Yes, I think, correct me if I'm wrong, it's the gene for Mahogany I looked it up when we were discussing it on the old Marans thread. I can't quite remember which web site I pulled this up from at the time,
Mahogany red :Mh/Mh (and Mh/mh+) it enhances present red into dark red.
Mh is very strong and it does 3 things
- Mh makes s+ (gold) dark red;
- Mh has a columbian like action on black pigment;
- Mh restricts black to the outer ends of the feather, by extension of red.
If Mh is absent (theoretically) the gold would be more pale.
So from what I understood in reading it and looking at other sources, ER/ER birds can end up with one of these variations of Mahogany: Light: mh+mh+ Medium: Mhmh+ Dark red MhMh.
MhMh is the strongest expression of the dark red color in the hackles on this genotype
Please jump in if I am wrong here.