Car traffic driving micro-evolution?

It’s hard to think that you can evolve to avoid fatal car crashes, but apparently, you can. Well not you, but other creatures like cliff swallows can.

Ecologist Charles Brown at the University of Tulsa, Oklahoma has been observing a population of the birds in southwest Nebraska with his wife, University of Nebraska ornithologist Mary Bomberger Brown. The couple has watched the population for over 30 years now and have just published a new study in Current Biology.

The group of swallows nest in highway overpasses, so the Browns could count on finding a number of swallows killed by passing cars every year. But lately, the body count has been going down.

So the Browns began to look at the birds’ physiology. They found that over the last three decades, the birds’ average wing length dropped from 111 millimeters to 106 millimeters. Moreover, the average wing length of birds killed by cars in 2012 was 112 millimeters.

Birds with shorter wings are more adept at pivoting, rolling and changing direction, all very handy skills when it comes to dodging fast-moving cars. Though more research is needed, the Browns claim that the car and truck-laden environment is selecting for birds with shorter wings.

It’s selection… but not quite natural selection.


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