Edible bird's nests, also known as swallow nests (), are bird nests created from solidified saliva by edible-nest swiftlets, Indian swiftlets and other swiftlets of the genera Aerodramus, Hydrochous, Schoutedenapus and Collocalia, which are harvested for human consumption.
Swallow nests have been used as a delicacy for over 400 years, most often as soup. They are particularly prized in Chinese cuisine due to the rarity, high protein content and rich flavor, and are among the most expensive animal products consumed by humans, with prices up to about depending on grading. The type or grading of a swallow nest depends on the bird species, as well as the shape and color of the bird's nest. It is usually white in color, but there also exists a red version that is sometimes called "blood nest" (). According to traditional Chinese medicine, it promotes good health, especially for the skin.
Etymology
The Chinese name for edible bird's nest, (), translates literally as "swallow's (or swift's) nest"; in Indonesia "sarang burung walet" often serves as a synonym for bird's nest soup.
Culinary use
The best-known use of edible birds nest is bird's nest soup, a delicacy in Chinese cuisine. When dissolved in water, the birds' nests have a flavored gelatinous texture utilized in soup or sweet soup (tong sui). It is mostly referred to as 燕窩 (yànwō) unless references are made to the savory or sweet soup in Chinese cuisine. According to the Qing dynasty manual of gastronomy, the Suiyuan shidan, bird's nest was regarded as a delicate ingredient not to be flavored or cooked with anything overpowering or oily. While it is rare and expensive, it must be served in relatively large quantities; otherwise its texture cannot be fully experienced and enjoyed.
In addition to their use in soup, edible bird's nests can be used as an ingredient in other dishes. They can be cooked with rice to produce bird's nest congee or bird's nest boiled rice, or they can be added to egg tarts and other desserts. A bird's nest jelly can be made by placing the bird's nest in a ceramic container with minimal water and sugar (or salt) before double steaming.
Production and harvest
The most heavily harvested nests are from the edible-nest swiftlet or white-nest swiftlet (Aerodramus fuciphagus) and the black-nest swiftlet (Aerodramus maximus). Previous studies conducted by Lee et al. have reported that the nutrient composition of EBN is dependent on the country of origin, food intake of the birds, climate and breeding sites. Most 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 cement. Both nests have high levels of calcium, iron, potassium, and magnesium.
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 Southeast Asian shop-house ("rumah toko"/"ruko"). These nesting houses are normally found in urban areas near the sea, since the birds have a propensity to flock in such places. It has become an expanding industry as is evident in such places as the province of North Sumatra or the Pak Phanang District in Thailand. From those places the nests are mostly exported to the markets in Hong Kong, which has become the center of the world trade in bird's nests; the industry is valued at around HK$4.3billion per year, although most of the final consumers are from mainland China. China is the world's largest consumer of birds' nests, accounting for more than 90 percent of consumption.
In some places, nest gatherers (known in the Philippines as busyadors) have seen a steep decline in the number of birds and a rise in unexplained fatalities.
Color
Although bird's nest is usually white, there also exists a red version, called "blood nest" (), which is significantly more expensive and believed to have more medicinal value. In the market, a kilogram of white bird's nest can fetch up to , and a kilogram of red nests up to .
The reason for its characteristic redness has been a puzzle for centuries. Contrary to popular beliefs, red bird's nest does not contain hemoglobin, the protein responsible for the color of human blood. Researchers reported in 2013 that 'bird soil' containing guano droppings from bird houses were able to turn white edible bird's nests red, and that edible bird's nests' color is likely caused by environmental factors in cave interiors and bird houses.