I learned that although snow swallows and bird's nests are both precious tonics, there are obvious differences in their origin, appearance, foaming volume, taste and price. Bird's nests are nests built by some swifts and swiftlets using their saliva and other digestive substances. Snow swallows are made by scratching the trunks of trees of the genus Pincus, cutting the bark manually, collecting the gelatinous secretions, and air-drying them. The price of snow swallows is relatively low, while the price of bird's nests is higher.