young runner ducks how do you sex them?

[spish]

i have 9 young runner ducks and would like to know if they are male or female.... i know you can sex them pretty easily when they have 'adult' feathers, but is there any other way to do it when they are young?

 

[cymbaline]

They look old enough to be voice-sexed. The girls may not be honking/quacking 100% of the time, but if you separate one from the others it probably will. If they're over 6-7 weeks and you hear no honks...probably male. Check out this link to hear the difference between males and females: http://www.majesticwaterfowl.org/artquacks.htm