The skeleton of the bird is similar to that of other vertebrates, but it has some unique features that represent adaptations for flying.
The bird's skeleton is a strong bone and cartilage frame that has evolved to support the its internal organs while it is in flight and to provide an effective anchor for its flight muscles. The sternum, the bone that anchors like muscles directly, is usually wide and thick.
The spinal vertebra are rigidly connected and sometimes even fused to give the skeleton greater strength. The neck vertebra vary in number depending on the length of the birds neck. For example, the swan has 25 vertebra, a blackbird has 16. Not too much difference in number but the swan's vertebra are more flexible allowing the bird to move its head freely and twist and bend its long neck to preen and hunt fish.
It is also important for birds' bones to be light. Birds achieve this by having bones that are hollow, without marrow, and that are filled with air sacs.