• A Charles Sturt University research team recently collected audio recordings from Barmah-Millewa Forest on the Murray River
• The digital recording equipment was used as part of a project to detect a threatened species, the Australasian bittern
• Data will be used to inform water management decisions to protect threatened birds in the face of a changing climate

This Charles Sturt University research project involved perfect timing to record the sounds of animals, particularly the Australasian bittern, that were impacted by recent floods.

In collaboration with NSW National Parks and Wildlife Service, Charles Sturt Gulbali Institute for Agriculture, Water and Environment researcher Dr Elizabeth Znidersic (pictured) led a team that deployed acoustic recorders in the Barmah-Millewa Forest in spring in 2022.

Monitoring was brought forward from October to September because the flood waters were rising and researchers had a small window of opportunity to get into the wetland.

The 2022 to 2023 flood is the largest in a decade, with water levels rising by about three to four metres in the forest.

The Charles Sturt team deployed digital acoustic recorders by boat and kayak and recorded sound continuously from September 2022 to February 2023. The recordings contain other vocal species of interest that were also impacted by the floods.

Data obtained will be provided to an open access platform, ‘Eavesdropping on wetland birds’, where interest groups and researchers can access the information.

There are an estimated 1,300 Australasian bitterns nationally, with a high percentage in the wetland matrix of Barmah-Millewa Forest, straddling the Murray River. Preserving and managing key habitat locations is critical to the survival of the species.

“Up until this time there has been limited monitoring of bittern population response to such a significant flooding event,” Dr Znidersic said.

“There has been significant work carried out in rice fields and how water levels affect Australasian bittern breeding success. However information from natural wetland systems has often alluded us.

“The data from the monitoring has identified changes in timing of the bitterns calling because of the flood.

“The research shows that male Australasian bitterns started their breeding calls just before the peaking flood waters, then recommenced later than usual in the season, after flood waters slightly receded and nesting habitat became available again.”

The recordings showed that the number of males calling was as many as there ever has been recorded.

Partner agencies, including NSW National Parks and Wildlife Services, NSW Government and Murray Darling Basin Authority, collaborated to allocate environmental water flow to key areas of the forest to ensure bitterns were able to successfully fledge chicks late in the season.

“Water for the environment is an important management tool capable of providing positive outcomes for endangered species,” Dr Znidersic said.