He shared it with Barbara Klump and Lucy Aplin, both researchers at the Max Planck Institute for Animal Behavior in Germany – and they were immediately fascinated.
“It was so exciting to watch such a ingenious and innovative way to access a food resource, we immediately knew we had to systematically study this unique foraging behavior,” said Klump, postdoctoral researcher at the institute in a press release.
It’s a five-step process for birds to open the lid of the bin, according to the study. The bird should open the lid with its beak, twist its neck to the side and jump to the edge of the tank, hold it open with its beak or foot, walk along the edge and finally open the lid.
It is difficult to demonstrate the evolution of new behaviors in animals for two reasons, said Major, senior researcher at the Australian Museum. First, it is difficult to detect the behaviors when they first occur because they start out as rare cases before spreading. Second, if populations in two different places behave differently, it is difficult to say whether this is due to a difference between the animals themselves or their environment.
This is why the Sydney Sulfur-crested Cockatoos, a very sociable parrot common in towns on the east coast, presented a rare opportunity. The whole country uses the same standardized public trash can – and cockatoos live in one of Australia’s largest cities, which means there are millions of locals who can help observe their behavior.
The research team launched an online poll asking Sydney residents if they’ve seen cockatoos lifting lids on garbage cans to feed.
Prior to 2018, this behavior had only been reported in three suburbs, but by the end of 2019, that number had risen to 44 suburbs, according to the study. And the behavior spread to neighboring neighborhoods faster than it reached farther afield, showing that the new behavior did not come about at random.
“These results show that the animals really learned the behavior of other cockatoos nearby,” Klump said in the statement.
The researchers also marked the cockatoos with paint dots to see which ones had learned to open trash cans, which turned out to be only 10% of the birds. The other cockatoos would wait, then help themselves once the trash cans were opened.
And not all birds open trash cans the same – the team found that regional subcultures had emerged among cockatoos, which had distinct styles and approaches. For example, in late 2018, a cockatoo from North Sydney reinvented the technique by opening the lids in a different way, prompting birds from neighboring neighborhoods to copy the behavior.
“There are different ways of doing it (opening the lids),” Major said. The fact that the groups developed different ways of doing it was “proof that they learned each other’s behavior, rather than solving the puzzle independently.”
It might seem like a trivial finding – that birds can open lids differently – but it’s important because it proves animals can learn, share and develop subcultures, Major said. He compared it to human dance, how each culture has its own, and how geographically close places can have more similar dance styles than in distant lands.
The study also sheds more light on how animals evolve in urban centers. There are always “winners and losers” as cities expand and land use changes, Major said – and animals able to adapt to new environments emerge as the winners.
There are many other feeding species, including the larger ibis, known as the “garbage chicken,” which digs through the city’s garbage. But “it’s easy for an ibis to see food in a trash can and take food out of it,” Major said. “For a cockatoo to lift a trash can to find food is another level of puzzle solving.”
“Cockatoos expand their diet, so they are able to exploit opportunities in an urban environment,” he added. “I hope that our research will help us learn to live with them as well as they learn to live with us.”