Literature Reference: In the mountains, a bird does not roost; at midnight, its chirping echoes. It seems to sing of the joy of returning home, causing travelers to weep as they listen. All suspect this mountain path is trodden by many southern-bound exiles. Their sorrow and indignation do not dissipate but condense into spirits. I say this mountain bird does not exist because of human life. Human hearts naturally yearn for their homeland, thus the bird sings of returning. - 'He Da Shi Shi Shou He Si Gui Le' by Bai Juyi.