One of the reasons why bird legs seem so thin is that their body is largely hidden by feathers, which can make them look much bigger than they really are. Birds have more muscular thighs that are by their feathers, and most birds have scaly skin on their lower legs, which makes these parts look very small and bare. Birds that have feathers to their toes — such as owls and some breeds of chickens — seem to have thicker calves than their featherless-legged relatives. But it’s not only a matter of perception: bird legs have some real differences from legs of other living animals. Birds are the descendants of theropod dinosaurs, a group of animals that walked on two legs and varied in size. most mammals that can walk on two legs — such as bears, chimpanzees and humans—who stand on their heels, dinosaurs walked on their toes and the front part of the foot, with the rest of their foot bones stretched and lifted off the . Living birds inherited some of these features. However, as birds became more adapted to flying, they also developed some distinct .