We had a lone duckling in our home for 3 months he slept inside our home and spent much of his time with us, he had a flock but was too young to be left unattended. His mama tried to kill him when he hatched. He was the most precious thing, then we went and got 3 girls just for him, yep he turned out to be a drake, well he was too young to notice them but boy did he notice me, it got to the point where i couldn't turn my back on him he would jump me. He was totally confused as to what he was and what I was to him. I thought for sure we were going to have to put him down. He was very assertive towards me, just like the drakes treat their girls. Then I got some very good advise on this forum as to how to deal with him, We had him outside alot during the daytime when we could be with him, and got to watch first hand how ducks act towards hormonal drakes that are young enough to be put in their place. So i started acting like that, I would flattren him out and hold him down till he relaxed when he would come after me, also I would pick him up and lay him on his back, telling him NO BITE. Another thing that worked was pushing him away with my foot. coming up under his chest so as not to hit him but push him. He is 1yr 4 months old now and madly in love with his 3 ladies but it took a while to convince him I wasn't going to be one of them. LOL. He knows now that his place in the flock and can still come up to get petted but as soon as hard biting starts thats it we're finished. When my one duck was weening so to speak her duckling this summer [also a drake] she would actually chase him away from her to let him know it was time to be on his own. If your duckling is feathered and can be outside for any length of time you may want to put up temp fencing so it can begin to get accustomed to the rest of the flock and begin to bond with them, honestly drakes don't make good house ducks especially when they become sexually mature. And let your duckling learn from the others where his/her place is in the flock as long as they aren't attacking him it is part of being in the family.