Did you know that the ancient Vikings navigated by depending on the instinct of birds. They took on board a number of ravens, and released them one by one as they sailed to the west. If the raven flew back along the course from which it had come, the Viking ships continued due west. But when a raven flew a different way, the ships would change course and follow its flight path to search for new lands.
"... and quoth the raven, nevermore..."