Big booming data: Monitoring Australasian Bittern using acoustic monitoring in Tasmania
The following abstract is part of the Bringing Back the Bunyip Bird Australasian Bittern Conservation Summit (Leeton, 1-4 Feb, 2022).
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Liz Znidersic, Charles Sturt University, eznidersic@csu.edu.au
Little is known about the status and distribution of Australasian Bittern in Tasmania. Detections have been consistent over the years at only a few sites regularly visited by recreational birdwatchers, however no large-scale survey effort has been attempted.
We deployed acoustic monitors at sites on the north and east coasts of Tasmania with historical detections and also at a few previously unsurveyed sites with suitable habitat. One of our objectives was to investigate whether acoustic monitoring was an effective and cost-efficient method to determine presence and, just as importantly, to confidently infer-absence. We also aimed to contribute information relating to distribution, population and life history of Australasian Bittern.
The acoustic monitors were programmed to record continuously for up to weeks or months at a time. We analysed the data using a Bittern call recogniser and long-duration false-colour spectrograms.
Our results indicate that acoustic monitoring is the optimal method to detect Australasian Bittern due to its irregular calling pattern which can differ from day to day and hour to hour. The ‘booming’ call was visually identifiable in long-duration false-colour spectrograms, but the call recogniser was more sensitive in detecting distant calls.
The vocalisation patterns identified by our analytical methods will provide cost and time efficient tools to scale up survey effort over the next few years in Tasmania. This will provide a more-reliable population estimate and knowledge of distribution to assist conservation efforts.