Question for my fellow Fm lovers who also have some genetic knowledge. Is Fm inheritable if it doesn't show in the parent? For instance I have a Fm roo who has a daughter (or son) w/ normal skin color, can their offspring then revert back and show Fm?
Yes and no..... yes because some other genes can "suppress" Fm from being visible and some Fm roosters hatch out with plainly discernible Fm but lose almost all trace of it as they mature to the point they don't seem to have it.
Lacking those genes and birds that go light as they mature, it is same as NN- if it's not visible, it's not there genetically at all.
My own experience- females tend to have much better Fm expression than males. for example in crosses or early generations it can almost seem the real dark skinned chicks have a way high chance of being pullets. but the not so dark ones can turn out to be pullets also. Not so simple and I don't know why either. It varies so much. For this reason, I would say if a daughter never showed any tint to skin as a chick(and assuming there are no suppressor genes) she is totally lacking the Fm gene.
Some well known genes that 'interfere' with Fm: barring, mottle, Id(dermal melanin inhibitor- makes clean yellow or white legs- birds with green or blue legs don't have Id), sometimes dominant white will mess with leg color but dominant white birds with very dark legs or skin is not that rare either..
If the daughter has all or mainly black feathers and her legs are black/blue/green and never showed any tint to skin as a chick would fall on the side of her not having Fm.
IF she has barring, mottle, white or yellow legs, then it can be hard to tell. Some will show a black spot(s) with crisp edges somewhere on body as the only hint of Fm.... some birds will show Fm traces only on the inside- sometimes you can get clues by exposing the cloaca. other than that the only real way to tell is breeding her with a roo lacking Fm and any of the suppressor genes and see if any chicks show up with dark skin.
Is she brooding? 
