OK, so as a fault in planning on my part, a small number of my flock will be four weeks older than the bulk of my flock. I'll have no problem brooding the two groups separately, but I'm worried about when and how I should introduce the younger chicks to the older? I've heard a lot about older chickens beating up on younger newcomers, but will mine be close enough in age that I can pretty much avoid any problems, or should I start planning for WWIII?