Many waterbird species can nest together, often in very large numbers, these include cormorants, pelicans, ibis, egrets and herons. We closely monitor waterbird breeding events so that water managers can adjust flows, ensuring chicks have the very best chance of survival and quantifying the success of each breeding event.

Widespread La Niña weather conditions in 2021-22 and 2022-23 water years resulted in above average rainfall and extensive flooding. These large events can be a trigger for waterbird breeding events, but sometimes need Commonwealth and NSW environmental water releases to guarantee water remains under nests long enough to ensure successful fledging. A combination of survey methods were used to monitor the 2021-22 and 2022-23 breeding events. This included aerial surveys completed by NSW Department of Climate Change, Energy, the Environment and Water staff (DCCEEW, formerly DPE) staff in fixed-wing aircraft, on ground surveys by CSU and NSW government staff on foot or kayak, intensive on ground monitoring of ibis breeding sites led by Dr. Kate Brandis at University of NSW (UNSW), and with the use of drone surveys as led by Dr. Roxane Francis (UNSW).

During the 2022-23 breeding season, 28 active breeding sites were detected across the Mid-Murrumbidgee wetlands and Lowbidgee Floodplain. Of these, 24 active breeding sites were monitored, including two large ibis breeding sites and a large pelican nesting site at Gayini Nimmie-Caira. Fourteen waterbird species were confirmed to be nesting in 2022-23 including: Australian white ibis (Threskiornis moluccus), straw-necked ibis (Threskiornis spinicollis), royal spoonbill (Platalea regia), yellow-billed spoonbill (Platalea flavipes), little pied cormorant (Microcarbo melanoleucos), little black cormorant (Phalacrocorax sulcirostris), Australasian darter (Anhinga novaehollandiae), great cormorant (Phalacrocorax carbo), nankeen night-heron (Nycticorax caledonicus), white-necked heron (Ardea pacifica), white-faced heron (Egretta novaehollandiae), eastern great egret (Ardea alba modesta), intermediate egret (Ardea intermedia) and Australian pelican (Pelecanus conspicillatus).

Large-scale waterbird breeding is often associated with widespread flooding. Environmental water can play a key role in supporting breeding sites with additional flows to extend the duration of inundation in breeding and neighbouring foraging habitats, after breeding is initiated, and where needed, increase water depths and maintain water quality to promote successful breeding.

Acknowledgements

Our thanks to the Nari Nari for allowing access to the Gayini Wetlands and to Jamie Woods and Mark Schneider (Nari Nari Tribal Council) for assisting with ground access and survey logistics. We also thank Mon Carmichael and Matt McClelland for advice on ground survey access for sites on Yanga National Park. Many thanks to landholders for permitting access to other sites in the Nimmie-Caira, North Redbank and Mid-Murrumbidgee wetlands. Ground surveys were completed by Sarah Talbot, Christopher Sundblom (CSU), Amelia Walcott, Vanessa Cain, Carmen Amos, Monique McKenzie-Gay (NSW DCCEEW-EHG) and Matthew Chapman (UNSW volunteer). The December aerial survey was undertaken by Alex Katopodis (NPWS Park Air), Jennifer Spencer, Anthony Conallin, Iris Xiao (NSW DCCEEW-EHG), Ali Borrell, Jane White (MDWWG) and Mal Carnegie. Drone surveys were completed by Matt Smith, Jana Stewart, Sophie Hewitt (UNSW) and Mal Carnegie (DPE Contractor). Our thanks also to Anthony Conallin (NSW DCCEEW-EHG) and Matt Herring (Murray Wildlife) for their assistance with surveys over the summer months. The ground surveys and drone surveys are approved under NSW NPWS Scientific Licencing and NSW DCCEEW-EHG and UNSW animal care and ethics committee approvals.