Swallows may be evolving to dodge traffic


Roadside-nesting cliff swallows have evolved shorter, more manoeuvrable
wings, which may have helped them to make hasty retreats from oncoming
vehicles, according to a study published in Current Biology.

The study’s authors discovered the trend after noticing that the
number of vehicle-killed birds had declined over the past three decades.
They suggest that the two findings provide evidence of roadway-related

“I’m not saying that it’s all because of wing length,”
says Charles Brown, a biologist at the University of Tulsa in Oklahoma
and one of the authors of the study. But, he says, the shortening does
support the idea that the birds are adapting to disturbed environments,
as other organisms presumably are.

Together with Mary Bomberger Brown, a ornithologist at the
University of Nebraska–Lincoln, Brown tracked roadside populations of
cliff swallows (Petrochelidon pyrrhonota) in western Nebraska for 30 years, mostly to study the birds social behaviors within their colonies.

Written By: Beth Marie Mole
continue to source article at nature.com



  1. “this is the best demonstration that they do have that capacity”.

    They have the capacity to what, adapt, to ‘evolve’? Why do I feel like she is suggesting that they have a choice here.

    the same thing happened in BBC’s Science club, E3, where the presenter was asking if we should save the Panda or not based on their worth to their environment, he noted that Pandas evolved to eat meat but ‘CHOSE’ to eat Bamboo and that ‘They did not help themselves’ when it came to their 3 days a year mating season. ARGH!

    • In reply to #3 by MarchOfTheRational:

      How sad that they have had to evolve in order to stop them from being killed in such a way

      I’m glad they have the ability. Now, if only the racoons and opossums could show the same adapability.


      • In reply to #4 by Agrajag:

        In reply to #3 by MarchOfTheRational:How sad that they have had to evolve in order to stop them from being killed in such a wayI’m glad they have the ability. Now, if only the racoons and opossums could show the same adapability.Steve

        All animals have the ability, it is not some choice they get to decide on.

        • In reply to #6 by veggiemanuk:

          animals have the ability, it is not some choice they get to decide on.

          Notice that I did not say it was a “choice”; what I said was: “if only the racoons and opossums could show the same adapability (sic).”

          Around where I live, these animals have not shown the necessary adaptability.


    • In reply to #3 by MarchOfTheRational:

      How sad that they have had to evolve in order to stop them from being killed in such a way .

      I don’t see it as sad, I see it as inevitable and somewhat unavoidable considering our species ability to develop the land around them to suit their needs. Regardless of what we humans do to better human society, some animal somewhere will suffer, be it in large quantities or small.

      If one realy found this sad, then one would not drive a car at all and if they were truly sad about any animal dieing due to human activity then they might as well not exist because it is a dead cert that the clothes on their back, the food they eat and the houshold items they use have ALL resulted (indirectly) in the killing of animals.

  2. A similar thing’s happened in the UK with Blackcaps since the nineteen fifties when garden bird feeders became fashionable, and that species no longer needed to migrate South to Spain in winter.

    Those which inherited thinner longer beaks could delve into the nets and holes in the boxes put out, whereas those who didn’t pick up on that trait had to fly south to crack open seeds etc with their thicker more powerful beaks.

    Because they no longer had to migrate, their wings also became smaller and their claws bigger.

    All that in just fifty years or so!

    And, what’s more, they are now to be found over wintering as far North as Sweden; that’s one in the eye for Global Warming doubters.

    • In reply to #8 by God fearing Atheist:

      I don’t know if this is an Urban Legend, or true, but I heard that hedgehogs used to curl up into a ball when they saw car headlights, but now run like hell.

      I like to imagine they’d evolve spines that could puncture tires. Drivers would then evolve to avoid hitting hedgehogs.

  3. With high traffic volumes and speeds, there is generally, a large supply of insect road-kill, as a road and road-side food source for birds and small insectivores – if they themselves can gather it without becoming road-kill!

  4. I live in a suburban area infested with deer. Several years ago, there were a few deer that would stop and look both ways before crossing the street. I wasn’t the only person that noticed this. We’d joke how we have smarter deer in our neighborhod. Unfortunately, I haven’t seen the likes of them since then, now deer just kick up their hooves and scatter at the sight of a car.

  5. I look forward to the day when humans have evolved to walk down the street in a straight line and not stand in busy shop doorways or block the supermarket aisles with their shopping trolleys. I support any initiatives to speed up the survival/non-survival process in this area.

  6. So, the shorter winged birds (that already existed in the population) have an advantage in maneuverability. They then survive selectively due to this insult in their environment, and when they breed, their offspring are more likely to have shorter wings. The shorter wing allele came about by random mutation, but the selection for it is absolutely not random. Soon, we have an allelic frequency change within the population, and, given enough time and continued divergence we end up with a new species (which simply means a new thing that cannot or will not breed with the older stock)…

    NOW, where have I heard this before?????

    Somebody text Robert Kubick, he needs to see this….

  7. Birds have to be excellent energy managers. Flight is expensive. I’ve seen mynah birds in New Zealand that avoided traffic by hopping over the centre-line, instead of flying away. They’d bet their lives that the approaching vehicle would act normally and stay on its own side of the line, in order to win the energy savings of not flying off. A fine balancing act, energy savings to the winner, death to the loser. Repeat for long enough and you get some pretty street-savvy birds.

    There’s also a David Attenborough documentary showing crows (I think) in Japan using traffic to break nuts, and then using traffic lights to let them recover the goods safely. Both these are learned behavior, so not the same as the evolving change in wing length, but I’d expect evolutionary pressure to favor brains that learn to cope with traffic, as much as wings that assist maneuverability.

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