Are Birds Evolving To Dodge Cars?

By Sean Kane , Mar 18, 2013 06:06 PM EDT

Are birds evolving to avoid cars in traffic?

A new study released today, published in the journal “Current Biology,” finds evidence that urban birds are quickly evolving to adapt to their environments.

The research focused on cliff swallows that live in the western United States, where birds live near a lot of traffic, near highway bridges, road culverts and overpasses. They also fly down to the road surface to swallow gravel that aids digestion and to sunbathe.

But as we’ve all known since (hopefully) a young age, hanging out in traffic is a terrible idea if you’re trying to not get hit by cars and survive to live another day.

The study focused on roadkill records in Nebraska, and it found that the road-kill index fell from about 20 cliff swallows found dead on the roads in 1983 to just two in 2012. Of course, this does not take into account the birds killed by traffic and not found or reported, but offers a good estimation.

Why are the bird road deaths decreasing, while the populations are not dropping and traffic isn’t decreasing either?

“These birds have been exposed to vehicles and roads for 30-plus years,” lead author Charles Brown told 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.” Brown is a professor of biological sciences at the University of Tulsa.

What the study found was that, in particular, longer-winged birds were the ones that were dying on the roads.

“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.”

And as we know in evolution, the birds that survive populate the future generations. “If the longer-winged birds are the ones being clobbered, then the shorter-winged birds are the ones passing on genes to the next generation,” said Geoff LeBaron, an ornithologist with the National Audubon Society.

Brown also points out that the birds are growing shorter wings, but also getting smarter. “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 study can be found here on Current Biology's website.

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