Behavior Gallery

 Note: All these behaviors serve a purpose for the bird.   
Hand Biting
Near the food dish
It is important to read and understand body language.
A bird does not just start biting, this is a learned behavior.  The bird is not biting because the bird is a jerk. Biting behavior serves as communication purpose.
On the shoulder
Between the bar
 The more you let the biting happen, the more the biting will become reinforce (become a stronger habit).
 All the time
 In your ears
All Birds make some form of noise. Birds like to chatter, whistle, and call out. 
It is important to know that screaming back to your bird does not tell your bird what to do.
Screaming behavior serves a purpose for the bird.
 Plucking can be a sign of stress, boredom, and so many reasons.
Yes, plucking serves a purpose for the bird. 
 Foraging and correct enrichment is very important in a bird's life.