Augury is divination by the observation of birds, their species, the direction and manner of their flight, their cries, and the quarter of the sky from which they come, and, by extension, the reading of signs that arrive unbidden rather than being deliberately sought. It is most famous as a formal institution of Roman religion, where the augures were an official college of priests whose task was not to foretell the future in detail but to determine whether the gods approved (or disapproved) of a proposed public action, the founding of a city, the holding of an assembly, the launching of a campaign.
Before major undertakings the magistrate would "take the auspices" (auspicium, "bird-watching"), marking out a sacred space of the sky (the templum) and watching for signs within it; unfavorable omens could halt state business entirely. So central was this to Roman public life that the very word inauguration descends from it. Related Roman practices included reading the appetite of the sacred chickens before battle. Bird-omens as messages from the divine appear far beyond Rome, in Greek epic, in Mesopotamian omen literature, and across many folk traditions, reflecting a widespread intuition that birds, moving freely between earth and sky, are fitting messengers between the human and divine worlds.