oh, none of our females had black smudges on thier backs? all yellow. I do know if you hold there wings out when young the males have on first 10 feathers two rows of feathers....will see a row close to top of wing then space with no feathers, then another row of feathers. Females have straight feathers no skipping and this is true we checked ours when we first got them and hoped it wasnt correct but..............if you google sexing of young chicks they have some clips on it and you can see what Im talking about, unfortunately I think they had to be very young to do this? Still learning myself
If you click on the link I posted above, it will show pictures of feather sexing. Unfortunately, not all breeds can be feather sexed.