We had two groups about 2 months apart in age. Older girls on one roost. Young'ns on the other. Eventually they started to mix it up a bit once the rooster picked his "favorite" girl and kicked everyone else off his roost. I let this go one for a couple weeks then took down his roost so he and his "Ol' lady" would be forced to move in with the established group on the other roost. it took one uneasy, cold night and then they all learned to share one roost in peace. mostly.
