I think it depends on a few things.. I dont usually introduce mine until they are older, 5 months, because I dont vaccinate for Mareks. At that point I put them in adjoining pens so they get to "know" each other. I also put them out in the run with divider between them. after a while I put them out in the run together... making sure they have room to run away if they need to. Depends on the other hens lol! I have a few I can put anyone with and they would never do anything and others that will grab them by the feathers and not let go... If I were introducing younger ones I would divide a run where the little ones would have access to both sides but the big ones couldnt get through to the "safe" area

Always keep an eye on the situation when introducing youngsters so no one gets hurt.