Hundreds of Greater Scaup arrived within view of Cesar Chavez Park this past week. They clustered in two loose rafts, shepherded by a handful of male Bufflehead. The male Scaup have the light grey backs, dark heads, and light blue bills. The female Scaup are dark all over except for a white band above their bills. Possibly there were three rafts of them, far out from the park shores. They generally spent their time paddling and diving at will for whatever bounty was to be had beneath the surface. Being ducks, they feed on snails, insects, and crustaceans, as well as seaweed and other plant matter. They can dive more than 20 feet deep.
As I watched them from the north side of the park, one raft of them took flight. It started with a few birds, and when these flew just over the heads of birds still sitting in the water, these also took off, and in a few seconds the air was full of wings. At first there was some random flying, as if to escape a predator, but soon the airborne flock cohered and flew eastward, and then turned around and headed westward. One small group of six flew faster than the rest and headed higher, toward Mt. Tam, until they got out of my camera range. Wikipedia says they can fly up to 75 mph.
There’s no way to know whether the flight of these particular birds was just a momentary panic, or whether they were continuing their migration to greener pastures. The next day, however, revealed no scarcity of Scaup on the North Basin. A very sizable raft of the birds had moved into the middle of the North Basin, a bit south of the Open Circle viewpoint. I apologize for the uneven nature of this panoramic take, below. Still, if you care to, you could use the video to count the birds. My guess is 250. Comments on this post are open.