Thank you for the responses. I have checked the birds for lice, and I really do not think there are any. Mites are another issue, and I've got to do a more thorough search (thanks, aart). I live in dusty, dry Wyoming. I don't think mites are much of an issue up here but I'm at a loss and I am searching for things to try.
It's a strange situation- out of 11 chickens, 3 or 4 of them are losing feathers in different patterns. One has feather loss just on the top of her head, another on the back of her neck and her belly, another just on the front of her throat, and egg production is down. (I have no roosters and haven't identified a particular feather picker but will keep watching.) They have lots of room, often roam outside their substantial chicken yard, and get plenty of protein. I just lost a chicken to something- not sure what- seemed like sour crop but she went quickly. So, I've been searching for potential problems to fix.
I, too, prefer natural remedies and use chemical products only if I really need to. I've tried food grade DE for a number of things, but unfortunately it has never seemed to do much. I appreciate the link to the permethrin spray info-- should I need to eliminate an infestation, I'll go that route.
Happy Saturday to all!