Thank you so much! So good to know, and will do!!Welcome to BYC!
If you have multiple drakes, I would not put two or three female ducks in with them. That's very nearly animal abuse, as they'll turn from fighting each other to raping the females and fighting over them. It'll be much worse in the spring.
You can keep one drake with one or two females, depending on personality. If you have two or more drakes, though, they'll find the weakest female and go after her every time they have the urge. They'll breed the other females, of course, but the weakest female is in serious trouble.
Either get a lot of females (3+ per male is pretty much absolute minimum if you have multiple drakes) or get rid of a lot of drakes.