I have been reading the book Raising Ducks, Written by Dave Holderread. He says that you can sex ducks like, Mallards, Rouens, and other birds of that pattern by bill color. Could this work for ducklings? Mine are 3 weeks and already 3/4 are showing orange bills found in hens, the other, a darker color, almost black. Could that one be the drake? It also seems to be fairly quiet. I hope so! Thanks and if there is any other ways to sex young Rouen, Mallard ducks please post.