"‘There was a Cheyenne sub-chief named Whistling Elk. There was also an animal, or a ghost-animal, in the mythology of several tribes, the Cheyennes, the Sioux, the Osages, and the Comanches. There is something spooky about this Whistling Elk in the legends, for real elks do not whistle. The Whistling Elk is an apparition, a ghost, a messenger of death. He is also the one who gives the birds the signal to migrate. They would not know when to mill and fly away, and they would perish of the cold and hunger, if the Elk didn't give them the signal. The Whistling Elk is sometimes associated with the Bird-Master, who is variously known as the ‘shape-changer’ and the ‘cloud-shaper’."  —R. A. Lafferty