Alenzj, I was talking about your new chicks. I am not sure were the 4 months came in but i would do 4 weeks. By that time they can be intoduced to the cold. I think were the 4 months came in was to introduce them when they are roughly the same size. With doing this the older hens will be less llikely to kill or hen peck to severly. Someone else might have better advice but this is what I have alway's done with no problems. Also by doing the introducing them at night the hens wake up and think were did these guy's come from instead of beating them up right away.