We have been having this problem with our chickens since the summer! (So 9+ months). In the summer a chick was born in the coop, and when we brought it inside it was not thriving. I was looking at it and thought I saw something by its eye, but it disappeared. Later in the day it happened again, and as I sat there and watched I saw little black mites crawling over it! I picked it up and was determined to get the bugs off, but it was impossible to find them - they are tiny and quick! The chick ended up dying.
All of that is to say it is VERY hard to tell when your chickens have mites! The chick was the only proof that we had them - no signs anywhere else, except the missing feathers. They are missing just above the tail on the back, and now on the shoulders/wing area. I am pretty sure this is a result of the chickens pecking their own feathers due to the irritation from the bugs. I have seen them reach their heads around and scratch at the exposed area, and it's exactly where they can reach. We dusted them with Sevin and thought that should do the trick, but there was no improvement. One time is apparently not enough - the Sevin kills the live bugs, but I believe the insect eggs laid on the bird hatch and need another application. I would imagine it'll take 4-6 treatments to break that life cycle, but I need to research that more. We also cleaned out and dusted the coop with Sevin, but no help.
Also, we have several varieties. Our Buff Orpington and Delawares don't have any feather loss. Our red sexlinks and Barred Rocks are the ones with the missing feathers. Interesting ...
I read the wild birds can often introduce bugs and parasites to your flock, and we have these little tiny birds that can fit in through the chicken wire holes of our coop, so I think they have introduced this problem. If anyone has more suggestions I would be very happy to hear them! This problem and the ugly birds are making me re-think my backyard chickens ...
