* Birds bones are hollow. This makes them much lighter than the solid bones of other animals, which is an important adaptation for flying.
* Birds bones are thin-walled. This also helps to reduce their weight, but it also means that they are more fragile.
* Birds bones are highly vascularised. This means that they have a rich supply of blood vessels, which helps to keep them strong and healthy.
* Birds bones contain a protein called osteocalcin. This protein helps to make the bones stronger and more flexible.
* Birds bones grow continuously throughout the life of the bird. This is necessary because birds lose a lot of bone tissue as they fly.
The unique structure of birds bones is a key adaptation for flying. It allows birds to achieve the high speeds and agility that are necessary for catching prey and avoiding predators.