Bufflehead are very small, compact ducks with large, rounded heads and short, wide bills. They measure 32 to 40 centimeters in length, with a wingspan of approximately 55 centimeters. Adult male Bufflehead have a white body, black back, and a dark head with a large white patch that wraps around the back of the head. Females and first-year males are gray-brown overall with an oval, white cheek patch. In flight adult males have a large white patch on the upperwing; females and first-year males have a smaller white wing patch. Bufflehead dive underwater to catch aquatic invertebrates. When courting females, male Buffleheads swim in front of them, rapidly bobbing their heads up and down. In flight, you can identify Bufflehead by noting their small size, fast wingbeats, and pattern of rocking side-to side as they fly. Bufflehead are most widespread in migration and winter, when they move south to coasts and large bodies of water, particularly shallow saltwater bays. They breed near lakes in northern forests where conifers mix with poplars or aspens. Bufflehead nest in tree cavities, especially old Northern Flicker holes. This species is of low conservation concern.
Unlike most ducks, the Bufflehead is mostly monogamous, often remaining with the same mate for several years.
Bufflehead fossils from the late Pleistocene (about 500,000 years ago) have been found in Alaska, California, Florida, Illinois, Kansas, Texas, and Washington. One California fossil that resembles a modern Bufflehead dates to the late Pliocene, two million years ago.
Bufflehead normally live only in North America, but in winter they occasionally show up elsewhere, including Kamchatka, Japan, Greenland, Iceland, the British Isles, Belgium, France, Finland, and Czechoslovakia. In some of these cases, the birds may have escaped from captivity.
Source: Bufflehead Overview and Identification Information, All About Birds, The Cornell Lab of Ornithology