You don't want to keep more than one drake in a group of four, as any more and they'll make the ducks' lives a misery. You might not want to hear it but the place for spare drakes is in the freezer. Fingers crossed you've got three ducks and one drake hey?
And as GP says, swapping the one you keep for an unrelated one would be genetically much better if you're going to breed from them.
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