Easter eggers (I think its a vastly used term accross the atlantic) are chickens that have the blue egg gene, but can't be classified as pure breed. So any mix of ameraucan or araucana would be an Easter egger. :)
Basically (or so I'm told, I don't have much experience) all cuckoo breeds are autosexable if the roo used for breeding is homozygous (much lighter in colour). Here marans roos have to be homozygous to conform to standard, so almost all marans chicks are autosexable.
Other than the cuckoos from...
@Eowyn : lucky you, lots of beautiful brown eggs, though cuckoo marans roos are stunning too :)
@Pinkaboo : I had a chat with a Marans breeder the other day and basically : well defined light spot = roo, no spot = pullet, not so clear spot or fuzzy around the edges = one or the other.
50% of...