I have a cuckoo Marans cockerel and a solid blue Marans pullet, I got the cuckoo Marans cockerel by accident he happened to be in the same pen as the black copper Marans the breeder had, I am debating on selling this cuckoo, but before I sell him I want to understand how genetics work in cuckoo Marans I know that there is a blue cuckoo and a silver cuckoo so I wasn’t sure what if anything would happen if I crossed him with the solid blue hen (blue cuckoos?) he is from a very well known breeder with great lines so I do not want to get rid of him too quick, but if there is nothing to be done with him then I’ll probably rehome. TYIA 
