Yesterday afternoon I got distant looks at a female Tufted Duck in the large scaup flotilla in the northeastern section of the lake. She has a very small but noticeable tuft, which is how I first picked the bird out while it was sleeping. This bird has a small amount of white at the base of the bill, significantly smaller and less contrasting with the head than in female scaup of either species. If you want to try to pick this bird out, I highly recommend bringing a scope.
The male Tufted Duck was next to the fountain, snoozing a few feet from shore, and 5-6 Barrow's Goldeneyes were on the lake further south.