Major weather event prompts behavioural change in Aussie birds: 'Almost like human culture'
Endangered Carnaby's cockatoos have adapted to the 'Great Browning' of forests in Australia's west in a remarkable way.
A dramatic weather change in Australia’s southwest has sparked new behaviour in flocks of rare birds. Carnaby’s cockatoos are no longer heading into the bush where thousands of trees have died from extended drought as there are few seeds to eat.
Instead, they are feasting on canola crops which are regularly watered and provide a dependable source of food. And because they no longer need to fly to the forest, they now have more time available to play.
“This year we haven’t seen a bird fly off to the national park. They spend the whole day close to the canola, and their kids are fed it for breakfast, lunch and dinner,” the University of Western Australia’s Dr Peter Mawson explained to Yahoo News.
The Adjunct Professor of Biological Sciences has been studying the endangered species’ remarkable ability to live for decades in the wild — often for 35 years — with the results published by the CSIRO overnight. During their time with the birds, Mawson and his colleagues have also witnessed the impact of the “great browning” ecological event that has spread across Western Australia’s southwest, wiping out natural food sources.
“There are clear indications the birds are aware there is no food to be had... so they're not wasting their time trying to look for it," Mawson said.
“Because they've got all that spare time on their hands — because they don't have to fly very far, and it takes a lot less time to collect the canola — we're seeing these large flocks of birds wheeling around, flying, talking, socialising.
“It's almost like human culture. Once they've got to the stage where they've got a food surplus, they can engage in extra culture.”
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Concern young cockatoos may not learn key survival skill
Mawson and his team have seen flocks of up to 140 birds milling around together during the breeding season, which is unusual because ordinarily much of their time would be spent scavenging for food in pairs.
Research indicates canola has almost the same energy content as the forest seeds the Carnaby’s cockatoos would ordinarily forage for. But it’s unclear whether it has the same micronutrients.
“Clearly they have no choice this year. But you can raise a kid on hamburgers, and if it’s a newborn it’s not going to complain because it doesn’t know any different,” Mawson said.
The bigger concern for the birds is whether this year’s babies will learn the necessary foraging skills to survive after their parents leave. It’s possible there could be a spike in mortalities at the one-year mark after their parents head to the breeding grounds.
Canola is a small grain, and as the weather changes the supply will disappear, so after the expected rains in January and February, the juveniles will be forced to find a new supply of food.
“The question will be how big an influence has the drought had on the ongoing supply of native foods,” Mawson said.
Breeding behaviour changes following intervention
Like many native birds, Carnaby’s cockatoos lay their eggs in tree hollows and raise them inside until they’re ready to fly. But unfortunately, there are few available for them to nest in.
The problem arose after forest surrounding Perth was felled to create farmland for Western Australia’s Wheatbelt. But supply has been temporarily solved with the installation of artificial nest boxes which are secured to trees.
“In the past, we always thought they didn’t start breeding until four years of age, but now we see some three-year-old females will attempt to using the nest boxes,” Mawson said.
“The situation has certainly improved. We’ve gone from 41 breeding attempts at our study site in Coomallo Creek [in the northern Wheatbelt] to 147 just by providing artificial nest hollows and also repairing natural nest hollows that had started to fail.”
Major concern threatens Carnaby's cockatoos' future
The research suggests because Carnaby’s cockatoos are long-lived, their need to breed and replace themselves with offspring has been evolutionarily delayed.
Between 20,000 and 40,000 individuals are left in the wild after numbers plummeted over 50 per cent over the last half-century. Because the species is now protected, the adult birds alive today are unlikely to be lost any time soon, giving researchers time to devise plans to help populations rebound.
While the artificial hollows have been a success, the challenge researchers face is that the remaining natural hollowed trees are crumbling, and the birds are refusing to use them.
“That decline continues unabated. It shows us that the breeding trees have a finite life,” Mawson said.
“They grow so slowly that none of the trees standing are in a state where they are starting to produce hollows big enough for the cockatoos. And we've certainly seen no recruitment of tiny trees that started as natural seedlings.
“That's really alarming, because that means in the next 150 to 250 years there likely will not be any trees left for them. And we’ll face the challenge of what do we hang those nest boxes on.”
Longevity in Carnaby’s Cockatoo (Zanda latirostris) was authored by Denis Saunders, Peter Mawson, and Rick Dawson.
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