[1] Despite the almost identical and highly apomorphic nuptial plumage of their males, which continues to puzzle scientists, they seem well distinct species, as indicated by a wealth of behavioural, morphological, and molecular data.

[3][17] From a distance, the drakes in nuptial plumage appear grey, with a dark head, a yellowish behind, and a white stripe running along the flanks.

[17] In non-breeding (eclipse) plumage, the drake looks more like the hen; it is more uniform in colour, with a dark head and vestigial facial markings.

Males in eclipse plumage, females and immatures are best recognised by their small size, calls, and the speculum; they are hard to tell apart from the green-winged teal however.

For example, in the United Kingdom and Ireland a small summer population breeds, but far greater numbers of Siberian birds arrive in winter.

In the Caucasus region, western Asia Minor, along the northern shores of the Black Sea, and even on the south coast of Iceland and on the Vestmannaeyjar, the species can be encountered all year, too.

[17] In winter, there are high densities around the Mediterranean, including the entire Iberian Peninsula and extending west to Mauretania; on Japan and Taiwan; as well as in South Asia.

Its numbers are mainly assessed by counts of wintering birds; some 750,000 are recorded annually around the Mediterranean and Black Seas, 250,000 in temperate western Europe, and more than 110,000 in Japan.

In 1990 and 1991, a more detailed census was undertaken, yielding over 210,000 birds wintering in Iran, some 109,000 in Pakistan, about 77,000 in Azerbaijan, some 37,000 in India, 28,000 in Israel, over 14,000 in Turkmenistan and almost 12,000 in Taiwan.

It appears to be holding its own currently, with its slow decline of maybe 1–2% annually in the 1990s – presumably mainly due to drainage and pollution of wetlands – not warranting action other than continuing to monitor the population and possibly providing better protection for habitat on the wintering grounds.

The IUCN and BirdLife International classify the Eurasian teal as a species of Least Concern, unchanged from their assessment before the split of the more numerous A.

In flight, the fast, twisting flocks resemble waders; despite its short legs, it is also rather nimble on the ground by ducks' standards.

In the breeding season, it is a common inhabitant of sheltered freshwater wetlands with some tall vegetation, such as taiga bogs or small lakes and ponds with extensive reedbeds.

[17] The Eurasian teal usually feeds by dabbling, upending or grazing; it may submerge its head and on occasion even dive to reach food.

In winter, it shifts to a largely granivorous diet, feeding on seeds of aquatic plants and grasses, including sedges and grains.

After the females have started laying, the males leave them and move away for shorter or longer distances, assembling in flocks on particular lakes where they moult into eclipse plumage; they will usually encounter their offspring only in winter quarters.

The maximum recorded lifespan – though it is not clear whether this refers to the common or the green-winged teal—was over 27 years, which is rather high for such a small bird.