Self mutilation in birds can be divided into 3 separate categories but is usually referred to by the general term "feather picking".
Feather-snapping involves the breaking of the feather shaft. The feather shaft might be snapped near the outer end, resulting in feathers ending in a "v" shape. The feather shaft might be snapped near the base leaving no feathers visible outside the down.
Feather-plucking involves pulling feathers out, sometimes resulting in the bird version of an "ouch". This might be ongoing or a temporary response to dirty or damaged feathers and is especially common around the vent or the preening gland at the base of the tail.
Feather-chewing or shredding, the most common form of self-inflicted damage, begins with injury to the edge of the feathers. This might be related to: soiled feathers; boredom; falling; anxiety; feelings of abandonment; poor diet; or inadequate lighting.
Feather picking is not only one of the most frustrating of all pet bird problems, it is also one of the most common problems seen in avian veterinary practice. Published information on feather picking in pet birds suggests a number of possible etiologies (causes). However, in the majority of cases, a cause is never identified, no matter how dedicated or aggressive the diagnostic approach. Therapeutic trials utilizing antibiotics, anti-inflammatory drugs, antidepressants and tranquilizers have all produced inconsistent results. Unfortunately, bird owners are often left extremely frustrated since feather picking is incurable in a substantial number of cases.
Many different disorders can contribute to feather picking in pet birds. Causes can be broken down into three categories: external disorders of the skin or feathers, systemic (internal) diseases, and psychological disorders. Literature often reports that the three primary causes are mites, malnutrition and boredom, but in fact these are rarely the cause.
Disorders of the feathers and skin are the easiest to identify. Unfortunately, external causes of feather picking are not very common, and some of them, while easy to identify, are difficult or impossible to treat.
Systemic diseases as a cause of feather picking can be far less obvious. Although almost any infectious process or organ disease has the potential to cause feather picking, the connection between internal disease and picking is inconsistent. For example, sometimes the discovery and treatment of an intestinal infection may stop a bird from feather picking. In other cases, a bird may continue to pluck feathers despite the successful diagnosis and treatment of an intestinal infection. In these cases, either the picking became a habit that couldn't be broken, or there was really no connection between the enteric disease and feather problem to begin with.
Possible causes of feather picking External parasites – Pet owners frequently believe that mites are a common cause of feather picking. However, mite infestations occur in a very small percentage of the pet bird population. When mites are, in fact, present, they are very easy to detect and curing the bird of the problem is extremely simple.
Inadequate grooming – This is a common cause of feather picking. Many birds become covered with dirt, oils, and chemicals, such as make-up, from being handled extensively by their owners. The practice of "bathing" birds by spraying them with water from a spray bottle is inadequate in these cases. A small amount of baby shampoo added to the water (1 tbs. shampoo to 16 oz. water) helps remove the foreign material, but the bird should be gently but thoroughly showered to rinse off the shampoo.
Pyoderma (Bacterial infection of the skin) - Staphylococcus aureus is a bacterial infection of the skin that can cause enough itching and discomfort to cause feather picking.
Fungal dermatitis – Rarely, fungal infections of the skin or feathers may cause picking. When present, fungal dermatitis is usually a secondary, opportunistic infection.
Inadequate photoperiod – Occasionally, a lack of proper exposure to normal lighting cycles (photoperiods) can lead to delayed molting. Feathers may age and become the target of excessive preening by the bird with a resultant "picking" problem. If coupled with malnutrition, the feathers may deteriorate more rapidly than normal. These feathers appear ragged, mimicking the appearance of feather picking.
Viral Diseases – Emerging feathers that have been damaged by infection with Psittacine Beak and Feather Disease virus (PBFD) often have a characteristic appearance. These feathers grow in like twisted porcupine quills, then fall out, revealing crimped sections at the roots. Other diseases occasionally produce these signs, so a positive diagnosis based on laboratory work is mandatory, since PBFD is often a fatal disease. Polyomavirus may cause similar appearing feather lesions in young birds. Birds with feather lesions due to Polyomavirus are more likely to recover than those with lesions caused by PBFD.
Liver disease – Several diseases of the liver, such as Chlamydiosis (parrot fever, Psittacosis), Hepatic lipidosis (fatty liver syndrome), Tuberculosis (TB), Bile Duct Carcinoma (liver cancer), Lymphoma (cancer) and many others have been connected with feather picking.
Kidney disease has been observed in connection with feather picking, often with the picking focused over the lower back where the kidneys are located. In one case, removal of a benign tumor of the kidney led to complete resolution.
Aspergillosis is a fungal disease that forms plaques on air sac surfaces. Birds with this condition may pick because of allergic-type reactions to substances produced by the fungus. In addition, these birds often have compromised immune systems and the feathering may reflect generally poor condition.
Intestinal infections – Giardia, an intestinal parasite, can cause severe itching and feather picking in some species of birds. Other intestinal infections, such as Candidiasis, a fungal infection of the intestinal tract, or bacterial enteritis, may also cause feather picking.
Thyroid disorders can lead to poor quality plumage and delayed molting. Feathers can become brittle and devitalized.
Toxins – Heavy metals, such as lead and zinc have been associated with feather picking.
Reproduction, while not a disorder or disease, often leads to feather picking. Females may pick at the lower abdomen to prepare the "brood patch" (the area of the abdomen that will be in contact with the eggs) for nesting. Both sexes may pluck to line the nest with feathers in preparation for the eggs. Many claims exist of single birds picking out of frustration from not having a mate. Some of these birds however, when given a mate, will pick the mate as well as themselves.
Psychological causes of feather picking are by far the most difficult to resolve, and probably the most common. Sudden changes in routine, the absence of a consistently present owner or unfamiliar disturbances can lead to violent episodes of generalized picking. When the cause is sudden and it's a single episode, the plumage will often regrow without complication. If, however, the cause is not identified, the picking may progress indefinitely with no response to attempts at intervention. Many owners caught in this situation have a strong desire to utilize tranquilizers, antidepressants, or sedatives. However, only a small number of birds respond to treatment with these drugs. Not long ago, a news story that discussed the use of one of these drugs prompted a flood of requests for the drug from desperate owners. No further documentation of this drug's effectiveness was ever produced, and owners were once again gravely disappointed.