You might expect city-dwelling birds to be savvy about traffic. Birds didn't evolve around giant, motorized predators made of metal—but once they realize how quickly a cab or bus can bear down on them, they should take heed. A recent study, though, found that pigeons do just the opposite. Travis DeVault is a wildlife biologist for the U.S. Department of Agriculture's National Wildlife Research Center. Based in Ohio, he looks for ways to keep birds, bats, deer and other animals from being struck by cars, planes and helicopters. These kinds of collisions are bad news for the animals, obviously, but are also dangerous for humans. For the new study, DeVault and his colleagues asked whether experience with cars teaches birds to avoid them. After seeing how fast these fuel-powered animals can travel, do birds give them a wider berth? The researchers used pigeons. The 105 birds had grown up in a barn and never seen traffic; they traveled to and from the laboratory in covered cages so they'd remain clueless. The researchers divided the pigeons into three groups: One group would be trained by seeing a vehicle repeatedly zoom past at 60 kilometers per hour (37 mph). Another group would see the vehicle traveling 120 kph (75 mph). The third group—the control birds—would only hear the sound of the vehicle, and never see it. The training happened over the course of several weeks. Birds waited in cages next to a closed road at a research station. Then the vehicle (a 2002 white Ford Ranger pickup, usually driven by DeVault) zoomed by, passing within 2 meters of the cages. The truck passed the birds at either 60 or 120 kph, depending on their group. The control birds were in a nearby cage with their view blocked, so they never saw the truck. Each group got buzzed a total of 32 times. "We have conducted several experiments over the past few years that required us to drive trucks towards birds or other animals," DeVault says, "so we have become pretty good at it." Once their training was complete, the pigeons returned to the lab for testing. Now that the birds had seen how fast cars can travel, the researchers wanted to know whether they'd act more cautious around traffic. Specifically, had training had made the pigeons any better at saving their own tails when a car was bearing down on them? Since the scientists didn't want to actually flatten any animals, they used a video simulation. One by one, the pigeons entered a video playback room. They saw the same truck from their training zooming toward them on a screen. But instead of passing close by the birds as in the training, the truck came straight at them. Then it seemed to pass (splat!) right overhead. The researchers recorded how soon their pigeons started running or flying away when they saw the truck approaching. The training had made a difference, they saw—but it was the opposite of what they expected. "We did expect the experienced birds to learn about the high speed of the vehicle and exhibit safer (earlier) responses than the control group," DeVault says. Yet the trained birds waited longer before trying to escape. They seemed to think the truck was no big deal. Pigeons that had never seen traffic took off sooner, giving the truck more space. "We were somewhat surprised by our results," DeVault says. Earlier studies had suggested that either result was possible, depending on the animal and the circumstances. DeVault says an experiment with another bird species might have turned out differently. But his pigeons showed that some birds, at least, may get more comfortable with traffic as they see more of it. "We cannot assume that experience always results in less risk of collision," he says. Even the more cautious, inexperienced birds in his study didn't fare well in their virtual collisions, though. Out of 90 pigeons that saw the truck video, only one bird took off soon enough to survive.
Image: YU CHIH-WEI (via Flickr)
DeVault, T., Seamans, T., Blackwell, B., Lima, S., Martinez, M., & Fernández-Juricic, E. (2017). Can experience reduce collisions between birds and vehicles? Journal of Zoology, 301 (1), 17-22 DOI: 10.1111/jzo.12385
