Science & Technology

Birds in the City Have Evolved to Solve Problems

Birds are everywhere. From pigeons perched on statues to sparrows flitting carefree through warehouse stores to the constant bald eagle problem in the unfortunate city of Unalaska, they've managed to make themselves an intractable part of urban life. Clearly, something about the chaos of city life is amenable to avian activity. But what you might not have guessed is that just being around a lot of people makes birds better at solving problems.

Bird Brains of a Feather

Despite the moniker, "bird brains" are actually pretty well equipped to handle whatever life throws at them. Crows, in particular, have a reputation for solving problems. In one highly publicized case, carrion crows in the Japanese city of Sendai developed a foolproof method for cracking open tough walnuts. They'd bring the nuts to places in the city where traffic was slow, then throw them down right in front of the front tires of the vehicles. Soon, the practice lots of the city's driving schools and every hairpin turn on a city street came to be littered with shattered shells — the slowness of the vehicle makes it easier for the crows to get in and out safely, you see. The method grew more elaborate as time went on. They learned to place the nuts at intersections, where they knew to wait on the traffic light until it changed to red. Then, they'd swoop down with their walnuts, place them gently on the ground, and fly back to safety. In the years since, birds in other Japanese cities have been spotted employing the same method — but carrion crows elsewhere never have.

If you're thinking that might mean that birds communicate among each other to pass on puzzle-solving techniques, well, you might be right. One study set out to see exactly how information could spread among a community of great tits. The tits of Wytham Woods have been very well documented since researchers have outfitted each one with a transponder chip in a leg ring, which can be used to identify and track the bird's movements through the park. That meant that when lead author Lucy Aplin taught two males from each of the park's five sub-populations how to open a puzzle box to reveal some tasty mealworms, she could track exactly how that information traveled from bird to bird.

Because they could track the birds so exactly, the researchers also knew which particular birds liked to hang out together. And as you might expect, it was the trained birds' best friends who first learned how to open the puzzles on their own. There was another quirk of this research, too. The puzzle boxes could be opened in two ways: by turning a lever to the right or to the left. The birds that had been taught to do it one way inevitably taught their compatriots the same method, and that was true even after a year had passed since they originally learned.

Smarter in the City

If birds learn by teaching each other handy tricks, then it sort of makes sense that city birds would learn faster. After all, they're the ones who are surrounded by both a lot of other birds and a lot of food-hiding puzzles (like trash cans with lids) to solve. But it goes beyond a mere numbers game. There's strong evidence that urban birds have actually evolved traits that make them better at problem-solving.

The thing is, you can't solve a puzzle if you never want to try something new. A lot of animals are naturally afraid of new sights and sounds, and that makes sense for surviving in the wild. But a crow that's afraid of cars will never crack a walnut — and studies bear that out. For example, a 2016 study published in Scientific Reports showed that urban birds actually prefer strange sights. When a few birdfeeders in Polish cities were adorned with a strange bright green object bearing a shock of orange fur, the rural birds steered clear, but city birds showed a clear preference for the weird feeders. Another study from the same year showed that the distance a bird would allow a human to approach was directly linked to how long the population had been in the city. The longer they'd been in the city, the closer they'd let people get. That's not something they learned — it's a clear sign that a willingness to be around people is gradually bred into a species. And that evolved fearlessness could be a key ingredient in the problem-solving prowess of urban avians.

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The impressive intelligence of birds is definitely one of our favorite topics here in the Curiosity office. If you'd like to learn more about how whip-smart your feathered friends really are, check out "Bird Brain: An Exploration of Avian Intelligence" by Nathan Emery. We handpick reading recommendations we think you may like. If you choose to make a purchase, Curiosity will get a share of the sale.

Written by Reuben Westmaas May 21, 2018

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