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Rare waterbirds, Little Bitterns, head south in search of drought refuge

By Lucy Robinson and Cherie von Hörchner, Monday January 21, 2019 - 08:02 EDT
Audience submitted image
Measuring about 35cm long, Australian Little Bitterns are small and even lesser-known. - Audience submitted

Rare waterbirds appear to be increasingly moving into South Australia to escape dry conditions in northern areas of the country, according to wildlife experts.

Six Australian Little Bitterns were recorded at Bool Lagoon in the state's south-east during the most recent survey of the species' numbers.

While the count may seem small, Birdlife South East SA convenor Bob Green said it was a "staggering" result for the notoriously elusive species, which is classified as endangered in South Australia.

"We've been keeping records in the south-east since our group's formation almost 20 years ago," he said.

"In that time we've only had three individual [Little Bitterns] recorded … one was in Lake Alexandrina and the other two were in Bool Lagoon.

"So to actually have six recorded on the one night in one location is staggering."

, the Little Bittern is skilled at camouflaging itself among reeds.

Mr Green said that posed significant challenges for researchers trying to monitor and predict the species' movements.

"You don't get a very good look at them generally," he said.

"It's really hard to determine where they might turn up. Some years they don't turn up at regular sites and other years they turn up where you've never seen them before.

"It's just a really elusive and difficult species."

Little Bittern numbers low in NSW Riverina

A migratory species, the Little Bittern can be found mainly in south-eastern and south-western Australia during spring and summer.

The birds live in small patches of wetland vegetation including urban lakes or drains, as well as larger expanses of water.

It's still unknown exactly where they go during the other months, but some of the population spends winter in Papua New Guinea.

Wildlife ecologist Matt Herring has been conducting surveys of Australasian and Australian Little Bitterns in New South Wales' western Riverina and believes recent drought has contributed to changes in their movements.

"Most of the sites where we get Little Bitterns in summer in the Riverina of New South Wales are dry at the moment," he said.

"We've had a really bad drought as many people would appreciate so there's not a lot of wetland habitat.

"I think that Bool Lagoon acting as a bit of a drought refuge is a really plausible idea.

"Overall I'd have to say the numbers are probably down [in the Riverina] and perhaps they're looking for sites that they don't normally go to."

He said they had found good numbers of the species, including two active nests, in areas around the lower Murrumbidgee River where there had been environmental flows.

"With the other [Australasian] bitterns and other waterbirds, a lot of them are being pushed to the coast to more permanent wetlands," he said.

"We keep an open mind because they're such a poorly known bird.

"I think one of the most interesting things about them is that we don't know exactly where they come from.

"In the future we'd love to get satellite transmitters on these Little Bitterns, like we've done with the Australasian Bitterns, and actually see where they spend the non-breeding season."

Big dry pushes waterbirds south

In October and November each year, a small team of researchers take to the sky to count waterbirds in the Murray-Darling basin and throughout eastern Australia.

Professor Richard Kingsford from the University of New South Wales has been monitoring the state of the wetlands and the environment for more than 30 years and isn't surprised that the Little Bitterns have taken up home in South Australia.

"Essentially what they're doing is they're chasing water," he said.

"Because Australia's such a land of droughts and floods — and they're capable of going these incredible distances — they'll move around to where the water is, much more than other birds do in other parts of the world.

"In Australia in particular, they're able to capitalise on finding where the latest flood has been because that's where the food will be for them and that's where the opportunities are for them to get through a dry period."

Professor Kingsford said the migration appeared to have begun over a year ago.

"In 2017 it was starting to dry back and we were seeing a few more birds in the south-east of South Australia," he said.

"Because it was that much drier in Queensland and NSW, it wasn't a great surprise to see that that was even more accentuated last year when our survey finished."

Professor Kingsford's team counts the birds by buzzing over their habitat in a low-flying Cessna 208.

"We fly at about treetop level — about 50 metres — and they fly up and we see their wing patterns.

"We count into tape recorders, then we take that home at night and then write down all the numbers."

The scope of the survey, conducted over two months and encompassing wetlands from northern Queensland to just south of Melbourne, provided Professor Kingsford's team with an accurate and alarming picture of the state of the waterways.

"We survey all the major wetlands sites in the Murray-Darling … it was very dry and [there was] very little water anywhere.

"Most of the water and the waterbirds were essentially down in the south-east of the Murray-Darling, in the Lower Lakes and in the Coorong, and some places where there have been environmental flows being released such as the Macquarie Marshes and also into the Gwydir wetlands and the Lachlan."

Environmental flows needed

Such environmental flows have been drastically reduced during the recent drought conditions, and Professor Kingsford believes restoration of the water flows is critical.

"All of it used to go to the environment," he said.

"Now we're really talking about a remnant, a fraction of what used to go there.

"So reinstating some of that is really important. The big challenge is working out when to release it and how much and how often.

"I think that's a challenge for water managers.

"One thing about waterbirds and rivers generally is that we've changed a lot the way our rivers respond by building dams and taking too much water out of the rivers.

"As a result you don't get as many, or as often, the sort of flooding that we have had in the past, which is really the habitat for a lot of these waterbirds."

Professor Kingsford said in the 30-plus years that he had been conducting the surveys, the waterbird population had fallen by about 70 per cent.

"We've got this long-term signature, long-term trend of declining waterbirds over time," he said.

"And that's largely to do with the way we've changed our rivers. Things like putting more environmental flows back into the rivers are essential."

Waterbirds tackle pests, boost dollars

Professor Kingsford said the waterbirds had positive impacts on the environment.

"For example, the fish-eating birds like the cormorants and the pelicans are feeding on a lot of carp," he said.

"The ibis, particularly the straw-necked ibis, are out there feeding upon pest species that can affect crops. They do a great job in feeding upon locusts."

He said the birds also had economic value.

"Then there's the inherent value of these places and species in terms of the economies of those places like the Coorong and the Lower Lakes. People go there to see waterbirds. They make an economic input into these areas as well.

"Particularly in Victoria and South Australia, there are people who are duck shooting, so there's a contribution they make to people's lives and economies that way," Professor Kingsford said.

Working with MDBA and state governments

Professor Kingsford and his team work closely with water authorities, sharing survey results.

"Victoria, South Australia, New South Wales and Queensland [Governments] fund the eastern Australia survey and the Murray-Darling Basin Authority funds the surveys we do of the major wetland sites in the Murray-Darling," he said.

"We provide both a and we do that daily.

"We also provide our results to the Government each year.

"In the longer term we do a lot of analysis around responses to different types of flows, both in modelling what would happen if you had more or less flows [and] looking at the effects of climate change."


© ABC 2019

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