The 'enduring' mystery of how birds know when Kati Thanda-Lake Eyre is filling with water

Australia Broadcast Center

27-06-2025

The most arid corner of Australia is about to burst with life, as Kati Thanda-Lake Eyre braces to reach capacity for just the fourth time in the past 160 years.
While the usually-barren salt flats rapidly fill with floodwater from south western Queensland, migratory waterbirds like seagulls, swans, ducks and pelicans will begin descending to the inland oasis in the hundreds of thousands.
So — with the lake expected to become entirely full in the coming months — how do birds know that this once-in-a-generation event is happening?
The question is one University of New South Wales Professor Richard Kingsford has been striving to answer for the majority of his career.
He's spent the past four decades monitoring water birds through aerial surveys.
"Birds can go incredible distances," Professor Kingsford said.
"Unlike water birds in other parts of the world, that sort of regularly migrate between spring and winter — we don't see any of that.
Professor Kingsford said while the majority of the waterbirds found at Kati Thunda-Lake Eyre are native to Australia, some species will travel from as far as China, Russia and Antarctica.
He said the birds will capitalise on the opportunities to breed at varying times based on the availability of vegetation, invertebrates and fish.
"There's that huge smorgasbord of food," Professor Kingsford said.
"It sort of triggers that cascade of different types of species coming in at different points.
"You get these wonderful sort of pulses of productivity depending on which waterbird you're talking about."
Professor Kingsford said — while still complex — tracking waterbirds had become somewhat easier in recent years with the arrival of satellite tracking technology.
"And it it is one of the great mysteries for Australia is how do these birds know where the water is and head off?
"We are starting to get some ideas of how they probably do it though."
Ecologist Reece Pedler became fascinated by the movements of waterbirds while living in the remote South Australian town of Roxby Downs for a decade.
"I now live up in the Strzelecki Desert … so I see this stuff first-hand in my life in the outback that birds are flying around and doing these amazing things," Mr Pedler said.
"Birds can arrive really rapidly and their ecology is geared to these unpredictable events.
"But we don't know exactly how they know."
Mr Pedler, who is the coordinator of the Wild Deserts Project in Sturt National Park, previously studied the breeding behaviour of the banded stilt using solar-powered trackers as part of his PhD.
The threatened bird species is most commonly found in Australia's saline coastal wetlands, such as the Coroong or at St Kilda Beach, north of Adelaide.
"Those banded stilts might be there for months and months on end or live there year round, " Mr Pedler said.
"Then suddenly they disappear when places like Lake Eyre or other lakes in the Western Australian desert fill.
Mr Pedler said the abundance of brine shrimp at Kati Thanda-Lake Eyre creates a rare breeding-ground for the threatened species.
"They don't breed anywhere else around the coast … so they have to wait years or decades for those opportunities," he said.
"And when they breed, they breed in real style, they have thousands of pairs.
Mr Pedler said while it was once thought the birds only flew after significant wet events, minimal rainfall was enough to trigger the stilts to leave the coast and head inland.
"There's some really complex triggers too because this water that's flowing into Kati Thanda-Lake Eyre now fell in western Queensland in the last week of March," he said.
"So the stilts and other water birds that would be turning up at Lake Eyre now are not responding to rainfall or atmospheric queues that have happened in the days prior.
"There's potentially lots of different mechanisms occurring and it may be that some different groups of birds have different ways of sensing these things."
Several theories of how birds know when Kati Thanda-Lake Eyre is filling exist, including them having the ability to detect infrasound, barometric pressure or smell the flooded salt flats on the breeze.
"There's been theories like scouts … if pelicans send up observers to go and recce inland sites and come back and tell their mates that there's food on offer," Mr Pedler said.
"I guess there's some rationale for that because pelicans can fairly easily fly long distances, they get up to high altitude on thermals and then they can cruise and go for a look.
"It's still an open case and there's a lot more work to understand this really fascinating behaviour."
Professor Kingsford said as more technology emerges and becomes cheaper, the more scientists like himself will be able to shed light on how birds are able to do what they do.
"What's most important about that is working out when are the critical times that we need to protect particular habitats in their life cycle," he said.
"I'd love to try and work out what's going on and others are too.