Researcher Charles Brown of the University of Tulsa has collected dead swallows that became roadkill over the past 30 years.
Swallows are known to build nests on concrete bridges of major highways, making them prone to becoming traffic fatalities.
Brown has measured the wings of such dead birds in relation to those snagged in nets.
Writing in the journal Current Biology, Brown says he found the wings of vehicle-killed birds grew longer over the study period while the general population of the birds grew shorter wings.
It’s believed that the shorter wings allow birds to make sharp turns more quickly, and escape being hit by vehicles.
But Brown says other forces of evolution may also be at work. He found that after an unusually cold May in 1996 killed vast numbers of insects, and nearly half of the nesting starlings died from starvation, wing lengths shortened significantly.
He theorizes that it was because the shorter wings allowed the surviving birds to more effectively catch what few insects were still around.
Photo: Charles Brown