Generally, kind of sorta, if they are getting along when you are watching them, they are when you are not. But that is not 100%. Hence, people come back and there is a mess, or a war going on.
Space is crucial and so are hideouts. Introducing a single bird is very difficult, it is better to add in pairs or more. You can create a pair by pulling one of the flock and adding it to the new comer. They will fight and squabble too, but it is one on one, not a flock on one. Once they get over it, you can add the pair back to the flock. The flock will have forgotten its member so it is like adding two new birds. There will be squabbling, but it is spread out over two, and that helps.
Again, it is best to have escapes, and space.
Mrs K
Space is crucial and so are hideouts. Introducing a single bird is very difficult, it is better to add in pairs or more. You can create a pair by pulling one of the flock and adding it to the new comer. They will fight and squabble too, but it is one on one, not a flock on one. Once they get over it, you can add the pair back to the flock. The flock will have forgotten its member so it is like adding two new birds. There will be squabbling, but it is spread out over two, and that helps.
Again, it is best to have escapes, and space.
Mrs K