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General and References

Alternative Names (Synonyms)

American merganser
Fish duck
Gänsesäger (German)
Harle bièvre (French)
Serrata grande (Spanish)
Mergánsar (Spanish)
Grote Zaagbek (Dutch)
Storkrake (Swedish)
Mergus merganser merganser Eurasian goosander
Mergus merganser comatus Oriental goosander
Mergus merganser americanus American goosander

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.

Aviculture information:
J23.13.w4, J23.13.w7, J23.13.w8
B7, B29, B30, B40, B94, B97, B128.w1, 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:

  • Common merganser (Goosander) drakes may be aggressive to smaller species, but may be kept with swans, geese and large ducks. They may kill and eat ducklings and even very small teal; provision of a separate pen may be preferable. A large stretch of water in which they can catch their own food is ideal. A high-protien diet should be fed, supplemented with fish such as whitebait and sand eels.
  • These ducks are bred sporadically. Raised nest boxes should be provided, and these ducks often lay in boxes already being used by other species. Nest boxes should be set on poles 0.7 to 1.0metres above water, facing into the pond and with a ramp to within 5cm of the entrance hole. Suggested box size 45cm by 30cm by 30cm (18 by 12 by 12 inches), with an entrance hole up to 13cm diameter close to the top of the box, and soil (5cm deep), peat (2.5cm deep) and a handful of dry grass in the bottom (J23.13.w4); (12x12x14 inches i.e. 30x30x40cm, with a 4 inch (10cm) entrance hole also suggested B128.w1) Eggs are usually laid April to May.
  • Parent rearing is likely to result in large losses from predation, lack of natural food and aggression of other waterfowl. A broody or artificial incubator may be used. Starter crumbs ground and made into a mash, may be made more attractive initially with finely chopped hard boiled egg and livefood such as mealworms, although the ducklings should be encouraged to feed mainly on the mash. A solitary duckling is unlikely to do well and should be placed with other, similar-sized ducklings.
  • Hybridisation reported with Lophodytes cucullatus - Hooded merganser, Bucephala clangula - Common goldeneye, Anas platyrhynchos - Mallard and Aythya americana - Redhead.

(J23.13.w4, J23.13.w7, B29, B30, B40, B94, B97, B128.w1, B129, D1).)

Aviornis UK Ringing Scheme recommended average ring size: N 13.0mm (D8).

Individual Techniques linked in Wildpro

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External Appearance (Morphology)

Measurement & Weight

Length 21-27 inches 51-68cm (B3); 58-66cm
Adult weight General 898-2160g (B1).
Male Average about 1600g (B3).
Female Average about 1200g (B3).
Newly-hatched weight --
Growth rate --

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Adult Bill Male Red with blackish dorsal stripe (culmen and nail).
Variations (If present) --
Eyes (Iris) Male Brown.
Variations(If present) --
Juvenile Bill Red with blackish dorsal stripe (culmen and nail).
Eyes (Iris) Brown.

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Adult Male Deep red.
Variations (If present) --
Juvenile Deep red.

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Adult Male
Click Illustration for full-page view
Head and upper neck glossy green-black with smooth ‘puffy’ crest. Lower neck, breast, flanks creamy (all washed pink), underparts creamy, tail, upper tailcoverts, and rump mid-grey. Upperparts white with black centrally (mantle and inner scapulars).

Wings black outer parts, white inner with black markings on inner secondaries.

Variations (If present)
Click Illustration for full-page view
Female: head and upper neck, cinnamon, including slightly-ragged crest, darkest on head above eyes, white chin and throat, otherwise grey, upperparts darker, central underparts white. Wing ash-grey with black primaries and primary coverts, white secondaries and greater coverts.

Eclipse: similar to female but male wing pattern, whiter flanks, blacker mantle.

Mergus merganser americana: black line across base of greater coverts.

Juvenile Duller, less patterned.

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Newly-hatched Characteristics

General: Upperparts dark brown, crown to below eyes tawny brown, white patches on wings and back, underparts white. Blackish line bill to eyes and from below nape to eyes, divided by light tawny ban, rest of cheeks and sides of neck chestnut.
Bill: Yellow-brown.
Feet: Yellow-brown.

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Reproductive Season

Time of year Begins March-May.
No. of Clutches One. Re-nests if clutch lost.

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Nest placement and structure

Treehole or other cavity (use nestboxes if provided), down-lining.

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Egg clutches

No. of Eggs Average 8-12 (B1).
Range 6-17 (B1); 8-15 (B8).
Egg Description Ivory to very pale buff.

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30-32 days (B1); 30-35 days (B8).

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60-70 days (B1, B8).

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Sexual Maturity

Males Two years old.
Females Two years old.

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Feeding Behaviour

Adults Dive from surface (scan with submerged head), occasionally feed on surface.
Newly-hatched --

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Parental Behaviour

Nest-building Solitary or in loose groups. Nest prepared by female.
Incubation By female.
Newly-hatched Tended by female, brooded at night when small, sometimes carried on the back.

Become independent about fledging time.

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Social Behaviour

Intra-specific Mainly gregarious.
Inter-specific --

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Sexual Behaviour

Seasonal pair bond, possibly occasional polygamy.

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Predation in Wild


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Activity Patterns

Circadian Crepuscular (dawn and evening) feeding.

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Natural Diet


Fish main part of diet, also aquatic invertebrates, amphibians, small mammals and birds. Little plant material.

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Range and Habitat

Distribution and Movement (Migration etc.)

  • Mergus merganser merganser Palearctic. Iceland eastward to Kamchatka and southward to central Europe, northern China, northern Japan
  • Mergus merganser orientalis Central Asia (north-eastern Afghanistan eastward through Tibet and Himalayas to western China)
  • Mergus merganser americana North America: Alaska to Newfoundland, southward to northern and western USA.

Partially migratory: birds from most northerly areas move to lower latitudes. South as far as Mexico, Mediterranean basin, southern areas of former USSR, northern India, south-east Asia.

London: In the London Area, "regular winter visitor, very rare in summer." In 2000, seen at 63 sites, with a few tens of birds on some reservoirs in January to march, and December. (J322.65.w1)

Occasional and Accidental

Occasionally seen further south.



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Clear freshwater lakes, pools, rivers, preferably with trees nearby. Winter large unfrozen lakes, rivers, lagoons, and brackish marshes.

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Intraspecific variation


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Conservation Status

Wild Population -

Not threatened (B1).

CITES listing --
Red-data book listing --
Threats Persecuted by anglers and fish farmers (B1).

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Captive Populations

Fairly scarce in collections (B8).

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