I keep Lavender Arry's, the females tend to get a bit of a crest of feathers, the comb on the boys is a lot wider, and they don't seem to have the crest like the girls, i wait till they are older 16 weeks or so and you can normally tell. They are late layers as well can be 26-30 weeks before you start getting eggs. Hope that is of some help, i have only been keeping chooks a couple of years so no expert.