TCB (Texas Clear Body.)

Tcb is a sex-linked mutation, carried on the sex chromosomes, so females only need one TCB chromosome to be visual TCB, whereas males need two. Hence cockbirds can be split for TCB but hen birds can't.
The chest and throat markings are often very diluted almost completely, with the color getting progressively darker around the legs, with the rump usually be the darkest in color. The Darkest color on the body is often diluted 50% or more.