Cliff Swallows May Have Developed Shorter Wings to Avoid Cars
Human inventions tend to cause a lot of problems for wildlife. Some species are better able to adapt than others. A few months ago we wrote about how some birds were using cigarette butts in their nests to ward of parasites. Now, it appears that cliff swallows in Nebraska have actually changed their bodies to keep them safe from humans.
A new paper in the March 18th issue of Current Biology provides evidence that over the last thirty years the cliff swallow’s wingspan has gotten dramatically shorter. Since cliff swallows tend to live in dangerous high trafficked places like highway bridges and overpasses, they need to be able to move and turn faster. Shorter wings allows for that adjustment.
While the wings were getting shorter, fewer swallows were being killed on the road. Scientists found that birds who were killed by cars tended to have longer wingspans. If those particular birds are dying, and their shortwinged brethren are the ones procreating, it would follow that the descendants of the surviving cliff swallows would give birth to babies with similar traits.
The paper’s coauthor, Charles R. Brown, said, “Evolution is an ongoing process. Exert selection pressures in a way we don’t usually think about.”
The scientists say that other factors, like learning based on their increasingly busy habitats, could have also played a factor in the fact that fewer birds are dying.
One can only home wildlife like polar bears and wolverines do as good a job adapting to an ever changing world as these cliff swallows. However, when it comes to physically changing, species with shorter life spans will have a much easier time.
Via LA Times