Unfortunately, even if you go to ASBC (american silkie bantam club) website, the main answer is wait till it crows or lays eggs! Some varieties are easier to sex by the color variations in the feathers. The males usually have a larger surface area for the comb, and the skin will be a little bumpier there. I assume you are dealing with chicks? If they are older, post pics. There is always someone here that can help!