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< >  Mergellus albellus - Smew (Click photographs/illustrations: full picture & further details)
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General and References

Alternative Names (Synonyms)

Zwergsäger (German)
Harle piette (French)
Serrata chica (Spanish)
Bech de serra petit (Spanish)
Nonnetje (Dutch)
Salskrake (Swedish)
Mergus albellus

Names for newly-hatched

Duckling, downy.

Names for non-breeding males or other colour-phases


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Species Author

Debra Bourne

Major References

B1, B2, B3, B6, B8, B19, B25, B26, B27.

Other references:

Aviculture information:
J23.13.w4, J23.13.w8
B7, B29, B30, B40, B94, B129,
D1, D8

(UK Contacts)

(Further Reading)
Click image for full contents list of ELECTRONIC LIBRARY

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TAXA Group (where information has been collated for an entire group on a modular basis)

Parent Group

Specific Needs Group referenced in Management Techniques

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Aviculture Information


General information:
  • Seaducks are generally winter-hardy and sociable. They are preferably kept on a large area of clean, cold, deep water, at least some of which (preferably half the area) should be more than 60cm and preferably more than1m deep. As with other diving ducks, most species are relatively ungainly on land and ponds should have shallow sloping banks. Some cover along the pond edges will generally be appreciated. Preferred nesting sites vary greatly within this group, from open ground nesting to thick vegetation and tree holes.
  • Diets of grain, pellets fish and seafood may be used, also bread. These ducks generally need a higher-protein diet than most waterfowl species and high-protein pelleted diets specifically designed for seaducks are now available, although supplementation with fish may still be important particularly for breeding.
  • Feeding in troughs containing stones may avoid the development of overgrown bills. Provision of salt water may decrease the incidence of fungal and other infections.
  • Ducklings may be given high-protein starter crumbs and live food, and provided with access to deep water for swimming from an early age.
  • Mergansers, also known as "sawbills" and "fish ducks", require a large area of deep, clean water, with marginal vegetation providing cover along the edges. Very active and playful, the larger species may be belligerent and upset other ducks in a mixed collection. Breeders pellets, floating pellets and addition fish such as sprats or sand eels should be fed. These species are at particular risk from Foreign Body Ingestion, due to their tendency to pick up, play with and occasionally swallow, a wide variety of objects. Sawbills will nest in boxes or barrels, on the ground or raised, sometimes at a distance from water. Ducklings should be provided with access to swimming water from an early age.

(J23.13.w4, J23.13.w8, B7, B29, B40, B94, B129, D1)

Species-specific information:

  • Smew are winter-hardy and suitable for mixed collections; a large water area containing natural food is preferred and a high-protein diet should be provided.
  • They have been bred with some regularity, although they are not considered easy to rear. These small mergansers will nest in small raised barrels, hollow tree trunks or raised nestboxes, and may also lay in natural vegetation. One nest design uses a hollow tree trunk, approximately 1m high, with a roof, and a 7.5-10cm entrance hole about 23cm from the top, the floor being 30cm below the hole. This should be placed at the edge of the water with a ramp leading to the entrance hole (J23.13.w8). Eggs are usually laid May to June.
  • Ducklings may be difficult to rear. Starter crumbs may be supplemented with e.g. hard-boiled egg, trout fry, minced eel.
  • Hybrids reported with Goldeneye.

(J23.13.w8, B29, B30, B40B94, B97, B129).

Aviornis UK Ringing Scheme recommended average ring size: J 9.0mm (D8).

Individual Techniques linked in Wildpro

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External Appearance (Morphology)

Measurement & Weight

Length 14-16 inches 35-40cm (B3); 35-44cm (B1)
Adult weight General 515-935g (B1).
Male 540-935g (B3).
Female 515-650g (B3).
Newly-hatched weight --
Growth rate --

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Adult Male Greyish.
Variations (If present) --
Juvenile Greyish.

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Adult Male Head and neck white, shaggy drooping crest on crown to nape, black patch from bill to just behind eye, black around nape. Breast and underparts white with two black lines in inverted ‘V’ down sides of breast, flanks vermiculated grey; rump, tail and uppertail coverts grey. Upperparts black centrally otherwise mainly white: mantle black, scapulars white, tertials black (inner) and white (outer).

Wing blackish with white over median coverts and white tips to greater covers and secondaries.

Variations (If present) Female: upper parts of head and hindneck chestnut, darkest around eyes, lower part of head and neck, including chin and throat, white. Breast and flanks mottled grey shading into abdomen and undertail coverts white, upperparts and tail generally dark grey. Wing similar to male but less white

Eclipse: Similar to female but upperparts darker and retains more white on wing.

Juvenile Similar to female but underparts greyer and broader white tips to secondaries and greater coverts.

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Newly-hatched Characteristics

General: upperparts including upper breast black, underparts including face below eyes and spots on wings and sides white.
Bill: Dark grey.
Feet: Grey.

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Reproductive Season

Time of year Begins April/May.
No. of Clutches One.

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Nest placement and structure

In tree hollow (use nest boxes), lined with feathers and down.

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Egg clutches

No. of Eggs Average 7-9 (B1).
Range 5-11 (B1); 6-10 (B8).
Egg Description Cream to pale buff.

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26-28 days (B1, B8).

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About 70 days (B8).

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Sexual Maturity

Males Two years old.
Females Two years old.

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Feeding Behaviour

Adults Dive for food.
Newly-hatched --

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Parental Behaviour

Nest-building Solitary nests or in loose groups. Nest prepared by female.
Incubation By female only.
Newly-hatched Tended by female.


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Social Behaviour

Intra-specific Gregarious for most of the year.
Inter-specific --

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Sexual Behaviour

Seasonal monogamous pair bond. Male leaves female during incubation.

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Predation in Wild


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Activity Patterns

Circadian --

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Natural Diet


Aquatic invertebrates, particularly insects and larvae, also amphibians, fish, some plant material.

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Range and Habitat

Distribution and Movement (Migration etc.)

Normal Sweden eastward to east Siberia; winters in western and central Europe, eastern Mediterranean basin, Black Sea, southern former USSR, Middle East, Eastern China, Korea, Japan.

Migratory. Winters further south including Britain.

London: In the London Area, "winter visitor in highly variable numbers." In 2000, up to 166 individuals from 30 sites were reported in January, with the last birds leaving in march and the first winter arrivals in November. (J322.65.w1)

Occasional and Accidental




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Forested pools, lakes, slow rivers. Winters on larger lakes, estuaries, and coastal brackish lagoons.

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Intraspecific variation


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Conservation Status

Wild Population -

Reasonable numbers.

CITES listing --
Red-data book listing --
Threats Hunting, oil.

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Captive Populations

Common in collections, particularly in Europe.

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