Cliff swallows that nest in highway overpasses have evolved shorter wingspans over the last 30 years to help them survive close encounters with highway traffic, according to a new study in scientific journal Current Biology.
The conclusion was reached by Charles Brown, a University of Tulsa researcher who’s spent the last three decades picking dead birds off roadways, New Scientist noted.
Brown particularly noticed a sharp decline in roadkill in southwestern Nebraska since the 1980s, even as cliff swallows were building nests near highways in record numbers. After extensive studies of dead birds recovered from Nebraska highways, Brown spotted the trend: mortality went down as more of the birds were born with shorter wings.
The swallows’ shorter wingspans enable greater mobility in flight and faster take-offs. It’s also possible that it gives them an advantage when hunting insects, which could explain why more shorter-winged birds were better able to survive unusually cold weather.