Conflict between cockatoos and humans leads to arms race

Urban living sulfur-crested cockatoos in some Australian cities have learned how to open the garbage disposal bins and access delicious food in the form of bread and other throwaway titbits. This has had residents up in arms as they try to control the birds’ access to the rubbish using innovative bin lid modifications. You see, although the cockatoos are pretty ingenious at opening the bins, they never close them again and this means garbage gets spread all over the street, leading to conflict between the birds and the local residents.

Previously, researchers have documented the ingenious bin-opening behavior of sulfur-crested cockatoos in suburban Sydney, and have found that this behavior is learned and transmitted culturally between sub-populations. Now, in a follow-up study, published in the journal Current Biology, they note the techniques used by people to confound the cockatoos, and describe how these birds are learning all the tricks and overcoming the obstacles. 

“When I first saw a video of the cockatoos opening the bins I thought it was such an interesting and unique behavior and I knew we needed to look into it,” said study lead author Barbara Klump, a behavioral ecologist at the Max Planck Institute of Animal Behavior. She explained that the cockatoos’ motivation is waste food. “They really like bread. Once one gets a bin open all the cockatoos in the vicinity will come and try to get something nice to eat.”

The birds typically pry the bins open with their beaks and then maneuver themselves along a small rim while retaining a grip of the lid in their beak. When they reach the back (hinge side) of the bin, they simply flip the lid open. It’s a community affair. “We could actually show that this is a cultural trait,” said Klump. “The cockatoos learn the behavior from observing other cockatoos and within each group they sort of have their own special technique, so across a wide geographic range the techniques are more dissimilar.”

Local residents have responded to the problem by trying to secure the lids using bricks, rocks and other contraptions to keep the birds out of the bins. The bin lids still need to open when the bins are tipped upside down and emptied by an automated arm on the garbage truck. This has led the humans to develop some fairly innovative solutions to restrict access by the parrots. A survey conducted by the researchers found that some people strap full water bottles to the lid, rig ropes to prevent the lid from flipping open, or use sticks or bottles to block the hinges. “There are even commercially available cockatoo locks for bins,” said Klump. 

The researchers identified 5 different categories of bin alteration that had been adopted by residents in order to deter or thwart the efforts of the birds. Level 1 represented no alteration whatsoever, while level 2 involved no functional alteration (e.g., a rubber snake). Level 3 alterations included unfixed objects, such as rocks and bricks designed to prevent lifting, while level 4 included the use of objects to prevent flipping of the lid (e.g., bottles, sticks or shoes jammed in the hinges). Level 5 represented the greatest investment on the part of the human, for example an attached weight suspended on a rope. 

The researchers found that while level 2 and 3 protection devices could be opened by the cockatoos, level 4 and 5 devices had not yet been conquered by the birds. Interestingly, they noted that the protection method used by humans was not randomly distributed around the suburbs; instead, protection methods appeared to be clustered within streets, implying that the residents in a street are learning from and copying each other. 

Residents also reported that they switched techniques on a regular basis, just as soon as the cockatoos had worked out how to deal with a particular bin modification. This is akin to an innovation arms race because each time the cockatoos learn their way around a bin modification, the humans come up with a new technique and share it with others.

“It’s not just a social learning on the cockatoo side, but it’s also social learning on the human side,” said Klump. “People come up with new protection methods on their own, but a lot of people actually learn it from their neighbors or people on their street, so they get their inspiration from someone else.”

Klump won’t say whom she expects to win the race for control of the bins, but she and her colleagues plan to look at how the cockatoos’ behavior varies from season to season.

Klump expects we will see more of these kinds of human-wildlife interactions in the future. “As cities expand, we will have more interactions with wildlife. I’m hoping that there will be a better understanding and more tolerance for the animals that we share our lives with.”

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By Andrei Ionescu, Earth.com Staff Writer