I think the main problem is the bird is alone most of the time. In general, cockatoos are known to be relatively quiet compared to other larger birds. These are animals that need LOTS of attention. One should not have a cockatoo if they are unable to provide it with enough love and attention. I'm certain this bird is screaming only because its upset, lonely, or bored. If he is left alone most of the day, I'm sure he's doing it out of boredom. Poor bird. He needs more attention.