Round, crumbly things at base of tail feathers

[shfen]

One of our chickens was acting unusual today. She stayed in the nesting box all day even after I removed the 2 eggs underneath her. Was alert but no interest in going in to the run with our other 2 chickens. I picked her up and put her on grass and she walked around then went into run for a bit and was acting fine. She had mites many months ago which we treated but decided to check her butt to make sure there wasn't anything there. At base of her tail feathers there are these whitish, round, crumbly things (can't think of a better term). She tends to have a poopy butt which you can see in the pics but these things are at the part of her feathers that attach to her body. Anyone have any idea what they might be?

 

[CaliforniaMountainChicks]

They appear to be lice eggs/nits! Do you see any live lice on her body?

 

[nuthatched]

Those are lice egg casings, you need to completely clean out your coop, apply a permethrine based product and get new bedding and litter. You'll also want to treat your birds.