Are these mite eggs in the tail feathers? Or just dirt? Or something else? Background: They are 11 week old pullets, moved outside 5 weeks ago. They are in an enclosed coop and run (Wichita Cabin Coop style) so no contact with wild birds. We have seen no evidence of rodents or other evidence of mites (ie. have seen no adult mites). They *are* losing some feathers, but we attributed this to them just losing their juvenile feathers / the current colder weather (fall in Atlantic Canada). They are very happy and healthy otherwise (not lethargic, no blood or bald spots, eating and drinking well). The smaller flecks present on the rest of the white tail feathers in the picture are present on all 5 girls. The feather that is the worst (ie. has the most black) is only on this one bird. It has been there 2 weeks or so. Any advice would be most appreciated.