The head spot just tells you that the chicks will grow up to be barred. If the rooster that bred these chicks was barred then all his offspring will be barred, so all the chicks would have a head spot. Black sex links are created by using a red rooster over a barred hen. The hen can only pass the barring gene to her male offspring and this is how black sex links are produced. If you don't know whether the father or mother was barred or possibly both, the head spot has no meaning as regards their sex.