That will largely depend on what the SOP calls for, as for Pattern, the Birchen phenotype is just a crow wing phenotype, some SOP calls for a lot of pattern on the breast(for example Modern Game Bantams and Silver Sussex)I breed my Birchens to Columbian every few years. It seems to really improve the Birchen pattern in my birds.
But for example, the Black Copper Marans(gold based birchen) don't have any.
What does the SOP calls for Birchen Orps? What type of Birchen do you have?