Keeping your arms straight, hands open, swing them fast around and around. Feel the air? For a bird, the thickness and palpability of the air must be a little bit like water feels to us when we swim. Birds need to feel the air currents going past the tips of their wing feathers to be able to respond to the needs of flight. Their long flight feathers act as levers, transmitting the sensation of air pressure to the nerves in the birds' bodies at the bases of their feathers.