Is it a parot?? A quail?? We need more information

Yeah we really need more information. If it is a parrot it could be going insane from being alone. Assuming you don't spend time with it. No more speculation until you provide more information. However, if your bird seems hurt, a vet visit is always a good idea.

How much time do you spend with it? I don't know about parrots, but parakeets and canaries will rapidly pluck their feathers if they feel neglected. If you don't think that's the case, another explanation would be an illness, so I'd take it into the vet.

Parots, parakeets, etc... are all very social birds that don't handle isolation well. Lack of social interaction causes stress which can manifest in self destructive behaviour, such as the violent self plucking / mutilation.

That isn't to say that there couldn't be a medical problem as well. My first suggestion would be a visit to the vet to rule out any medical problems and then a discussion with an experienced bird handler to learn how you can reduce stress and promote a happier, healthier bird.

A responsible pet owner knows that there is far more to caring for an animal then just feeding & housing. By caring for the total well being of a pet you are helping to promote a long life that will do as much for you as you do for the pet.