I had a broody buff orpington hen that I bought some fertile eggs. None hatched (after 25 days) but I slipped 3 one day old chicks under her and took away the eggs. The chicks are 3 weeks old. I have the mother hen and the three chicks in the separate area to the five other hens (they are 7 months old). How old do the baby chicks have to be to put them with the adult hens? I do not have a rooster. The breeds I have are Wyandottes, Buff Orpingtons, and Ameraucana hens.