There’s a story in every hollow of the grey-white trunks of wandoo woodland at Coomallo Creek, 220km north of Perth in Western Australia. The handsome eucalypts stand like leafy islands in a sea of floral heath. From the 1950s, farmers cut a swathe through the native bush to tame and clear it for agriculture. By 1969 land was released for farming around Coomallo Creek and clearing had begun. That was the year “Cocky Whisperer” Dr Denis Saunders AM first visited Coomallo Creek. Exploring ridge tops and breakaways where the wandoo grows, Denis was transfixed by the open woodland’s beauty and age. He realised the knotted trunks were so old they’d been standing long before Captain Cook arrived in Tahiti to monitor the Sun’s eclipse in 1769.
Tree age was important in Denis’s quest to study Carnaby’s black-cockatoos (Calyptorhynchus latirostris), the handsome white-tailed black parrots that habitually nest and fledge their young at Coomallo Creek. “They’re wonderful to look at and very placid, and they’re graceful in flight,” Denis says. “We’ve got a history of all the birds that have bred here and that come back to nest in hollows within 60m of where they fledged.” The birds’ preferred hollows have taken 120 years or more to form – knock down any tree, and you have to wait a century before nature etches out a metre-deep hollow in its trunk or branch.
Four generations of the Raffan farming family have owned Coomallo Creek, and three have lived there. On their 2000ha property, they’ve left intact a north–south tree corridor that extends about 1km wide by 9km long across three other properties. “It [the tree corridor] was due to a lot of foresight by my father and grandfather,” James Raffan says, the family’s third-generation farmer. “They didn’t clear all the land and they left many trees as shade for stock. We’re fortunate, and the birds keep coming back, generation after generation.”
James was born in 1969, the same year that the tall, rangy CSIRO scientist Denis first visited Coomallo Creek. As James grew, so did Denis’s list of scientific papers and credits – including an Order of Australia. With each visit, Denis applied his skills of keen observation and scientific rigour in one of the nation’s most detailed studies on Carnaby’s black-cockatoos. Certainly, his is the longest-running research on the species led by the same individual. Throughout the years, each generation of the Raffan family has been involved with Denis’s research. Now there’s a fourth generation: the three children of James and his wife, Bec. The couple offer researchers a bed and a hand with data collecting.
A deep sense of place
On survey trips to Coomallo Creek from September to November, the Cocky Whisperer – who these days flies in from his home in Canberra – is joined by other committed researchers. There’s Rick Dawson PSM, a former senior wildlife officer, and Dr Peter Mawson, former head of research at Perth Zoo. The companionable trio has jointly written 25 papers on Coomallo Creek’s cockatoos. They rise at dawn each morning and head out to monitor nest hollows. Rick mounts a ladder to peek into a hollow or uses a camera on a pole to probe its depths. “I’ll climb it if we want to see exactly what’s on the nest floor,” he says. “At 20 days, the nestlings are large enough to be banded. By measuring the length of its folded left wing, we can age it to within a day or two.”
Down on the ground, Denis is writing detailed notes. “Denis is a legend,” Rick says admiringly. “He’s so particular about the way he handwrites his observations and the young ones watch him, noticing his diligence. You need that old-school example of the way he does his science. There’s no flippancy.”
Sometimes the trio recognises the number on a bird’s leg band. “If you walk around and scratch the side of a tree, the females will come out and look at you,” Denis says. “If they’re very kind, they’ll present their leg in a way that allows you to photograph the ring.”
If Coomallo Creek has inspired loyalty in humans who love the place, it has imprinted a deep sense of place in every cockatoo nestling that emerges unsteadily from the nest. “We think females have site fidelity – where they’ve fledged is where they will return to lay their eggs, in some cases to within a few hundred metres of where they fledged,” Denis says.
They have been helped by the installation of about 80 new homes – artificial hollows – and “home maintenance” to repair 90 natural hollows. “We’ve nicknamed it Cockatoo Club Med – you build it right and they will come,” Rick says with a laugh. “A Carnaby’s will move readily from a natural hollow to an artificial one, just like it will move from eating banksia to eating pine cones. They’re adaptable.”
The impact of land clearing on bird reproduction was notable. “When I started my research, we recorded 88 breeding attempts, but by 1996, we had 37,” Denis says. “The area was starting to be cleared, so the numbers dropped. In 2011 we started putting up artificial hollows, and we saw a marked increase in breeding attempts. Last year there were 142.”
Other benefits from installing artificial hollows emerged. “In all the time I’ve been studying them, I’ve never observed a bird younger than four years breeding. We now have three-year-olds breeding and, in some cases, successfully raising young. It would seem to indicate that when hollows were scarce, they were kept out of the system by older birds,” Denis says.
While Carnaby’s black-cockatoos go about their bird business, the rest of Coomallo Creek is devoted to growing canola, wheat and barley, and raising sheep. James is convinced that growing grain has improved the prospects for Carnaby’s cockatoos in his region. “In the ’90s, people started growing canola and that’s a big factor. It gives the birds another food source,” he says.
Yet elsewhere, the clearing of large trees and surrounding native vegetation has taken its toll. With their seed larder gone, adult birds are forced to fly longer distances to forage, leaving hungry nestlings alone for longer. Rick once found a carpet python curled up in one hollow. “She’d eaten the nestling, and was lying there torpid,” he says. “The female came in and the python threw a coil around it and killed it. So we had a bulging python coiled up around a dead cockatoo.”
A Carnaby’s black-cockatoo must live for at least 16 years before producing enough offspring to replace itself. The female lays two eggs, but one baby will often die soon after emerging from the egg. On average, the eggs are laid eight days apart and will hatch at different times.
The researchers gather DNA by taking a couple of feathers from the nestling’s breast, which tend to have rich blood in the quills. “And if we have a dead nestling, we take the toe,” Rick says. The DNA evidence has cast a question mark over the belief that Carnaby’s cockatoos are largely monogamous and pair for life. The researchers have discovered that young birds from the same nest can have different DNA, meaning different fathers. They’ve dubbed it “sneaky f—er syndrome”. “Every year, we learn something new,” Rick says. “I think we can make a difference, and Coomallo is the barometer.”
Yet even at Coomallo Creek, the once common sight of Carnaby’s black-cockatoos flying in massive flocks is rare. “They used to fly over the Perth skyline in a thick black flock of thousands of birds,” Denis says. “I’ve seen it – they practically blocked out the sun!” He has no illusions about the fate of Coomallo Creek’s cockatoos. “The future of these birds, like so much else in nature, hangs on our actions. The battles go on as we whittle away at what little native vegetation remains, so clearing has to stop. You can say, ‘We’ll put up a whole lot of artificial nesting boxes’, but without trees, what are you going to hang them off? You can’t put them on a pole in the full sun – they become ovens. And they need a larder around them.
“The birds are in pretty good condition at the moment, but without long-term revegetation across the landscape, in areas within their range, then all we may be seeing is the walking – or flying – dead.”
Still, Denis is proud of his lifetime’s work tracking generations of birds at Coomallo Creek. “To me, it’s the most beautiful agricultural property I’ve ever worked on,” he says gratefully.
