The White Duck is a Russian fairy tale collected by Alexander Afanasyev in Narodnye russkie skazki. Andrew Lang included it in The Yellow Fairy Book.
A king had to leave his newly-wed wife for a journey. He sternly warned her against leaving the women's quarters and listening to bad advice. But a wicked witch lured her into the garden and into a pool, and turned her into a white duck, herself taking the queen's own form and place.
Meanwhile, the white duck built a nest, laid three eggs, and hatched two fluffy ducklings and one ugly drake. She warned them against the castle, because an evil witch lived there, but one day the witch saw them and lured them inside. The ducklings slept but the drake stayed awake, and when the witch called if they were asleep, the drake answered. But after two answers, the witch went in to see, and saw the ducklings were asleep, so she killed them.
The white duck found the bodies and lamented over them. The king wondered at it, and although the witch tried to persuade him it was nothing but quacking, he ordered that the duck be captured. His servants could not, but he went himself, and she flew to his hands and became a woman. She told of a bottle in the nest in the garden -- or, they sent a magpie for magic water -- which, sprinkled on the ducklings and drake, turned them into three lovely children. The evil witch was then put to death through dismemberment and nothing remained of her.