In birds the pectoral girdle is made of three bones, rather than two as in humans. The pelvis is long and has a forward opening to facilitate egg laying. The thigh bones are generally shortened and sturdy. The foot and ankle bones are fused and elongated. The visible backward bending leg joint corresponds to the ankle joint in humans.
Birds stand on their toes.
Several vertebrae are fused except for those in the neck region. The number of neck vertebrae for birds in general varies from 15 or fewer in small birds with short necks to 20 or more in large birds with long necks. More neck vertebrae means increased mobility of the head and neck. The bird's large eyes are separately supported and protected by an encircling ring of small, shinglelike bony plates called the sclerotic ring. Light, air-filled bones are an adaptation for flight.