1, Only Jin Siyan of Swift Family and many swallows of the same genus can become bird's nest if their saliva is mixed with down feathers, and the bird's nest directly picked can't be eaten immediately, and it can only be eaten after processing.

2. Bird's nest can be divided into "house swallow" and "cave swallow" according to the nesting place. The color of cave swallow is different due to the influence of minerals, including Bai Yan, Huangyan and Hongyan, while house swallow is only ivory white. Bird's Nest is one of the traditional precious foods that have been eaten in China since the Ming Dynasty. The so-called "blood swallows" on the market are said to be made by artificially cultured house swallows through "bird droppings".

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