Hongyan is a large migratory bird, which moves southward every autumn, often causing homesickness and wandering sorrow. Hongyan's biography refers to communication. There are also letters referred to by Hongyan.
Hongyan handed over a book [hóng yàn chun shū], which refers to correspondence and correspondence with Hongyan.
According to Records of the Historian, during the reign of Emperor Wu of the Han Dynasty, Su Wu, the envoy, was detained by Xiongnu and held in the bitter and cold land of Beihai for many years. Later, the Han Dynasty sent messengers to ask the Huns to release Su Wu, and the Huns Khan lied that Su Wu was dead. At this time, someone secretly told the truth of the matter to the Han ambassador, and gave him advice to tell the Huns that Emperor Xian of Han had shot down a wild goose in Shanglinyuan, and Su Wu's silk book was tied to the goose's foot, which proved that he was really not dead, but was trapped. In this way, Xiongnu Khan could no longer lie that Su Wu was dead and had to put him back in the Han Dynasty. Since then, the story of "Hongyan Legend" has become an eternal story. And Hongyan has become a messenger.