This is probably an immature herring gull passing through -- not a common sight at our millpond. Clearly, however, it’s old enough to have some impressive fishing skills (it seems to have caught a bluegill or a pumpkinseed at middle right). It looked a bit like a giant hummingbird with its eye on the fish below water. The merganser seems mildly interested, certainly not worried, to share the water with the larger gull.