Peach has had this for over a year an I thought they were just dirty feathers. I was cutting them off as I noticed they were moving. None of my other 5 hens have this.
Hi,
I would first separate this hen from the others. Clean the coop well bedding and all.
It may also be fleas. I would clean the hen well. IMO it's ok to bring her indoors and clean her with soap/water mixture. Don't mix her with the others till your certain it's gone.
Good luck
Hard to tell with the photos. But the missing feathers is a sign it's something. If your in a warm climate then wash her outside. I would be using gloves while handling her.
I wouldn't wash her, just dust her with Permethrin powder and treat your roosts and nests with the same powder. Washing her will not remove mites nor kill them.
1
Purchase a commercial poultry parasite treatment. There are a number to choose from, such as Permectrin, Ravap or Rabon. You can find them at any farm supply store or purchase online.
Discard old food and water. Wash all dishes in a mild mixture of vinegar and water. Rinse well, refill and place well, refill and place back into the coop.
Those look like mites. I agree with Beekissed on not bathing. I have used 5% Sevin dust successfully, and sprayed with Permethrin after completely cleaning out the coop and nest boxes. Here are 2 excellent links that have good pictures to show you what to look for : http://anrcatalog.ucdavis.edu/pdf/8162.pdf
htmlhttp://ohioline.osu.edu/vme-fact/0018.html