The best thing to do if you have the facilities is wait until they are 4 months old, or about the same size as the adults. If you are not set up for that, then it is best to wait as long as possible. You can always set up a different daytime run for the chicks and put them in the coop at night in a dog travel crate or something (or garage). Make sure you give them protection from hot sun and rain, and windbreaks also for daytime.
I finally had to move my 7 & 8 wk old chicks out to the coop with the older ones (4 months to 1 yr) last week. They were way to small so I put them into cages (one rabbit cage & one dog cage). Yesterrday I sectioned off an area (5 x 10) out of the main coop to keep them in. They are about half the size od the others, and this gives them time to get used to seeing each other for awhile. Even when out in the run, they were chased by the older ones. Im hoping in another month they can be combined-Hope this helps?
