Osteology
Avian bone tissue contains more inorganic compounds than mammalian bone tissue (84% minerals versus 70% respectively). Avian bone therefore is hard and poorly elastic and splinters easily. Structurally, three types of bone are found: compact bone, cancellous bone and medullary bone. In adult birds, especially good flying birds, some bones are hollow. Respiratory air sacs form air pockets in these bones.