How did the skeleton change during bird evolution?

(answer with just 1 or 2 sentences please)

reduction in birds skeleton

Explanation:

The reduction in a bird's skeletal weight is largely a result of hollow construction of the skeleton. The fusion or loss of individual bones reduces the number of movable joints in the bird's skeleton, making it rigid and better adapted as the internal framework of a flying machine.

imagine a line passing through the center of earth that goes through both the north pole and the south pole. this imaginary line is called an axis. earth spins around its axis, just as a top spins around its spindle. this spinning movement is called earth's rotation. at the same time that the earth spins on its axis, it also orbits, or revolves around the sun. this movement is called revolution.