Hat tip to Terrierman for this one. It is a good read from the DC Birding Blog about raptors, talons, and how they kill their prey in the wild.
Given the prominent role that a raptor's feet play in seizing prey, it makes sense that the shape of their feet might vary with how a raptor uses them. This is in fact the result reached by a team of graduate students after they photographed and measured the feet of hundreds of bird specimens, both raptors and non-raptors. (Most specimens were held by Montana State University; others were from the American Museum of Natural History.)
Give it a read.