Bird’s nest is a nest made of saliva or a mixture of saliva and down feathers by swiftlets of the same genus. The demand for bird’s nest is so high that it has become a valuable tonic, which has led to a serious problem of counterfeiting, adulteration, mixing, manufacturing and selling. Bird’s nest is usually divided into 3 categories, namely red “blood bird’s nest”, white “official bird’s nest” and black “hair bird’s nest”. Blood swiftlets are the least and most precious; “official swiftlets” are the first nests made by cave swiftlets every year; the worst quality are “hairy swiftlets”, which contain a lot of debris and must be removed before consumption. The intact ones are semi-circular and metaphorical in shape, with a sunken nest in the middle, which is customarily called “bird’s nest” (attached to a flat rock surface, slightly convex outside), 6.5-10 cm long and 3-5 cm wide, with mucus arranged in layers, neat and wavy, and rough inside the nest, with yellowish-white translucent filaments interlaced to form a loofah. The incomplete ones are fragmented, sticky or studded with tiny feather fragments. The texture is hard and brittle, and the cross section is slightly horn-like. The color is white, with a few down feathers occasionally; the color is gray, with more gray and black feathers; the blood swallow contains russet blood filaments. The smell is slight and the taste is sweet. Empirical identification: water-soluble swelling test: 0.5 g sample, respectively, placed in a clean test tube, add 10 mL of water, add 1 drop of hydrochloric acid, heated to boil 2 min. results of the genuine product to see the body swollen and soft, crystal and transparent, silvery white, elastic (light pull will stretch); heated volume expansion of more than 50 times, and a transparent paste solution; such as the appearance of yellow, not stretching is a fake. Foam test: take the above test tube, shake hard and place, the result of the genuine product to see the foam accounted for about 2 / 5 of the volume of the whole tube, a long time does not disperse; counterfeit products are no foam, colloidal. Cautery test: pick a few samples with anatomical needles, placed on the alcohol lamp cauterization, the results of the genuine product slightly burst, dissolved bubbles, no smoke, no odor, ashes white light, small amount, soluble in hydrochloric acid; counterfeit burst sparks, crackling, black smoke and burnt odor, ashes are black tuberous, more, insoluble in hydrochloric acid.