Thanks!The specific site of insertion - according to the research referenced, is the same between American (north and south) and European chickens who possess blue egg laying genetics. According to the paper, the same type of ERV responsible also inserted itself in a different but closely related section in the Chinese fowl creating the same phenotype and these remained geographically isolated to China. So far, 2 separate ERV insertion points are known. I imagine that they included the Cream Legbar in this research considering it is an older breed.
I FINALLY FOUND IT! The original paper which I am going to save!
We have to keep in mind ERVs are not like a normal virus. They insert themselves into the genome of the animal and are passed down to the next generation. When they insert themselves, it is never in the same place each time. Meaning if you find an ERV in the exact same location in two different animals those animals shared a common ancestor that the ERV was inserted into.
It is great to have these post here.