APA member April Howington shared this information. This is a very good picture showing feather mite damage.
Tip for the day! Feather mites are a horrible addition to your show birds! Watch for them like a hawk. See the little horizontal lines on this black feather? It’s the trail that the mite leaves as it eats it’s way across. You probably won’t see the mite but you will see the trail. I’ve seen them on chicks as young as three weeks of age. Dust your wooden brooders, nest boxes, and roosts with sulphur powder, 7-dust, or pyrethrum powder. Forget about DE! It doesn’t work:)