Male buffleheads have an iridescent green and purple head with a large white patch that extends around the back of the head. (Photo: Karl Niemi)

The buffleheads have arrived! What’s a bufflehead, you ask? Buffleheads (Bucephala albeola) are small, energetic diving ducks found in Massachusetts during the winter. They are North America’s smallest diving duck – weighing about a pound. These ducks are often found in pairs or small groups; they do not gather in large flocks. The name comes from the word buffle, an obsolete variant of buffalo. This duck has a large, puffy, buffalolike head compared with its small body.

In the spring and summer, buffleheads breed near ponds and lakes in western and central Canada. They prepare for their fall migration by putting on fat reserves. By the time they begin migrating south in the fall, more than a quarter of their body weight is fat that they use for fuel during their arduous journey. When the first freeze hits in the north, buffleheads fly south at night to overwinter where the water is not frozen. Buffleheads from central Canada move east across the prairies toward the Atlantic Ocean. They stop over in Minnesota and Wisconsin, Lake Erie and finally the Atlantic coast. Each stopover is about 500 miles apart – a distance these fast fliers can cover in one night. Buffleheads overwinter in Massachusetts from October to April.

Female buffleheads have a dark brown head with a small white patch under and behind the eyes. (Photo: Karl Niemi)

These diving ducks feed on aquatic insects (such as dragonflies and their larvae), small fish, mollusks (snails, clams, mussels) and crustaceans (crabs, shrimp). Unlike dabbling ducks that feed at the surface, buffleheads forage underwater, and swallow their food whole there. A group may dive all at the same time, though not through vegetation; they feed in areas without dense underwater plant growth, yet in the fall and winter, they may eat some bulrush or pondweed seeds.

The legs of diving ducks are set farther back on their bodies than those of dabbling ducks, which helps propel them through the water but makes them clumsy on land. For this reason, you will rarely see this duck on land. A female waddles on land only when leading her just-hatched ducklings to water, or when she and her ducklings need to change ponds. Similarly, they have large bodies compared with their wings, so they run along the water during takeoff. Once airborne, they are strong fliers.

A male bufflehead splashes to chase away another male in Stoneham on Nov. 22. (Photo: Karl Niemi)

Even though buffleheads breed in the far north, they begin their courtship displays in the winter. These displays become more intense as spring approaches. These ducks are usually quiet, but while courting, the males get louder. A male drives away other males by rushing or diving at the interloper and coming up beneath him in the water. He splashes vigorously and chatters loudly. If you see a lot of splashing in a winter pond, look closely – it might be two sparring male buffleheads. To court females, the male raises the feathers on its head and lifts its wings. It flies over a female and lands with its feet and wings outstretched (called water skiing because of its resemblance to this activity). Unlike most ducks, buffleheads are monogamous: pairs stay together for several years.

A bufflehead takes off from the Charles River in Cambridge on Jan. 26, 2021. (Photo: D. Dentzer)

As soon as northern ponds thaw In the spring, buffleheads migrate again – this time to Canadian breeding grounds. Most pairing occurs during the migration, and by the time they arrive, couples have been united or reunited. Because there are more males than females, a fair number of males remain unpaired. Unlike other ducks, buffleheads usually do not nest near rivers or large lakes, which might have pike in them that often feed on baby ducklings. Buffleheads are especially vulnerable because of their small size.

A male bufflehead takes flight in Stoneham on Nov. 22. (Photo: Karl Niemi)

Soon after arrival at the breeding ground, females find a nesting cavity in an aspen or poplar tree – usually left by a northern flicker. Little buffleheads are the only tree-nesting ducks that can use flicker cavities for nests. The female lines the hole with down from her chest and lays eight to 10 eggs, one every day or two. After she lays the last one, the male leaves the female to molt. The female raises the young on her own. She keeps the eggs warm until they hatch in about a month.

A day or two after the chicks hatch, the mother encourages the youngsters to jump out of the tree cavity, which is two to 10 feet off the ground, then leads the ducklings to water. The chicks feed themselves, but the mother keeps them warm as needed. If the weather gets too cold or wet, young chicks may die, and chicks that get separated from their mother may join another family. Sometimes two families merge. Predators eat about half the youngsters before they are two months old. At 50 days, the youngsters may try their first flight. In two years, these chicks will be setting up nest sites of their own.

A bufflehead flies in Stoneham on Nov. 22. (Photo: Karl Niemi)

In late summer, adult birds retreat to their favorite lakes to molt, and cannot fly for those three weeks in July or August. By September, all buffleheads – young and old – have their fall plumage. They work to build up their fat reserves in preparation for their southern migration.

If you get a photograph of a bufflehead, consider yourself lucky: Unlike mallards, these fast-moving ducks move away from shore when people appear, diving frequently. In addition, it is difficult to get the dark parts of their head properly exposed without overexposing the white parts of the head.

A male and female bufflehead on the water in Revere on Jan. 22. (Photo: Richard George)

Reliance on the cavities of northern flickers for nest sites means this bird cannot breed in prairies or tundra, and its size makes it difficult to nest in areas with dense ground vegetation. Therefore, this bird nests in open forest areas threatened by logging and wildfires. Buffleheads are also easy to shoot, and hunters kill about 250,000 a year. They are one of the scarcest ducks in North America – and to the delight of birdwatchers, the population appears to be stable.

Have you taken photos of our urban wild things? Send your images to Cambridge Day, and we may use them as part of a future feature. Include the photographer’s name, date and the general location where the photo was taken as well as any other relevant information.

Jeanine Farley is an educational writer who has lived in the Boston area for more than 30 years. She enjoys taking photos of our urban wild things.