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. 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. 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.
copyright: Josep del Hoyo
The species is dark brown with buffy markings. The face and throat are pale with a white ring around the eye. The bill is bluish grey and the iris is red.[
Andaman Teal used a variety of habitats at different times. Feeding locations in summer were shallow areas with sparse vegetation, whereas during the breeding season (autumn) they foraged among reeds, Phragmites karka and Scirpus sp., with thicker cover nearer to the nest. Teal were found loafing in open water or resting on wooden logs, mounds, small trees, or bushes in water or on the banks and mud banks. Teal were in single species flocks or mixed flocks with the Lesser Whistling duck endrocygna javanica. Detailed analysis comparing feeding and nonfeeding sites showed that insects and small molluscs in the soil were crucial factors in determining feeding locations for Teals.
Molluscs and arthropods formed the major part of the Andaman Teal?s diet. Seasonal differences in food were observed: a higher proportion of animal food (88%) was found in the diet in summer than during the monsoon (60%), similar to observations of Grey Teal in North Queensland. Andaman Teal was previously recorded as mostly vegetarian, feeding also on invertebrates.
Not yet evaluated
Andaman Teal Anas (gibberifrons) albogularis, endemic to the Andamans, is scarce and has recently declined, and is likely to have been affected by the tsunami because of its coastal distribution. This duck is usually treated as a subspecies of Sunda Teal Anas gibberifrons, but it has been proposed that it should be treated as a full species (this proposal is currently under review by the BirdLife Taxonomic Working Group)
The breeding season is July to October and nests in reed patches. Altogether 13 nests were found in two locations during 1997 and 1998, six at Mohanpur and seven at Hanspuri; birds were apparently breeding at 10 further sites but nests could not be located. Nesting was found from July to October with a variation in the peak, depending on the monsoon. The nest is a platform of grass or reed mat 20-35 cm above water among the reeds, 20-50 cm from open water. Nesting pools were 20-50 cm deep, mainly brackish and located in coastal areas, 50-100 m from the high tide line. All these wetlands had natural or man-made bunds for collecting rainwater which reduced salinity. This species selected a nesting site based on optimum water levels and availability of food for the young. Nesting success was high during the study (85%) as there were very few predators. However, poaching of eggs by humans and predation by Water Monitor Lizards were the major causes of egg loss. Predation by raptors may also occur. Parents with ducklings spent most of their time in thick vegetation, coming into open water with sparse vegetation only for very short periods.
Range: Oriental Region : Andaman Is., Cocos Is. New Guinea to New Caledonia and Australia to New Zealand