Just like Survivor...people, and chickens stay with the original tribe! lol...Sure. Will the little ones get roughed up by the larger birds? Yes, quite often. Will the little ones scoot whenever they see the larger bird coming? They'll sure learn to do so.
I find that birds brooded together have a bonded flock attachment. Integration happens between differing groups, but those brooded together tend to maintain their bond within the flock.