A 30-year study of birds and roadkill may have given us a look into how animals respond to man-made changes in the environment. According to a study published last week in Current Biology , an area in southwestern Nebraska has seen a marked drop in cliff swallows found as roadkill. At the same time, the average wing length in the group decreased, with one exception: birds who were found dead on the roadside had a wingspan that was “significantly larger than in the population at large.” One plausible explanation? In areas with roads, cliff swallows tend to nest in overpasses, bridges, or culverts, putting them at risk of death. But those with shorter wings can manage a more vertical takeoff, getting them out of the way of incoming..