Gadwall (Anas strepera)

Gadwall

[order] ANSERIFORMES | [family] Anatidae | [latin] Anas strepera | [authority] Linnaeus, 1758 | [UK] Gadwall | [FR] Canard chipeau | [DE] Schnatterente | [ES] Anade Friso | [NL] Krakeend

Subspecies

Genus Species subspecies Region Range
Anas strepera NA, EU widespread

Genus

Anas is a genus of dabbling ducks. It includes mallards, wigeons, teals, pintails and shovelers in a number of subgenera. Some authorities prefer to elevate the subgenera to genus rank.[1] Indeed, as the moa-nalos are very close to this clade and may have evolved later than some of these lineages, it is rather the absence of a thorough review than lack of necessity that this genus is rather over-lumped. The phylogeny of this genus is one of the most confounded ones of all living birds. Research is hampered by the fact the radiation of the two major groups of Anas ? the teals and mallard groups ? took place in a very short time and fairly recently, roughly in the mid-late Pleistocene. Furthermore, hybridization may have long played a major role in Anas evolution, with within-subgenus hybrids regularly and between-subgenus hybrids not infrequently being fully fertile.[1] The relationships between species are much obscured by this fact, and mtDNA sequence data is of dubious value in resolving their relationships; on the other hand, nuclear DNA sequences evolve too slowly to resolve the phylogeny of the subgenus Anas for example. Some major clades can be discerned. For example, that the traditional subgenus Anas, the mallard group, forms a monophyletic (in the loose sense, i.e. non-holophyletic) group has never been seriously questioned by modern science and is as good as confirmed (but see below). On the other hand, the phylogeny of the teals is very confusing. For these reasons, the dabbling duck lineages more distantly related to mallard group (which includes the type species of Anas) than the wigeons should arguably be separated in their own genera. These would include the Baikal Teal, the Garganey, the spotted black-capped Punanetta group, and the shovelers and other blue-winged species. Whether the wigeons, which are very distinct in morphology and behavior, but much less so in mtDNA cytochrome b and NADH dehydrogenase subunit 2 sequences, should also be considered a distinct genus Mareca (including the Gadwall and Falcated Duck) is essentially the one remaining point of dispute as regards the question which taxa should remain in this genus and which ones should not.

Physical charateristics

Gadwalls are medium-sized ducks characterized by a general lack of bright coloration. Males are gray-brown, with a white belly, and a black rump. In flight, a white speculum and chestnut and black portions on the wing coverts are displayed. The bill is slate-gray and the legs and feet are yellow. The male utters a short “nheck” and a low whistle. Female gadwalls are similar to males, but have a mottled brown appearance, a yellowish bill with dark spots, and a smaller white speculum. She utters a repeated “gag-ag-ag-ag-ag” higher in pitch than the mallard.

Listen to the sound of Gadwall

[audio:http://www.planetofbirds.com/MASTER/ANSERIFORMES/Anatidae/sounds/Gadwall.mp3]

Copyright remark: Most sounds derived from xeno-canto


wingspan min.: 78 cm wingspan max.: 90 cm
size min.: 46 cm size max.: 56 cm
incubation min.: 24 days incubation max.: 26 days
fledging min.: 45 days fledging max.: 26 days
broods: 1   eggs min.: 8  
      eggs max.: 12  

Range

North America, Eurasia : widespread

Habitat

Female gadwall nest in fields and meadows, and on islands and dikes in wetlands. They are found in reservoirs, farm ponds, and coastal fresh and brackish marshes.

Reproduction

Gadwall breed near seasonal and semi-permanent wetlands, mainly in the shortgrass, tallgrass, and mixed prairie regions of the US and Canada. Substantial numbers also breed in wetland habitats of the Great Basin. Gadwall tend to begin breeding later than most ducks. Female gadwall nest in fields and meadows, and on islands and dikes in wetlands and lay an average of 7 to 12 eggs.

Feeding habits

Aquatic vegetation makes up the majority of the gadwall’s diet. As a result, they are often found feeding far from the shoreline, in deeper water than most other dabbling ducks. Gadwall up-end to feed on leafy portions of pondweeds, naiad, widgeon grass, water milfoil, and algae and the seeds of pondweeds, smartweeds, bulrush, and spike rush. They also feed on aquatic invertebrates, such as crustaceans and midges.

Video Gadwall

httpv://www.youtube.com/watch?v=lvPsu9oOxEE

copyright: youtube


Conservation

This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend is not known, but the population is not believed to be decreasing sufficiently rapidly to approach the thresholds under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
A species breeding in the temperate regions of North America and Eurasia. The breeding populations of the western parts of the European Union are more or less sedentary, but they are increased in winter by migratory birds from the Baltic region. This population is totalling 30000 individuals, and seems to have increased during the last decades (Scott & Rose). The birds breeding in Greece or visiting Greece in winter belong to a more oriental population, estimated at 75000-150000 individuals but currently declining
Gadwall status Least Concern

Migration

Partially migratory; northernmost breeding birds descend to lower latitudes in winter, but breeders of more temperate regions mostly sedentary.

Distribution map

Gadwall distribution range map

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