Cliff swallows’s wings got shorter to survive on road.
We see a sharp decline in bird mortality over the last 30 years. It is not even 100 years that birds getting killed in America. But birds have already evolved to have shorter wings. Can changes take place so quickly? I am amazed. But is it true?
Eighty million US birds are killed by traffic each year. Cliff swallows (Petrochelidon pyrrhonota) have taken to nesting on road bridges, so may be especially vulnerable.
Charles Brown of the University of Tulsa in Oklahoma has been picking up dead swallows for 30 years. Roadkill numbers have steadily declined since the 1980s, even as the number of roadside nests has risen. The killed birds have longer wings than birds caught in mist nets for research, and on average the caught birds’ wings have got shorter.
It makes sense: shorter wings are better for a quick vertical take-off, and improve manoeuvrability.
“Everything fits with the idea that it’s vehicular selection,” says Ronald Mumme of Allegheny College in Meadville, Pennsylvania.
So, evolutionary changes have been occurred not by ‘natural selection’ but by unnatural selection, artificial selection, practical selection or vehicular selection! Isn’t it amazing?
Birds get killed by feral cats too. But they have to survive. Birds with Shorter wings are better to escape quickly.
Cliff Swallows are the new victims of human influenced evolution! We have made fish grow quickly!
Roads, vehicles, humans’ commercial greed are perhaps part of nature. We should think twice before calling those selections unnatural selections.