Feathers are missing at the base of the tail feathers and around the vent. I have 9 hens in my backyard flock. They are about one year old. Back in November (nearly 5 months ago) One of my girls, "Chicken Miss Nugget", started losing feathers around her vent and the base of her tail feathers. The skin is intact and she's laying eggs regularly. She had been the only one with this problem until recently. Now I have 4 more girls that are beginning to lose feathers around the base of their tail feathers. Is this a parasites problem? What do I do to fix this? I'll see if I can attach a picture.