Rocks - Male or Female?

[jcabral]

Good Grief! I hope not! At what age, besides fully mature, would I know for certain?

I'm about 99 percent certain now. Your original guesses are spot on. For sure though with any chick it is when you see an egg or hear a crow.

 

[BantamLover21]

I have a dozen chickens, and wasn't able to get pictures of all of them. However, this is a good representation of the chicks. Your help is appreciated.

Picture 4: Rooster?

This one is definitely a cockerel. I'm not sure about the others, but if I had to guess, I would say they are cockerels, too.