Help! Missing feathers and sore skin

[city kid farm]

One of my five chickens (a GLW) is missing feathers on her belly/underside leading up to her vent. The skin looks sore and raw. She's happy and eating and acting normal, but it looks awful. It's been a hard, long first winter for the birds and they've spent a lot of time in the coop. That said the rest of the birds all look fine.

Any ideas what this might be? Can I do anything to help her skin?

 

[Enchanted Sunrise Farms]

Has she been spending a lot of time in the nest box? Can she be picking her feathers out to line a nest? Other than that, i would suspect lice or mites. You may want to treat your flock as a precautionary measure. Lice are easy to see, but i have a hard time seeing mites.