Before the experts answer this question, I would like to add my own concern. I'm sorry I don't have any pictures this moment, but I bought six chicks four weeks ago, two of them are Black Australorps. They were equals at the time of purchase, but now one still looks like a fuzzy little chick, more or less, and the other is the biggest of all my chicks by far (almost double) and quite dominant. She (or he) is also the least friendly, really not friendly at all, never has been. Some of my other chicks I am sure are pullets have also been growing their combs already, but this BA in question has not... nor has "it" grown any tail feathers whatsoever; still just a fuzzy chicken butt.
So, with that bit of background out of the way, my two direct questions would be:
1. Is growth rate an indicator of sex?
2. Would a BA roo have a comb (or tail feathers) started by now (at four weeks)?
Thanks.