2. Blood Swallow is the bird's nest in Jin Siyan, which is made up of moss, seaweed and soft plant fibers mixed with their feathers and saliva. After refining and processing, it becomes the most precious bird's nest.

3. The Bird's Nest is an edible part of the nest built by Jin Siyan, an agile animal, and many other similar swallows. It is made of saliva and feathers. As far as nutritional value is concerned, it is only a low-grade food. After all, this is just a nest made of saliva and feathers by Jin Siyan. Just to reproduce and live a peaceful life, the nutrition is not rich. The spread of bird's nest is actually a result of the hype of merchants, and its purpose is to serve commercial interests.

4. The Bird's Nest is formed by the saliva secreted by the well-developed mucous glands in Jin Siyan's throat, which condenses into a solid in the air. This is a white bird's nest, built by insects, algae and whitebait ingested by Jin Siyan. After being digested, it is called Bai Yan. Some bird's nests picked from caves are reddish brown or bloody, which is mainly considered to be the result of the interaction of air, humidity, rocks and other environments in which bird's nests are located. This part of bird's nest is called blood swallow. It is generally believed that blood swallow is rich in minerals and its nutritional value is higher than that of Bai Yan.