Like, with secondary sex-characteristics? For instance, I noticed that four of my nine chicks have bushy little tails and lots of feathers, the other four have less feathers, sparse tails and combs that appear slightly larger than the "tailed" birds, also maybe thicker legs. So I am thinking (and actually quite convincing myself) that the more-feathery birds are females, and the less feathery more comby ones are males. I still can't tell with the runty one though, it barely has wing feathers, much less tail feathers. Here's a picture of one that I think is a 'roo purely on the fact that it is not as feathered up. Here's the runty "who-knows" one standing in front of the above chick.