Anatinae

The Anatinae are a subfamily of the family Anatidae (swans, geese and ducks). Its surviving members are the dabbling ducks, which feed mainly at the surface rather than by diving. The other members of the Anatinae are the extinct moa-nalo, a young but highly apomorphic lineage derived from the dabbling ducks.

There has been much debate about the systematical status and which ducks belong to the Anatinae. Some taxonomic authorities only include the dabbling ducks and their close relatives, the extinct moa-nalos. Alternatively,[1] the Anatinae are considered to include most "ducks", and the dabbling ducks form a tribe Anatini within these. The classification as presented here more appropriately reflects the remaining uncertainty about the interrelationships of the major lineages of Anatidae (waterfowl).[2]

Dabbling ducks
Temporal range: Late Miocene–present
Pacificblackduck
Pacific black duck (Anas superciliosa)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Anseriformes
Family: Anatidae
Subfamily: Anatinae
Leach, 1820
Type species
Anas platyrhynchos
Genera

See text

Systematics

The dabbling duck group, of worldwide distribution, was delimited in a 1986 study[3] to include eight genera and some 50–60 living species. However, Salvadori's teal is almost certainly closely related to the pink-eared duck, and other genera are likewise of unresolved affiliation.[2][4] The peculiar marbled duck, formerly tentatively assigned to the dabbling ducks, is thought to be a diving duck or even a distinct subfamily.[2]

This group of ducks has been so named because its members feed mainly on vegetable matter by upending on the water surface, or grazing, and only rarely diving. These are mostly gregarious ducks of freshwater or estuaries. These birds are strong fliers and northern species are highly migratory. Compared to other types of duck, their legs are placed more towards the centre of their bodies. They walk well on land, and some species feed terrestrially.

"Puddle ducks" generally feed on the surface of the water or feed on very shallow bottoms. They are not equipped to dive down several feet like their diving counterparts. The most prominent difference between puddle ducks and divers are the size of the feet. A puddle duck's feet are generally smaller because they do not need the extra propulsion to dive for their forage.

Another distinguishing characteristic of puddle ducks when compared to diving ducks is the way in which they take flight when spooked or are on the move. Puddle ducks spring straight up from the water, but diving ducks need to gain momentum to take off, so they must run across the water a short distance to gain flight.

History of classification

Traditionally, most ducks were assigned to either the shelducks, the perching ducks, and the dabbling and diving ducks; the latter two were presumed to make up the Anatinae. However, the perching ducks turned out to be a paraphyletic assemblage of various tropical waterfowl that happened to evolve the ability to perch well in their forested habitat. Several of these, such as the Brazilian teal, were subsequently assigned to the Anatinae.

As for the diving ducks, mtDNA cytochrome b and NADH dehydrogenase subunit 2 sequence data[2] indicates that they are fairly distant from the dabbling ducks. The morphological similarities[3] are due to convergent evolution.

In addition, the genus Anas, as traditionally defined, is not monophyletic; several South American species belong to a distinct clade which would include the Tachyeres steamer-ducks.[2] Other species, such as the Baikal teal, should also be considered distinct.

Dabbling Spot billed Ducks 01
Spot billed ducks dabbling

Genera

Spot-billed Duck (Anas poecilorhyncha) in Hyderabad W2 IMG 8867
Spot-billed duck (Anas poecilorhyncha) in Hyderabad, India

The following genera are (with one exception) unequivocal dabbling ducks:

Philippine duck
Philippine duck, Anas luzonica

The 3 known genera and 4 known species of moa-nalos all became extinct around 1000 AD. They formerly occurred on the Hawaiian Islands and were derived from dabbling ducks, possibly even a close ancestor of the mallard:

Subfossil remains of a small, flightless dabbling duck have been recovered on Rota in the Mariana Islands.[5] These cannot be assigned to a known genus, but probably are closest to Anas. A most bizarre ducklike bird, Talpanas lippa has been found on the Hawaiian island of Kauai.[6] Because of its unique apomorphies (it seems to have had small eyes high and far back on its head), the placement of this anatid is likewise unresolved; only dabbling ducks and true geese are with certainty known to have colonized the Hawaiian archipelago.

Another bizarre insular anatine was Bambolinetta from the Late Miocene of Tuscana, then part of the Tuscano-Sardinian insular landmass. Flightless or at least a poor flyer, it instead shows adaptations for wing-propelled diving, occupying a similar ecological niche to that of penguins and plotopterids.

Frequently placed into the Anatinae are these genera, whose relationships must be considered uncertain at present:

On the other hand, the following genera, usually considered to belong into the Tadorninae, may actually be dabbling ducks:

References

  1. ^ Terres, John K. & National Audubon Society (1991): The Audubon Society Encyclopedia of North American Birds. Wings Books, New York. Reprint of 1980 edition. ISBN 0-517-03288-0
  2. ^ a b c d e Johnson, Kevin P.; Sorenson, Michael D. (1999). "Phylogeny and biogeography of dabbling ducks (genus Anas): a comparison of molecular and morphological evidence" (PDF). Auk. 116 (3): 792–805. doi:10.2307/4089339.
  3. ^ a b Livezey, Bradley C. (1986). "A phylogenetic analysis of recent anseriform genera using morphological characters" (PDF). Auk. 103 (4): 737–754.
  4. ^ Sraml, M.; Christidis, L.; Easteal, S.; Horn, P.; Collet, C. (1996). "Molecular Relationships Within Australasian Waterfowl (Anseriformes)". Australian Journal of Zoology. 44 (1): 47–58. doi:10.1071/ZO9960047.
  5. ^ Steadman, David William (1999). "The Prehistory of Vertebrates, Especially Birds, on Tinian, Aguiguan, and Rota, Northern Mariana Islands" (PDF). Micronesica. 31 (2): 319–345. Archived from the original (PDF) on 2004-07-05.
  6. ^ Burney, David A.; James, Helen F.; Burney, Lida Pigott; Olson, Storrs L.; Kikuchi, William; Wagner, Warren L.; Burney, Mara; McCloskey, Deirdre; Kikuchi, Delores; Grady, Frederick V.; Gage, Reginald II; Nishek, Robert (2001). "Fossil Evidence for a Diverse Biota from Kauaʻi and Its Transformation since Human Arrival". Ecological Monographs. 71 (4): 615–641. doi:10.2307/3100038. hdl:10088/109.

External links

  • Media related to Anatinae at Wikimedia Commons
Anseriformes

Anseriformes is an order of birds that comprise about 180 living species in three families: Anhimidae (the 3 screamers), Anseranatidae (the magpie goose), and Anatidae, the largest family, which includes over 170 species of waterfowl, among them the ducks, geese, and swans. Most modern species in the order are highly adapted for an aquatic existence at the water surface. With the exception of screamers, all have phalli, a trait that has been lost in the Neoaves. Due to their aquatic nature, most species are web-footed.

Baikal teal

The Baikal teal (Sibirionetta formosa), also called the bimaculate duck or squawk duck, is a dabbling duck that breeds in eastern Russia and winters in East Asia.

Bambolinetta

Bambolinetta lignitifila is a fossil species of waterfowl from the Late Miocene of Italy, now classified as the sole member of the genus Bambolinetta. First described in 1884 as a typical dabbling duck, it was not revisited until 2014, when a study showed it to be a highly unusual duck species, probably a flightless, wing-propelled diver similar to a penguin.

Brazilian teal

The Brazilian teal or Brazilian duck (Amazonetta brasiliensis) is the only duck in the genus Amazonetta.

Bronze-winged duck

The bronze-winged duck (Speculanas specularis) also known as the spectacled duck, is a dabbling duck and the sole member of its genus Speculanas. It is often placed in Anas with most other dabbling ducks, but its closest relative is either the crested duck or the Brazilian duck, which likewise form monotypic genera. Together they belong to a South American lineage which diverged early from the other dabbling ducks and may include the steamer ducks.

Named after the "bronze" speculum this species is also known as "pato perro" or "dog-duck" after the harsh barking call of the female.

The bronze-winged duck lives among forested rivers and fast-flowing streams on the lower slopes of the South American Andes, in central and southern Chile and adjacent parts of Argentina.

The sexes are alike.

As noted by Johnsgard (2010): "Most observers agree that heavily forested rivers that are relatively swift-flowing are the preferred habitat of this species, although they also occur on slow-moving rivers and on pools or ponds of the adjoining forest areas. They are said to consume both vegetable and animal materials, and have been observed eating small snails that abound on stony shingle beaches. Stomach remains from two birds that were examined contained the seeds of water crowfoot (Batrachium), water milfoil (Myriophyllum), and a bulrush, leaves of water crowfoot, foliage and seeds of a pondweed, and caddis fly larvae as well as a few other aquatic insect remains (Phillips, 1922–26). In captivity at least the birds seem to spend a good deal of time on land and have not been observed diving for food."

Crested duck

The crested duck or South American crested duck (Lophonetta specularioides) is a species of duck native to South America, the belonging to the monotypic genus Lophonetta. It is sometimes included in Anas, but it belongs to a South American clade that diverged early in dabbling duck evolution. There are two subspecies: L. specularioides alticola (Andean crested duck) and L. specularioides specularioides (Patagonian crested duck). The Patagonian crested duck is also called the southern crested duck and its range lies in the Falklands, Chile, and Argentina.

Diving duck

The diving ducks, commonly called pochards or scaups, are a category of duck which feed by diving beneath the surface of the water. They are part of Anatidae, the diverse and very large family that includes ducks, geese, and swans.

The diving ducks are placed in a distinct tribe in the subfamily Anatinae, the Aythyini. While morphologically close to the dabbling ducks, there are nonetheless some pronounced differences such as in the structure of the trachea. mtDNA cytochrome b and NADH dehydrogenase subunit 2 sequence data indicate that the dabbling and diving ducks are fairly distant from each other, the outward similarities being due to convergent evolution.

Alternatively, the diving ducks are placed as a subfamily Aythyinae in a subfamily Anatidae which would encompass all duck-like birds except the whistling-ducks.

The seaducks commonly found in coastal areas, such as the long-tailed duck (formerly known in the US as oldsquaw), scoters, goldeneyes, mergansers, bufflehead and eiders, are also sometimes colloquially referred to in North America as diving ducks because they also feed by diving; their subfamily (Merginae) is a very distinct one however.

Although the group is cosmopolitan, most members are native to the Northern Hemisphere, and it includes several of the most familiar Northern Hemisphere ducks.

This group of ducks is so named because its members feed mainly by diving, although in fact the Netta species are reluctant to dive, and feed more like dabbling ducks.

These are gregarious ducks, mainly found on fresh water or on estuaries, though the greater scaup becomes marine during the northern winter. They are strong fliers; their broad, blunt-tipped wings require faster wing-beats than those of many ducks and they take off with some difficulty. Northern species tend to be migratory; southern species do not migrate though the hardhead travels long distances on an irregular basis in response to rainfall. Diving ducks do not walk as well on land as the dabbling ducks; their legs tend to be placed further back on their bodies to help propel them when underwater.

Hartlaub's duck

The Hartlaub's duck (Pteronetta hartlaubii) is a dark chestnut-coloured duck of African forests. Formerly included in the paraphyletic "perching duck" assemblage, it was later moved to the dabbling duck assemblage. However, it is fairly distinct from the "typical" dabbling ducks, and is placed in the monotypic genus Pteronetta to reflect this.

Analysis of mtDNA sequences of the cytochrome b and NADH dehydrogenase subunit 2 genes suggests that it belongs into a very distinct clade—possibly a subfamily of its own—together with the blue-winged goose, another African species of waterfowl with uncertain affinities.Hartlaub's duck is resident in equatorial West and Central Africa, from Guinea and Sierra Leone east through Nigeria to South Sudan, and south to Gabon, Congo and Zaire.

This bird is named after the German naturalist Gustav Hartlaub.

Malacorhynchus

Malacorhynchus is a genus of duck within the family Anatidae. It has one living species, the pink-eared duck (M. membranaceus), while one species, Scarlett's duck (Malacorhynchus scarletti), became extinct in New Zealand in the 16th century.

Marbled duck

The marbled duck, or marbled teal (Marmaronetta angustirostris) is a medium-sized duck. The scientific name, Marmaronetta angustirostris, comes from the Greek marmaros, marbled and netta, a duck, and Latin angustus, narrow or small and -rostris billed.

Matanas

Matanas enrighti is an extinct duck from the Miocene of New Zealand. It was described from fossil material (a left humerus) collected from a Saint Bathans Fauna site near Mata Creek, in the lower Bannockburn Formation of the Manuherikia Group, in the Manuherikia River valley in the Central Otago region of the South Island.

Maui Nui large-billed moa-nalo

The Maui Nui large-billed moa-nalo (Thambetochen chauliodous), also known as the Maui Nui moa-nalo, is one of two species of moa-nalo in the genus Thambetochen. Moa-nalo are a group of extinct, flightless, large goose-like ducks, which evolved in the Hawaiian Islands of the North Pacific Ocean.

Mergini

The seaducks (Mergini) are a tribe of the duck subfamily of birds, the Anatinae. The taxonomy of this group is incomplete. Some authorities separate the group as a subfamily, others remove some genera from the group and keep others. Most species within the group spend their winters near coastal waters. Many species have developed specialized salt glands to allow them to tolerate salt water but these are poorly developed in juveniles. Some of the species prefer riverine habitats. All but two of the 20 species in this group live 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 and are often known as "sawbills". Other seaducks forage by diving underwater, taking molluscs or crustaceans from the sea floor. The Mergini take on the eclipse plumage during the late summer and molt into their breeding plumage during the winter.

Mergus

Mergus is the genus of the typical mergansers, fish-eating ducks in the subfamily Anatinae. The genus name is a Latin word used by Pliny and other Roman authors to refer to an unspecified waterbird.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 goldeneyes (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 somewhat 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.Mergus 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.

Moa-nalo

The moa-nalo are a group of extinct aberrant, goose-like ducks that lived on the larger Hawaiian Islands, except Hawaiʻi itself, in the Pacific. They were the major herbivores on most of these islands until they became extinct after human settlement.

Oxyurini

The Oxyurini are a tribe of the duck subfamily of birds, the Anatinae. It has been subject of considerable debate about its validity and circumscription. Some taxonomic authorities place the group in its own subfamily, the Oxyurinae. Most of its members have long, stiff tail feathers which are erected when the bird is at rest, and relatively large, swollen bills. Though their relationships are still enigmatic, they appear to be closer to swans and true geese than to the typical ducks. The highest diversity is found in the warmer parts of the Americas, but at least one species occurs in a major part of the world.

Their habitus resembles a freshwater diving duck, particularly when moving on dry land. Their legs are set far back, making them awkward walkers, so they rarely leave the water. When at rest, their tails are a notable difference as per above, and in the water they often swim very deep-set. Their unusual courtship displays involve drumming noises from inflatable throat sacs, head throwing, and erecting short crests. Most display singly with a very elaborate and peculiar display, but musk ducks congregate at leks and have a more limited display.

Oʻahu moa-nalo

The Oʻahu moa-nalo (Thambetochen xanion) is one of two species of moa-nalo in the genus Thambetochen. Moa-nalo are a group of extinct, flightless, large goose-like ducks, which evolved in the Hawaiian Islands of the North Pacific Ocean.

Patagonian crested duck

The Patagonian crested duck (Lophonetta specularioides specularioides), also known as the southern crested duck, or the grey duck in the Falkland Islands, is the nominate of two subspecies of the crested duck.

Perching duck

The perching ducks were previously treated as a small group of ducks in the duck, goose and swan family Anatidae, grouped together on the basis of their readiness to perch high in trees. It has been subsequently shown that the grouping is paraphyletic and their apparent similarity results from convergent evolution, with the different members more closely related to various other ducks than to each other.The species previously included, and their current subfamilial allocation, are:

Plectropterinae

Spur-winged goose Plectropterus gambensisTadorninae

Salvadori's teal Salvadorina waigiuensis (initially placed in Anatinae)

Blue duck Hymenolaimus malacorhynchos

Torrent duck Merganetta armataAnatinae

Brazilian teal Amazonetta brasiliensisIn addition, several species cannot with certainty be allocated to a subfamily, though they do not form a distinct clade. Rather, their characters are too ambiguous to allow unequivocal placement based on the available data:

Comb duck Sarkidiornis melanotos: Tadorninae or basal Anatinae?

Pink-eared duck Malacorhynchus membranaceus: Tadorninae or Oxyurinae?

Hartlaub's duck Pteronetta hartlaubi: Anatinae or a very distinct clade?

Green pygmy goose Nettapus pulchellus: Anatinae or a Gondwanan clade?

Cotton pygmy goose Nettapus coromandellanus: Anatinae or a Gondwanan clade?

African pygmy goose Nettapus auritus: Anatinae or a Gondwanan clade?

Muscovy duck Cairina moschata: Anatinae or Tadorninae?

White-winged duck Cairina scutulata: Anatinae or closer to Aythyinae?

Wood duck Aix sponsa: Anatinae or Tadorninae?

Mandarin duck Aix galericulata: Anatinae or Tadorninae?

Ringed teal Callonetta leucophrys: Anatinae or Tadorninae?

Maned duck Chenonetta jubata: Anatinae or Tadorninae?

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