young got all his back feathers plucked off by escapee ducks it has now been about 2 1\2 months and majority of his back is healed but the tail just wont heal we have tried everything we have put saddles on him we have completely wraped it we put on a dog cone we have segragated the chickens who were pecking it but he is his own enemy
he literally picks himself
Likely the preening gland is impacted/infected. Can you tell if any oil is coming out of it?
Having an avian vet take a look at it would be best.
If not, you can try warm compresses to see if you can get it to loosen up and give a round of antibiotics to see if that clears it up.
https://www.beautyofbirds.com/birdoilgland.html