The size and shape of the claws and the way the toes are arranged as well as the length of the toes and the degree of webbing are all dependent on what a bird uses its feet for and where it lives. Like a bird's bill its feet reveal a lot about its lifestyle and the next time you have a chance take a close-up look at the fascinating feet of birds.
Do Birds Have Thumbs? http://bit.ly/qK21qAWhy would birds develop backward knees? http://bit.ly/pEt9mS