A close look at museum collections of 851 songbird specimens belonging to 21 species shows that most of the birds evolved pointier wings after their forests were fragmented by clear-cutting. Others in re-foresting areas evolved less-pointy wings. The reason for the wing changes: nothing less than the drive to procreate.
Pointier wings can help birds who are long-distance commuters fly more efficiently. More rounded wings, however, are better over short distances.
http://ashepp3.newsvine.com/_news/2010/02/17/3910226-american-songbirds-evolve-with-forests
Eastern North American songbirds are a pretty adaptable bunch, says a scientist who discovered some remarkable changes in their wings over the last 100 years.