Smew
Scientific Name: Mergellus albellus
The Smew (Mergellus albellus) is a small duck, which is somewhat intermediate between the typical mergansers (Mergus) and the goldeneyes (Bucephala). It is the only member of the genus Mergellus; sometimes included in Mergus, this genus is distinct (though closely related) and might actually be a bit closer to the goldeneyes. The Smew has interbred with the Common Goldeneye (B. clangula). (source: Wikipedia)
