Severa Qs on a pyscho Conure?

Is it Pretty Bird pellets? for the plucking, my female African grey plucked for a while and I found it it was due to the artificial dies in the food, changed the food and she's fine. How often do you take the bird out of the cage? We have two Green Cheeks and a Sun Conure, they scream like crazy when they know we are home and want out of their cages. Is he banging his head against the cage by chance? That too is an attention thing. The biting will stop with a while. He is probably scared and doesn't want to get used to anyone knowing he might have to change homes again. One of our Green Cheeks is only 5 months old. He ALWAYS bite me when I took him out of the cage, after about two weeks of sternly saying no when he bit and handling him daily, he only bites now when he's scared or when he's loosing balance when I'm walking around the house with him.