I have no idea but those are some cute sleepy chicks!!! How old are they? It wouldn't seem like they're old enough to crow yet.
I have no idea either but I am sure you will hear from someone who knows. I agree with rangnarok100 that he does not look quite old enough for crowing but it is not unheard of for some to try around 5 weeks or so.
I actually just wanted to tell you that he is a little cutie and I love the sleeping/sunbathing pic!