This is just for fun, for anybody who would be excited by being able to see the difference in sex between younger chicks. This is my first time ordering chicks, and I specifically ordered two male RIR and some female RIR, in my batch of 15, from McMurray. Even at about 3 weeks, I was starting to see a difference is the prominence of the comb. Now at 5 weeks, I can even see the start of the wattles on the cockerel. It's silly, but I am really thrilled to be able to tell the difference myself - it's kind of a milestone for me, being pretty inexperienced with raising little ones. This is the first time I've had a known mix of male and female of the same breed, so it's been really educational.