Bitterns boom in border wetlands

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Bitterns are booming in wetlands along the Murray River. Scientists estimate upwards of 200 Australasian bitterns are currently nesting in the Barmah-Millewa forest, enjoying the benefits of environmental water.

This endangered bird can be hard to spot in the wild, but its distinctive booming call is cause for celebration in the border wetlands.

Environmental water has been flowing into the forests for a number of months triggering an explosion in the food chain and providing ideal conditions for the bitterns to feed and breed.

Monitoring has yielded some promising and surprising results.

Just last month, staff from the NSW Office of Environment and Heritage and Commonwealth Environmental Water Office observed three Australasian bitterns circling above the wetlands at Reed Beds Swamp, south of Deniliquin.



The Australasian bitterns take flight over Reed Beds Swamp in southern NSW. Photo E Wilson OEH.

The behaviour is quite unusual for the mainly solitary and secretive bird, but it hints at the density of breeding animals within the wetland.

OEH Water Manager Paul Childs said the bitterns demonstrated just one response of natural wetlands to environmental watering.

“The Australasian bittern is one important animal in an entire ecosystem benefitting from environmental water,” Mr Childs said.

When environmental water arrives at a wetland, nutrients are mobilised, insect numbers surge and higher order predators like fish, frogs and birds, move in to feast.

“The bitterns are nesting among the reeds and hunting for food in the wetland shallows.

“To know that around 20 per cent of the estimated Australasian bittern population is now occupying the Barmah-Millewa forest is really significant from an ecological point of view.

“But there is also the cultural significance of having them here.

“The booming call of the bittern is thought to have inspired the legend of the bunyip – a central character in Aboriginal storytelling and one that invoked fear in the minds of early European settlers,” he said.

As well as Australasian bitterns, many other native animals have responded to this water delivery including little bitterns, egrets, grebes and a diversity of frogs.

“The Barmah-Millewa forests are also home to a rare expanse of grassland known as the Moira grass plains,” Mr Childs said.

“This wetland grass adds oxygen and filters flows, provides nesting material for birds, shades the water below for the benefit of fish and frogs, and mulches the wetland as the water recedes.

“Nearby river red gums are being watered too.

While this water has reached just 10 per cent of the Millewa forest, we are seeing improved red gum health further out from the inundated area.

“This suggests that the root systems of trees are reaching into ground-water reserves that have been partly recharged by this environmental water.

“These results show us we are on the right track in developing the strategies that will keep the floodplain environment healthy and productive for plants, animals and people alike,” he said.

The National Parks and Wildlife Service (NPWS) is monitoring both the bittern and general waterbird response to the recent environmental flows.

NPWS Rehabilitation Officer Rick Webster said the large diversity of waterbirds including Australasian bitterns (listed as endangered under the EPBC Act) reflected the good health of sites targeted for watering.

“The results to date are pleasing,” Mr Webster said.

“Bitterns can be difficult to see so we have used a combination of techniques to find them.

“NPWS staff and contractors head out to the wetlands at dawn and dusk, listening for the bittern boom and determining how many are present at each site.

“As well as Australasian bitterns, our monitoring has detected large numbers of colonial waterbirds including white-necked and white-faced herons, Nankeen night herons, eastern great and intermediate egrets, Australasian darters, little pied cormorants, white bellied sea-eagles, whiskered terns, black winged stilt and Australian white and straw-necked ibis.

These birds are revelling in the diversity of aquatic plants that have emerged as the watering event continues.

“Some of these aquatic plants include Moira grass, wavy Marshwort, water ribbons and milfoil.

“During our surveys we have also observed large numbers of frog eggs and tadpoles.

“All-in-all, it’s a pleasing outcome,” he said.

Commonwealth Environmental Water Holder David Papps said it was great to see Australasian bitterns enjoying the wetland habitats throughout the Barmah-Millewa forests following recent environmental watering events.

“Using environmental water to conserve the Australasian bittern in the Barmah-Millewa forest is part of a collaborative effort between multiple agencies,” he said.

This environmental watering event has been a collaborative effort between several government agencies with water supplied by the Commonwealth Environmental Water Holder, Murray-Darling Basin Authority (under The Living Murray program) and NSW Office of Environment and Heritage.

NSW OEH staff and the Goulburn Broken Catchment Management Authority have provided advice to the River Murray Operations Advisory Group (MDBA) which has co-ordinated the flow in collaboration with WaterNSW, the Victorian Environmental Water Holder and Goulburn-Murray Water.

Monitoring is being carried out by the National Parks and Wildlife Service supported in part by The Living Murray program.

The Living Murray is a joint initiative funded by the NSW, Victorian, South Australian, Australian Capital Territory and Commonwealth governments, co-ordinated by the Murray-Darling Basin Authority (MDBA).


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