Can you determine gender of a chick by behavior?

[MegP]

I have four week and a half old chicks that I bought from mypetchicken, and one of them (an australorp) is literally twice the size of the others and seems to more inquisitive and almost protective of the group. I could be reading into it too much and she could just be exhibiting alpha tendencies but I'm totally new at this and figured I'd ask the experts what you all think. How soon can you really tell if you have a rooster or not?

 

[Cloverleaf Farm]

When they crow. hee hee. sorry but true. I would've sworn my BO was gonna be a roo when she was little...very agressive and protective of the other chicks...but she's a she. Also, right now I have sex-linked chicks in the brooder, and the biggest one is a female....

 

[Mahonri]

Most of mine that ended up roos were just a tad cocky!