Stickers:
You say you have Blue/Blue Coppers in with your BCM's. Does that mean some of your Blue Coppers don't show copper and are solid blue or are they supposed to be pure Blue? If they are supposed to be genetically blue and not Blue Copper, I would separate them from your BCM's if you want to keep your Blue/Black Copper lines pure.
Technically, BCM's are Birchen as well. Just with Gold instead of Silver, and with Mahogany to make the copper color.
But Birchens are genetically quite different from Black/Blue/Splash. It sounds like these Blue Birchens are mixed with Black/Blue Marans?
I don't know what you're breeding for, but I don't know of too many lines of Black Marans (from which the blue are produced) that have great egg color.
In addition, if you want to sell Birchen or Blue Birchen hatching eggs at any point, it will be very hard to create pure lines since the Blue genetics dominate the Birchen, and
some of your pure Blue Birchens will look just like Blues. Kind of a breeding nightmare/crapshoot.
But if you just want pretty blue birds, and don't care about dark eggs or selling pure hatching eggs, I wouldn't worry about it.
You say you have Blue/Blue Coppers in with your BCM's. Does that mean some of your Blue Coppers don't show copper and are solid blue or are they supposed to be pure Blue? If they are supposed to be genetically blue and not Blue Copper, I would separate them from your BCM's if you want to keep your Blue/Black Copper lines pure.
Technically, BCM's are Birchen as well. Just with Gold instead of Silver, and with Mahogany to make the copper color.
But Birchens are genetically quite different from Black/Blue/Splash. It sounds like these Blue Birchens are mixed with Black/Blue Marans?
I don't know what you're breeding for, but I don't know of too many lines of Black Marans (from which the blue are produced) that have great egg color.
In addition, if you want to sell Birchen or Blue Birchen hatching eggs at any point, it will be very hard to create pure lines since the Blue genetics dominate the Birchen, and
some of your pure Blue Birchens will look just like Blues. Kind of a breeding nightmare/crapshoot.
But if you just want pretty blue birds, and don't care about dark eggs or selling pure hatching eggs, I wouldn't worry about it.