New Zealand has a very complex population of mallard X grey duck. It is difficult to find pure grey ducks anywhere in the country, and most mallards show varying degrees of hybridisation (and also a lot of domestic genes). Lots of muscovy genes around as well.
Although infertile, the female hybrids will lay and incubate. I'm not sure if it's only the cross one way or both that lays. Some that I watched, dived freely for food. Some perch a lot, like Muscovies.
