Their clothes are their feathers, and only birds have them - no other animal can claim feathers, unless they steal them from a bird. Some birds have more feathers than others. All feathers are light and many capture the air due to their shape.
Feathers also come in a dazzling array of colors, shapes and sizes.
Because of their colors, many birds' feathers have been prized through the ages. Many indigenous peoples have used feathers as part of their culture's celebrations, or as decoration in headdress. In the late 1800's, feathers became so fashionable to wear in the United States and Europe, that some species became endangered and the price of certain feathers was greater than their weight in gold. Today, thankfully, the practice of wearing wild bird's feathers is illegal. For example, the eagle and the albatross can soar for hours without flapping a wing.