Are bones lightweight?

bones are the strongest part of your body as well as the hardest part they protect you but they are a little heavyer then light their more like sort of light for some but some can be more then light....

spongy bone. And it is usually at the end of a bone next to the joint

Birds have hollow bones to help them fly. Solid bones would add to much weight and make it impossible to fly. They have an inner crisscross structure to provide support.

Birds are very lightweight boned animals. :)

Trabecular bone.