmanian Wedge-tailed Eagle population. We term this 'critical impact level'.
The cumulative modelling was undertaken for the species using the Biosis Research avian collision risk model. The assessment is based on existing and currently proposed wind farm sites.