The seaducks, Merginae, form a subfamily of the duck

Duck

Duck is the common name for a large number of species in the Anatidae family of birds, which also includes swans and geese. The ducks are divided among several subfamilies in the Anatidae family; they do not represent a monophyletic group but a form taxon, since swans and geese are not considered...

, goose

Goose

The word goose is the English name for a group of waterfowl, belonging to the family Anatidae. This family also includes swans, most of which are larger than true geese, and ducks, which are smaller....

 and swan

Swan

Swans, genus Cygnus, are birds of the family Anatidae, which also includes geese and ducks. Swans are grouped with the closely related geese in the subfamily Anserinae where they form the tribe Cygnini. Sometimes, they are considered a distinct subfamily, Cygninae...

 family of bird

Bird

Birds are feathered, winged, bipedal, endothermic , egg-laying, vertebrate animals. Around 10,000 living species and 188 families makes them the most speciose class of tetrapod vertebrates. They inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from...

s, Anatidae

Anatidae

Anatidae is the biological family of birds that includes ducks, geese and swans. The family has a cosmopolitan distribution, occurring on all the world's continents except Antarctica and on most of the world's islands and island groups...

.

As the name implies, most but not all, are essentially marine outside the breeding season. Many species have developed specialized salt glands to allow them to tolerate salt water, but these have not yet developed in young birds. Some of the mergansers prefer riverine habitats.

All but two of the 20 species in this group occupy habitats in far northern latitudes.

The fish-eating members of this group, such as the mergansers and Smew, have serrated edges to their bills to help them grip their prey. These are therefore often known as "sawbills".

Other seaducks take molluscs or crustaceans from the sea floor.

There are twenty living species in ten extant genera.

Subfamily Merginae

• Genus Chendytes, the diving-geese. These birds became extinct in prehistoric times. They were large, goose-like ducks with reduced wings which were unfit for flying, but could assist in diving as in the Great Auk
  Great Auk
  The Great Auk, Pinguinus impennis, formerly of the genus Alca, was a large, flightless alcid that became extinct in the mid-19th century. It was the only modern species in the genus Pinguinus, a group of birds that formerly included one other species of flightless giant auk from the Atlantic Ocean...
  
  . At least one species survived to the Holocene
  Holocene
  The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
  
  .
  • Chendytes lawi
• Genus Polysticta
  • Steller's Eider
    Steller's Eider
    The Steller's Eider is a medium-large sea duck that breeds along the Arctic coasts of eastern Siberia and Alaska. The lined nest is built on tundra close to the sea, and 6-10 eggs are laid....
    
     Polysticta stelleri
• Genus Somateria, the eiders. These are large marine ducks The drakes have body plumage showing varying amounts of black and white, and distinctive head patterns.Females are brown.
  • Common Eider
    Common Eider
    The Common Eider, Somateria mollissima, is a large sea-duck that is distributed over the northern coasts of Europe, North America and eastern Siberia. It breeds in Arctic and some northern temperate regions, but winters somewhat farther south in temperate zones, when it can form large flocks on...
    
     Somateria mollissima
  • Spectacled Eider
    Spectacled Eider
    The Spectacled Eider is a large sea duck that breeds on the coasts of Alaska and northeastern Siberia.The lined nest is built on tundra close to the sea, and 5–9 eggs are laid. This species dives for crustaceans and molluscs...
    
     Somateria fischeri
  • King Eider
    King Eider
    The King Eider is a large sea duck that breeds along northern hemisphere Arctic coasts of northeast Europe, North America and Asia. The birds spend most of the year in coastal marine ecosystems at high latitudes, and migrate to Arctic tundra to breed in June and July...
    
     Somateria spectabilis
• Genus Histrionicus
  • Harlequin Duck
    Harlequin Duck
    The Harlequin Duck is a small sea duck. It takes its name from Arlecchino, Harlequin in French, a colourfully dressed character in Commedia dell'arte. The species name comes from the Latin word "histrio", "actor". In North America it is also known as Lords and ladies...
    
     Histrionicus histrionicus
• Genus Camptorhynchus
  • Labrador Duck
    Labrador Duck
    The Labrador Duck was a striking black and white eider-like sea duck that was never common, and is believed to be the first bird to become extinct in North America after 1500. The last Labrador Duck is believed to have been seen at Elmira, New York on December 12, 1878; the last preserved specimen...
    
     Camptorhynchus labradorius
• Genus Melanitta, the scoters. These are stocky marine ducks. The drakes are mostly black and have swollen bills. Females are brown.
  • Common Scoter
    Common Scoter
    The Common Scoter is a large sea duck, 43-54 cm in length, which breeds over the far north of Europe and Asia east to the Olenyok River. The American/E Siberian M. americana is sometimes considered a subspecies of M. nigra.It winters further south in temperate zones, on the coasts of Europe as...
    
     Melanitta nigra
  • Black Scoter
    Black Scoter
    The Black or American Scoter is a large sea duck, 43 to 49 centimeters in length. Together with the Common Scoter M. nigra, it forms the subgenus Oidemia; the two are sometimes considered conspecific, the Black Scoter then being referred to as M. nigra americana...
    
     or American Scoter Melanitta americana (sometimes considered a subspecies
    Subspecies
    Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
    
     of M. nigra)
  • Velvet Scoter
    Velvet Scoter
    The Velvet Scoter , also called a Velvet Duck or whitewing , is a large sea duck, which breeds over the far north of Europe and Asia west of the Yenisey basin. A small, isolated population nests in eastern Turkey...
    
     Melanitta fusca
  • White-winged Scoter
    White-winged Scoter
    The White-winged Scoter is a large sea duck.-Description:It is characterised by its bulky shape and large bill. This is the largest species of scoter. Females range from 950-1950 grams and 48–56 cm , averaging 1180 grams and 52.3 cm . She is brown with pale head patches...
    
     Melanitta deglandi (sometimes considered a subspecies of M. fusca)
  • Surf Scoter
    Surf Scoter
    The Surf Scoter is a large sea duck, which breeds in Canada and Alaska. It is placed in the subgenus Melanitta, along with the Velvet and White-winged Scoters, distinct from the subgenus Oidemia, Black and Common Scoters.It winters further south in temperate zones, on the coasts of the northern USA...
    
     Melanitta perspicillata
• Genus Clangula
  • Long-tailed Duck
    Long-tailed Duck
    The Long-tailed Duck or Oldsquaw is a medium-sized sea duck. It is the only living member of its genus, Clangula; this was formerly used for the goldeneyes, with the Long-tailed Duck being placed in Harelda...
    
     or Oldsquaw Clangula hyemalis
• Genus Bucephala
  Goldeneye (duck)
  Goldeneye are small tree-hole nesting northern hemisphere seaducks belonging to the genus Bucephala. Their plumage is black and white, and they eat fish, crustaceans and other marine life....
  
  , the goldeneyes. These are less marine than some species in this group, and will winter on fresh water. Drakes have white bodies with black backs and distinctive head markings. Females are grey with chestnut heads.
  • Common Goldeneye
    Common Goldeneye
    The Common Goldeneye is a medium-sized sea duck of the genus Bucephala, the goldeneyes. Their closest relative is the similar Barrow's Goldeneye....
    
     Bucephala clangula
  • Barrow's Goldeneye
    Barrow's Goldeneye
    Barrow's Goldeneye is a medium-sized sea duck of the genus Bucephala, the goldeneyes. This bird was named after Sir John Barrow....
    
     Bucephala islandica
  • Bufflehead
    Bufflehead
    The Bufflehead is a small American sea duck of the genus Bucephala, the goldeneyes. This species was first described by Linnaeus in his Systema naturae in 1758 as Anas albeola.-Description:...
    
     Bucephala albeola
• Genus Mergellus (sometimes included in Mergus)
  • Smew
    Smew
    The Smew is a small duck, which is somewhat intermediate between the typical mergansers and the goldeneyes . It is the only member of the genus Mergellus; sometimes included in Mergus, this genus is distinct and might actually be a bit closer to the goldeneyes...
    
     Mergellus albellus
• Genus Lophodytes (sometimes included in Mergus)
  • Hooded Merganser
    Hooded Merganser
    The Hooded Merganser is a small duck and is the only member of the genus Lophodytes.Hooded Mergansers have a crest at the back of the head which can be expanded or contracted. In adult males, this crest has a large white patch, the head is black and the sides of the duck are reddish-brown...
    
     Lophodytes cucullatus
• Genus Mergus
  Mergus
  Mergus is the genus of the typical mergansers, fish-eating ducks in the seaduck subfamily . The Hooded Merganser, often termed Mergus cucullatus, is not of this genus but closely related...
  
  , the typical mergansers. These are the least marine of this group, only Red-breasted being common on the sea. These are large saw-billed ducks which dive for fish.
  • Brazilian Merganser
    Brazilian Merganser
    The Brazilian Merganser, Mergus octosetaceus, is a duck in the typical merganser genus.It is one of the six most threatened waterfowl in the world with possibly fewer than 250 birds in the wild and none kept in captivity...
    
     Mergus octosetaceus
  • Auckland Merganser Mergus australis
  • Red-breasted Merganser
    Red-breasted Merganser
    The Red-breasted Merganser is a diving duck.-Taxonomy:The Red-breasted Merganser was one of the many species originally described by Linnaeus in his 18th-century work, Systema Naturae.-Description:...
    
     Mergus serrator
  • Common Merganser
    Common Merganser
    The Common Merganser or Goosander Mergus merganser is a large duck, of rivers and lakes of forested areas of Europe, northern and central Asia, and North America. It eats fish and nests in holes in trees...
    
     or Goosander Mergus merganser
  • Scaly-sided Merganser Mergus squamatus