Tim, out of curiosity, if a RIR rooster over a Silver Laced Wyandotte gives a Red Sex Link, why would a RIR rooster over a Silver Laced Polish not give a Red Sex Link? Is there something special about the Polish?
Polish are birchen at the E locus. The chicks are black backed and show non-black on the face; the color may only show on the chin in some birds. The colors on the face are not reliable. White faced chicks are sometimes females.
I believe birchen based birds can be used in a red sex linked cross but the females would have to be genetically breed to do so. A person would have to synthesize a black tailed white variety ( columbian and dark brown restricted)and use a buff or ginger male ( wheaten columbian and dark brown restricted).
This is a wheaten/ birchen female- I believe a birchen female,( I am working on that ) would look similar to this female but have more black in the tail and wings. But then homozygous birchen could be like the female- I will have to wait and see. The female does not have dominant white in her.
The male part would look similar to this
These birds are some of my breeders for my Missouri Topknots. I am still working on the different varieties.
Wyandotes are brown at the E locus. This is not the best locus to use as the female side of the cross but much better than birchen. Wheaten on wheaten is the best.
You can use birchen in a black sex linked cross- as long as the parental male and female have the correct genotypes.
This is what the girls will look like. Since I haven't done any sex-linked ones yet, I can't show you exactly what the boys will look like. They will be a little lighter and less colorful (brown) than these though.