The letter-winged kite has watched on as Australia’s arid zone has lost 32 native mammal species in a couple of centuries.
Now, this unique animal is under threat.
From the heights of the rare Acacia peuce, this raptor holds its own place in the evolutionary tree as the only bird among its order of eagles, hawks, falcons and others, which hunts by night.
“They overlap with owls, that’s unheard of on a global scale,” says CSIRO research scientist Dr Chris Pavey.
“We refer to it rather romantically as the moon kite. It generally hunts most effectively on nights when the moon is bright.”
Here in the Simpson Desert where it hunts, those lost species—many of them once prey to the letter-winged kite—represent 42 per cent of the mammal fauna at the time of European settlement, an extinction rate unmatched anywhere else in the world. It’s here that Pavey has spent 15 years studying the Elanus scriptus, at what he calls the frontier of Australian conservation.
“They’re beautiful against a bright blue sky. They’re an enigma. They’re not there and then all of a sudden when rodent numbers build up they appear. At our study site in the Simpson over 15 years they’ve only turned up three times.”
Pavey says that although numbers have declined over the decades it was only last year that there was a consensus about the plight of this bird.
“It has now entered the conservation conscience,” Pavey says.
At the mercy of the boom-bust cycle
As he explains, they’re called an irruptive species or, in this part of the world with one of the most unpredictable rainfalls on Earth, a boom-bust species. They are believed to retreat to refuge areas in south-western Queensland, along the Diamantina and Cooper Creek, in drought and then every 5-10 years when good rains arrive and their food sources dramatically multiply, they cover a vast area of the Australian arid zone.
“When times are good they breed almost constantly, the young breed at an early stage. They’ll be eating all the rats and mice and, as things dry up and the rodents disappear, the kites disappear and they’ll be gone seemingly without a trace which isn’t unusual in the desert. It makes it very hard to monitor from a conservation perspective,” explains Pavey.
The last State of the Environment report, released in 2011 when the big rains had broken the Millennium Drought, predicted that many species, like the moon kite, would return.
The letter-winged kite is perhaps the best example of the species that didn’t return in the numbers expected. At a field site on Andado Station in the south-eastern Northern Territory that had up to 126 birds during the wet period of 2000–01, there were only 9 birds recorded in 2011. However, the appearance of good numbers in the winter of 2016 has raised hopes that all is not lost.
A changed food chain
The letter winged-kite is an apex predator in the trophic ecology of central Australia.
But it now flies over a changed food web where foxes and cats are taking out many native small mammals. The fox and cat are also predators of the letter-winged kite.
“If you look at the climate modelling in the arid zone there’s a universal agreement: We know the temperatures will increase and we know there’s going to be an increase in extreme events, big rain events and then droughts,” says Pavey.
“The increase in extreme events is going to work in favour of cats and foxes, especially in this particular system. That might mean the prey of the letter-winged kite will be under increased predation pressure.”
The loneliest tree
The other part of the story is the letter-winged kite needs places to nest above ground.
In the Simpson there is the Acacia peuce, known as the 'Akerre' by the Southern Arrente people. To scientists, it’s known as a keystone species because of its important role as a nesting site. And to some, it’s been described as the loneliest tree in Australia.
But even the grand Acacia peuce, which can remarkably grow up to 18m tall, cannot always provide protection from cats and is also under threat.
Much of the letter-winged kites’ breeding zone and a significant proportion of threatened fauna in the Australian arid zone exist on pastoral leases rather than the formal reserve system.
Among this list of species are many charismatic animals including mulgaras, dunnarts, kowari, kultarr and plains mouse.
Working to protect the refuges
Pavey has been working on a number of projects.
One is to monitor population cycles of species of threatened and near threatened rodents and dasyurid marsupials, and to understand the species interactions within this system particularly the trophic ecology of key species and how this changes between “boom” and “bust” periods.
Another project is to develop approaches to manage threatened species outside of the reserve system on pastoral land. This approach focuses on the refuges of small mammals such as the plains mouse and aims to carry out targeted management of predators and other threats.
“We’re advocating a local-scale, targeted management of these refuges. We are talking about low-tech approaches that are easy to implement; baiting foxes, shooting and trapping cats and foxes. By focussing in on the refuges the idea is to target the areas that are most important for biodiversity rather than being overwhelmed by the vastness of the landscape. “
Pavey believes that pastoralists are well placed to be effective biodiversity managers and to protect refuges.
“There’s a lot of ecological knowledge among pastoralists that is completely under appreciated.”
Read highlights from the Biodiversity chapter from the 2016 State of the Environment Report.