Sexing?

[bryan8]

I have 3 rouen ducks it was suposed to be one male and one female but they included an extra by accident. And I also ordered one male and one female white pekin.

Anyways there 9 weeks old. When and how will
I be able to tell the sex ?

 

[houndit]

As soon as they have adult voices the Drakes will have a very soft raspy quack. The females have the actual quack quack quack. In breeds like Rouens the females will have different coloring than the males. Can you post pictures?