Edible bird's nests, also known as swallow nests, are bird nests created from solidified saliva by edible-nest swiftlets, Indian swiftlets and other swiftlets of the genera Aerodramus, Hydrochous, Schoutedenapus and Collocalia, which are harvested for human consumption. Wikipedia

Swiftlet bird nests made from saliva and harvested for human consumption Wikidata

The nest of certain species of swiftlet, especially the edible-nest swiftlet, Aerodramus fuciphagus or the black-nest swiftlet, Aerodramus maximus, made by the male swiftlet from its gelatinous saliva, and highly prized in Chinese cuisine for delicacies such as bird's nest soup. Wiktionary

Nest of certain species of swiftlet. Wiktionary (translation)