I found this from a google search. We still don't know what age they start!
How do you tell the HENS from the TOMS?
Once they mature, the toms are larger and have longer legs.
Toms grow a beard (long black feathers) in the middle of the chest (breast). Very few hens grow a beard.
A male turkey's head and wattle (growth under the chin) is larger.
The tom's snood (a fleshy growth on top of the bill) is longer and hangs down the side of his face.
Male turkeys gobble. Hens do not. Hens make a clicking or clucking sound.
Male turkeys strut about, gobbling loudly and holding their heads high. They stick out their chests, fan their large tails and drag their wings on the ground. They do this to attract the attention of the female turkeys.