The eagle features on all US documents. It was chosen by Congress as the national bird in 1782. This is a reference to Ancient Rome, with whose virtues the founding fathers sought to associate. The eagle in Rome was, however, not a symbol of the State but an emblem of the legions. Anyway, it spawned many symbolic descendants. The eagle was the emblem of the Byzantine Empire, of the empire of Charlesmagne, of Imperial Russia, of the Austro-Hungarian Empire and the kingdoms of Poland and Prussia. (Chaline, Eric: Fifty Animals that Changed the Course of History. Buffalo, New York: Firefly Books, 2011: 103)