A recently developed watering guide will improve how NSW environmental water managers support one of Australia's most endangered and cryptic native waterbirds - the Australasian bittern.
Despite its endangered status, efforts to manage and protect the Australasian bittern have been limited by gaps in knowledge, inconsistent monitoring, and a lack of clear, coordinated guidance. Analysis of years of acoustic data, as well as collaboration and ecological investigation, are now helping to fill some of these gaps.
The project began by re-examining years of NSW Saving our Species southern bell frog acoustic data to locate Australasian bittern calls buried within the recordings.
'Developing a watering guide was always a key aim of the project, but first we needed a clearer picture of where Australasian bitterns actually were in the landscape,' NSW Department of Climate Change, Energy, the Environment and Water Scientist Ali Borrell said.
Supported by the SoS Science and Research Fund, this work identified previously unidentified sites in the Murrumbidgee and Lachlan catchments where male Australasian bitterns had been calling for extended periods.
Although the species is nationally endangered, very little research exists on its environmental watering requirements. As a result, water managers have lacked the data needed to guide decisions about water delivery for habitat and breeding.
'Bitterns are incredibly secretive, highly mobile and difficult to monitor,' Ali says.
'That's part of why they've slipped through the cracks. There was a real need to pull together best available information into one place.'
Collaboration with NSW environmental water management officers shaped the structure of the guide, aiming to make its recommendations reflect real-world decision making across dry, average and wet years. Additional modelling and technical input strengthened the recommendations.
Acoustic data dating back to 2017 in the Lower Murrumbidgee and from 2021 in the lower Lachlan were analysed to document the distribution of the species across these 2 neighbouring floodplain wetland systems. This year, real time acoustic analysis also helped confirm where bitterns occurred in the Greater Cumbung Region, directly informing decisions about whether top-up watering was needed.
The guide is already proving valuable on the ground.
'Environmental water is one of the most important levers we have for managing habitat for Australasian bitterns in south-western New South Wales,' Ali explained.
'That's why it was so important to complete this guide.'
Lachlan environmental water manager Dr Jo Lenehan says the guide has become an essential planning tool.
'The watering guide for the Australasian bittern is always the first resource I turn to when planning any watering, management, or monitoring activities for this rare and hard to find waterbird,' Dr Lenehan says.
'In the Lachlan Valley, the Greater Cumbung Region is one of the few places where we aim to actively support Australasian bitterns. When we recently developed a water management plan with the Commonwealth Environmental Water Holder, the guide proved extremely useful, as it already contained the key ecological goals, targets and watering strategies we needed.'
The guide to environmental watering guide and its supporting technical report are now available, providing a much-needed resource to help protect one of Australia's most elusive and threatened waterbirds.
To view the guide, visit Australasian bittern.
