No, but there is a good chance that he will over mate a single female. Be on the lookout for it and be prepared to step in and add more females. I've found that my single drake needed 4+ females.
Probably not, but the suggestion of being overmated is a real concern. Generally i like at least 3-4 ducks per drake. There are always exceptions though, if you cannot add more keep an eye and be prepared to step in if need be.
