chicks

Question
How do you tell boy from girl on baby chickens?

Answer
"Chickens"?  Do you mean chicks?  With budgies, you can tell by the color of the area above the beak.  Blue or pink is a boy, purplish brown is a girl.  If you really do mean chickens, the easiest way to tell is to wait and see if they grow combs; if they do, they're males.  You can also tell by behavior.  Males play fight and try to crow.