Cliff swallows (Petrochelidon pyrrhonata) in Cayucos, CA. Photo courtesy of Wikimedia Commons and Marlin Harms.
Swallows evolve shorter wings to avoid cars, study suggests.
Over the past few years, I’ve grown increasingly skeptical of such headlines. Still, sometimes the research really does live up to the media hype. This would seem to be the case here, in an NBC News story about the recently published work of Charles Brown and Mary Bomberger Brown.
Collecting and studying the “salvageable specimens” of cliff swallows killed along the roads surrounding southwestern Nebraska’s Cedar Point Biological Station over the past 30 years, Brown and Brown found the numbers of road-killed birds “declined sharply.”  And the trend couldn’t be explained by the population of swallows living nearby (which increased over the study period), traffic volume (which “either did not change significantly or increased, depending on the metric used”), or the number of avian scavengers in the area (“as none showed significant increases in our study area”).
“Thus, none of the obvious factors that confound most road-kill surveys applied to our study,” explain the researchers in the most recent issue of Current Biology. 
So why the decrease in swallow mortalities? Read more