I have 3 modern game chicks that are now 9 weeks old. I noticed that at a very young age one of them made a little "alarm" call when it saw something out of the corner of "his" eye. Just like the big roosters! Well it was easy to check because the males and females feather in different colors. I put a band on his leg and yes hes a he. Last night I read this somewhere as a tool to sex chicks at a very young age. Just throw a soft object over their heads and watch and listen to them. Its cute to know the little guys are doing their job so early. Maybe not so cute if you are hoping for a pullet.