I have 4 RIR (2 roos and 2 hens) that are about 3 months old. Yesterday, I acquired 5 Buff Orphington hens and 5 guinea hens. Since I had my other RIR hen and her 7 chicks in the little coop, these all went into the big coop. I was a little apprehensive at first, especially with the guineas going in but I think it all worked out. First rattle out of the box, Horatio, the biggest Roo strutted up to the biggest Buff hen "Pearl" and threw out his chest like he was saying "Hello.....girls!!!!" All the hens looked at him like he was crazy!