A package from the bush
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Not many people would be able to instantly recognise the call of the enigmatic and understudied Western Grasswren.
Yet to University of Western Australia PhD student Aline Gibson Vega, their songs are as familiar as the back of her hand.
In fact, Aline is so attuned to their songs, she can hear the difference between a bird from Bush Heritage’s Hamelin Station Reserve, 250km north of Geraldton, and a bird from Francois Peron National Park, about 100km further north.
“Bird song is culturally learned. Like a human language or dialect, you learn it from your parents, it’s not genetic. So I can hear something and say: that’s probably a bird from Peron or that’s a bird from Hamelin,” she says.
Aline’s research aims to shed light on the differences between these two Western Grasswren populations and uncover for the first time how genetically and socially distinct they are.
Do they speak the same dialect? Do they communicate in the same way? Do they have the same family ties? How much genetic diversity is there in each population?
The answers to these questions will feed directly into the Dirk Hartog Island National Park Ecological Restoration Project, an epic 12-year plan to return all 11 native species that have gone locally extinct on Dirk Hartog Island, or Wirruwana to the Malgana Traditional Owners, since the Dutch sea captain landed there in 1616.
The Western Grasswren is one of these 11 species – the only bird and the species about which least is known.
Once, this well-camouflaged wren, bigger and sturdier than its Fairywren cousins, would have been found across much of south-western Australia.
However, a reduction in viable habitat due to overgrazing by rabbits and goats plus predation by feral cats saw its range gradually shrink westwards, and today, the Hamelin and Francois Peron birds are the only two remaining populations of the western subspecies, Amytornis textilis textilis.
It’s this element of mystery that initially attracted Aline to her PhD topic.
“You look at the literature and there’s so much on Fairywrens and then Grasswrens almost nothing,” she says. “They’re really cryptic…and there isn’t much known about their biology so there is no point of reference for planning a translocation.”
Over the past two years, Aline has spent many months in the field at Hamelin and Francois Peron mist netting, banding individual birds, collecting DNA samples, doing nest counts and recording vocal displays; building, block-by-block, a complete Western Grasswren data set.
The analysis of this data won’t be complete until Aline finishes her PhD but initial observations provide a fascinating insight into the bird’s behaviour, including the intriguing question of song dialect.
Understanding whether the Hamelin and Francois Peron birds recognise each other’s calls is important to the success of their eventual translocation to Dirk Hartog Island.
As Bush Heritage senior ecologist and one of Aline’s project supervisors Dr Michelle Hall puts it:
“Will the birds consider each other the same - will it be like a super sexy French accent - or will they think the other bird’s call sounds terrible and not be interested?”
“[Translocation] is already such a stressful situation… so you don’t want the birds to have new neighbours that they perceive as really aggressive,” Aline adds. “That’s something to consider in the release design – should we release all the Hamelin birds together and the Peron birds somewhere else? Over time they would mix but the initial placement could be separate.”
To test this, the songs of 19 different male Western Grasswrens from Francois Peron were played back to birds at Hamelin. The same experiment was repeated at Francois Peron with Hamelin songs.
“At times I saw the birds approach the speakers straight away, so upset about the rival intruding on their territory,” Aline says. “Other times I’ve seen them approach, but no singing, so they’re vigilant but not willing to engage. Some of them go immediately back to their original behaviours while others stay alert for a lot longer.”
This information about the birds’ compatibility will be added to the package of genetic data ultimately informing the Dirk Hartog Island project. Aline’s findings will also inform the Hamelin Reserve management strategy.
Michelle says that Bush Heritage’s hard work destocking feral goats and managing pest species on the reserve should help grasswren habitat recover from overgrazing.
“Our reserve managers have done a lot of work trapping goats every year and the numbers are now dramatically lower than they were,” Michelle says. “The Grasswrens seem to be in reasonable shape but knowing about their genetic status will help us understand their condition in more detail – whether there are any signs of inbreeding that we might need to do something about, or whether the population has good genetic diversity to help them adapt to change.”
For Aline, the thought that her work will contribute to the Western Grasswren’s future on an island sanctuary is reward enough.
“I wanted to work on something that had tangible conservation outcomes,” she says. “The bonus is that I am working with a species that not very many people get to see, and that not many people know about. I want the birds to do well.”
Aline’s research is supported by the inaugural Paul Hackett Memorial Scholarship for Bird Research, created to encourage research on our wonderful bird life.
Right up in the northern corner of Scottsdale Reserve, up near the Murrumbidgee River, there's a rocky outcrop that retains much of its pre-European beauty, having never been ploughed or pasture improved.Read More