Smew (Mergellus albellus)


[order] ANSERIFORMES | [family] Anatidae | [latin] Mergellus albellus | [authority] Linnaeus, 1758 | [UK] Smew | [FR] Harle piette | [DE] Zwergsager | [ES] Serreta Chica | [NL] Nonnetje


Monotypic species


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).
An unnamed fossil seaduck, known from a humerus found in the Middle Miocene Sajovolgyi Formation (Late Badenian, 13?12 million years ago) of Matraszolos, Hungary, was assigned to Mergus. However, the authors included the Smew therein, and consequently, the bone is more properly assigned to Mergellus?especially as it was more similar to a Smew’s than to the Bucephala remains also found at the site. It is sometimes argued that the Matraszolos fossil is too old to represent any of the modern seaduck genera, but apparently these were all well-distinct even back then. The living species is known to exist since about 2 to 1.5 million years, as attested by fossils from the earliest Pleistocene found in England.

Physical charateristics

Male smews have a white crested head with a black face and v-shaped black patch beneath the crest. The back and rump are dark gray to black and the flanks are vermiculated white and black. The breast is white with two black stripes extending forward from the back. The wings are blackish-gray with white wing patches. The long narrow serrated bill is black and the legs and feet are grayish. Female: Female smews have a chestnut head with a white cheek patch, chin, and throat. The breast and flanks are dull gray and the upperparts are dark gray. The wings are dark gray with white wing patches. The bill, legs, and feet are similar to the males.

Listen to the sound of Smew


Copyright remark: Most sounds derived from xeno-canto

wingspan min.: 60 cm wingspan max.: 69 cm
size min.: 38 cm size max.: 44 cm
incubation min.: 26 days incubation max.: 28 days
fledging min.: 0 days fledging max.: 28 days
broods: 1   eggs min.: 6  
      eggs max.: 10  


Eurasia : widespread


Smews prefer forested wetland systems during breeding and winter on lakes, rivers, and estuaries, also on inland water.


The smew breeds from northern Scandinavia east through northern and central Russia and northern Siberia. There are no breeding records of the smew in North America. Smews prefer forested wetland systems where they nest in tree cavities or nest boxes and lay an average of 6 to 9 eggs.

Feeding habits

Smews dive to feed on small fishes and aquatic invertebrates

Video Smew


copyright: youtube


This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
Mergellus albellus breeds mainly in northern Russia and Fennoscandia, with Europe
accounting for less than a quarter of its global breeding range. Its European breeding
population is small (as few as 5,300 pairs), and its range contracted markedly between
1970-1990. Although most European populations-including the sizeable one in
Finland-were stable or increased during 1990-2000, the stronghold population in
Russia declined, and the species underwent a moderate decline (>10%) overall.
Smew status Least Concern


Migratory. Small to moderate numbers wintering northern parts Germany, also Denmark, Netherlands, and Britain, must account for breeders of Fenno-Scandia; but also some from north-west Russia. Dividing line in Russia between breeders migrating west to Baltic and North Seas, and much larger numbers going south to Balkans and south Russia, not known. Winters commonly Sea of Azov, with smaller numbers in western Black Sea, Hungary, northern Greece, and Turkey; on Caspian Sea largest flocks in west. Small numbers pass south from Caspian into Iraq and Iran. Additionally, occurs in winter irregularly or in very small numbers in southern Norway and Sweden, Ireland, Belgium, and (especially in hard weather) central and western European countries south to Mediterranean. Much rarer in western Mediterranean basin than in east.
Autumn departures from breeding areas begin September, completed early October; main passage through Swedish hinterland and Baltic countries mid-October to November, early records North Sea countries October but main arrivals not until December or January following cold weather further east. Proportion of adult males highest northern Germany, falling to south and west; in England females and juveniles far outnumber adult males. Return movement conspicuous by March, and most wintering waters vacated then; stragglers in April and even May, and immatures often summer south of breeding ranges.

Distribution map

Smew distribution range map

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