Mallard
Anas platyrhynchos

One of the most common ducks in the world, the Mallard extends across the Northern Hemisphere with introduced populations in many countries, such as New Zealand and Australia. They are native to Japan, but primarily overwinter. They are large ducks at 50-60 cm in length.
 

1: Kasai Rinken Koen, Tokyo, 23/05/2012.