I have been looking on Ameraucana breed forums and it does look like Blue Ameraucanas in particular are based in E^R (birchen) while blacks are based in E (extended black). Blues can however be based on either E locus but to breed for a better laced blue, E^R is recommended. I had mistakenly...
I don't believe genetically she'd be silver birchen. She's likely just black with silver leakage! This cross should give you half black and half blue chicks. Delawares are silver which is where the leakage is coming from. I believe Blue Ameraucanas are based on extended black and Delawares on...
Blue is just a diluter of black and black covers most varieties, dominant white being a common exception. It would make sense that all chicks would turn out to be blue or black! Genetics are interesting!! :D