Some of mine pair up but I have seen 2 boys on one girl before. I will separate into pairs in pens next spring for proper mating and hatching.
With domestic ducks they usually flock together where theres one drake to about three hens. If you want to put them together i would suggest getting more hens or getting rid of some drakes. When you have a bad Drake to hen ratio it can go badly for the hens and the less dominate drakes. The hens can get overbred and that could lead to other problems and i have had drakes pick at each other until one had no chest feathers.
