Pacific Black Duck – leucisticPacific Black Duck - Anas superciliosa
I’m fairly sure that this is a leucistic Pacific Black Duck. There was actually quite a little discussion about it on the Australian Bird ID group on facebook last night. Someone else posted a photo of the same bird, asking for an ID. There are at least two of them there, which does make leucistic seem more unlikely, but not impossible. But the appearance definitely makes it the most likely.