About The Sex-Linked Gene In Muscovy
There is a gene in Muscovy that, when paired a certain way, will produce auto-sexing offspring – that is, offspring whose gender is determined at hatch by their color. The chocolate gene is sex-linked in males, so the auto-sexing ability only works in chocolate or chocolate-based (lilac, buff, and cream) males when they are paired with females who are not chocolate or chocolate-based.
If you take a chocolate drake and breed him to a black hen, you’ll get black males that are split to (carrying secretly, not visually displaying/expressing) chocolate and chocolate females.
Going a bit further in, if you take a buff drake and breed him to a black hen, you’ll get blue males and lilac females. Buff in Muscovy is chocolate + silver, so the sex-linked chocolate gene is present. As the chocolate gene is sex-linked, it can only be carried by males. Therefore, all blue ducklings will be male, carrying chocolate and all lilac ducklings will be female. Females can never carry the chocolate gene.
Splits
I want to go over splits in regards to chocolate. First, I’d like to point out that Bronze, Lavender, and Chocolate are the only three colors a Muscovy could carry. Remember, females can’t ever carry chocolate because it is sex-linked to males.
There are a lot of times that folks acquire birds unaware of their genetic background. Even if they have an understanding of the color genes, when they pair two birds together expecting a particular outcome, they get surprised by other mystery colors. I refer to this as “unintentional test breeding” even though it’s more akin to a regular test breeding, which is done when one has less of an idea of what genes are present, as in breeding to distinguish lavender from silver.
The chocolate phenotype (what we see) is caused by a recessive gene, which means it can lay dormant and get passed down generationally for years until the right pairing causes it to present itself in the offspring.
If one acquires a drake who is carrying chocolate unbeknownst to them, it can pop out in the offspring when paired with a non-chocolate or non-chocolate-based hen.
The chocolate gene in males has the same result whether the male is displaying it or carrying it. The only difference is with males that are carrying chocolate. Those males have a 50% chance of passing the chocolate gene to each of their sons. Whether or not the sons carry that gene themselves can only be determined by a test breeding.
If you take a black drake and breed him to a blue hen, you’ll get black and blue ducklings in both genders.
However, if you take a black drake who is carrying chocolate and breed him to that same blue hen, you’ll get blue, lilac, black, and chocolate offspring. Both males and females will be blue and black, but the chocolate or chocolate-based ducklings (in this case, lilac and chocolate) will be distinguishable as females at hatch. The drake has a 50% chance of passing his chocolate gene to his blue and black sons.
Just remember, you can’t create chocolate without first having it present. So if you ever breed two visually non-chocolate-based Muscovy together and end up with ducklings that are chocolate and/or chocolate-based, you will know your drake was secretly carrying chocolate. You will also know that all chocolate and/or chocolate-based ducklings will be females.
Thank you, science, for being both so incredibly helpful and frustrating all at the same time!
Note: It’s not just Muscovy who have this ability, but most breeds of poultry as well. Any breed of poultry that has a chocolate genotype can produce auto-sexing offspring. Pigeons, turkeys, chickens, geese (there’s no chocolate gene in geese, but the buff gene works the same way), mallard-based ducks…