Hi. I know how frustrating this can be, I just integrated a new flock of 8 pullets into my existing flock of 5 older hens. This same process can be used for integrating a recovered-from-injury hen back into the existing flock as well. Here's what I did and what's usually recommended:
1. If you have space available in your coop or run, create a "Look But Don't Touch" pen area for the hen/hens. In my 32ft by 16ft run, we sectioned off a back corner of it for the new little ones (see photos). The little ones were fully protected by fencing, but could still see the older hens in the remainder of the run. In the evenings, I would let the older hens out, close up the run and then let the little ones run around the entire coop/run space to get used to it. The little ones were in their Look-But-Don't-Touch pen for about 4 weeks.
2. If you don't have space available, you can try and get an XL dog crate and put it in your coop/run. Same idea as Item #1, but on a smaller scale. I had to do this earlier this Spring when my Buff was being reintegrated due to a leg injury.
3. After a few weeks of being separated but still visible to each other, we were ready to integrate everyone. I first let out the older hens into the yard, my husband baited them with treats to a neutral space in our yard. Then I let the little ones out and they came over to where the treats were being dispensed. We closely watched over them for any serious fighting, feather pulling, etc. While my husband was dolling out treats, I had a high power squirt bottle to blast anyone who got too rough. We did this every day for a week, changing to a different spot in our yard every time.
4. After that, it was time to full integrate into the pen. We first let the little ones out first into the run, followed by the older ones. Husband was again dishing out treats and I was manning the squirt bottle. We still kept the baby area accessible to the little ones in case of an escape and had plenty of hiding areas for the little ones. We also put down piles of grass clippings and mulched leaves to add to the distraction.
5. After that, we just monitored as needed. They all pretty much got along, there was some obvious pecking order squabbles, but for the most part, it went pretty smoothly. If there was a bully chicken, we punished her by putting her in a small milk crate for an hour or two and then released her. It seemed to do the trick.
Hope that helps you, let me know if you have any other questions, I'll be happy to help!
