That I believe is the truth for many. After careful observation I think most will see what are essentially separate groups, or tribes cohabiting when a new group is introduced. The idea of full integration has never struck me as a good thing in any species. It denies the right of choice in a way. It doesn't mean the various groups need to be in conflict. It just means that one has to accept that a lot of creatures are basically tribal.It's more like 2 flocks that roost together but it's getting better.