Nature designed the perfect scarecrow 50 million years ago — birds of prey evolved into the ultimate avian terror for corellas and other feathered nuisances.
Science is now measuring how effective they may prove as a taloned tool for cropping farmers facing a white wipe-out.
Falconer and bird handler Graeme Coles, from Full Flight Birds of Prey in Miners Rest, is trialling live eagles, falcons and other predatory birds as a non-lethal control measure for flocks which may otherwise decimate agricultural yields.
While the study is ongoing, early observations are encouraging.
Federation University ecologist Rob Wallis is tracking the performance of the predatory birds.
Professor Wallis says the theory has merit even if widespread commercial use is a long way off.
"Corellas and [other] cockatoos do all sorts of damage to human enterprises such as farms, orchards, even buildings," he said.
"Our idea is a humane way to deal with the [corella] problem.
"This humane way involves flying birds of prey, which are their natural predators, over them to disperse them somewhere else.
"These birds have been captive-bred or hand-reared.
"They might have been injured and people have handed in to my colleague's wildlife centre.
"They are tame, licensed birds trained specifically to fly over areas and come back to the handler.
"In their flights, they will disturb aggregations of lots of birds which may be causing damage.
"These birds of prey don't actually attack the birds.
"They move them somewhere else.
"You do it a number of times; hopefully they won't come back."
The genesis of the Federation University study was a meeting between David Brennan, then with the Department of Environment and Sustainability, and Mr Cole.
Mr Brennan was open to a novel solution to protect the Ballarat Botanical Garden from marauding corellas.
After some promising results, Mr Cole said the idea needed scientific investigation.
Enter Professor Wallis.
A variety of birds of prey have been trialled in a number of scenarios since under his watchful eye.
"In some instances, there has been 100 per cent success, such as some of the golf courses where the birds have been tearing up greens," Professor Wallis said.
"Others we have had less success.
"At this stage it is a bit hard to quantify in terms dollar value.
"The aim is to increase the chances of success."
One successful application was at a large almond orchard in northern Victoria.
"The corellas were coming in from their roost sites on the Murray River, and attacking the almonds at pre-harvest time," Professor Wallis said.
"What we would do is fly an eagle from the roost site over the almond farm.
"It would fly over for a few minutes and be called back by waving a particular lure with food on it."
"After a week or so, we would record how many corellas were doing the damage."
Using tame predatory birds to disperse native birds is not sanctioned at present in Victoria.
Federation University worked in conjunction with the then Department of Sustainability and Environment and Mr Coles to develop Victoria's testing of the program.
Agriculture has not been the only application of the raptors, nor are corellas the only target.
Mr Coles said falcons were used to disperse seagulls from horse racing events, following a nasty incident at Sandown Racecourse where seagulls flew onto the course during a race.
A natural solution
Beyond any commercial use, the deployment of these native raptors gives an insight into the role wild birds of prey play in nature.
Nature writer and ecologist Tanya Loos says some of the successes show the benefits of encouraging rather than discouraging eagles and hawks to occupy farming and other properties.
"A range of birds of prey on any bush block or farm is always an advantage," she explained.
"Eagles are an essential part of any integrated pest management program for rabbits, for example.
"Kestrels, brown falcons and black-shouldered kites eat mice and locusts.
"It is just important to make sure your chook shed and run are bird-of-prey-proof so the local goshawks don't feast on your chickens.
"Birds of prey use calls to communicate with one another — for example between pairs at mating season.
"They do not use calls while hunting — so recorded calls of birds of prey will not scare away cockatoos or corellas.
"Most of the hunting by birds of prey is done by stealth and ambush."
Birds of a feather
Eagles are clever and relatively easy to keep on track.
Goshawks, on the other hand, are more temperamental.
Here's how Graeme Close describes some of his hunters.
- Wedge-tailed eagles (Aquila audax) – They require a lot of space, so are in their element in open crops. Having an eagle around, even if not flying, is enough to intimidate many birds.
- Peregrine falcon (Falco peregrinus) – They are very versatile, and take a broad range of prey, from sparrows to cockatoos and even swans. Could be deployed in stone fruit orchards, for example.
- Nankeen kestrel (Falco cenchroides) – This small falcon is too small to deter larger birds like corellas but will attack starlings and mynas. As such they may have a role with managing small birds in buildings, such as food halls.
- Brown goshawk (Accipiter fasciatus) – They are temperamental with strong predatory instincts. The "sharks of the bird world", their effect on prey species is extreme. Pigeons will be especially agitated by them.
- Barking owl (Ninox connivens) – These birds are something of an unknown, although they are used by falconers in the United States for hunting. Contrary to reputation, barking owls and masked owls will hunt during daylight.