Cave swallows, also known as rock swallows, are the most primitive wild bird's nests and are mostly found in caves on coastal cliffs. The nests built by wild golden brown swifts with pure saliva are called natural cave bird's nests.

Since the wild golden swifts feed on unpolluted insects, fish and shrimps from the mountains and forests, and build their nests in primitive caves, they absorb many rich minerals and the essence of the sun and moon in nature, so the cave swallows contain

It is particularly rich in protein and nutrients, and contains far more minerals than house swallows.