Literature Reference: 梁上有双燕，翩翩雄与雌。衔泥两椽间，一巢生四儿。四儿日夜长，索食声孜孜。青虫不易捕，黄口无饱期。觜爪虽欲敝，心力不知疲。须臾十来往，犹恐巢中饥。辛勤三十日，母瘦雏渐肥。喃喃教言语，一一刷毛衣。一旦羽翼成，引上庭树枝。举翅不回顾，随风四散飞。雌雄空中鸣，声尽呼不归。却入空巢里，啁啾终夜悲。燕燕尔勿悲，尔当返自思。思尔为雏日，高飞背母时。当时父母念，今日尔应知。——《燕诗示刘叟》 白居易 On the beam, a pair of swallows, graceful and elegant, build their nest between two rafters, raising four chicks. The chicks grow day and night, chirping incessantly for food. Catching green insects is no easy task, and the young ones are never satisfied. Though their beaks and claws grow weary, their hearts and strength remain tireless. In moments, they fly back and forth, fearing the nest may go hungry. After thirty days of toil, the mother grows thin while the chicks grow plump. She murmurs, teaching them words, and meticulously grooms their feathers. Once their wings are fully grown, she leads them to the branches of the courtyard tree. They flap their wings and fly away without looking back, scattering with the wind. The parents cry in the air, their calls unanswered, and return to the empty nest, chirping in sorrow all night. 'Oh, little swallows, do not grieve; reflect upon yourselves. Think of the days when you were fledglings, flying high and leaving your mother behind. What your parents felt then, you should now understand.' Source from 'Yan Shi Shi Liu Sou' by Bai Juyi.