Look closely at the skin. Do the feathers look as if they are being chewed off? (you will see the stubs of the feather on the skin.) Or are they being plucked out completely? (you will only see smooth skin)
If this has been going on quite a while and you see stubs of the feathers, she may have depluming mites. You will also see horizontal lines of thinness in other feathers, especially tail and primary wing feathers. These mites irritate the bird living up in the feather shaft and the birds chew their feathers off at skin level. These thin horizontal thin lines in other feathers are tell tale signs of depluming mites.
If there are no stubs there at the skin level, others may be plucking her feathers out. Either by boredom, they need the protein or from habit. If she roosts above other birds, sometimes they will pluck the bird above them. The bird herself may be plucking them out if she needs the protein, she is bored or out of habit as well.
