I know my kids will love to try this.
Crazy enough, we hatched out some Maran x Australorps and one was crowing... a teeny, tiny crow...at just 8 days old!
I thought my kids were just pulling my leg until my son caught him on video. He is now 2 months old and crows with the big boys every morning.
His tail came in more than a week before the others so I watched the second hatch and sure enough there is another with a tail while the others have none. I am guessing we have a second cockerel. He has crowed only once and is 11 days old.