I believe they are native to china... hence the origin of the word "mandarin". I suppose being migratory a few could get lost and find they're way around the world? I know Pintails banded in Japan have been recovered in the US according to acounts in DU magazine. Also I read somewhere that a lot of the non native species such as the Mandarin Duck that are found in the wild escaped from bird habitats and/or sanctuarys... Places that have exoctic species on display for the public and sometime the birds find their way out. Could have what you saw Phil shoot be a Harlequin Duck? They are about the same size somewhat similar in the coloration just different patterns? Thats just a thought. The Harlequin duck is native to the northern pacific flyway...