If I may reword what you posted....
Mallards will "R"ape anything
I wonder if all the wild Mallard_X_AnyDuck are analyzed then most will end up having Mallard fathers and no Mallard mothers. Mallard drakes are just unbelievably frisky as Tiger Woods.
They have just about wiped out the pure Pacific Black Ducks of New Zealand and I believe in the next couple of decades our North American Black Ducks will also be hybridized by them completely.