Bostonburbs
Chirping
We have 8 spring chickens who have all gotten along famously in our Boston suburban backyard as our pets....until two weeks ago. They have plenty of space and entertainment in their run, and we were getting them out for a couple of hours each day, which has been shortened as the temps have dropped. 16% layer feed, but I did recently switch from crumble to pellets in a very slow transition, offering both forms for a week.
Two weeks ago, I noticed that one of my EEs was bare around her neck, and missing feathers at the base of her tail.
Unfortunately, that same day, my Salmon Faverolle was attacked by a hawk. By some miracle, she escaped with only a strained wing. I felt it would be better to keep her with the others, and kept a close eye on her. She was fully recovered within 3 days.
During that time, I was able to observe the bully: another EE. She mostly picked on the SF. I separated the bully during the day (within sight of the rest) for a few days, but put her back with them at night. (I wasn’t sure what you are supposed to do about egg-laying and roosting for a chicken jail candidate...)
The SF does not seem to be losing feathers or showing ANY signs of injury from the bullying. My husband said I should let them be.
But then yesterday I started observing my BO bullying the original EE bully, pecking at her chest feathers while the EE just stood there. So now we have two active bullies.
I give up. I sort of wish we had just gotten a dog.

Attaching some pictures. The run is secure, and “chicken jail” (third photo) is much less so; chicken wire wrapped around the trees and secured at the base with rocks and wood. Not the best, but it was all we could manage for now. Won’t work with precipitation!