Just want to share my experience. I had a HUGE feather pecking issue with my chickens. I started with 24 chickens, hand raised them all from couple day old chicks. It started with small featherless places on just 1 or 2 chickens. Never had an issue until they started laying eggs. Because these were my 1st chickens, I had no clue what was happening. But within a matter of days, while trying to figure out what was going on, it went from featherless places into bloody injuries on numerous chickens. I sat for hours and watched and finally seen the several chickens pecking. It seemed when the main hen started the pecking, other chickens picked up the bad habit too. I ended up having chickens separated everywhere in temporary coops I had to build due to bloody injuries, it was so very stressful! I posted about my issue here on BYC and I tried every single suggestion I was given. My coop was big enough, tried adding more protein, I tried boredom busters, flock blocks, blu kote which in my case made it worse, I tried pick-no-more, and nothing worked. I made chicken saddles and they helped but only for the back areas not for under vent and etc. I ended up sadly getting rid of all my chickens but 10, it just became too stressful and too much for me to handle on my own and I could not stop the feather picking. Then, out of the 10 I had, all was good until the boss hen started feather picking the chicken at the bottom of the pecking order, seemed out of 8 nest boxes they liked the same nest box and started it. I have a camera installed to keep an eye on the chickens now and that is how I knew who started it. By the next day 2 others started pecking feathers too, the fluffy vent feathers. Chickens learn bad habits easily from other chickens. I was disheartened thinking I would end up having to just get rid of all my chickens if it did not stop. Then in my desperate search again for ANYTHING to stop this, I came across an article on chicken peepers, never came across anything about them when it started the 1st time. I was willing to try anything at this point. I felt so guilty putting them on my chickens, but it was a last resort for me, and they have been WONDERFUL!!! They still peck on each other at times, but it is not picking feathers intentionally like what they were doing before. My chickens liked to peck around the vent area, the fluffy feathers, and ANY molting feathers they'd pick until bloody. The peepers have made a HUGE difference and pretty much stopped the feather picking. I can tell you from my experience, any chicken with any injury will need to be separated. I was told when 1st dealing with this, that the featherless spots were okay and the chickens did not need separating unless bloody. But the chickens all were drawn to the featherless spots and it took nothing to make bloody wounds of them quick. Chickens will just pick and pick and pick. I use a large animal crate I got at Tractor Supply cheap and keep chickens in them inside the coop when I need to separate any of the 10 chickens. Was not that easy when I had 24! I am still new to having chickens and still learning as I go, but just want to share my experience with feather picking. I wish I had learned about the chicken peepers sooner.