Incidentally, birds do have ears. Not our fleshy external pinna, just tiny holes beneath the feathers on either side of the head. The song a young bird hears sends sound waves into his ear and vibrates the hair cells there. These are ten times as dense as ours, and much more varied, allowing birds to detect high-pitched sounds beyond our range, as well as the soft rustling of insects beneath soil or leaves. (If a bird’s hair cells are damaged by disease or loud noises—say, by the blasting decibels of a rock concert in a domed stadium—they can regenerate. Ours can’t.)
