He is at the age of speaking, he wants your attention, a very cool thing you can also use are little box recorder with mirrors that record your voice and it plays when they press the button.Your bird is very intelligent and needs stimulation, lots of attention, rather than ignoring him, pick him up and let him watch t.v. with you. Pick him before the behavior begins or when he quiets down when he is told. Let him watch kids channels when your gone, change his toys up 1x a month, and put a cover on his cage when he is suppose to sleep. This is his way of saying "hey budy, Im here hello I have a weird sound coming out help me talk". Without attention these birds can begin behavioral problems like feather plucking, biting, and self mutilation. I see alot and it cause other issues that are very sad, so help him before it gets there. He really just wants to be part of whatever you and the family are doing, they are very curious. Remember African greys have a mental level of a 4 yr old child.
