A few years ago, Australian scientist Richard Major took a video of a cockatoo in Sydney opening a closed trash bin lid with its beak and foot to access the gold mine of leftover food inside.
He shared it with Barbara Klump and Lucy Aplin, both researchers at the Max Planck Institute of Animal Behavior in Germany – and they were immediately fascinated.
“It was so exciting to observe such an ingenious and innovative way to access a food resource, we knew immediately that we had to systematically study this unique foraging behavior,” said Klump, a postdoctoral research fellow at the institute in a news release.
It’s a five-stage process for the birds to open the bin lid, according to the study. The bird has to pry open the lid with its beak, twist its neck sideways and hop onto to the edge of the bin, hold it open with its beak or foot, walk along the rim, and finally flip the lid open.
On Thursday, the scientists published their findings in the journal Science, which found that the iconic Australian bird species learned this foraging skill from each other and showed innovation by developing different ways of opening the bins.
It’s difficult to demonstrate the evolution of new behaviors in animals for two reasons, said Major, principal research scientist at the Australian Museum. First, it’s difficult to detect behaviors when they first arise because they begin as rare instances before spreading. Secondly, if populations in two different locations perform the behaviors differently, it’s hard to tell whether that’s due to a difference in the animals themselves or their environments.
That’s why the Sydney sulphur-crested cockatoos, a highly social parrot common across East Coast cities, provided a rare opportunity. The whole country uses the same standardized public trash bin – and the cockatoos live in one of Australia’s biggest cities, meaning there are millions of residents who can help observe their behavior.
The research team launched an online survey asking Sydney residents if they had seen cockatoos lifting trash bin lids for food.
Before 2018, this behavior had only been reported in three suburbs – but by the end of 2019, that number shot up to 44 suburbs, according to the study. And the behavior spread among nearby neighborhoods faster than it reached far-flung ones, showing that the new behavior wasn’t randomly popping up.
“These results show the animals really learned the behavior from other cockatoos in their vicinity,” Klump said in the release.
The researchers also marked cockatoos with paint dots to track which ones had learned to open the trash cans – which turned out to be only 10% of the birds. The other cockatoos would wait, then help themselves once the trash cans had been opened.
And not all birds open trash cans the same way – the team found that regional subcultures had emerged among the cockatoos, who had distinct styles and approaches. For instance, in late 2018, a cockatoo in northern Sydney reinvented the technique by opening the lids a different way, prompting birds in neighboring districts to copy the behavior.
“There are different ways to go about (opening the lids),” said Major. The fact that groups have developed different ways to do it was “evidence they learned the behavior from each other, rather than them solving the puzzle independently.”
It may seem like a trivial finding – that birds can open lids differently – but it’s significant because it proves animals can learn, share and develop subcultures, Major said. He compared it to human dance, how each culture has their own, and how places that are geographically close may have more similar dance styles than in countries far away.
The study also sheds more light on how animals are evolving in urban centers. There are always “winners and losers” as cities expand and land use changes, Major said – and the animals who can can adapt to new environments emerge as the winners.
There are plenty of other species who forage – most notably, the larger ibis, known as the “bin chicken,” that digs through the city’s trash. But “it’s easy for an ibis to see food in a bin, and get food out of it,” said Major. “For a cockatoo to lift a bin to find food, that’s another level of puzzle solving.”
“Cockatoos are broadening out their diet, so they’re able to exploit opportunities in an urban environment,” he added. “I hope our research will help us learn to live with them as well as they’re learning to live with us.”