The smew (Mergellus albellus) is a species of duck and is the only living member of the genus Mergellus. The genus is closely related to Mergus and is sometimes included in it; genetic studies have shown that it is the sister taxon to Mergus and Lophodytes. The smew has hybridised with the common goldeneye (Bucephala clangula).
Taxonomy
The smew was formally described in 1758 by the Swedish naturalist Carl Linnaeus in the tenth edition of his Systema Naturae under the binomial name Mergus albellus. Linnaeus based his account on the description published in 1757 by another Swedish naturalist, Fredrik Hasselqvist, who collected one in Smyrna (now İzmir) in Turkey. Linnaeus specified the type locality as Europe but this was restricted to the Mediterranean near İzmir in Turkey on the basis of Hasselqvist's travels. The smew is now the only living species placed in the genus Mergellus that was introduced in 1840 by the English naturalist Prideaux Selby. The species is monotypic, with no subspecies recognised.
Etymology
The genus name Mergellus is a diminutive of Mergus, a Latin word related to mergo, to dive or submerge, used by Pliny for an unspecified diving bird. The specific epithet albellus is a Latin diminutive of meaning "white".
The term smew has been used since the 17th century and is of uncertain origin. It is believed to be related to the Dutch ("wigeon") and the German or , "wild duck". It is probably derived from smee, a dialectal term for a wild duck.
Description
thumb|left|Mergellus albellus female, Northumberland, England
The smew is long,
Adult drake smew, with its 'cracked ice' or 'panda' appearance, is unmistakable, and looks very black-and-white in flight. The females and immature males are grey, with chestnut forehead and crown, white chin and cheeks, and black lores; they are often known as "redhead" smew. Young males moult into adult plumage late in their first winter, when about 8–10 months old; adult males have an eclipse plumage when they become similar to females, but retaining more white in the wing, in late summer and autumn. It has oval white wing-patches in flight. The smew's bill has a hooked tip and serrated edges, which help it catch fish when it dives for them.