They coat their feathers with oil from a special gland and constantly preen to keep feathers overlapping like tiles on a roof. Because of the size and position of their eyes, ducks can see everything around them for approximately 340 degrees without turning their heads. Feathers make up about one-sixth of a bird s weight. Hummingbirds have the fewest feathers, some having less than 1,000. Some swans have more than 25,000.
Birds are the only animals with feathers.
When you look at a perched bird, most of the feathers you see are small ones that give its body a warm, smooth covering. When flying, birds show the larger, stiffer wing feathers used for flight. A single feather may have more than one million parts. Feathers become worn with use and are usually replaced every year. This is called molting and is generally gradual, enabling birds to fly reasonably well.