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A sulphur-crested cockatoo opens the lid of a household garbage can.

Barbara Klump/Max Planck Institute of Animal Behavior

Australia’s cockatoos are masters of dumpster diving—and now they’re learning from each other

Sulphur-crested cockatoos have distinctive yellow crests, calls, and—according to a new study—dumpster-diving skills. In recent years, some cockatoos living in the Sydney suburbs have figured out how to open household garbage cans, unlocking a food bonanza of sandwiches, fish bones, and fruit. Other cockatoos have picked up on the trick, and the behavior is quickly spreading. What’s more, birds in different locations use slightly different methods to open the cans, making this the first time a parrot has been found with local foraging “subcultures,” say the authors of the new paper.

To figure out the extent of the dumpster diving, behavioral ecologist Barbara Klump at the Max Planck Institute of Animal Behavior and her colleagues surveyed citizen scientists in Sydney. Through social media and mailing lists for organizations like the Royal Botanic Garden, they ran two public surveys in 2018 and 2019, asking residents whether they had seen such behavior—and, if so, when and where. More than 1300 people responded. The resulting map was far more accurate than many citizen science efforts because it included negative answers, says Corina Logan, a behavioral ecologist at the Max Planck Institute for Evolutionary Anthropology who wasn’t involved in the new work. That “greatly increases the value of the study,” she says.

Before 2018, cockatoo dumpster diving had only been reported in three suburbs. By late 2019, it had spread to 44 out of nearly 500 in the survey. And the spread had a clear pattern: It started near those three, original suburbs and trailed off as locations got farther and farther away, the researchers report today in Science. That suggests the birds were learning from one another and spreading the behavior through the city, Klump says. In one distant neighborhood, dumpster diving seemed to pop up on its own, suggesting that a new batch of cockatoos had hit on the strategy independently. There are also anecdotal reports of the behavior elsewhere in Australia, Klump says.

To get a clearer picture of what the raven-size cockatoos were doing, the researchers caught and marked 486 birds in some of the garbage can–opening hot spots. After filming 160 successful dives, they noted several common steps: First, a bird lifted the can’s lid at the front corner with its bill; then, they held it slightly open while waddling toward the hinges; finally, they flipped up the lid suddenly so that it fell open and yielded its treasure trove of trash.

Individual birds used slightly different techniques: Some held the handle of the can’s lid, whereas others just held onto the lid itself. And some held it with both bill and foot, whereas others just used the bill. The farther apart the dives were geographically, the more the birds’ techniques differed. “That really means that they socially learn, not just that you can open [a garbage can], but how to open it,” Klump says. It also suggests local knowledge about dumpster diving is passed along, creating “regional subcultures.” Local cultures, or “dialects,” have been found in parrot calls, but this is the first time it has been found in parrot foraging. That means cockatoos join a select group of animals, like some primates and whales, that have culture in both communication and food gathering.

The results are exciting—and the number of birds the researchers caught and marked for the study is “astronomical,” Logan says: “Studying culture in wild populations is extremely difficult, because you have to track the start and spread of an innovation.”

But Claudio Tennie, a cognitive scientist at the University of Tübingen, says the cockatoo culture conclusion is premature. It’s a “neat study,” he says, that does a good job showing the cockatoos learn from each other. But to show the birds have real cultures—the way humans have cultural differences in things like language or cooking—the researchers would have to clearly identify at least one can-opening sequence that is “locally unique,” he says. The researchers found that the sequences broadly differed with distance, but they didn’t show that any given technique was restricted to one place. “I like [the paper],” Tennie says. “But it’s not the full monty. It’s not like human culture—yet.”