Mergus
Encyclopedia
Mergus is the genus
of the typical mergansers, fish-eating duck
s in the seaduck subfamily (Merginae). The Hooded Merganser
, often termed Mergus cucullatus, is not of this genus but closely related. The other "aberrant" merganser, the Smew
(Mergellus albellus), is phylogenetically closer to goldeneye
s (Bucephala).
Although they are seaducks, most of the mergansers prefer riverine habitats, with only the Red-breasted Merganser being common at sea. These large fish-eaters typically have black-and-white, brown and/or green hues in their plumage, and most have shomewhat shaggy crests. All have serrated edges to their long and thin bills that help them grip their prey
. Along with the Smew
and Hooded Merganser
, they are therefore often known as "sawbills". The goldeneyes, on the other hand, feed mainly on mollusks, and therefore have a more typical duck-bill. They are also classified as "divers" because they go completely under-water in looking for food. In other traits, however, the genera Mergus, Lophodytes, Mergellus, and Bucephala are very similar; uniquely among all Anseriformes
, they do not have notches at the hind margin of their sternum
, but holes surrounded by bone.
Some fossil
members of this genus have been described:
The Early Oligocene
booby
"Sula" ronzoni was at first mistakenly believed to be a typical merganser. A Late Serravallian
(13–12 million years ago) fossil sometimes attributed to Mergus, found in the Sajóvölgyi Formation of Mátraszõlõs, Hungary
, probably belongs to Mergellus. The affiliations of the mysterious "Anas" albae from the Messinian
(c.7–5 million years ago) of Hungary are undetermined; it was initially believed to be a typical merganser too.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of the typical mergansers, fish-eating 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...
s in the seaduck subfamily (Merginae). The 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...
, often termed Mergus cucullatus, is not of this genus but closely related. The other "aberrant" merganser, the 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), is phylogenetically closer to goldeneye
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....
s (Bucephala).
Although they are seaducks, most of the mergansers prefer riverine habitats, with only the Red-breasted Merganser being common at sea. These large fish-eaters typically have black-and-white, brown and/or green hues in their plumage, and most have shomewhat shaggy crests. All have serrated edges to their long and thin bills that help them grip their prey
Piscivore
A piscivore is a carnivorous animal which eats primarily fish. Piscivory was the diet of early tetrapods , insectivory came next, then in time reptiles added herbivory....
. Along with the 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...
and 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...
, they are therefore often known as "sawbills". The goldeneyes, on the other hand, feed mainly on mollusks, and therefore have a more typical duck-bill. They are also classified as "divers" because they go completely under-water in looking for food. In other traits, however, the genera Mergus, Lophodytes, Mergellus, and Bucephala are very similar; uniquely among all Anseriformes
Anseriformes
The order Anseriformes contains about 150 living species of birds in three extant families: the Anhimidae , Anseranatidae , and the Anatidae, which includes over 140 species of waterfowl, among them the ducks, geese, and swans.All species in the order are highly adapted for an aquatic existence at...
, they do not have notches at the hind margin of their sternum
Sternum
The sternum or breastbone is a long flat bony plate shaped like a capital "T" located anteriorly to the heart in the center of the thorax...
, but holes surrounded by bone.
Species
- †Auckland Merganser, Mergus australis (extinctExtinctionIn biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
, c.1902) - Common MerganserCommon MerganserThe 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 - Brazilian MerganserBrazilian MerganserThe 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 - Red-breasted MerganserRed-breasted MerganserThe 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 - Scaly-sided Merganser, Mergus squamatus
Some fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
members of this genus have been described:
- †Mergus miscellus is known from the Middle MioceneMioceneThe Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
Calvert Formation (BarstovianBarstovianThe Barstovian North American Stage on the geologic timescale is the North American faunal stage according to the North American Land Mammal Ages chronology , typically set from 16,300,000 to 13,600,000 years BP, a period of . It is usually considered to overlap the Langhian and Serravallian...
, c.14 million years ago) of VirginiaVirginiaThe Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...
, USAUnited StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
. - †Mergus connectens lived in the Early PleistoceneEarly PleistoceneCalabrian is a subdivision of the Pleistocene Epoch of the Geologic time scale. ~1.8 Ma.—781,000 years ago ± 5,000 years, a period of ~.The end of the stage is defined by the last magnetic pole reversal and plunge in to an ice age and global drying possibly colder and drier than the late Miocene ...
about 2–1 million years ago, in Central and Eastern Europe.
The Early Oligocene
Oligocene
The Oligocene is a geologic epoch of the Paleogene Period and extends from about 34 million to 23 million years before the present . As with other older geologic periods, the rock beds that define the period are well identified but the exact dates of the start and end of the period are slightly...
booby
Booby
A booby is a seabird in the genus Sula, part of the Sulidae family. Boobies are closely related to the gannets , which were formerly included in Sula.-Description:...
"Sula" ronzoni was at first mistakenly believed to be a typical merganser. A Late Serravallian
Serravallian
The Serravallian is in the geologic timescale an age or a stage in the middle Miocene epoch/series, that spans the time between 13.65 ± 0.05 Ma and 11.608 ± 0.005 Ma...
(13–12 million years ago) fossil sometimes attributed to Mergus, found in the Sajóvölgyi Formation of Mátraszõlõs, Hungary
Hungary
Hungary , officially the Republic of Hungary , is a landlocked country in Central Europe. It is situated in the Carpathian Basin and is bordered by Slovakia to the north, Ukraine and Romania to the east, Serbia and Croatia to the south, Slovenia to the southwest and Austria to the west. The...
, probably belongs to Mergellus. The affiliations of the mysterious "Anas" albae from the Messinian
Messinian
The Messinian is in the geologic timescale the last age or uppermost stage of the Miocene. It spans the time between 7.246 ± 0.005 Ma and 5.332 ± 0.005 Ma...
(c.7–5 million years ago) of Hungary are undetermined; it was initially believed to be a typical merganser too.