Hi! I told you about the one duck I have that had the droopy wing similar to your duck, and told you what my vet had told me. I took my duck back to my vet this morning for a follow up on that same wing (also because he has some crooked feather growing), and when the vet stretched out the duck's wing I too noticed several really small feather. The little feathers are not as numerous as the ones on your duck, but they are in the same place.
Since you had shown the pictures and inquired and since I noticed them on my duck too, I asked my vet about it. The vet said that the feathers had either been pulled out and were just now growng in again, or he said that those little feathers may just be very sow growing and that the duck just may be delayed in that area. He wasn't worried about the feathers affecting its flight. Perhaps this is the same for your duck.
I just wanted to share what I had learned.
