Be aware tho that using peroxide can slow the healing process. It is great for cleaning immediately after an injury occurs but if used any time after that it will slow the healing process since the bubbling kills off bacteria and healing cells. We tell people to use an antibacterial soap to clean wounds or a betadine or nolvasan solution. We use a triple antibiotic ointment on dogs and cats all the time, I would imagine it would be fine to use on your duck I would just use a very small amount so as not to get him greasy and if it doesn't feel weird to him he is less likely to bother at it