I have two young Muscovy ducks. The brown one is about 12 weeks old. The black and white one is about 7.5 weeks old (and just got fully-feathered last week). I THINK that the brown one is female and the other is male, but what do you guys think? The younger one definitely seems to be growing faster, and has a much more fan-shaped tail. You can see in the picture of him that he's as large as a fully-grown hen already (the white female in the foreground).