The bird in the distance is a male bufflehead from UBNA, the second picture is of a female bufflehead from the nearby Magnuson Park.
For more information on the habitat and vegetation of the Union Bay Natural area, please see the journal entry for April 12, 2012 in my written journal and, for information on the weather of the day this was found, please see the journal entry for April 19, 2012 (Union Bay Natural Area) here on iNaturalist. This picture of the bufflehead isn't nearly as good as it could be. The few buffleheads I saw in the Union Bay itself were diving for food too far off shore for me to get a better shot and the ones floating in the small pond in the center of the Union Bay Natural Area kept going behind trees and out of range of my camera. I was able to identify them as buffleheads by their black and white coloring, which was obvious even from that distance, and from their diving, as buffleheads are diving birds. These birds are known as sea ducks and they are among the smallest American duck species. I could not get an accurate idea of the size of the bird I observed, but I think it might have been about a foot long. It was most certainly male, as the females are brown with a small white patch on the sides of their heads. They are common in open inland waters and coastal areas on the east and west coasts of the United States, which explains why they were living in and around the Union Bay Natural Area. As I mentioned, they are diving birds and eat crustaceans, mollusks, insects, fish eggs, and aquatic plants. Buffleheads are monogamous and they go to the same breeding sites every year. They are popular among bird watchers for their black and white plumage.