Feathers point backward. Bills are lighter and more streamlined than the heavy jaws of mammals and reptiles. Most bird bones are hollow and filled with air from the bird's lungs. Even the wishbone is hollow. Next time you eat chicken or duck, look at the hollow bones.
Birds move through the air by pulling themselves forward like a person rowing a boat.
They push air down and back with the broad side of the wing, then slightly turn and fold the wing to move it forward. Some birds with great, broad wings can soar and glide for long periods without flapping. Other birds have short wings and have to flap fast to stay up. Bird wings and airplane wings have a similar shape. This shape causes an airfoil that provides lift.