How old are ducklings when they start to affect a flock ratio?

[SweetLilDuckies]

I have 12 unsexed ducklings(runner mixes) I'm planning on using to balance out my hen to drake ratio, (1 hen to 3 drakes is quite backwards). Their two weeks old and with my hen, my drakes are in their own pen. Once they get their voices I'll move the drakes to be with the other drakes(as I'll most likely have to rotate them out of the hen flock). I'm hoping for all hens so I can just move my drakes in with my hen, but I know I'll get at least 2 drakes out of the brood. How long do I have to wait after they get their voices to introduce one or more drakes to the hen flock? (I will keep the ratio intact).

 

[EverythingDucks]

You can voice sex them at around 4-6 weeks old. The older they get the easier it is

 

[TomCahalan]

Don't move the drakes as soon as they can be voice-sexed. That is too young. They will be beaten up by the older drakes. Wait until 8 weeks at least, but you can wait quite a bit longer.