Contrary to popular belief, birds do not locate earthworms in the ground by hearing them. Birds find food by the sense of sight, The cocking of their heads while seeking worms and other foods creates the illusion that the sense of hearing is involved. But this gesture simply helps the birds in seeing their prey. Not having bifocal vision, as humans do, they can see an object more sharply by concentrating a single eye directly on it. On the whole, a bird's eyesight is superior to a human's.