This is an informational post, with the hopes of offering helpful suggestions to others who may be experiencing this problem. For many months, my chickens had been losing their feathers, and some became close to being without any feathers. I read everything I could regarding what could be the problem. The literature indicated there were two types of mites that could be causing this problem - northern fowl mite and the roost mite (and less common, scaly leg mite, and there's also the possibility of lice). But try as I might, I could never find any evidence of any of these mites/lice. So I treated the birds and their coop and run with all the suggested remedies, sevin, permethrin, (powder and liquid), ash, DE, etc. When that didn't work, I even bathed them in a lice shampoo (permethrin based), and I contacted a veterinarian who advised I could try ivomec injection (which I did as directed). These things all still did not work. So I kept researching and found that there is a THIRD type of mite that is not reported on much - the knemidokoptes laevis var. gallinae. This is a very tiny mite (not seen by the naked eye), that is similar to the scaly leg mite. This mite lives in the base of the feather shaft and they eat the feathers. Small wild birds are a likely culprit in spreading this mite. The only effective treatment I found was sulfur treatments. On Amazon I purchased sulfur dip, which you mix with warm water pursuant to bottle directions and have the chickens sit in the bath for a few minutes, making sure to work in the sulfur in all the feathers and skin. I did this twice (seven day intervals), and then suddenly, after 9 months of not seeing any progress, my birds started growing new feathers. Now that it is cold, I rub NuStock (also purchased on Amazon), which is a sulfur, pine oil and mineral oil mix, on their skin and I am still seeing progress and now most of my chickens are getting back to normal. And inside their coop I'm spraying Bonide, which includes sulfur. So if you are experiencing broken feathers/feather loss, please consider this as a possibility, that your chickens may have this tiny mite, and the only affective treatment I have found is sulfur.