From The Hindu:
Humans are inadvertently manipulating bird genetics by innocently providing birds with feeders in winter, according to findings by German researchers. Over less than 30 generations, birds visiting British and European gardens in winter have evolved different-shaped wings and beaks, the scientists say.
In time, they could eventually become a distinct species. The birds breed side-by-side in the same Central European forests, but began to follow different winter migration routes after some discovered rich pickings from humans in Britain.
Eventually they divided into two reproductively separate groups. One continued to fly south for the winter, migrating to Spain to forage for olives and other fruits. The other got into the habit of flying a shorter distance north-west to Britain, where bird-lovers fed them.
If you’re interested and with journal access, here is the scientific paper the story is based on (from current biology).