Human trash can be a cockatoo’s treasure. In Sydney, the birds have learned to open rubbish bins and litter the streets as they search for scraps of food. People are now fighting back.
Bricks, pool floats, spikes, shoes and sticks are just a few of the tools Sydneysiders use. to breed Sulphur-crested Cockatoos (galerita cockatoo) to open garbage containers, researchers report on September 12 in current biology. The goal is to prevent birds from lifting the lid while the bin is upright, but still allow the lid to open when a bin is tilted to empty its contents.
This battle between species could be a case of what’s called an innovation arms race, says Barbara Klump, a behavioral ecologist at the Max Planck Institute for Animal Behavior in Radolfzell, Germany. when the cockatoos Learn to flip the lids on trash canspeople change their behavior, using things like bricks to make the lids heavier, to protect their trash from being thrown away (SN Explore: 10/26/21). “Usually it’s low-level protection and then the cockatoos figure out how to defeat it,” says Klump. That’s when people increase their efforts and the cycle continues.
Researchers are closely watching this climb to see what birds and humans do next. With the correct method, the cockatoos could fly by and continue looking for a different target. Or they could learn to avoid it.
In the study, Klump and his colleagues inspected more than 3,000 bins in four Sydney suburbs where cockatoos invade rubbish to see if and how people were protecting their rubbish. The observations, along with an online survey, showed that people who live on the same street are more likely to use similar deterrents, and those efforts increase over time.
Tricks like trying to scare parrots with rubber snakes don’t work very well, says Klump. Also don’t block access with heavy objects like bricks; cockatoos use brute force to push them off. Hanging weights from the front of the lid or placing items like sneakers and clubs on the back handles of a container works best. The team did not see any birds enter containers with these higher levels of protection.
The findings point to an arms race, Klump says, but the missing piece is how birds will respond as people try new ways to lock containers. Some survey responses suggest that parrots are learning.
“The bricks seemed to work for a while, but the cocky ones got too smart,” one respondent wrote. “Neighbors across the road suggested sticks. They work.”
It would be interesting to explore the benefits and problems of the different methods from the perspective of humans and birds, says Anne Clark, a behavioral ecologist at Binghamton University in New York who was not involved in the work. “I’m curious how much effort people put into this and if sometimes that effort limited the use of one solution over another.” Some people, for example, may not have time to put a small weight on the lid of the container or may rely on their children, who cannot lift heavy bricks, to take out the garbage.
In the same way, cockatoos can steer clear of tactics that take too long to beat. Bricks, for example, are easy to get out of a container quickly; breaking sticks or pool noodles stuck through the back handle of the container could take longer. Perhaps if enough people in a neighborhood adopt a highly effective method, Clark says, the cockatoos may not find it worth visiting.