The Bufflehead - Bucephala albeola - is a small American sea duck and it rivals the Green-winged teal as the smallest American duck.

Adult males are striking black and white, with iridescent green and purple heads with a large white patch behind the eye. Females are grey-toned with a smaller white patch behind the eye and a light underside.

The name Bufflehead is a combination of buffalo and head, referring to the oddly bulbous head shape of the species. This is most noticeable when the male puffs out the feathers on the head, thus greatly increasing the apparent size of the head.

They are migratory and most of them winter in protected coastal waters, or open inland waters, on the east and west coasts of North America and the southern USA. The Bufflehead is an extremely rare vagrant to western Europe and Asia. Their breeding habitat is wooded lakes and ponds in Alaska and Canada, almost entirely included in the boreal forest or taiga habitat.

Buffleheads are monogamous, and the females return to the same breeding site, year after year. They nest in cavities in trees, primarily aspens or poplars.

Average clutch size is 9 (range 6–11), and eggs average 50.5 by 36.3 mm. Incubation averages 30 days, and nest success is high (79% in one study) compared to ground-nesting species like the Teal. A day after the last duckling hatches the brood leaps from the nest cavity.

These diving birds forage underwater. 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 one of the most popular birds amongst bird watchers. 

Habitat degradation is the major threat to this bird, since they depend on very limited coastal habitat on their wintering grounds, and very specific habitat in their boreal breeding grounds .