Along the north side of the park this Saturday afternoon I spotted a flocklet of exactly seven duck-type birds that I hadn’t seen before. They were on the small side, with smallish white bills tipped with black, and most of them had a white stripe on their foreheads and a green stripe from the top of the eye to the back of the head down to the neck. The tail was black with a white patch in front of it. Returning home I searched the Audubon and Cornell Bird websites for an identification. The valuable Merlin BirdID website unfortunately is down for maintenance. I searched the few duck names I know — mallard and merganser — and came up empty. But I kept on clicking and finally was rewarded. My mystery bird is an American Wigeon.
The American Wigeon is a dabbling duck, not a diving duck. This means it prefers shallow water and low tides. But, as the audubon.org website tells us, it’s also often found in deeper water in the company of diving birds. What’s it doing there? It’s a pirate, attacking the diving birds and stealing their food as they bring it up. The Scaup who are very numerous in the North Basin are said to be among the favored targets of this thievery. How this rather little duck gets away with that behavior I don’t know. I’ll be watching.
This bird likes to spend the winter in estuaries (places where fresh water flows into a body of salt water). The North Basin (the water on the east side of the park) is such an estuary, being fed by Schoolhouse Creek. And of course the whole of San Francisco Bay is an estuary fed by the Sacramento and San Joaquin river, among other sources. These birds may pair up during the winter. Two members of the little flock of seven that I saw looked to be a pair. There may have been more Wigeons in the North Basin but they were too far away to identify. These birds are said to be common and have the capacity to show up in much larger flocks.