I found this particularly interesting not only because it's the species that Darwin observed (and the one that everybody quotes as an example of real fast evolution) but also in that, within the same species, there are individuals that present the beak shape gene in one way while others present it in another. I wonder how it's inherited... if one is more dominant than the other, etc.
http://www.sciencedaily.com/releases/20 ... 153923.htm