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.
The first formal description of the Baikal teal was by the German naturalist Johann Gottlieb Georgi in 1775 under the binomial name Anas formosa.[3][4] A molecular phylogentic study published in 2009 found that the genus Anas as then defined was non-monophyletic.[5] Based on this analysis the genus was split into four proposed genera with the Baikal teal placed in the resurrected genus Sibirionetta that had been introduced by the German zoologist Hans von Boetticher in 1929.[6][7] The name Sibirionetta is derived from the Latin sibiricus for Siberia and the Ancient Greek nētta for a duck. The specific epithet formosa is from the Latin formosus for "beautiful".[8]
At between 39 and 43 centimetres (15 and 17 in), this duck is slightly larger and longer-tailed than the common teal. The breeding male is unmistakable, with a striking green nape, yellow and black auriculars, neck, and throat. It has a dark crown, and its breast is light brown with dark spots. It has long dropping dark scapulars, and its grey sides are set off on the front and rear with white bars.
The female looks similar to a female green-winged teal but with a longer tail, and a distinctive white spot at the base of the bill and a white throat that angles to the back of the eye. She also has a distinct light eyebrow bordered by a darker crown. The underwing is similar to the Green-winged Teal also, but has a darker leading edge. The green speculum has an indistinct cinnamon-buff inner border.[9] Some "females" have "bridle" markings on their faces, but it has been suggested that at least some of these bridled "females," if not all, are in fact juvenile males.[9] The juvenile has a plumage similar to that of the female and can be distinguished from the Common Teal by the pale loral spot.
In non-breeding (eclipse) plumage, the drake looks more like the female, but plumage is a much richer reddish-brown (rufous) colour.
It breeds within the forest zone of eastern Siberia from the Yenisey basin eastwards to Kamchatka, northern Koryak, eastern Magadan Oblast, northern Khabarovsk Krai, southeastern and northern Sakha east central Irkutsk Oblast, and northern Krasnoyarsk Krai. It is a migratory species, wintering in South Korea, Japan, Taiwan, northern and eastern China, from Beijing down the coast to the Vietnam border, and west to Yunnan then north to Chongqing and Henan.[1][10]