I have 2 cute chicks, one is Braekel and second is Paduan (a day younger). Do you have any suggestions how and when I can determine their sex? I already have a rooster, but he seems to be infertile (SLW of unknown age, maybe 3+ years), as none of the eggs my hens have tried to hatch have shown any development. Anyway, I hope I have at least one pullet, but I think they are a bit too young to tell the sex. The brown chick is Braekel and about 10-11 days old, the yellow chick is Paduan and about 9 days old. Any thoughts?