What does "crow knows how to feed back" mean?

The crow feeds back is an idiom, which means to support the filial piety of the elders.

From "Compendium of Materia Medica Poultry Department": "Ciwu: This bird is born, the mother eats for 60 days, and the long food for 60 days."

Crow is an ugly bird. It is said that when crows grow up under the care of their mothers, when their mothers are old and weak, blind and unable to fly, birds will feed the food they find into their mouths to repay their mothers' kindness. When the crow grows up, it will not leave home like other birds, but will "support" its parents like its parents in the past. Revelation: Crows know filial piety to their parents, and people should do it even more. Crow feeding back is worth learning!

Young birds are strong and can fly, but they can eat and feed back. -"Introduction Notes on Birds"

Sheep have the grace of kneeling and nursing, and crows have the meaning of feeding back. -"Augmented Sage"