BackYard Chickens - Learn How to Raise Chickens

Both chocolate and white are recessive so would need two genes to show either, but if you have a duck with two white genes they will be white no matter what, even if said duck also carries two chocolate genes... (I think). Have you tried posting in the duck forum?

I'm pretty good with duck genetics!

So sorry you lost her. So, both those genes are recessive. White is simple recessive, and chocolate is sex-linked recessive. I'm gonna have to break this up due to character limit, so this is gonna be in a few posts here.

What with having both a white drake (pekin) and a chocolate drake (runner), you could actually produce either color duckling with the pekin hen. Any ducklings she had from the pekin drake would be white. If she was the only other white bird you had, and you don't think any of your other females are carrying white, then if you hatch white ducklings they are hers.

Now, white 'hides' all the other color genes, but with pekins usually they are black bibbed genetically 'under' the white. This is not always the case though, so take this with a grain of salt. If she was black bibbed and not chocolate 'under' her white, she could produce female chocolate ducklings with the Runner - only females. If she WAS chocolate, she could produce both genders in chocolate with him.