I guess it's hope, not truth, that's the thing with feathers (two points if you get the reference without Google) but here's the lowdown (down, get it?) on the duck. (Well, I could've said "the poop" and I didn't.) Those of you voting for a cross, you seem to be right on the money. From Laura Erickson, the Dr. Ruth of
Ornithology, via RevJen.

"It's a cross between a Mallard and a domesticated duck. It has a lot of natural Mallard features, but also plenty of the white of a "Pekin Duck," which was originally domesticated from wild Mallards. There are a lot of variations on the Mallard/domesticated duck theme in parks. The line at the back of the neck is rather Pintail-like, but the bird itself is too bulky to be more than a tiny part Pintail. The word "Mallard" comes from Old French, the "mall" related to masculine or male, and the "ard" pejorative, as in drunkard or sluggard, because Mallards epitomize the worst of masculinity. Males will mate with anything that will hold still long enough--I've even watched them mating with rocks."

And you non-birders wonder what it is we birders are watching.