I've been in two minds as to whether I should post this or not but it's possible that someone far more knowledgeable than me might be able to shed some light, so here goes.
Last week we came upon this Tawny Owl which was perched on the edge of a nest box. After we'd been viewing for about 20 seconds or so the bird jumped back down into the box (we thought it was asleep). It was only when I was looking at the image later that day that I realised that a lot of the breast plumage was missing. You can clearly see the shafts/spines of the feathers. I posted the image with a request for information in one of the forums but the best anyone could do was possibly feather mite. A brood patch was ruled out because the feather shafts are still there.
In the meantime I have advised the local authority (on whose land the box was sited) because at the very least the nest box could probably do with cleaning out.
So I was just wondering if anyone here might be able to say what the problem is?