Sulphur-crested cockatoos are defying human efforts to keep them out of bins by copying each other’s tricks, but more effective strategies to thwart them are passed on between humans too
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Residents of Sydney, Australia, are caught in a battle of wits with cockatoos, as they try to stop the crafty birds raiding their rubbish bins for food.
As fast as they come up with new ways to stop the sulphur-crested cockatoos (Cacatua galerita) from opening the bins, the birds are working out ways to defeat them. It is a classic example of an arms race in cultural evolution, says Barbara Klump at the Max Planck Institute of Animal Behavior in Radolfzell, Germany.
The saga began when cockatoos discovered that people’s bins often contain food, with bread and fruit being particular favourites. The lids are heavy, but a few birds found they could pry them open at the front, grip the lid in their beak while walking around the rim towards the hinge, and flip the lid over.
The trick was seen in only three suburbs of Sydney in 2018, but by 2019 it had spread to 44 suburbs as cockatoos learned the trick by copying each other, Klump’s team reported previously. The behaviour is a nuisance for residents since the birds often toss rubbish over their front yards and streets.
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The team has continued studying this culture war – this time focusing on the human side of the conflict.
The researchers observed the protection strategies being used on 3283 bins in four suburbs where bin-raiding by cockatoos had been reported, and gathered responses from 1134 residents in an online survey.
Some residents started putting bricks and other items on top of their bin lids, but some of the hungry birds figured out they could nudge the bricks off with their heads.
Some Sydneysiders put bricks on their bins to try to foil cockatoos
Barbara Klump (CC BY-SA)
A more sophisticated tactic – which hasn’t yet been defeated – is to wedge a stick or a pair of trainers between the hinges and the bin to stop the lid from flipping over.
“Bricks seemed to work for a while, but cockies got too clever,” one resident told the researchers. “Neighbours on [the] other side of [the] highway suggested sticks. They work.”
The researchers found that protection tactics tended to cluster among neighbouring houses, leading them to conclude that they are copying each other’s tactics just like the birds do.
Once it was thought that only humans have culture, in terms of innovations that spread between groups, but examples have now been seen in several animals, such as chimpanzees, whales and even insects. “We know that a lot of animals are similar to us in the way they learn [from each other] and have their own local traditions,” says Klump.
Journal reference: Current Biology, DOI: 10.1016/j.cub.2022.08.008
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