You won't find these Hooded Mergansers in the 'hoods of Phoenix. They prefer the swanky and grandiose ponds around Fountain Hills for their wintering, where they rub shoulders with other aristocratic waterfowl like Northern Pintails and Buffleheads while cavorting near the world's tallest fountain. In fact, this is about the only place to consistently find these saw-billed ducks in Phoenix, though I've also seen them at the Papago Ponds (1 female) and at the Box Bar recreation sight.
When I made it out to Fountain Hills the Merganser numbers were still pretty low. I only counted three individuals--all male--but their numbers may well exceed a couple dozen by December, and they can even be seen indulging in mating displays and other vanity festivals. Gordon Karre has some exceptional photos of the Fountain Hills Merganser here.
They stayed a little bit distant for me, but it was still neat to watch them cruise around with their unique and jaw-dropping headgear. This Ruddy Duck seemed to think that, since he also had white on his face, he could be a part of the gang.
Wood Ducks may be the most colorful indigenous waterfowl in North America, but it's a challenge to find any waterfowl more eye-catching than a Hoody gettin' on his hood. It will not surprise me at all if the recent Mars rover discovery turns out to be Hooded Mergansers hanging out on Mars. The headpiece strikes me as very martian.