By Ken Billington (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons -
Asia. Almost all of the Philippine Islands.
I can find no documented escapes but they have clearly happened. The species is described as winter-hardy and easy to breed but is prone to hybridise with Mallard and the Mallard's close relative, the Pacific Black Duck.