This is what I did. When my chicks were about 8 weeks old I put them into a big dog crate inside the main coop. I forget how long they were in the crate but it allowed everyone to get used to one another as best they could. Eventually I let them loose one morning when the chicks were physically big enough to fend for themselves. I also put out lots of scratch and other treats to distract the older hens. The first couple of weeks the "chicks" kept apart but over time they integrated into the flock with minimal issues.
I did a similar thing with 2 older hens I incorporated into the flock. After a month of quarantine I put them into the coop in the same big crate. In their case I only left them in the crate for a few days. When I let them loose I again put out tons of treats but also the whole flock had access to the run and my large garden (it was fall). It took them longer to incorporate into the flock then it did the youngsters. The two of them kept to themselves for quite a while. We also had to put them into the coop at night for a good week before they would go in on their own.
I did a similar thing with 2 older hens I incorporated into the flock. After a month of quarantine I put them into the coop in the same big crate. In their case I only left them in the crate for a few days. When I let them loose I again put out tons of treats but also the whole flock had access to the run and my large garden (it was fall). It took them longer to incorporate into the flock then it did the youngsters. The two of them kept to themselves for quite a while. We also had to put them into the coop at night for a good week before they would go in on their own.
