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Dendrocygna viduata
with permission from my brother, Curtis Whiteway
Nice spotting. You have two duck species here. They are:
White-faced Whistling Duck (Dendrocygna viduata)
Black-bellied Whistling Duck (Dendrocygna autumnalis)
Since there are more of the former than the latter you should probably focus on the White-faced Whistling Duck as the name of this spotting.