I have 6 hens that are two years old and they are the sweetest things in the world. Three weeks ago we got two babies, and they are currently in the brooder. When they get their feathers I will put them outside. I have separate coops and runs (but I can open them into one big run if need be) so I figured I would put the babies by themselves in their own coop/run until they're old enough, and to give the other girls a chance to see and hear them before I mix them together. My question is...how old should they be before I can let them all mix together? I don't want anything to happen to the little ones.