This very distant photo was taken at TVA Lake at Allen Power Plant in Ensley Bottoms of Memphis.
Even in this poor shot several features of Mottled are present. The bird was well-marked with broad buff edges and internal markings to the body feathers, but these were lost in the grain of the photo. The bright yellow bill and black gape spot are visible, the face and throat are a unmarked buffy color, and you can barely make out the narrow white borders to the speculum.

For a very few minutes Don Manning and I had an American Black Duck within just a few feet (but not the Mallard with it in this photo) for a not too often had direct comparison. The Mottled, though a very dark duck, was slightly lighter in overall tone than the Black which lacked the buff edges and internal markings of the feathers, and the face and throat were distinctly lighter, lacking the gray tone of the Black. The bill of the Mottled was a bright yellow, not the greenish of the Black, and the Black lacked the gape spot. Also, the Black Duck lacked any visible white in the border of the speculum. Both ducks left at the same time, each with a couple of Mallards, and each group went seperate directions. The white trailing edge of the secondarires of the Mottled was obvious in flight, but not as distinct as the Mallards it was flying with.