Hello! I've read older posts on broken feathers and thought I would add my an updated post with my observations and experience. I live in New England and the past few seasons, starting in the late spring, I have noticed my girls with broken feathers just before the downy part starts. Initially, a couple of seasons ago, I thought- Great! We have mites! I went through all the hens and inspected thoroughly during the day, dusk and at dark. Nothing noted. I thought maybe I was missing something so I meticulously bathed the girls early in the day so they could dry out, cleaned the coop and let it thoroughly air out, dusted every thing with permethrin and diatomaceous earth. I kept up on the permethrin and DE as suggested from multiple sources and despite all the work, nothing improved. My coop is generously big enough for 9 hens, and they free range on average every other day. They also have free calcium available at all times. When the Fall came everyone molted and looked like a typical chicken with all their feathers from the Fall all the way through to the Spring. As the Summer began and the heat started up the usual suspects from the previous season started back up with feather breakage! Based on the past few season my best conclusion is heat stress. All birds are New England hardy. Everyone gets along ( I have spent a lot of time observing for bullies or dominance). It's only a few birds this happens to from year to year. I hope this post is helpful and reassuring to many.