Endoskeleton

The pigeon's skeleton is strong but built to be as light as possible: many of its long bones are hollow and filled with air rather than marrow, a feature called pneumaticity, which substantially reduces the overall weight of the flying body. The sternum (breast bone) is enlarged into a broad plate of bone that is drawn out ventrally into a deep, blade-like keel or crest, which provides the large surface area needed to …