Originally Posted by Chaos18
And what does sex-linked mean?
There are sex-linked traits in people too, like color blindness and hemophilia, both of which are found much more often in males than females. It's just not exploited in people because sex determination at birth is not an issue (fortunately!!).
In birds, the sex chromosomes are reverse from people, the males have 2 of the same and the females have 1 each. Because the females only have 1 sex chromosome that "matches" the 2 the males have, any traits on that chromosome will only be passed from the female to the male offspring. The other one, that determines the chick will be a female (like the Y chromosome make a male in people) does not have the genes for these traits, so the female offspring gets their only copy from the father.
Because the only copy is from the father, if the father is "pure" (homozygous) for the recessive version of the trait (let's use gold/silver as an example - so "gold" like a RIR) and the mother has the dominant version (silver, like a Delaware), then all the males get the mothers dominant gene and will be silver (yellow chicks) while the females will all get the gold only from their father and be reddish. The male chicks will carry gold (from their father), but not show it. They are useless as sex-linked breeders because you need a pure gold male to make the cross work.
Reading over this, it's not as clear as I had hoped, but maybe it will help someone.