They will mature at their own pace but you should see a drake feather somewhere around 15-20 weeks of age. Voice change happened first with mine. The drake will develop a raspy sort of quack while the females will quack like the Aflac duck. Also, the bill on the drake will begin to lighten usually before they develop their drake feather.I have read around and haven't found a real answer so I will ask here. About what age can you tell a female from a male KC? I have 3 that I picked up at TSC about a month ago and I was wondering how soon I should be able to tell their sex.