Many pet parrots and cockatoos have problems with losing feathers. Many people assume that the bird must be plucking its feathers because it is just bored, but the reality is much more complicated than that.
Causes of feather loss falls in two main categories, either the feathers are falling out or the bird is pulling them out. Knowing which is occurring is not always easy but is important to determining the cause.
Feathers dropping out by themselves are always due to a disease. Beak and feather disease (circovirus) is the most common cause but many other causes are possible so it is important to get the bird checked out.
There are many different things that will drive a bird to pull its own feathers out. Usually the feathers are removed from the easier to reach areas like the chest and wings but left on the head. Feathers that are falling out tend to come out from everywhere.
One of the common causes of feather plucking is that the bird is itchy. Plucking feathers in birds is similar to a dog or cat chewing out its hair. Parasites like bird lice and mites are not especially common but food allergies are common especially in Galahs and Cockatoos. Sunflower seeds are the most common culprit.
Sometimes the cause can be behavioral. It is rarely due to out right boredom more usually due to anxiety and stress. Some birds like some people are more susceptible to life's stresses and take it out on them selves. Many pet birds suffer from separation anxiety, they are very attached to their owner and pull their feathers out when their owner goes to work. Medications and some behavioral modification can help these birds cope. People often recommend buying another bird for company but as pet birds often think they are human they don't always relate well to another bird.