Right now I have three muscovy ducks, a muscovy drake, and three other ducks (Pekin, Khaki Cambell, and Runner) in a 17x17 foot pen. A friend has recently offered us a runner drake. Would we have to build a new pen in order to keep the two drakes separate? It'd be nice to not have to build a separate pond. I'm also thinking of relocating them all (and the pond) to a new, shadier pen. It'd be a lot bigger, say 20 feet by 50. Would the space be enough for the two drakes? And would the two species interbreed, or would it be safe to assume that the muscovy drake would stick with his girls and the mallard-derivative with his? If not, would the ducklings be identifiable when they hatched, or would we have to always be wondering if this was a sterile mule or not? Thanks.