Lesser Scaup (Aythya affinis)

Beacon Hill Park's lake is a favored spot for ducks at any time of year so I thought I might find something interesting there. While the vast majority are Mallards or Wigeons, after watching for a while I noticed the duck above. This is one of two related species, the Lesser or the Greater Scaup. The major difference is size and the shape of the head. For those reasons I lean towards identifying this as a Lesser Scaup (Aythya affinis). It's called a scaup because it makes a noise like "scaup." The Lesser Scaup is a member of the diving duck (Aythyinae) family. Below are a series of photos showing a dive sequence. Had there been a fourth photo it would only have showed the ripples on the surface since when these ducks dive, they swim around underwater. Dabbling ducks such as Mallards, on the other hand, just tip themselves perpendicularly in the water, leaving their bottoms above the surface.

There were two of these Lesser Scaup mixed in with a large group of Mallards and Wigeons and at first I didn't notice the Scaup because they stayed in the water when the Mallards and Wigeons came up onto the shore to feed for some bird seed someone had scattered, visible in the photo below. I thought that perhaps the scaup were just shy but I have since discovered that Mallards and Wigeons are members of a different family, the dabbling ducks (Anatinae), who feed on or near the surface of the water. The legs of diving ducks such as the Lesser Scaup, in order to provide superior propulsion and steering when diving more deeply beneath the surface, are located further back on their bodies than is the case with dabbling ducks. This means that they don't walk as well or easily as dabbling ducks so they tend to stay in the water, while the Mallards and Wigeons scrabble about quite happily on the shore.