I have a small original flock of two hens and a rooster and a new flock of three hens we got from a friend when he was moving and had to get rid of them in a hurry. The original introductions, about a month ago, didn't go well. All three new hens challenged the rooster and he was particularly nasty to them. Two days later one of the new hens sustained a significant injury (although I didn't see it happen and I don't know who caused it). Because my original flock had just lost it's lead hen to put everyone in together in and hope for the best since the numbers were equal. After the injury, I scrapped the original plan, obtained a second coop and set the new girls up separately next to the original flock. Since then they've free-ranged a few times side by side but both groups tried their best to ignore the other. Today we finally had some decent weather, and I let them out to forage. One of the new girls ventured into the original flock's coop, the rooster followed her in and mated her. She was calm and submissive about it, which was a huge change since the last time they were together. Yay! Never thought I'd be so happy about two chickens mating. But I feel like they're finally starting to integrate and hopefully I'll be able to get them into a single coop/run shortly.