"Feathers evolved from reptilian scales, and in fact birds still possess scales in the lower parts of their legs and feet. Feathers grow quickly and are then sealed off at the base. Once fully developed a feather is a dead matter like your finger nails, though there are still muscles attached the base of each feather which can move each individual feather to help keep it in place. Feathers do not last for ever, they become worn and battered and are replaced regularly by the bird once or twice a year depending on species. This replacing of old feathers is called 'MOULT' or the moult or moulting." [source http://www.earthlife.net/birds/feathers.html] "In most birds, feathers grow out of little pits in the skin called follicles. Follicles form neat rows in patches called feather tracts. Feathers grow in thickly and overlap so no skin shows. As a feather begins to grow within a covering called a sheath, it develops its central shaft, color, and pattern. Blood vessels nourish the growing feather until it is fully formed, then the blood vessels wither away. The sheath bursts open and falls off, or the bird removes the sheath with its beak." [source http://www.dnr.state.mn.us/young_naturalists/feathers/index.html]