Commonly known as Bai Yan (also known as Yan Guan) and Huang Yan (commonly known as Huang Yan Jin Siyan), these two names are actually another name of Jin Siyan. The bird's nest made in Jin Siyan is usually white at first, but with the passage of time, it will be different because of the food Jin Siyan eats and the nesting environment. Although it was built in the same environment, it will have different colors due to different time. Generally speaking, the color of bird's nest will gradually change from pearl white to gray (commonly known as Bai Yan, also known as Yan Guan) or pearl yellow (commonly known as Huang Yan) after it has existed for a long time. This is the result of oxidation, which is a natural phenomenon, similar to peeled pears, which change color because of contact with oxygen in the air. In most Jin Siyan, it takes about 80 days to 1 1 1 day from nesting, spawning, hatching and growth to the time when Xiaoyan leaves the nest. Generally, the time to collect bird's nest is when Jin Yan Jr. has left the nest. In order to allow Jin Siyan enough time to breed the next generation, the collection interval will exceed three months, so the color of the bird's nest is natural.

About Blood Swallow: Some early dictionaries, such as Nutrition Encyclopedia, recorded that the third nest made by the swallow near the spawning period was called Blood Swallow's Nest after the second nest was picked, because the gum it spit out contained bloodshot blood. Therefore, it is constantly criticized by environmentalists and believers. But the blood swallow is not the result of Jin Siyan vomiting blood, because the red hemoglobin will only be oxidized to dark brown methemoglobin. Blood swallow is related to the consumption of coastal algae and insect food in Jin Siyan. Blood swallow is not as expansive and fragrant as Bai Yan, but it has higher mineral content, so it is more expensive because it is scarce.