Mallards frequently interbreed with the Black Duck, the Pintail and domesticated species, leading to various hybrids. Mallard drakes clearly go after other ducks without courtship.
We saw one of these this morning; a “bib” duck which shows features of the Black Duck and the Mallard.
Here is a Mallard / Pintail hybrid:
Species list: trumpeter swan, Canada goose, mallard, American black duck, ring-billed gull, herring gull, rock pigeon, downy woodpecker, hairy woodpecker, blue jay, black-capped chickadee, Carolina wren, American robin, house sparrow, northern cardinal, American goldfinch, dark-eyed junco, white-crowned sparrow, fox sparrow. (19 species)
Till I scarcely more than muttered “Other friends have flown before—
On the morrow he will leave me, as my Hopes have flown before.”
Then the bird said “Nevermore.” – Edgar Allan Poe (1809–49)