A western ground parrot (Pezoporus wallicus flaviventris), one of eight in captivity. (WA Department of Environment) The Endangered western ground parrot is under increasing threat from feral cats.
HALTING THE DECLINE of one of Australia's most threatened birds is proving difficult, say researchers in south-western Australia.
Recent tracking of feral cats - funded by a generous $19,000 donation from the Australian Geographic Society - may help explain why only 100 western ground parrots (Pezoporus flaviventris) are believed to remain in the wild.
Ecologist Sarah Comer says cats in the wild are, quite literally, eating into the parrot populations. "They are the ultimate hunting machine," she says.
Sarah, who is coordinating a ground parrot recovery team in the WA Department of Environment and Conservation, says Australian Geographic's donation has enabled the team to collar feral cats and lay baits at Cape Arid National Park, 120km east of Esperance.
"We were surprised how many cats are out there. We collared 20 cats with GPS tags that allow us to follow their movements and see how effective our baits are in ultimately removing cats from the landscape."
Western ground parrot highly vulnerable to extinction
Two areas in Western Australia's coastal southwest are the last known refuge of this Endangered bird: Cape Arid and Fitzgerald River national parks. With numbers reduced to such small known populations, this mottled green and black parrot remains highly vulnerable to being wiped out by events like bushfire.
Recent monitoring of western ground parrots' main haunts has recorded fewer bird calls than five years ago. The parrots call at dusk as they fly back to their night roosts; they can be heard clearly after other bird species have ceased tweeting.
"In some places there used to be a cacophony of parrots, and every now and then you could see them against the dimming light in the sky," says Sarah. "More often, you'd just hear them, up to 300 to 400 metres away."
The drop in recorded calls in several key locations is puzzling, she says. "The parrots have always been fairly sedentary, and a few years ago you would have heard a lot of birds, so we're very worried."
Her colleague Dr Allan Burbidge, a senior DEC researcher, says that a research team, in 2000, surveyed the same part of Fitzgerald River National Park and heard at least 90 calls on some nights.
"There were times when, in such areas, you might even flush a bird out walking back to your vehicle," he says. "But not now."
Fox baiting allowed feral cats to thrive and hunt birds
He says successful fox baiting may have inadvertently made it easier for feral cats to survive and thrive. "It may have knocked out foxes as cat predators, causing an eventual rise in cat numbers," he says. The recent cat-tracking program showed that almost half the tagged cats were killed by taking specially prepared baits.
Cats are more efficient hunters than foxes because they stalk through dense bush as well as along cleared tracks. "They may predate chicks and eggs because the parrot nests on the ground in a scrape under the bush," says Sarah. "They are great ambushers."
A feral cat with a tracking device is released into the wild. (Credit: WA Department of Environment)
Climate change impact on the western ground parrot
Allan agrees that the bird's decline is probably cat-related, but there may be other factors. "It could be related to climate change, although the average annual rainfall hasn't changed in their locations. What we haven't looked at yet is whether seasonality has changed - later rains or temperature variance whose implications we don't understand."
He adds: "It may be that western ground parrots are the classic canary in the coal mine, indicating environmental change that could affect other creatures like dibblers, a native marsupial that occurs in similar habitats."
Captive breeding the last hope for ground parrot
There are eight western ground parrots in captivity and they have produced eggs but as yet no live chicks. Funding to continue the captive-breeding program is being sought, says Sarah. "Our long-term goal is re-establishing parrot populations back into the wild."
Environmental consultant Alan Danks says halting ground parrot decline is proving more difficult than the case of the noisy scrub bird, another rare south-west bird thought to be extinct until it was re-discovered in 1961. Alan led a successful scrub bird recovery program in the 1980s which returned captive-bred birds to the wild.
But Alan says keeping up the numbers of western ground parrots is an even greater challenge. "We're watching a process of decline and we're not yet able to halt it and begin the task of getting them back to viable populations," he says.