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Cliff Swallows May Have Developed Shorter Wings to Avoid Cars

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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

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  • commonsense

    By this articles “logic”, during a game of dodgeball kids evolve to be faster and thinner, since as the game progresses there are fewer fatter and slower kids. I thought evolution believers thought everything took millions of years? Stupid as stupid does.

    • Karl Malloy

      Well, the life span of a cliff swallow is 4-5 years generally, so your comparison is wrong. You’re talking that a change could have taken place over 6 generations or more of the species, which is plenty if the cost of the disfavorable trait is death. I won’t comment on this case in particular since I haven’t read the articles, but this sounds like a hypothesis that could make sense but needs more data to confirm.

      There are 100% confirmed cases of evolution both in nature and in controlled environments, such as the peppered moth in the UK, which adapted to high rates of dark coloration during the industrial revolution and then back to white when the pollution was cleaned up, because in each case it was matching the tree trunk coloration in its environment (for camouflage), and the Michigan State experiements showing that bacteria underwent genetic modification under controlled conditions to consume citrate buffer as a source of energy, when before they could only use sugar, and had population growth benefit as a result.

      The second example was repeatable, happened in a specific window of number of generations regularly (around 31,000 – the experiments have been ongoing since 1988), and only happened in groups that took a specific prior evolutionary pathway genetically. In other words, the results are awesome and strongly support all known evolutionary theory.

      • commonsense

        I was really just expecting an LOL or two, but I will say the most important word in your post is the last one – theory. As for the swallows and the dodgeball kids, the bigger, less agile targets are easier to hit. Chameleons and other reptiles are pretty good at that color changing thing, too. I’m not so sure the ability to adapt and a beneficial genetic mutation are the same thing.

        • Karl Malloy

          I’m sure they aren’t but I’m also sure that I understand the mechanism in this case – and it wasn’t that the same creature was changing color. It was that its genes were coded at birth for a specific color, it had offspring of different colors, and offspring of the right color procreated, while offspring that were the wrong color got eaten and didn’t.
          I’m all for the last word of a post being the most important. People can believe evolutionary theory or they can believe creationist bullshit.

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