Are male ducklings larger than females?

[Blackberry18]

So, I have five Khaki Campbell ducklings, two males and three females. They are currently a little more than three weeks old, and I've noticed that three of them are larger than the other two. I'm worried that the hatchery incorrectly sexed one and sent three males and two females. Not sure if male ducklings are larger though, does anyone know?

I've tried voice sexing, but I've never had ducks before, so haven't had much luck.

 

[sourland]

Initially some female ducklings grow as fast as or faster than the males - don't worry yet. 3 weeks is too young for voice sexing.

 

[cheezenkwackers]

My 2 male Khakis were originally smaller than my three girls. Later they passed them up.