I have a severe macaw and a goffin cockatoo I had the severe macaw since born and the goffin was at my fathers house since born both hand fed but I use to bring my macaw over for visit at first my macaw was scarred and attacked the other birds(my father had another severe macaw,goffin cockatoo,Quaker in the same cage) not to fight but to get away from him over time my macaw became the bully pushed all of them away once he got big around 7 months then my father gave me the goffin cockatoo,Quaker,and he got rid of the severe macaw and I got rid of the quaker ,well now my macaw 1 year is in the same cage as my fathers cockatoo 4 years and there best friends both love to be out the cage,the macaw taught the cockatoo how to eat pellets,veggies,fruits,and the cockatoo taught the macaw how to brake toys lol I seen them feading each other ,they shower with each other and they sleep side by side I sworn I even herd them talking once but maybe I was just loosing it ,but the point is find a friend who has a parrot and get them use to seeing other parrots there not going to know there are other parrots if they never seen one, once that happens then find a bird that's the same age as the other bird if my macaw is 1 year old find a bird around 1-2 years old you don't want a 6 year old parrot hanging out with a 1 year old because he's young .you hang out with your crowd not younger or older get me? 3rd if there is a problem btw the 2 I like to put them in different cages but side by side so they see each other but can't get to each other (I had doves who would attack other doves pull feathers out poke them so on I put them side by side they talked got to know each other settle there problems(so I think ) a week or two later I put them in the same cage never had a fight , now my macaw and cockatoo do fight every now and then but never bleeding or feathers missing they just need there own space a good size cage and same perches should settle
Everything another thing I tell friends wen bringing any new bird into a cage with another bird take all sticks,toys foodbows out clean them move them around and put them back then put the birds in so there is no this is my spot or this is mines,I do this normally anyways so the bird doesn't get to use to everything but then again my macaw was raised like that some birds like old better then new,
Hopefully i didn't bore you and you learned something new and hopefully its usefull
Enjoy Henry