A tiny, tiny duck.
Bufflehead female on Eel Pond a few days ago.
Bufflehead are North America’s smallest diving duck; they benefit by using old flicker nests that larger ducks such as goldeneyes and mergansers cannot fit into. In winter they occur mainly near the coast (although they can be found in smaller numbers inland). They use shallow, sheltered coves, harbors, estuaries, or beaches, avoiding open coastlines.
Amy's Bird Blog 