Bird claws and bird of prey talons: Where is the difference?

The questions asked were (1) whether claws and toes of birds of prey are actually different from those of other perching birds, and, if so, (2) what parameter can describe such a difference. The structure of toes and claws of the first and third toe was then evaluated in three groups of birds: Falconiformes, Strigiformes and non-raptorial species. One adult male per species was considered, and, among non-raptorial birds, only species belonging to typically or partially perching families. Only one specimen per species was chosen, from museum skin bird collections. All species examined occur in the western Palearctic, according to Cramp & Simmons ( 1977-1994 ). Discriminant Function Analysis showed clear separation of the groups. In particular, the first canonical function segregated Falconiformes from Strigiformes, whereas the second separated Strigiformes from non-raptorials. However, Falconiformes and non-raptorials partially overlapped and were not separated. The characteristics segregating Falconiformes from Strigiformes mainly concerned claw curvature, claw length in relation to toe length, and the last phalanx shape, thin or rounded. Characters contributing to segregate Strigiformes from non-raptorials were claw curvature in relation to their radius and the shape, thin or rounded, of both claws and last phalanxes. Results indicate that Strigiformes toes and claws only superficially resemble those of Falconiformes and the shape of claws and toes of Falconiformes are much more similar to those of non-raptorial species than they are to those of Strigiformes.