You know it could also be their personality....I had a pet rooster (not sure if i mentioned it before) and he never crowed...he was really tame and he would sometimes stay when held... However he only started to crow maybe when he got almost a year old. But still even then he didn't always crow...
in reply to Angelchicks10:
This is what I concluded from my many years of having roosters and chickens. Roosters will crow all the time if there is a lot of other roosters. Not only in the morning but regularly through the day as needed though. I think once they establish who is the boss...