aoxa, you're doing well if you can tell by eight weeks. I thought for sure I had six cockerels and three pullets my last batch of Blue/Black Ameraucanas. Luckily I was growing them all to 21 weeks so I could decide which I wanted for breeding, because around week 14 the true cockerels' combs became huge and bright red and some of my "cockerels" were clearly pullets with early reddish combs. Turned out I actually had six pullets and three cockerels! Of course, no black birds were male. I'd specifically wanted a black Am cockerel to make sex-linked EEs with. Isn't that always the way?