You know I read somewhere that when they get excited, the energy they feel
is a lot similar to their anxious or angry energy, and therefore leads to aggression.
So it's quite possible that he's getting too excited, and is exerting that energy through biting.
Alex does that sometimes too, and when she gets too excited, she either gets
really aggressive, or ends up flying around the room several times because of the energy.
Doesn't help the fact that she's also the most excitable out of all of them.
I would reccomend trying to encourage independent playtime, where he's playing with his own toys as opposed to looking to you for playtime. That way he'll focus all his excitable aggression on his own toys.
Plus, the more used to independent play that a bird is, the better the chances you would have to be able to do your own thing in peace with your bird still in the room. Of course this doesn't keep my own birds (Alex especially) from trying to "help" me type on my laptop or do anything on my iPad, but I digress.