The knob-billed duck (''Sarkidiornis melanotos''), or African comb duck, is a
duck
Duck is the common name for numerous species of waterfowl in the family Anatidae. Ducks are generally smaller and shorter-necked than swans and geese, which are members of the same family. Divided among several subfamilies, they are a form t ...
found in tropical wetlands in
Sub-Saharan Africa
Sub-Saharan Africa is, geographically, the area and regions of the continent of Africa that lies south of the Sahara. These include West Africa, East Africa, Central Africa, and Southern Africa. Geopolitically, in addition to the List of sov ...
,
Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
and the
Indian Subcontinent
The Indian subcontinent is a list of the physiographic regions of the world, physiographical region in United Nations geoscheme for Asia#Southern Asia, Southern Asia. It is situated on the Indian Plate, projecting southwards into the Indian O ...
from northern
India
India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
to
Laos
Laos (, ''Lāo'' )), officially the Lao People's Democratic Republic ( Lao: ສາທາລະນະລັດ ປະຊາທິປະໄຕ ປະຊາຊົນລາວ, French: République démocratique populaire lao), is a socialist ...
and extreme southern
China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
.
Most taxonomic authorities split this species and the
comb duck
The comb duck or American comb duck (''Sarkidiornis sylvicola''), is an unusual duck, found in tropical wetlands in continental South America south to the Paraguay River region in eastern Paraguay, southeastern Brazil and extreme northeastern Ar ...
from each other. The supposed
extinct
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually 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 ...
"Mauritian comb duck" is based on misidentified remains of the
Mauritius sheldgoose
The Mauritius sheldgoose (''Alopochen mauritiana''), also known as the Mauritius shelduck, is an extinct species of sheldgoose that was endemic to the island of Mauritius. While geese were mentioned by visitors to Mauritius in the 17th century ...
(''Alopochen mauritiana''); this was realized as early as 1897,
[ but the ]mistaken identity
Mistaken identity is a defense in criminal law which claims the actual innocence of the criminal defendant, and attempts to undermine evidence of guilt by asserting that any eyewitness to the crime incorrectly thought that they saw the defendan ...
can still occasionally be found in recent sources.
Description and systematics
This common species is unmistakable. It is one of the largest species of duck. Length can range from , wingspan ranges from and weight from .''Sarkidiornis melanotos'' (Comb duck, Knob-billed duck)
biodiversityexplorer.org Adults have a white head freckled with dark spots, and a pure white neck and underparts. The upperparts are glossy blue-black upperparts, with bluish and greenish
iridescence
Iridescence (also known as goniochromism) is the phenomenon of certain surfaces that appear to gradually change color as the angle of view or the angle of illumination changes. Examples of iridescence include soap bubbles, feathers, butterfl ...
especially prominent on the secondaries (lower arm feathers). The male is much larger than the female, and has a large black knob on the
bill
Bill(s) may refer to:
Common meanings
* Banknote, paper cash (especially in the United States)
* Bill (law), a proposed law put before a legislature
* Invoice, commercial document issued by a seller to a buyer
* Bill, a bird or animal's beak
Plac ...
. Young birds are dull
buff
Buff or BUFF may refer to:
People
* Buff (surname), a list of people
* Buff (nickname), a list of people
* Johnny Buff, ring name of American world champion boxer John Lisky (1888–1955)
* Buff Bagwell, a ring name of American professional ...
below and on the face and neck, with dull brown upperparts, top of the head and eyestripe.
[ Knob-billed ducks are generally larger in size when compared to comb ducks, and flanks are usually lighter (light grey, in females sometimes whitish).
Immature knob-billed ducks look like a large greyish female of the ]cotton pygmy goose
The cotton pygmy goose or cotton teal (''Nettapus coromandelianus'') is a small perching duck which breeds in Asia, Southeast Asia extending south and east to Queensland where they are sometimes called white-quilled pygmy goose. They are among ...
(''Nettapus coromandelicus'') and may be difficult to tell apart if no other birds are around to compare size and hue
In color theory, hue is one of the main properties (called color appearance parameters) of a color, defined technically in the CIECAM02 model as "the degree to which a stimulus can be described as similar to or different from stimuli that ...
. However, knob-billed ducks in immature plumage
Plumage ( "feather") is a layer of feathers that covers a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage differ between species and subspecies and may vary with age classes. Within species, ...
are rarely seen without adults nearby and thus they are usually easily identified too.[
The knob-billed duck is silent except for a low croak when flushed.]
Gallery
File:Sarkidiornis melanotos - Royal Museum for Central Africa - DSC06799.JPG, Specimens from the Royal Museum for Central Africa (female, male)
File:CombDuck DSC0264.jpg, knob-billed duck at edge of lake near Jodhpur, Rajasthan, India, feeding alongside feral pigeons.
File:CombDuck.jpg, Flying knob-billed duck / comb duck at Chilika Lake
Chilika Lake is a brackish water lagoon, spread over the Puri, khordha and Ganjam districts of Odisha state on the east coast of India, at the mouth of the Daya River, flowing into the Bay of Bengal, covering an area of over . It is the bigge ...
, Odisha, India
Knob-billed duck (Sarkidiornis melanotos) female in flight Jojawar.jpg, female, Jojawar, India
File:Male knob-billed duck in water.jpg, Male knob-billed duck at Austin Roberts Bird Sanctuary in Pretoria, South Africa
File:Knob-billed Duck, Bharatpur.jpg, Knob-billed Duck (Sarkidiornis melanotos) alongside Eurasian Coot
The Eurasian coot (''Fulica atra''), also known as the common coot, or Australian coot, is a member of the rail and crake bird family, the Rallidae. It is found in Europe, Asia, Australia, New Zealand and parts of North Africa. It has a slaty-bla ...
((Fulica atra) in Keoladeo National Park
Keoladeo National Park or Keoladeo Ghana National Park (formerly known as the Bharatpur Bird Sanctuary) is a famous avifauna sanctuary in Bharatpur, Rajasthan, India, that hosts thousands of birds, especially during the winter season. Over 350 ...
, Rajasthan
Rajasthan (; lit. 'Land of Kings') is a state in northern India. It covers or 10.4 per cent of India's total geographical area. It is the largest Indian state by area and the seventh largest by population. It is on India's northwestern si ...
, India
India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
File:Knob-billed Duck AaMSM9151.jpg, Male at Jamnagar
Jamnagar () is a city located on the western coast of India in the state of Gujarat of Saurashtra (region), Saurashtra region. It is the administrative headquarters of the Jamnagar district and the fifth largest city in Gujarat. The city lies ...
, India
India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
File:Knob-billed Duck Male AMSM8872.jpg, Close-up Male
Uncertainty surrounds the correct systematic placement of this species. Initially, it was placed in the dabbling duck
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 yo ...
subfamily
In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zoologi ...
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 you ...
. Later, it was assigned to the "perching duck
The term perching ducks is used colloquially to mean any species of ducks distinguished by their readiness to perch high in trees
Until the late 20th century, perching ducks meant ''Cairinini'', a tribe of ducks in the duck, goose and swan family ...
s", a paraphyletic
In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...
assemblage of waterfowl most of which are intermediate between dabbling ducks and shelduck
The shelducks, most species of which are found in the genus ''Tadorna'' (except for the Radjah shelduck, which is now found in its own monotypic genus ''Radjah''), are a group of large birds in the Tadorninae subfamily of the Anatidae, the biologi ...
s. As the "perching ducks" were split up, the knob-billed duck was moved to the Tadorninae
The Tadorninae is the shelduck-sheldgoose subfamily of the Anatidae, the biological family that includes the ducks and most duck-like waterfowl such as the geese and swans.
This group is largely tropical or Southern Hemisphere in distribution, w ...
or shelduck subfamily
In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zoologi ...
.
Analysis of mtDNA
Mitochondrial DNA (mtDNA or mDNA) is the DNA located in mitochondria, cellular organelles within eukaryotic cells that convert chemical energy from food into a form that cells can use, such as adenosine triphosphate (ATP). Mitochondrial DNA ...
sequence
In mathematics, a sequence is an enumerated collection of objects in which repetitions are allowed and order matters. Like a set, it contains members (also called ''elements'', or ''terms''). The number of elements (possibly infinite) is calle ...
s of the cytochrome ''b'' and NADH dehydrogenase
NADH dehydrogenase is an enzyme that converts nicotinamide adenine dinucleotide (NAD) from its reduced form (NADH) to its oxidized form (NAD+). Members of the NADH dehydrogenase family and analogues are commonly systematically named using the for ...
subunit 2 gene
In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a ba ...
s, however, suggests that it is a quite basal member of the Anatidae, vindicating the earliest placement. But its closest living relatives cannot be resolved to satisfaction without further study.[
]
Ecology
It breeds in still freshwater
Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. Although the term specifically excludes seawater and brackish water, it does include ...
swamp
A swamp is a forested wetland.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p. Swamps are considered to be transition zones because both land and water play a role in ...
s and lake
A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much large ...
s in the tropics
The tropics are the regions of Earth surrounding the Equator. They are defined in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in
the Southern Hemisphere at S. The tropics are also referred to ...
. It is largely resident, apart from dispersion in the wet season.
This duck
Duck is the common name for numerous species of waterfowl in the family Anatidae. Ducks are generally smaller and shorter-necked than swans and geese, which are members of the same family. Divided among several subfamilies, they are a form t ...
feeds on vegetation by grazing or dabbling and to a lesser extent on small fish, invertebrate
Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...
s, and seeds. It can become a problem to rice farmers. Knob-billed ducks often perch in trees. They are typically seen in flocks, small in the wet season, up to 100 in the dry season. Sometimes they separate according to sex.[
The knob-billed duck is declining in numbers locally, but due to its wide range it is not considered globally threatened by the ]IUCN
The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...
. It is one of the species to which the '''' applies.
Reproduction
African birds breed during and after the rainy season and may not breed if the rain is scanty. Knob-billed ducks nest mainly in tree holes, also in tall grass.
Males may have two mates at once or up to five in succession. They defend the females and young but not the nest sites.
Females lay 7 to 15 yellowish-white eggs.
References
External links
Species text in The Atlas of Southern African Birds
{{Taxonbar, from=Q426968
Sarkidiornis
Birds of Sub-Saharan Africa
Birds of India
Birds of Southeast Asia
knob-billed duck
The knob-billed duck (''Sarkidiornis melanotos''), or African comb duck, is a duck found in tropical wetlands in Sub-Saharan Africa, Madagascar and the Indian Subcontinent from northern India to Laos and extreme southern China.
Most taxonomic au ...
Taxa named by Thomas Pennant