Evolving Shorter Wings To Stay Safe From Speeding Cars, Study Suggests Birds Safer Now Than Before

Driving along the vast swaths of prairie in Nebraska will surely afford some magnificent views of Middle America's natural beauty. Spotting roadkill is also likely; some 80 million birds are killed annually by vehicles in the United States.

But if researchers are correct, fewer bird carcasses will be found along the roadside, because birds, specifically the cliff swallow, have evolved shorter wings, which may help them avoid being killed by speeding cars.

The cliff swallow is a bird species commonly found in the western United States, where they tend to nest around highway overpasses and bridges. They frequently sit on the roadside pecking at the gravel.

"These birds have been exposed to vehicles and roads for 30-plus years," said Charles Brown, the lead author of the study, in a report by USA Today. "During that time, they have evolved to avoid being killed by traffic. Evolution can happen very rapidly, and some animals can adapt to urban environments very rapidly."

Even as the number of roadside nests has risen, number of cliff swallows found dead on the road has decreased since the 1980s when Brown, who is a professor of biological sciences at the University of Tulsa, began studying the birds.

The killed birds have longer wingspans than birds caught live for research; the average caught bird's wingspan has become shorter, the study found, suggesting that the bird's shorter wings make it easier for quick vertical take-of and increased  chances of survival in life on the road.

"Everything fits with the idea that it's vehicular selection," said Ronald Mumme of Allegheny College in Meadville, Pa., in a report by New Scientist.

The roadkill index fell from about 20 dead cliff swallows a year in Nebraska in 1983 to an estimated two birds a year when the study ended in 2012.

"Longer-winged swallows sitting on a road probably can't take off as quickly, or gain altitude as quickly as shorter-winged birds, and thus the former are more likely to collide with an oncoming vehicle," says Brown

Brown also said that the cliff swallows are able to learn from watching other birds, which may also have contributed to the decreased numbers cliff swallows killed by cars.

 "Birds that have the ability to learn are more likely to survive and produce more babies," he said. "Over time, the population will have smarter birds."

The article, published in the journal Current Biology, can be found here.