who does the quote involving "quick sparrows over the black earth whipping their wings down the sky through mid air" have to do with imagery and fertility/sexuality

The earth is often a symbol of fertility and growth (both the Greeks and the Romans has a goddess of Earth, Ceres and Demeter) since when seeds are planted then there is a "conception" as the earth sprouts that which lives. The imagery of the "whipping" wings could indicate the frenzy that comes along with intimate relations between two beings who are involved in the sexual act.