When your bird preens, he grooms himself by passing each feather on his body through his beak. With thousands of feathers to tend to, preening can occupy a lot of your bird's time. It's worth it: preening plays an important role in your bird's health and his ability to fly.
Cleaning
Preening removes dust, dirt and foreign objects from your bird's feathers. It also untangles the small downy feathers and sets each flight feather back into its exact position. If your bird has an mite or tick infestation, preening will also remove some of these pests from his body. You can encourage your bird to clean himself through preening by misting him daily with tap water.
Barbs and Barbules
Each feather is made up of a series of vanes that extend from the main shaft and make up the soft part of the feather. Attached to these vanes are short hair-like structures called barbs. The barbs have small hooks, or barbules, on the ends. The barbules interlock and give the feather strength. As your bird moves around and bumps his feathers on objects, the barbules can come unhooked from each other. When he preens each feather, the hooks are zipped back together, making the feather smooth and strong again.
Oil and Powder
Some birds, such as parakeets, cockatoos, finches and most parrots, have a uropygial gland, also known as a preening gland, near the base of their tail. This gland produces a special oil that moisturizes and conditions your bird's feathers. Other birds produce a fine powder, instead of oil, that cleans and protects their feathers. Your bird uses his beak to pick up a small amount of oil or powder and then spreads it over his feathers as he preens.
Molting
When your bird molts, old feathers fall out as the new ones come in. Preening keeps this process moving as your bird removes the old feathers to make room for the new ones. This is different from feather plucking, which is an unhealthy activity; new feathers should already be coming in as the old ones are removed. Preening also pulls the protective sheath off the new feathers as they grow.
Over-Preening
It is normal for your bird to spend several hours preening each day. During a molt he may preen constantly, but it is not a problem unless he is damaging feathers or creating bald spots. If your bird preens too often, especially when he's not molting, he may end up damaging his feathers. Frayed, broken and missing feathers are signs of over-preening. Stress, anxiety and boredom, as well as health problems, can all cause your bird to preen too much. Have him examined by a veterinarian to rule out any physical cause for his behavior.