The Bufflehead (Bucephala albeola) is a small American sea duck of the genus Bucephala, the goldeneyes. 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 United States. The Bufflehead is an extremely rare vagrant to western Europe. Their breeding habitat is wooded lakes and ponds in Alaska and Canada, almost entirely included in the boreal forest or taiga habitat.
Buffleheads have evolved their small size in order to fit the nesting cavity of their "metabiotic" host, a woodpecker, the Northern Flicker. Due to their small size, they are highly active, undertaking dives almost continuously to sustain their high metabolism. They do not tend to collect in large flocks; groups are usually limited to small numbers. One duck will serve as a sentry, watching for predators as the others in the group dive in search of food.
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.
Source: en.wikipedia.org/wiki/Bufflehead - 0.910.2010