Swallows that nest on roadsides appear to have evolved shorter wings to help them manoeuvre better and avoid cars, claim a team of scientists from the University of Tulsa in Oklahoma. They have been studying cliff swallows that live near roads, and observed that the number of vehicle-killed birds has declined over the past three decades, despite the fact that the overall population has increased.
The researchers then compared the wings of birds killed by cars to those killed accidentally in nets used to catch birds for study.
The results, published in Current Biology, show that the wings of vehicle-killed birds have lengthened over time, while those that died accidentally in nets -- and are representative of the entire population -- developed shorter wings over time. That's enough for the researchers to claim that, overall, the population is evolving to better avoid cars. Shorter wings, they say, allow the animals to "make a 90-degree turn more rapidly".
In turn, more agile flyers survive longer, creating more short-winged offspring, and so the survival of the fittest has its way. Critics have suggested other factors -- traffic patterns, predators, diseases and scavengers -- may be at play, but the researchers claim to have taken such issues into account. If it really is the case that these swallows are evolving to avoid cars, though, it's a major testament to the power of evolution right there. [Current Biology via Nature]