Green-winged Teal
Encyclopedia
The Green-winged Teal is a common and widespread duck
that breeds in the northern areas of North America
except on the Aleutian Islands. It was considered conspecific
with the Common Teal
(A. crecca) for some time but the issue is still being reviewed by the American Ornithologists' Union
; based on this the IUCN and BirdLife International
do not accept it as a separate species at present. However, nearly all other authorities consider it distinct based on behavioral, morphological, and molecular evidence.
This dabbling duck is strongly migratory
and winters far south of its breeding range. It is highly gregarious outside of the breeding season and will form large flocks. In flight, the fast, twisting flocks resemble wader
s.
This is the smallest North American dabbling duck. The breeding male has grey flanks and back, with a yellow rear end and a white-edged green speculum
, obvious in flight or at rest. It has a chestnut head with a green eye patch. It is distinguished from drake Common Teals (the Eurasia
n relative of this bird) by a vertical white stripe on side of breast, the lack of both a horizontal white scapular stripe and the lack of thin buff lines on its head.
The females are light brown, with plumage
much like a female Mallard
. They can be distinguished from most ducks on size and shape, and the speculum. Separation from female Common Teal is problematic.
In non-breeding (eclipse) plumage, the drake looks more like the female.
It is a common duck of sheltered wetlands, such as taiga
bogs, and usually feeds by dabbling for plant food or grazing. It nests on the ground, near water and under cover. While its conservation status
is not evaluated by IUCN at present due to non-recognition of the taxon, it is plentiful enough to make it a species of Least Concern
if it were; it is far more plentiful than the Common Teal. It can be seen in vast numbers in the Marismas Nacionales of western Mexico
, a main wintering area.
This is a noisy species. The male has a clear whistle, whereas the female has a feeble "quack".
The American green-winged teal breeds from the Aleutian Islands, northern Alaska, Mackenzie River delta, northern Saskatchewan, Manitoba, Ontario, Quebec, and Labrador south to central California, central Nebraska, central Kansas, southern Minnesota, Wisconsin, Ontario, Quebec, Newfoundland, and the Maritime Provinces.
The American green-winged teal winters from southern Alaska and southern British Columbia east to New Brunswick and Nova Scotia and south to Central America. It also winters in Hawaii.
Within the above associations, Green-winged Teal commonly inhabit wetland communities dominated by bulrushes (Scirpus spp.), cattails (Typha spp.), sedges (Carex spp.), pondweeds (Potamogeton spp.) and other emergent and aquatic vegetation. Green-winged Teal frequently nest in grasses, sedge meadows, or on dry hillsides having brush or aspen (Populus spp.) cover. Near Brooks, Alberta, Green-winged Teal nests were found most often in beds of rushes (Juncus spp.), and in western Montana most nests were located under greasewood (Sarcobatus spp.).
Green-winged Teal become sexually mature their first winter. They lay 5 to 16 eggs. The incubation period is 21 to 23 days.
Green-winged Teals often fledge 34 to 35 days after hatching or usually before 6 weeks of age. Young Green-winged Teal have the fastest growth rate of all ducks.
Male Green-winged Teal leave females at the start of incubation and congregate on safe waters to molt. Some populations undergo an extensive molt migration while others remain on or near breeding grounds. Females molt on breeding grounds.
Green-winged Teal are among the earliest spring migrants. They arrive on nesting areas almost as soon as the snow melts. In early February, Green-winged Teal begin to depart their winter grounds, and continue through April. In central regions Green-winged Teal begin
to arrive early in March with peak numbers in early April.
In northern areas of the United States, Green-winged Teal migrating to wintering grounds appear in early September through mid-December. They begin migrating into most central regions during September and often remain through December. On their more southerly winter areas, Green-winged Teal arrive as early as late September, but most do not appear until late November.
than to the Common Teal. This would require that sexual dimorphism
either was lost in the Speckled Teal or that it evolved in near-identical forms in the Green-winged and Common Teal after the divergence of the Green-winged and Speckled Teal lineages.
Both hypotheses seem rather spurious initially, with the GWT and Common Teal's male nuptial plumage being unique and very complex, and the tendency to gain, not lose, strong sexual dimorphism overwhelming in the dabbling ducks. An alternative explanation given the high frequency of hybridisation in ducks
would be that the mtDNA of the present-day GWT is originally derived from Spotted Teal females by introgression
and thus the molecular data gives a misleading picture of the species' true relationships. This is supported by the observation that in Mallard
× American Black Duck
hybrids, females of both taxa
prefer the sexually dimorphic mallard drakes over the dull-plumaged Black Duck drakes; that the GWT is in some aspects—such as the less contrasting nuptial plumage—intermediate between the Common and Speckled Teal is also interesting to note.
Alternatively, the Common Teal might be derived from the GWT, with the molecular difference being due to genetic drift
or a founder effect
in the latter and possibly Speckled Teal introgression in the former. The three teals certainly belong to a superspecies
in the teals ("Nettion"); the ancestors of this group were most likely sexually monomorphic Southern Hemisphere
forms (Johnson & Sorenson, 1999; note that their "African" distribution includes Bernier's Teal
taxa which like many Madagascar
taxa is of Indo-Australian origin).
Another possibility is that the American lineage is derived from stray Common Teals, with the founder effect/genetic drift and/or hybrid introgression phenomena applying as above, only in the reverse direction for the former two. Still, this would require loss of sexual dimorphism in the ancestors of the Speckled Teal, but while extremely rare in dabbling ducks, it is not per se impossible.
The close Speckled-GWT relationship suggested by mtDNA data could of course still apply to the taxa in general, not just to sequences in 2 maternally inherited genes in a few individual ducks (for which it without doubt does apply), but the overall failure of Johnson & Sorenson to seriously take hybridization into account and their small sample sizes and obsolete conceptions of Indian Ocean
biogeography
do not help at all to resolve the issue, but in 1999, the methodology and interpretation were reasonable enough and in fact, the study was pioneering in many respects due to dense taxon-level sampling and still represents one of the default references for interpreting the pyhlogeny of the genus.
It is worthy of note that the post-copulatory displays of the Common and GWT are identical, but those of the Speckled Teal have some additional elements.
All in all, a firm conclusion cannot be reached at present beyond a tentative rejection of the phylogeny suggested by the mtDNA data. Nuclear DNA
sequence information is required, but may not be sufficient, to resolve the puzzling relationships in the crecca-carolinensis-flavirostris complex of teals.
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...
that breeds in the northern areas of North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
except on the Aleutian Islands. It was considered conspecific
Conspecificity
Conspecificity is a concept in biology. Two or more individual organisms, populations, or taxa are conspecific if they belong to the same species....
with the Common Teal
Common Teal
The Eurasian Teal or Common Teal is a common and widespread duck which breeds in temperate Eurasia and migrates south in winter. The Eurasian Teal is often called simply the Teal due to being the only one of these small dabbling ducks in much of its range...
(A. crecca) for some time but the issue is still being reviewed by the American Ornithologists' Union
American Ornithologists' Union
The American Ornithologists' Union is an ornithological organization in the USA. Unlike the National Audubon Society, its members are primarily professional ornithologists rather than amateur birders...
; based on this the IUCN and BirdLife International
BirdLife International
BirdLife International is a global Partnership of conservation organisations that strives to conserve birds, their habitats and global biodiversity, working with people towards sustainability in the use of natural resources...
do not accept it as a separate species at present. However, nearly all other authorities consider it distinct based on behavioral, morphological, and molecular evidence.
This dabbling duck is strongly migratory
Bird migration
Bird migration is the regular seasonal journey undertaken by many species of birds. Bird movements include those made in response to changes in food availability, habitat or weather. Sometimes, journeys are not termed "true migration" because they are irregular or in only one direction...
and winters far south of its breeding range. It is highly gregarious outside of the breeding season and will form large flocks. In flight, the fast, twisting flocks resemble wader
Wader
Waders, called shorebirds in North America , are members of the order Charadriiformes, excluding the more marine web-footed seabird groups. The latter are the skuas , gulls , terns , skimmers , and auks...
s.
This is the smallest North American dabbling duck. The breeding male has grey flanks and back, with a yellow rear end and a white-edged green speculum
Speculum feathers
The speculum is a patch, often distinctly coloured, on the inner remiges of some birds.Examples of the colour of the speculum in a number of ducks are:* Common Teal and Green-winged Teal: Iridescent green edged with buff....
, obvious in flight or at rest. It has a chestnut head with a green eye patch. It is distinguished from drake Common Teals (the Eurasia
Eurasia
Eurasia is a continent or supercontinent comprising the traditional continents of Europe and Asia ; covering about 52,990,000 km2 or about 10.6% of the Earth's surface located primarily in the eastern and northern hemispheres...
n relative of this bird) by a vertical white stripe on side of breast, the lack of both a horizontal white scapular stripe and the lack of thin buff lines on its head.
The females are light brown, with plumage
Feather
Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They...
much like a female Mallard
Mallard
The Mallard , or Wild Duck , is a dabbling duck which breeds throughout the temperate and subtropical Americas, Europe, Asia, and North Africa, and has been introduced to New Zealand and Australia....
. They can be distinguished from most ducks on size and shape, and the speculum. Separation from female Common Teal is problematic.
In non-breeding (eclipse) plumage, the drake looks more like the female.
It is a common duck of sheltered wetlands, such as taiga
Taiga
Taiga , also known as the boreal forest, is a biome characterized by coniferous forests.Taiga is the world's largest terrestrial biome. In North America it covers most of inland Canada and Alaska as well as parts of the extreme northern continental United States and is known as the Northwoods...
bogs, and usually feeds by dabbling for plant food or grazing. It nests on the ground, near water and under cover. While its conservation status
Conservation status
The conservation status of a group of organisms indicates whether the group is still extant and how likely the group is to become extinct in the near future...
is not evaluated by IUCN at present due to non-recognition of the taxon, it is plentiful enough to make it a species of Least Concern
Least Concern
Least Concern is an IUCN category assigned to extant taxon or lower taxa which have been evaluated but do not qualify for any other category. As such they do not qualify as threatened, Near Threatened, or Conservation Dependent...
if it were; it is far more plentiful than the Common Teal. It can be seen in vast numbers in the Marismas Nacionales of western Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
, a main wintering area.
This is a noisy species. The male has a clear whistle, whereas the female has a feeble "quack".
Distribution
All three Green-winged Teal subspecies occur in the northern hemisphere during summer and in winter extend to northern South America, central Africa, southern India, Burma, and the Philippines. In North America, ssp. carolinensis occurs across the continent and is joined in the Aleutian Islands by ssp. nimia, which remains there throughout the year. Anas crecca breeds in Iceland, Europe, and Asia. It is also seen occasionally during the winter in North America along the Atlantic Coast.The American green-winged teal breeds from the Aleutian Islands, northern Alaska, Mackenzie River delta, northern Saskatchewan, Manitoba, Ontario, Quebec, and Labrador south to central California, central Nebraska, central Kansas, southern Minnesota, Wisconsin, Ontario, Quebec, Newfoundland, and the Maritime Provinces.
The American green-winged teal winters from southern Alaska and southern British Columbia east to New Brunswick and Nova Scotia and south to Central America. It also winters in Hawaii.
Plant communities
Green-winged Teal are abundant in wetlands of the Canadian parkland and northern boreal forest associations. They occur more often in mixed-prairie associations than in shortgrass associations. They also inhabit arctic tundra and semidesert communities.Within the above associations, Green-winged Teal commonly inhabit wetland communities dominated by bulrushes (Scirpus spp.), cattails (Typha spp.), sedges (Carex spp.), pondweeds (Potamogeton spp.) and other emergent and aquatic vegetation. Green-winged Teal frequently nest in grasses, sedge meadows, or on dry hillsides having brush or aspen (Populus spp.) cover. Near Brooks, Alberta, Green-winged Teal nests were found most often in beds of rushes (Juncus spp.), and in western Montana most nests were located under greasewood (Sarcobatus spp.).
Major life events
Nesting chronology varies geographically. In North Dakota, Green-winged Teal generally begin nesting in late April. In the Northwest Territories, Canada, Green-winged Teal begin nesting between late May and early July. At Minto Lakes, Alaska, Green-winged Teal initiate nesting as early as June 1 and as late as July 20.Green-winged Teal become sexually mature their first winter. They lay 5 to 16 eggs. The incubation period is 21 to 23 days.
Green-winged Teals often fledge 34 to 35 days after hatching or usually before 6 weeks of age. Young Green-winged Teal have the fastest growth rate of all ducks.
Male Green-winged Teal leave females at the start of incubation and congregate on safe waters to molt. Some populations undergo an extensive molt migration while others remain on or near breeding grounds. Females molt on breeding grounds.
Green-winged Teal are among the earliest spring migrants. They arrive on nesting areas almost as soon as the snow melts. In early February, Green-winged Teal begin to depart their winter grounds, and continue through April. In central regions Green-winged Teal begin
to arrive early in March with peak numbers in early April.
In northern areas of the United States, Green-winged Teal migrating to wintering grounds appear in early September through mid-December. They begin migrating into most central regions during September and often remain through December. On their more southerly winter areas, Green-winged Teal arrive as early as late September, but most do not appear until late November.
Preferred habitat
Green-winged Teal inhabit inland lakes, marshes, ponds, pools, and shallow streams with dense emergent and aquatic vegetation. They prefer shallow waters and small ponds and pools during the breeding season. Green-winged Teal are often found resting on mudbanks or stumps, or perching on low limbs of dead trees. These ducks nest in depressions on dry ground located at the base of shrubs, under a log, or in dense grass. The nests are usually 2 to 300 feet (6–91 m) from water. Green-winged teal avoid treeless or brushless habitats. Green-winged teal winter in both freshwater or brackish marshes, ponds, streams, and estuaries. As they are smaller birds, they tend to stay in the calmer water.Cover requirements
Green-winged Teal nests are usually concealed both from the side and from above in heavy grass, weeds, or brushy cover. Cattails, bulrushes, smartweeds (Polygonum spp.), and other emergent vegetation provide hiding cover for ducks on water.Food habits
Green-winged Teal, more than any other species of duck, prefer to seek food on mud flats. Where mud flats are lacking, they prefer shallow marshes or temporarily flooded agricultural lands. They usually eat vegetative matter consisting of seeds, stems, and leaves of aquatic and emergent vegetation. Green-winged Teal appear to prefer the small seeds of nutgrasses (Cyperus spp.), millets (Panicum spp.), and sedges to larger seeds, but they also consume corn, wheat, barley, and buttonbush (Cephalanthus spp.) seeds. In marshes, sloughs, and ponds, Green-winged Teal select the seeds of bulrushes, pondweeds, and spikerushes (Eleocharis spp.). To a lesser extent they feed upon the vegetative parts of muskgrass (Chara spp.), pondweeds, widgeongrass (Ruppia maritima), and duckweeds (Lemna spp.). They will occasionally eat insects, mollusks, and crustaceans. Occasionally during spring months, Green-winged Teal will gorge on maggots of decaying fish which are found around ponds.Predators
Common predators of Green-winged Teal include humans, skunks (Mephitis and Spilogale spp.), red foxes (Vulpes vulpes), raccoons (Pryon lotor), crows and magpies (Pica spp.).Relationships
mtDNA data-wise, this species is more closely related to the Speckled TealSpeckled Teal
The Yellow-billed Teal is a South American species of duck. Like other teals, it belongs to the diverse genus Anas; more precisely it is one of the "true" teals of subgenus Nettion. It occurs in Argentina, the Falkland Islands, Chile, Peru, Bolivia, Uruguay, and Brazil...
than to the Common Teal. This would require that sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
either was lost in the Speckled Teal or that it evolved in near-identical forms in the Green-winged and Common Teal after the divergence of the Green-winged and Speckled Teal lineages.
Both hypotheses seem rather spurious initially, with the GWT and Common Teal's male nuptial plumage being unique and very complex, and the tendency to gain, not lose, strong sexual dimorphism overwhelming in the dabbling ducks. An alternative explanation given the high frequency of hybridisation in ducks
Bird hybrid
A bird hybrid is a bird that has two different species as parents. The resulting bird can present with any combination of characters from the parent species, from totally identical to completely different. Usually, the bird hybrid shows intermediate characteristics between the two species...
would be that the mtDNA of the present-day GWT is originally derived from Spotted Teal females by introgression
Introgression
Introgression, also known as introgressive hybridization, in genetics is the movement of a gene from one species into the gene pool of another by the repeated backcrossing of an interspecific hybrid with one of its parent species...
and thus the molecular data gives a misleading picture of the species' true relationships. This is supported by the observation that in Mallard
Mallard
The Mallard , or Wild Duck , is a dabbling duck which breeds throughout the temperate and subtropical Americas, Europe, Asia, and North Africa, and has been introduced to New Zealand and Australia....
× American Black Duck
American Black Duck
The American Black Duck is a large dabbling duck. American Black Ducks are similar to Mallards in size, and resemble the female Mallard in coloration, although the Black Duck's plumage is darker...
hybrids, females of both taxa
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
prefer the sexually dimorphic mallard drakes over the dull-plumaged Black Duck drakes; that the GWT is in some aspects—such as the less contrasting nuptial plumage—intermediate between the Common and Speckled Teal is also interesting to note.
Alternatively, the Common Teal might be derived from the GWT, with the molecular difference being due to genetic drift
Genetic drift
Genetic drift or allelic drift is the change in the frequency of a gene variant in a population due to random sampling.The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces...
or a founder effect
Founder effect
In population genetics, the founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population. It was first fully outlined by Ernst Mayr in 1942, using existing theoretical work by those such as Sewall...
in the latter and possibly Speckled Teal introgression in the former. The three teals certainly belong to a superspecies
Superspecies
A superspecies is a group of at least two more or less distinctive species with approximately parapatric distributions. Not all species complexes, whether cryptices or ring species are superspecies, and vice versa, but many are...
in the teals ("Nettion"); the ancestors of this group were most likely sexually monomorphic Southern Hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...
forms (Johnson & Sorenson, 1999; note that their "African" distribution includes Bernier's Teal
Bernier's Teal
Bernier's Teal Anas bernieri is a duck species of the genus Anas. It is endemic to Madagascar, where it is found only along the west coast....
taxa which like many Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
taxa is of Indo-Australian origin).
Another possibility is that the American lineage is derived from stray Common Teals, with the founder effect/genetic drift and/or hybrid introgression phenomena applying as above, only in the reverse direction for the former two. Still, this would require loss of sexual dimorphism in the ancestors of the Speckled Teal, but while extremely rare in dabbling ducks, it is not per se impossible.
The close Speckled-GWT relationship suggested by mtDNA data could of course still apply to the taxa in general, not just to sequences in 2 maternally inherited genes in a few individual ducks (for which it without doubt does apply), but the overall failure of Johnson & Sorenson to seriously take hybridization into account and their small sample sizes and obsolete conceptions of Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
biogeography
Biogeography
Biogeography is the study of the distribution of species , organisms, and ecosystems in space and through geological time. Organisms and biological communities vary in a highly regular fashion along geographic gradients of latitude, elevation, isolation and habitat area...
do not help at all to resolve the issue, but in 1999, the methodology and interpretation were reasonable enough and in fact, the study was pioneering in many respects due to dense taxon-level sampling and still represents one of the default references for interpreting the pyhlogeny of the genus.
It is worthy of note that the post-copulatory displays of the Common and GWT are identical, but those of the Speckled Teal have some additional elements.
All in all, a firm conclusion cannot be reached at present beyond a tentative rejection of the phylogeny suggested by the mtDNA data. Nuclear DNA
Nuclear DNA
Nuclear DNA, nuclear deoxyribonucleic acid , is DNA contained within a nucleus of eukaryotic organisms. In mammals and vertebrates, nuclear DNA encodes more of the genome than the mitochondrial DNA and is composed of information inherited from two parents, one male, and one female, rather than...
sequence information is required, but may not be sufficient, to resolve the puzzling relationships in the crecca-carolinensis-flavirostris complex of teals.
External links
- The Nature ConservancyThe Nature ConservancyThe Nature Conservancy is a US charitable environmental organization that works to preserve the plants, animals, and natural communities that represent the diversity of life on Earth by protecting the lands and waters they need to survive....
: Green-winged teal - Green-winged Teal – Cornell Lab of Ornithology
- Green-winged Teal – eNature.com
- Green-winged Teal – South Dakota Birds
- Green-winged Teal – USGS Patuxent Bird Identification InfoCenter
- Massachusetts Breeding Bird Atlas
- An article about hybrid Common × Green-winged Teal