I know that some have those crosses, at least I recall reading about them, and as a duck mom to twelve smallish girls (9 runners, 3 buffs), I would not feel really relaxed about a big Muscovy drake on top of my little 3.5 pound ducks. That's my feeling. I think Muscovy ducks are amazing and wonderful, and I think carefully about size differences, too.We have pet Muscovy ducks (two girls and a boy) that live with our laying hens. I am interested in getting a couple runner duck ladies to live with them. Can anyone tell me if the runner duck's eggs will be fertile after exposure to our male Muscovy? Both varieties of ducks have such nice personalities, it would be interesting to see what a cross would be like, just for fun. I know that Muscovies are able to breed with Pekin varieties, though sometimes this produces sterile offspring, sometimes not.