At what age do roosters start crowing?

[trudyg]

mine were 6 weeks old on monday and at least one has been crowing for at least the past week. Sounds like he's being strangled.

 

[lases77]

I have 8 chicks/pullets ranging from 6 to 8 weeks old. I am hoping none of them are roosters. I read somewhere that roosters start to crow around 6 weeks. Does anybody know if this is true, or if they can start later? By what age could I be pretty sure that, if the bird has not tried crowing yet, it is definitely not a rooster?

Mine started crowing at around 6-7 wks. He's a barred rock and I could tell he was a rooster at 4 wks. Maybe barred rocks are easier to differentiate??