My big boy austrolorp roo is 6 months old and just started crowing a couple weeks ago. We were very hopefull that he may have been a mute because he never made a sound all this time. He has even been trying to mate his hens. Flap his wings, fluff all up and mount them get off and strut around all proud, but not a sound.
A couple weeks ago we heard a sound like someone screaming while being choked. Ran to check our girls and all was fine....Keoki just found out he has a voice. Now we are hoping he will learn to crow like a real roo. Screams coming from the coop at 6am isn't good.
The first day I let the little chicks into the big outside at 6 1/2 weeks I am pretty sure that I heard something that was supposed to be a crow! That is the earliest I've ever had start.
We have had baby roos making odd little baby crows at about two weeks. I heard Rodney, my baby JG roo, try for the first time this morning. Rodney was hatched 2/28/08. They crow when they feel like it. There is no particular age.