Duck

It seems Mallard. Photo taken in Jan.2011 lake behind the Delhi Sectt.New Delhi. The Yello billed Duck with a beautiful greenish Head .

The Mallard ( /ˈmælɑrd/ or /ˈmælərd/), or Wild Duck (Anas platyrhynchos), is a dabbling duck which breeds throughout the temperate and subtropical Americas, Europe, Asia, and North Africa, and has been introduced to New Zealand and Australia.

The male birds have a bright green or blue head, while the female's is light brown. The Mallard lives in wetlands, eats water plants, and is gregarious. The Mallard is the ancestor of most domestic ducks, and can interbreed with other species of genus Anas. Among close relatives of the Mallard this hybridisation can cause genetic dilution, which is contributing to the decline of rarer species of a duck. Sources :- (Wikipedia)