Bird's nest soup is a delicacy in Chinese cuisine. A few species of swiftlet, the cave swifts, are renowned for building the saliva nests used to produce the unique texture of this soup.
The edible bird's nests are among the most expensive animal products consumed by humans. The nests have been used in Chinese cooking for over 400 years, most often as bird's nest soup.
The Chinese name for bird's nest soup, "yàn wo", translates literally as "swallow's nest". When dissolved in water, the birds' nests have a gelatinous texture used for soup or sweet tong sui. It is mostly referred to as "yin wo" unless references are made to the salty or sweet soup in Chinese cuisine.
The most heavily harvested nests are from the Edible-nest Swiftlet or White-nest Swiftlet (Aerodramus fuciphagus) and the Black-nest Swiftlet (Aerodramus maximus). The white nests and the "red blood" nests are supposedly rich in nutrients, which are traditionally believed to provide health benefits, such as aiding digestion, raising libido, improving the voice, alleviating asthma, improving focus, and an overall benefit to the immune system.
The nests are built during the breeding season by the male swiftlet over a period of 35 days. They take the shape of a shallow cup stuck to the cave wall. The nests are composed of interwoven strands of salivary laminae cement. Both nests have high levels of calcium, iron, potassium, and magnesium.
Hong Kong and the United States are the largest importers of these nests. In Hong Kong, a bowl of bird's nest soup would cost $30 USD to $100 USD. A kilogram of white nest can cost up to $2,000 USD, and a kilogram of "red blood" nest can cost up to $10,000 USD. The white nests are commonly treated with a red pigment, but methods have been developed to determine an adulterated nest.
The nests were formerly harvested from caves, principally the enormous limestone caves at Gomantong and Niah in Borneo. With the escalation in demand these sources have been supplanted since the late 1990s by purpose-built nesting houses, usually reinforced concrete structures following the design of the SE Asian shop-house ("ruko") These nesting houses are normally found in urban areas near the sea, since the birds have a propensity to flock in such places. This has become an extraordinary industry, mainly based on a series of towns in the Indonesian Province of North Sumatra, which have been completely transformed by the activity. From there the nests are mostly exported to Hong Kong, which has become the centre of the world trade, though most of the final consumers are from mainland China. It has been estimated that the products now account for 0.5% of the Indonesian GDP, equivalent to about a quarter of the country's fishing industry.