Very few people associate birds with having saliva. At the very least, few people associate bird saliva as having different uses; however, it does have applications outside of the bird's own mouth. Bird saliva can be used as a nest-building tool, a culinary ingredient, and a component of traditional medicine.
Some species of birds, including swifts and hummingbirds, use their saliva in the building of their nests. The swift, for example, projects a large amount of saliva against a surface, such as a tree trunk, providing an anchor for the nest. They then build up the nest in continuing layers of bird saliva along with the odd inclusion of objects such as feathers, twigs, and other plant material. The resulting nest is a fairly smooth, deep, bowl shape. Saliva is an ideal building component as it is thick and dries quickly.
Bird saliva also forms the base of a traditional Chinese delicacy, swallow's nest soup. The nests used in this very expensive dish are produced by male swiftlets, found mainly in China and Thailand. This dish is considered very prestigious and so is highly sought after. To keep up with demand, a number of nesting sites are man-made.
The most prized ingredient for this delicacy are the white nests produced by the Edible-nest and Pacific swiftlets. These are subsequently graded into levels of quality, with the highest being those nests collected first in the harvesting season before the chicks are hatched. Nests are cleaned after grading to remove any extraneous material.
The nests are composed almost exclusively of bird saliva. To make the soup, cooks soak the nests in water, causing them to swell and soften. This allows any embedded material to be removed. They then place the nests in a pot and cover them with water. After approximately 15 minutes of simmering, rock sugar goes into the pot. Cooks simmer this mixture for a further hour before serving.
The resulting soup is thick and gelatinous, with the majority of the nest having dissolved. Bird saliva soup is very popular in America and Hong Kong, who are the biggest importers of the nests. Eating the soup is thought to increase the libido and sharpen mental focus. The benefits from eating it are thought to be so important that no seasoning should be added.
Bird saliva is thought to have additional health benefits, and nests are popularly used in traditional Chinese and Vietnamese medicine. It is considered to be an excellent restorative for the lungs and is used to alleviate asthma and other respiratory disturbances. The nests, which contain calcium, zinc, and iron, are also thought to encourage growth and improve the circulation of the blood. Finally, the saliva has also long been used as an antiaging tonic and immune system enhancer, improving general health and helping to prevent colds and the flu.