The Duck Man is the most coherent of the Canting Crew, not that this is saying much. He is capable of reasonably accurate estimates of how much food can be bought with a certain (small) amount of money.

The reason that the Duck Man is called the Duck Man, and considered insane, is that there is always a duck sitting on top of his head, though he insists that there is not. In spite of occasional contradictions this causes in others' minds, the Duck Man is quite happy as he is.