I spent quite a while at McCuen Slang today (not the fishing access, but the small parking area on the east side of the road, near Whitney Creek), much of it staring at a distant mystery duck. My notes:
a little larger than two wood ducks that drifted by it at one point
red or red-brown head that looked like a slightly flattened ball
gray and brown top of body, orangy-tan on the sides at the water line
tail sort of pointed
a bit of white at the side just before the tail
fairly noticeable eye in a dark smudge
The closest I can come up with is a female Eurasian Wigeon.