<https://lh3.googleusercontent.com/-djY-72gU5Jk/WklDgiJ02lI/AAAAAAAAAO8/MaHX1F9y2pESxsDi-Prn6xfBUSyVWJGzACLcBGAs/s1600/Trumpeter%2BSwans%2B2.jpg> OK, I went out there this morning to take another look, and brought the scope along. From what I can tell, these are Trumpeter Swans, based on the size, the bill shape, and by comparing them with the Tundra Swan that is also out there. As Donald Jones noted, they are larger than the Tundra Swan, with stockier necks and bigger bills. The bill has a fairly straight edge along the side where it meets the feathers, and has a distinct U or V shape between the eyes where the dark beak meets the feathers. The Tundra Swan has more of a flat line between the eyes. I got a few pictures, but couldn't get one of them facing me to show the U shape. Views through the scope showed this quite clearly, however. The three larger swans seemed to stay together most of the time, with the smaller one getting a little farther away from the group from time to time.
On another note, while observing the large merganser flock, I spotted some Western Grebes along with another Grebe that looked like it could be one of the Red-Necked Grebes that were here recently. It was on the far side of the reservoir, and there was a light wind with a little fog, so I was not able to see it clearly, but the size and general coloration was right for a RNGR.