Birds, just like other pets, have their own ways of Communicating, or Bird Language.
Birds communicate to other birds and also communicate to their owners, in a variety of ways. While all species have their own unique methods of bird language, there are many generalities.
Birds use their body, body parts and voices to express a wide range of emotions.
Ways Birds Communicate
Barking Some birds give out a type of bark when excited or when trying to prove their dominance.
Beak Clicking When a bird is clicking it's beak, it is trying to tell others it is threatened or that it is protecting something.
Beak Grinding When a bird grinds it's beak bird is trying to communicate it is feeling secure and content.
Beak Wiping When a bird wipes it's beak bird is trying to communicate that he is aggravated or upset about something. Beak wiping is also typically normal behavior for birds when they are trying to clean beak or dislodge something stuck in it.
See Also Why Bird's Bite http://petcaretips.net/bird-biting.html
Chattering Some birds just like to talk, talk about anything; their environment, how they feel, state of union.... so to communicate their thoughts, they chatter, sometimes incessantly, sometimes loud, sometimes soft.
Young birds chirp or chatter when they want fed. Birds in wild often chatter as a warning sign to other birds that something is not right in their environment, or as a call to attract another bird's attention.
Crouching If bird is crouching with it's head toward owner, birds wants to be petted or scratched.
If crouching with head down, relaxed body and raised wings, bird wants attention.
If crouching with head down, eyes pinning, flared tail feathers, ruffled feathers, and a rigid body, bird is giving a warning to back off.
Flashing or Dilating Pupils Flashing or dilating pupils bird may be trying to communicate aggression, excitement, nervousness, or pleasure.
Growling Some birds communicate with a type of growl that means back off mister and leave me alone.