Is your bird feeder spurring evolutionary change? Maybe so, according to Gregor Rolshausen and three coauthors, writing in Current Biology (December 29, 2009).
Around 10 percent of Central European blackcaps fly from southern Germany to the United Kingdom every winter, lured by human-provided birdseed. The rest of these warblers head to Spain. The split migration has been going on since the 1960s, and the researchers report that the two groups have evolved differently. The UK blackcaps have rounder wings, reflecting the shorter distance they travel. And their beaks are longer and narrower, well suited to bird feeders. By contrast, the Spain-goers’ broader beaks are better for fruit trees. The ultimate result, the researchers say, may be two distinct species.
(Stephen Bates. “Findings.” The Wilson Quarterly Winter 2010: 13)