If its going to crow...

[Muscovies]

They start to crow at about 6 months to a year.

 

[crash0330]

All of mine started crowing at from 19- 28 weeks old and I have 12 roosters.

 

[jenjscott]

I think the main thing is in comparing them to their hatchmates of the same age that have had the same feed etc. One that looks kind of "ifish" may really stand out with his flockmates.

 

[math ace]

I've got some 6 week olds doing the strangle crow now . . ..

A few breeds are hard to call early, but 12 weeks is pretty big and should clearly exhibit either pullet or roo characteristics.

I agree with a previous poster - - - give us picture.