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A boom year for waterbirds in the Murrumbidgee

Authors: Jennifer Spencer, Kate Brandis, Damian Michael

Tens of thousands of breeding waterbirds were recorded in the Lowbidgee Floodplain this season. It has been the largest colonial waterbird breeding event in the Basin this year, both initiated and then supported by water that has been specifically set aside for the environment. In total, 17 active waterbird colonies in the Lowbidgee, and three active colonies in the mid-Murrumbidgee wetlands were detected during surveys completed from Spring 2020 to late Summer 2021. This included a large colony of 36,000 straw-necked and glossy ibis at Eulimbah Swamp in the Gayini wetlands, and five medium-sized and 14 much smaller-sized colonies with ibis, egret, spoonbill, heron and cormorant at sites across the rest of the Murrumbidgee Selected Area.

University of NSW Centre for Ecosystem Science Research Fellow, Dr Kate Brandis, who led the monitoring of the Eulimbah Swamp ibis colony said the event was a fantastic result for the Basin’s waterbird populations, and for water management in the Murray-Darling Basin.  She said:

“The fact that we can use water for the environment to stimulate the birds to breed and maintain nesting is really promising… these birds only breed when flooding conditions are right.”

In the past high rainfall has led to natural flooding which has resulted in even larger waterbird breeding colonies.

The Australian darter will often nest among other colonial species such as the little pied cormorant. Photo credit: Damian Michael

Fellow researchers, Dr Jennifer Spencer (NSW Department of Planning, Industry and Environment) and Dr Damian Michael (Charles Sturt University) led colony monitoring across the rest of the Murrumbidgee Selected Area, documenting stage of nesting and water levels at sites across Yanga National Park and neighbouring private wetlands.
Dr Jennifer Spencer said it has been a really great year for the Bidgee.

“In total, 13 colonially-nesting species were recorded breeding including royal and yellow-billed spoonbills, little pied cormorant, little black cormorant, nankeen night-heron, eastern great egret and intermediate egret.  Nationally endangered Australasian bittern and NSW listed blue-billed duck and freckled duck were also recorded at several sites in the Lowbidgee floodplain during the 2020-21 ground surveys.”

Waterbird breeding in the wetlands began in Spring 2020 with above average rainfall complemented with the targeted use of 200,000 megalitres of NSW and Commonwealth water along the Murrumbidgee River. More than 15,000 hectares of wetlands in the Gayini system were inundated by the water release, as well as a similar area in the adjoining Yanga National Park, reaching as far as Yanga Lake in the lower Murrumbidgee floodplain system near Balranald.

The eastern great egret, nankeen night-heron and yellow-billed spoonbill were among 13 colonial species that successfully bred in the Murrumbidgee catchment this season. Photo credit: Damian Michael
Thousands of straw-necked ibis travelled from all over Victoria, NSW and southern Queensland to establish a breeding colony in the Murrumbidgee catchment this season. Photo credit: Sankha Subhra

The breeding event was closely monitored and demonstrated successful fledging of thousands of young waterbirds, with close attention paid to keeping the water stable.  When water levels drop too quickly the birds abandon their nests, so our environmental flow deliveries need to be carefully timed for the birds to finish nesting and fledge their young.

Monitoring and management of this delivery of water for the environment has been a collaborative effort involving the Nari Nari Tribal Council, Murray-Darling Wetlands Working Group, Centre for Ecosystem Science UNSW, Charles Sturt University, NSW Department of Planning, Industry and Environment and the Commonwealth Environment Water Office.

The Murrumbidgee waterbird monitoring was funded through Flow-MER — the Commonwealth Environmental Water Office’s Monitoring, Evaluation and Research Program and NSW Department of Planning, Industry and Environment – Environment, Energy and Science.

Feature image: At its peak, the ibis colony on Gayini grew to approximately 36,000 birds. Photo credit: Roxane Francis

Our work in the Murrumbidgee

The Murrumbidgee is a lowland river system with large meandering channels, wetlands, lakes, swamps and creek lines. Our work here focuses on understanding how native fish, waterbirds, reptiles and amphibians, as well as wetland vegetation communities, benefit from these targeted environmental watering actions.

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