Ducks are birds and birds have hollow wings. I would take some vet wrap and wrap the wing so its a somewhat normal position to the bird's body and take the bird to a vet. The vet can pin the bird's wing, but the bird will not be able to fly again. If its a wild bird, I would suggest you taking it to your local wildlife center. They have vets on staff there that fix these types of things. If its a pet, find a vet in your area that deals with birds, especially chickens and ducks, lol. Not all of them do. Once the wing is fixed, keep it separate from the rest of the birds until the wing is healed.