More Crazy Proof Birds Are Evolving to Live With Cars

Researchers Charles R. Brown and Mary Bomberger Brown have been driving down the same roads in southwestern Nebraska for 30 years collecting and studying dead Petrochelidon pyrrhonota, or cliff swallows that make their mud homes on the undersides of bridges and overpasses. In all that time, the incidence of road kill among the species has plummeted dramatically. But the two most obvious explanations for the decline – a drop in either traffic volume or bird populations – don't seem to fully explain it.

In new research published in the journal Current Biology, the researchers propose instead that these swallows seem to have evolved in the past three decades to dart out of the way of passing traffic: They now have shorter wingspans, handy for quick take-offs and turns. Those longer-winged birds that haven't yet made the evolutionary transition appear more likely now to be hit by cars (the researchers know this by comparing road kill to birds that died of other causes).