I think I have one doing the same thing!! It is 3 weeks old and keeps stretching his neck up and opening it's mouth. No sounds just the stretch thing!! Could that be him trying to crow? I haven't seen any others do it, this is also the one that usually starts the "chest butting" game with the others!!
OK, I guess my guy isn't that abnormal then. I have 2 that are the same age and I've known (or at least suspected) that they were boys for awhile. They were doing lots of chest bumping and flying at each others faces, but the crowing is hysterical! We are keeping them inside the house for now and my husband heard it first thing this morning.
Of my three, I had them start as early as 3 weeks and as late as 15 weeks and I agree their first attempts are usually quite comical. The one that started at 3 weeks has always sounded a bit wolfish though (more so when he was a few months old) and scared the bejeezus out of us when we moved him out of the brooder and into the coop which is closer to the house.