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.