The North Basin — the estuary to the east of the park and north of University Avenue — was host to hundreds of Greater Scaup this evening. They are easy to identify by their light-colored bills and by their habit of clustering in large groups, called rafts. The males have white sides, the females brown. Enjoy them while you can because they typically spend the summers breeding in Alaska and other northern climes. They’ll take off en masse one of these days (and lucky will be the photographer who is present).
I classify them as Greater Scaup with some hesitation. Greater and Lesser Scaup are almost identical and next to impossible to distinguish from a distance. The Lesser are on average about ten per cent smaller than the Greater, but that isn’t much help unless you have two of them side by side for comparison. The most useful clue is the shape of the head. The Lesser tend to have a little bump on the back of the head, resulting in a less rounded head shape than the Greater. The birds in these pictures seem to have well-rounded heads. Flocks of Greater and Lesser are often found together in nature, and I’ve classified other Scaup that I’ve seen on my park visits as Lesser. With my fingers crossed.