Thanks, Liz, I can normally use all the help that I can get. Your post has caused me to do some more thinking about my replies to this member, so I think that I will try to share my thoughts again on this matter. Again thanks for the nudge.
I often fall short in those replies that concern cockatoos, but it is only because I do not have any of them so I have no actual personal experience to draw upon with them so I have to rely on things that I have read about them posted by other people that do have them as well as on general parrot behavioral information. I do much better when it comes to Greys as I do have one of them to draw upon.
Bird woman seems to have the most personal experience with cockatoos of any of the other members so I find that I listen very closely to what she has to share about them. I think that cockatoos will still very often bond with other cockatoos even after they have bonded with a human. I do not know if they will bond with other species of parrots, that are not cockatoos once they have their human or not so that might be a good question for bird woman, as it does relate directly to the original question posed here.
I do know that with Greys that there is a very good chance that once they have bonded with a human that they will not either bond with any other bird regardless of its species or even actually accept them. You just never know with a Grey, they are very peculiar birds and are very picky about who they accept or will bond with.
That is about the best that I can do as far as answering the question as it pertains to these two species, but I thought that I might elaborate upon it in a more general fashion.
Cages are a funny thing when it comes to birds and despite what anyone else may think, it seems to me that a cage is a cage regardless of its size or weather it has bars or walls such as a bird room or even the run of an entire house, it is still a cage. the reason for my making this point is that all of our birds live in a cage of sorts and the real differences are in the construction of the cage and in its size. Many people disagree with me that the size of the cage is really important, but this is simply because they do not see that the entire room or house is still just a cage as far as the bird is concerned. For those of us that only have a small number of birds that live in standard cages only when we are not with them or only to sleep a bird can do ok in some of the smaller cages. How small id very dependent on how much time that it must spend in the cage with the smaller the cage size the longer the bird needs to be let out into the room.
What I am trying to get at is that large cages such as aviaries work well when you have similar birds that will accept each other well enough that they will not attack each other provided they can get away from each other. Rooms are even better because you can often house birds that may not bond with each other in the same room as long as they are not aggressive to each other and have the room to get away from each other. These larger options for housing birds together also works best if all of the birds are fully flighted.
An example of what I am saying is this; I have a Senegal, a Grey and an amazon that do very well together in my living room although they are not friends. They have enough room to have their own space without bothering each other and they can fly to get away from each other. but if they were to be placed in a smaller area then there would be problems as they could not get out of each others way which would lead to them fighting for their own space.
More and better information concerning this could be had from both Bird woman and Pajarita as they have the space to use the bird room and/ or the aviary types of habitats and can give you more of the particulars of the flock dynamics involved.
I hope that this gives us all something to keep in mind and consider when it comes to how we house our birds.