Warm up crow??

I was just checking on my chicks and my roo was doing this weird thing with his mouth. Like he would open his mouth really wide, and have like a convulsion like a cat coughing up a hairball. I am a newbie with chickens, but it looked like the motion that roosters make when they crow....but no sound came out. He did it like three times in a row. Is that his warm up to crowing? He is 5 weeks old today. Even though I have been convinced that he is a roo for a couple of weeks now (see my avatar pic and you will know why ), I actually can't wait for the crow for it to be confirmed!!