Bird's nest is a kind of colloidal saliva secreted by swallow's mouth, which is dried by sea breeze after spitting out, thus forming bird's nest. This saliva, slender seaweed, down feathers and soft plant fibers make a nest called bird's nest.

Bird's Nest refers to a nest made of saliva secreted by some Swifts of Swift Family of Swift Order and several Jin Siyan species of Swift genus, and then mixed with other substances.

Also called Swallowtail, Swallowtail Root and Swallowtail. According to nesting sites, bird's nest can be divided into "house swallow" and "cave swallow". Due to the influence of minerals, Dongyan has different colors, including Bai Yan, Huangyan and Hongyan.