Mallard or wild duck (Vịt cổ xanh, Anas platyrhynchos) 

The mallard or wild duck (Anas platyrhynchos) is a dabbling duck that breeds throughout the temperate and subtropical Americas, Eurasia, and North Africa.

Males (drakes) have green heads, while the females (hens) have mainly brown-speckled plumage. 
Both sexes have an area of speculum feathers on their wings; males especially tend to have blue speculum feathers.

The name Anseriformes is derived from the New Latin word Anser, meaning "goose," and the Latin suffix -formes, meaning "having the form of".
The name Anas is the Latin for "duck".
The scientific epithet platyrhynchos comes from Latin Anas, "duck" and Ancient Greek πλατυρυγχος, platyrhynchus, "broad-billed" (from πλατύς, platys, "broad" and ρυγχός, rhunkhos, "bill").