Feather loss occurs either because the bird is truly losing feathers or because the bird, or its cage-mate, is picking out its feathers. Feather Destructive Behavior (FDB) is a general classification that describes the many types of damage a bird can do to its own feathers, including feather picking. Feather loss and feather-picking can also be caused by diseases that result in irritation or pain for the bird, or damage to, or inappropriate growth of feathers. Feather loss and feather-picking are complicated problems. For specific advice, your bird should have a thorough work-up by a veterinarian familiar with birds.