Hi Steve- I have a poultry fancier in the office and he steered me in the right direction. This is a Mallard cross with what is known as a Crested Pekin, which is a special Pekin Duck bred for the tuft of feathers on its head. The Pekin is the classic white duck bred for the table and for eggs.
Mallards are very closely related to many of the domestic duck breeds and so it's not a big stretch to have them interbreed. Indeed, Mallards frequently cross with American Black Ducks, Northern Pintails and other species in the wild.
One of these with an even bigger tuft that looked like a duck afro was resident at the University of Richmond while my brother was a student there. The students named him Duckwheat and he was quite the local celebrity.