in European countries, ducks and geese have a definite connection with devils and witches, who often have ducks’ or geese’s feet. There are many folk stories where all sorts of beautiful women and beings come along, but if you look at their feet you see that they have ducks’ or geese’s feet
Von Franz argues that geese function as a folkloric index of demonic or witch-nature, their feet serving as the tell-tale sign of evil concealed beneath attractive feminine appearance.
, Shadow and Evil in Fairy Tales, 1974thesis