Question

why birds have pneumatic/hollow bones?

Answer 1

The bird's hollow bones make the skeleton lighter for flying, and allow more oxygen to be absorbed from the air into the blood for that extra energy a bird needs. ... Trunkbones – including the vertebrae, breastbone and pelvic bones – also contain air sacs invading from the lungs. These are all called pneumatic bones.

Answer 2

They have hollow bones because they fly in air and to fly the weight should be less which is fulfilled by the hollow bones which eventually help in flying