2. Bird's nest. Bird's nest, also known as Swallow's Vegetable, Swallow's Root, Swallow's Vegetable, refers to the saliva secreted by some rainbirds of the Rainbird family and several species of swiftlets of the swiftlet genus, and then mixes with other substances to build a nest. Bird's nests can be classified into two types of nesting places, namely "House Swallows" and "Cave Swallows". Cave Swallows are different in color due to the influence of minerals, and are divided into White Swallows, Yellow Swallows, and Red Swallows.