A new Lesser, Ash HATES him!!!

I've just got a new pet Lesser last night, brought him home and everything goes well. When I just step into my bird's room with it, my sick grey suddenly scream like as if someone is going to murder him! He hates the new comer! Till now he still can't accept it, I don't know what to do. Can any exp breeder/keeper advise me? I have to cover his cage so that he can't see the cockatoo. This have never happen before and I wonder why he react that way, maybe he is jealous? But I ever handle other parrots infront of him and he is cool with it. Why only the new cockatoo? Is it because he is sick so he react that way?

ash recognize the bird room as his territory so he is protective of it. bring both the parrots to a neutral spot(e.g outside ur place, living room) and see how they react to each other there. if everything goes well then bring the too and ash into the room together. introducing 2 new birds to each other can take some effort especially when 1 of them is protective of it's space.

Thats what I think so too, but he is okay my flatmate's Eclectus. Sigh..

not all birds behave the same way to each other, every parrot have their own behaviour. just like why 2 same species, 1 parrot can do tricks well but can't talk, while the other is a very good talker but can't do tricks.