The Powerful Owl is Australia’s largest owl (about 60cm tall) and is facing significant threats from habitat loss and disturbance. These owls are relatively rare and are classed as a Vulnerable species on the Victorian Flora and Fauna Guarantee Act 1988 Threatened List. In Banyule, we are lucky to have Powerful Owls living in remnant habitat along the Yarra River corridor. For such large birds, Powerful Owls are not easy to detect. They have large territories and are very good at hiding during the day. They are most active at night, hunting for possums and gliders. This makes it difficult to tell how our local Powerful Owls use habitat and whether they are thriving.
The Powerful Owl has a distinctive double hoot call that gives away its presence. However, their territories span many kilometres and nocturnal outings to listen for calls are often unsuccessful. In 2023 the Society was fortunate to receive a Banyule City Council Environmental Grant to purchase and use audio monitoring techniques to detect Powerful Owls.
Miniature programmable audio recorders were purchased and deployed at strategic locations to pick up owl calls. Recordings were analysed as a spectrogram (plot of frequency versus time) and low frequency double hoot calls were readily detected (listen to the audio recording below).
From February to October 2023, Powerful Owl calls were detected on over 250 occasions at 13 sites from Yarra Flats to Westerfolds Park. Changes in the use of habitat were evident over the year and may be related to the winter breeding season. Call detection and observations on the ground suggest that there are three or four Powerful Owls in the area surveyed. The surveys have also recorded other nocturnal species including Krefft’s Gliders, Boobook Owls and Owlet Nightjars.
All data collected is reported to Banyule Council. The Powerful Owl is one of six key indicator species in Banyule being monitored as part of Council’s ‘No Local Extinction’ plan. To date, the project has now detected 293 Powerful Owl calls at various local sites along the Yarra River. This valuable information on the Powerful Owl’s landscape can be used in making evidence-based decisions for managing and protecting wildlife habitats.
We are pleased with how successful this project has been and grateful to the Banyule Council for the support they have provided.
For more about protecting Banyule’s biodiversity, visit www.banyule.vic.gov.au/biodiversity