Gone-Quackers
Chirping
Thanks for the info. So far I am only getting whitish eggs and I don't even know if Mrs. Pekin is laying for sure. Mrs. Pekin would get separated only she'd get rather cold and I doubt I'd get sleep as she'd carry on all night (she's the sole survivor of a raccoon attack and is recovering from PTSD-- she's still pretty neurotic. Just finished stress molting a couple weeks ago.). My mallard is actually an indian runner with a mallard pattern- so no worries there! Everyone is purebred runner except for Mrs. Pekin. Luckily Mrs. Pekin's owner loves Pekin/runner crosses which is great as I don't want any!It depends on what is hidden under the white of your Pekin. But if it's a solid color... I notice that most of your runners are /and white. When crossing /and white (Runner gene) with /and white, the babies will show the full white Runner markings on the solid background color. The babies from your mallard and, probably your Pekin, will have less or no white, because they will have at most one /and white Runner gene. This is an uncertain way to tell, as you will be selling the babies from the mallard also, but if you add this to the suggestions above it gives you a bit more information to select out the ducklings you don't want.
Personally, when I choose to keep eggs for hatching, I segregate the hens at night to make sure I get the right eggs. The rest of the time, I put all my hens together and eat the eggs.