I left home about 11 am and drove to the Jordan River Parkway. The temperature was in the high 30s, and the sky was sunny. I ran most of the 2 miles, although I made several stops to look at the ducks and to talk with a man taking pictures. I also did a couple of short walking breaks. Even with the stops and walking, I did more running that I did on Monday or Wednesday.
The man taking pictures told me the ducks with the white on their bodies are Goldeneye ducks. When I got home, I read Wikipedia about Goldeneye ducks and confirmed what the man had told me. Wikipedia confirmed that a whistling occurs when they flap their wings. The ducks are sea ducks and forage under water for food. They eat insects, small water plants, and similar things.