That is a possibility yes... although her being birchen with incomplete set of helper genes can't be totally ruled out. There is a big area of overlap in how the extendeds and birchens look when these helper genes are present in various combinations. Hope this makes sense?
That is the best guess yes, until the chicks hatch and grow up.
Breeding back to the dad will produce blacks- many with varying amounts of off color, probably lots of columbians and maybe a few surprises because a black chicken can be carrying lots of pattern genes that are also invisible.
So she might also be a birchen with lack of helper genes, right?
I guess that I won't get what I was hoping for with this cross. Long story short, I have to hatch chicks and see.
Is there any other color that could produce birchen with that roster?