As the owner of a feathered breed, I think I can help you. First, as has been suggested, check with your vet.
In the interim, wash DAILY with Hibiclens (medical wash); towel dry, and apply a silver sulfadiazine ointment. Wrap overnight.
Alternate treatment: combine powdered (food grade – available inexpensively on Amazon) sulfur with pure mineral oil. The mixture should be the consistency of oatmeal. WEAR GLOVES and apply the mixture to the affected area. DO NOT WASH OR BRUSH OUT – it will look and smell awful. After 2-3 days, the dried treatment will have crumbled and fallen off. Sulfur is antibacterial and the oil provides adherence. **Note: this formula also works as a bi-weekly preventative for feathered horses and will help bleach feathers white***.
Finally – clip the area as short as possible to allow the treatments to penetrate and, importantly, to allow the area to be as dry as possible.