If it's a male duck, he will eventually go after your hens (since you have no other ducks). Duck "apparatus" is very different from chickens, a drake can damage or kill a hen trying to breed her. NOT a good situation.
Welcome to BYC! I'm glad you joined our helpful community. I don't know much about ducks, but I do know that they are flock animals. It would not be a good idea, I think, to keep only one duck on its own. Chickens do not make the greatest companions for ducks. You may get some more helpful answers in the Ducks section: Ducks
