Look on the bottoms of that ones feet and go by that. If they're white/pink they're good. Yellow = bad. The darker legged birds its easier to tell by looking on the bottoms (soles) of the feet.
I'm not going to lie, I culled a line when I began with Marans for yellow shanks because I had no support other than people hollering at me to cull, cull, cull the entire line. Chooks man always advocates working with what you have. If you are going to be working with your birds to eventually sale and want to start over then that's one thing. If you are simply working with them for show or your own personal use, they're yours and what you do with them is up to you. Marans are a frustrating breed and no matter how anyone tries to spin it, you're going to see faults in any line. The fact is, you are never going to order eggs or chicks and get perfect chickens. Any bird you get will have faults, in one form or another. A recessive gene, is recessive gene, whether it be side sprigs, vulture hocks, yellow shanks, etc. They're there and will resurface, time and again. You have invested money and your blood, sweat, and tears into these chickens and I know your frustration. I've been there! If you decide to work with them we'll be here to support you. If you decide to cull and start over, we'll support you with that too.
If you want to work with what you have, cull the yellow legged ones and the hen(s) that produced them to your layer flock. Find another rooster, I'm sure I'll have one later that I could send you if you pay shipping. He wont be perfect but he wont have yellow shanks and my lines have never produced a bird with yellow shanks. Grow out your best pullets that have correct leg color and only use them. Always single mate that way you can pinpoint the origin of an issue easily. Wing band and record everything.
