The bufflehead (Bucephala albeola) is a small sea duck of the genus Bucephala, the goldeneyes. This species was first described by Carl Linnaeus in his landmark 1758 10th edition of Systema Naturae as Anas albeola. The genus name of this species is derived from ancient Greek and refers to the oddly bulbous head shape of the bird. The English name is a combination of buffalo and head, again referring to the head shape. This is most noticeable when the male puffs out the feathers on the head, thus greatly increasing the apparent size of the head.
Adult males of this species are striking black and white, with iridescent green and purple heads and a large white patch behind the eye. Females are grey-toned with a smaller white patch behind the eye and a light underside. Averaging 35.5 cm (14.0 in) and 370 g (13 oz), the bufflehead rivals the Green-winged teal as the smallest American duck.
Buffleheads breed in Alaska and Canada and spend the winter on the east and west coasts of North America and the southern United States. Their breeding habitat is wooded lakes and ponds, almost entirely included in the boreal forest or taiga habitat. On their wintering grounds, these ducks are usually found in protected coastal waters, or open inland waters.
Buffleheads spend all their life in water and only females can be seen on land when they lead their newly hatched ducklings from the nest to the water. They are diurnal birds spending the day swimming, feeding, preening, and sleeping. Due to their small size, buffleheads are highly active, undertaking dives almost continuously while sustained by their high metabolism. They do not tend to collect in large flocks; groups are usually limited to small numbers. One duck serves as a sentry, watching for predators as the others in the group dive in search of food. They prefer water depths of 1.2-4.5 m (3.9-14.8 ft) and can remain under the water for 12-20 seconds. Buffleheads are amongst the last waterfowl to leave their breeding grounds and one of the world's most punctual migrants, arriving on their wintering grounds within a narrow margin of time.
Buffleheads are mainly carnivores. In freshwater habitats, they eat primarily insects, and in saltwater, they feed predominantly on crustaceans and mollusks. Aquatic plants and fish eggs can often become locally important food items, as well.
Buffleheads are monogamous and form pairs that remain together for many years. They breed from late winter until early April. The females may return to the same nest site, year after year. They nest in cavities in trees, primarily aspens or poplars, using mostly old flicker nests, close to water. The average clutch size is 6 to 11 eggs and incubation averages 30 days. During the incubation period, the males leave their mates in order to molt. A day after the last duckling hatches, the brood leaps from the nest cavity, and the female leads them to water. The young typically fledge at 50-55 days of age.
Habitat degradation is the major threat to these beautiful ducks since they depend on very limited coastal habitats on their wintering grounds and very specific habitats on their boreal breeding grounds. Although buffleheads do use man-made nest boxes, they still need the forest habitat to thrive.
According to the IUCN Red List, the total population size of the bufflehead is above 1,200,000 individuals. Its population in Japan includes below 50 wintering individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List, and its numbers today are increasing.
