I have several coops and I normally introduce new chicks about 25 at a time, so I clear one of the coops for them. I will keep a light in the coop for warmth until they are well feathered. The older hens can see them as the front of each coop is hardware cloth, but I don't let the new chicks out to free range with the others until they are about 8 - 10 weeks old and about half adult size as the chicken pasture is not fenced to hold little birds. Because of the numbers involved, the large area available, and the through-the-fence introduction, I usually have no trouble with the old girls picking on the newbies. Perhaps you can use a variation of this method?
