"How is it that [birds] can withstand the pull of gravity that keeps the rest of us tied so firmly to the ground? The secret is a wing with a thick, rounded front edge that curves gently downwards toward the back edge which is very thin. As thin, in fact, as a feather. As the bird glides forward, the air flowing under the wing is impeded by the wing's downward curve so it becomes slightly compressed, and that pushes the wing up. At the same time, the air flowing across the top of the wing is deflected upwards by the wing's front edge, so reducing its pressure. If the air is moving fast enough, then the slight suction from above, combined with the push from beneath will be enough to lift the bird into the air [...] and ample to keep it aloft."