Blood Bird's Nest belongs to a kind of Cave Bird's Nest, which is a kind of swiftlet nesting in the rock wall of the cave. The minerals inside the rock wall slowly penetrate into the bird's nest through the contact surface of the bird's nest and the rock wall or through the drip of the rock wall, in which the iron element accounts for the majority of the time, it will be part of the irregular, stained rusty red color, which we will call as the Blood Bird's Nest.