the duck, strangely enough, especially in fairy tales which are concerned with the problem of evil, comes up as a saving factor; and, at least in European countries, the duck seems to be connected in one way with the principle of evil and in another way with that which rescues one from evil.
Von Franz establishes the duck’s fundamental ambivalence in European fairy-tale symbolism — simultaneously aligned with evil (witches, devils) and with deliverance from evil — while noting its tripartite mobility across land, water, and air as the basis for its symbolic range.
, Shadow and Evil in Fairy Tales, 1974thesis