Bufflehead

The Bufflehead is a diminutive diving duck closely related to the two goldeneyes, but smaller than either. Our smallest diving duck. There one minute, gone the next, then bobbing up to the surface again like a cork, a busy Bufflehead can suggest a toy duck. Common in the winter months in Sonoma County. Found in freshwater lakes and ponds, brackish water, and sheltered ocean bays. Among the most abundant of winter ducks at such locations as Bodega Bay, Spring Lake, and Lake Ralphine. May start showing up as early as mid-October, but most start arriving in late October to early November. Numbers start to thin by late April the following year. Most are gone by early May, but a few may linger or stay over the summer. Frequently seen in small flocks. Although I've never noticed it personally, The Birder's Handbook notes that a "sentry" will usually stay above water scanning for trouble while companions are diving--something to look for. Unlike most diving ducks, the tiny Bufflehead can take off almost vertically. The common name is said to refer to the outsized head of this small duck. According to the National Wildlife Federation field guide, "Buffalo Head" and "Butterball" are regional names. Usually nests in abandoned Northern Flicker cavities.

Male Buffleheads are easily recognized by their large dark heads and white "bonnet." Often the head simply looks dark, aside from the white patch, especially at long distances. In most lights, the dark parts of the head will appear a deep iridescent green (above). In bright light and at close quarters, however, the head flashes a mix of iridescent blue, purple, green and gold (left). The bird's back is black, but the flanks and breast are snow white. A male Bufflehead looks whiter overall than any other duck we commonly see in the county. The proportionately small bill is a slightly bluish grey, darker at the base. The white bonnet and flanks make male Buffleheads easy to spot even at great distances.

Kenn Kaufman, usually right on the money with his descriptions, inexplicably says the female's head is grey in his Field Guide to Birds of North America. In reality, it's a rich brown with a distinctive white cheek patch (photo below). The female has a blue-grey bill similar to the male’s but duller. Otherwise, she's grey and brown--dark brown on the back and greyish brown along the flanks and paler at the breast. Beginners sometimes confuse female Buffleheads with non-breeding male Ruddy Ducks, but the silhouettes of the two birds are quite different (note the Ruddy Duck's comically large, flat bill), and the Ruddy Duck has an almost entirely white cheek rather than a white cheek patch (photo below). Female Ruddy Ducks, meanwhile, have a pale brownish-grey cheek with a brown line through it.

The challenges of female duck identification (includes a quiz)