If we are going deep, can someone tell me and perhaps send a couple reliable quick links on feathered leg inheritance and mixing of comb types?
Feathered legs are more-or-less dominant. There are several genes that can cause them. In general, a chick with feathered legs will come from a parent with feathered legs. Tiny feather stubs can happen even from birds with two clean-legged parents. Unhelpfully, there is not a sharp division between "feathered" and "clean" legs, more a spectrum ranging from heavy feathering through light feathering to tiny stubs and then clean legs.
I’ll be mixing single, pea and rose combs.
Rose comb is dominant over single comb. Rose is completely dominant, so you generally cannot tell whether a chicken has one rose comb gene or two rose comb genes when you are looking at the chicken.
Pea is dominant over single. Pea comb is incompletely dominant. Two pea comb genes will generally make a comb that is smaller than one pea comb gene. The smaller pea comb usually goes with smaller wattles too. Of course there can be confusing in-between sizes where you cannot decide which group to put it in.
Pea and rose comb are caused by different genes, so it is possible for a chicken to have both the pea comb and rose comb genes. If you read genetics textbooks, that is called a walnut comb. If you read breed standards, it could be called a walnut comb, a strawberry comb, a cushion comb, and maybe a few other things. If a chicken with a walnut comb has two pea comb genes, the comb and wattles are generally smaller than if the chicken has only one pea comb gene.
For trying to sort them out as chicks or adults, I end up mostly paying attention to how wide the comb is. A single comb is skinny. A rose comb or walnut comb is wide. A pea comb is in between. (Yes, of course that means I can mistake a pea comb either direction.) As they get bigger, a single comb generally has points on top and a pea comb mostly does not. It can have three rows of rounded "pea" shapes, or it can be a smooth little blob, or it can stand up almost like a single comb but without the points. Or maybe a few other variations--after you see a bunch of them, it starts to be kinda obvious, but there will still be a few that leave you unsure.
I hear pea combs and the blue egg gene also go hand in hand when it comes to the usual EE/OE mixes.
Generally yes.
The pea comb and the blue egg gene are definitely linked, so they get inherited together. They can be linked in any combination:
pea comb/blue egg (Ameraucana)
pea comb/not-blue egg (Brahma)
not-pea comb/blue egg (Cream Legbar)
not-pea comb/not-blue egg (All white-egg and brown-egg breeds that have single or rose combs)
Side notes on feather color. Is blue always BBS or are there different types of blue?
There is the blue gene, also called "Andalusian Blue." That is the one that makes black/blue/splash. It turns all black on the chicken into blue or splash. It has little or no effect on red/gold colors (including most shades of brown). This gene is incompletely dominant: one blue gene turns black into blue, two blue genes turn black into splash. No blue genes means the black can still be black.
There is also the lavender gene. It is a recessive gene. It turns black into a shade of gray, and it turns red/gold colors into a light cream or yellow color. Lavender is sometimes called "self blue," which gets confusing.
This one is a bresse X blue copper maran, she has a less spotted sister and aunt who looks nearly identical. Is this considered splash? Mottled?
She probably has the gene Dominant White. It turns black into white, but sometimes misses a few bits. A chicken with two Dominant White genes will have fewer or no black bits. This gene affects black but has little or no effect on red/gold shades.
A chicken that is white with bits of black showing like that, caused by Dominant White on an otherwise black chicken, is often called Paint.
This white/cream EE is the mother to the blue one. Pretty dad sure was a BJG. Both have pea combs. I also have a bantam EE who is about the same color, she has 2 blue daughters also fathered by the BJG. I expected all the BJG offspring to be black but surprise surprise, 5/7 are blue! Why? How?
Two possible explanations.
One, could the Jersey Giant be a dark blue instead of black? If yes, he would give about a 50/50 split of black chicks and blue chicks.
Two, if the Jersey Giant really is black, then the blue chicks must have had a mother with the blue gene. If you didn't see any blue on the mothers, they could have been showing splash (often looks much like white if the chicken has it in a pattern with other colors). Or they could have been showing dominant white, which can hide blue by turning it to white. Any chick that inherits blue but not dominant white will show blue rather than black.
The 2/7 black ones where from a brown/grey EE hen. I really don’t get the finer details on feather color/pattern. I know EEs are a toss up with their mix of genes but I really thought extended black in the BJG would be dominant to nearly all other colors.
It looks like the extended black was dominant, as you expected, but then the blue gene turned all that black into blue.
