What's that mean? Are you saying that one of the girls would stress out because a male doesn't like her? Because that is more unlikely, it might happen to a male, but otherwise I wouldn't see what could happen. The male might have a likening for the other duck, but at one point he will get around to fertile both ducks eggs, some what like chickens. And by the way, the thing about the duck going away for a while and laying eggs in a private spot happened to me! I think they just want a bit more privacy laying eggs. So they just go to a warm spot, where it may be a bit darker, and they feel comfortable. Sometimes after, before, or while laying an egg, they have there own little kind of song like noise they make. It's pretty weird. But not that bad, but ya even worst with chickens. If you interrupt them while laying the egg, they will make a load clocking noise that seems to go on forever.... If any help is needed, feel free to ask. But if you want to ask about incubators. I might know some stuff!