Jin Siyan, birds, swifts, swiftlets, swiftlets, swiftlets. The body length is about 13 cm. The upper body feathers are black or brown, sometimes with blue luster. The lower body is gray and white. The wing tip is long. The feet are short, reddish, and all four toes are forward. Live in groups and eat insects. During the breeding period, the mixed glue of feathers, soil and so on is formed into a nest with saliva, and the nest is placed on the cliff in the sea rock, which is the famous tonic-bird's nest. Edible and medicinal. There are many species in the same genus, and only a few bird species build nests that are edible. Distributed in India and Malay Archipelago. China is distributed in Hainan, Tibet, Yunnan, Sichuan, Hubei, Guizhou and other provinces.