I have several BYM and am trying my best to narrow down which parents belong to each chick based off observable traits.
I don't think I've seen BYM before. Is it Barn Yard Mix?
Is that something too difficult if I know the possibilities?
In some cases it is easy, in some cases difficult, in some cases impossible. It depends on the breeds involved, and on which traits the chicks show.
I'm also curious as to possible sex linked traits. I understand how black sex links are determined, but what about red?
Gold father, silver mother produces gold daughters, silver sons.
(For easy sexing, some other details matter too: like not having black down all over.)
Can foot and leg feathers be sex linked?
To the best of my knowledge, no.
Are they a dominant trait?
Mostly yes. There are at least two dominant genes and at least one recessive gene that can cause feathered feet.
For chickens with very many foot feathers, they typically seem to be dominant. The chicks that get feathered feet from two clean-legged parents are more likely to have only a few tiny feathers instead of a really noticeable amount.
I have a few chicks in particular that I believe are from my RIR roo and light Brahma Hen. Would their offspring be sexable based off any certain traits?
Yes, offspring from that cross should be gold (daughters) or silver (sons).
I'm including a few pictures of some of these chicks. They all appear some shade of red, with feathered legs and feet. And all have "eyeliner." I only have 1 red roo, and 3 feather footed hens- a light Brahma and 2 Pavlovskaya. I'm assuming based on appearance that those are the only possible parents of these chicks.
If those are the only hens with feathered feet, and there are no roosters with feathered feet, then I think you are correct that all chicks with feathered feet must come from those mothers.
If the Brahma is the mother, the chicks in the photos should be female.
If the Pavlovskaya hens show gold feathers, then they can produce gold or red chicks of either gender.
Is the RIR the only possible rooster? If yes, it makes things much easier to sort out. If you have other roosters as well as other hens, it can get more complicated.
Most comb types are dominant over single comb. So look for a pea comb on chicks from the Brahma.
Crest, muff/beard, and duplex comb are all caused by dominant genes. So any chicks with those traits would have a mother with those traits, assuming the father is the RIR, who obviously does not have any of those things. (I'm not very familiar with Pavlovskaya, so I looked up photos and saw lots of crests, beards, and v-combs.)