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Bird Saliva Provides a Prized but Contentious Food
© Rosemary Drisdelle
Aug 23, 2014
What is bird’s nest soup, and why is it a source of conservation concern after centuries of East Asian tradition? Edible-nest swiftlets are in decline.
What is bird’s nest soup?
Bird’s nest soup has been an Asian culinary tradition for centuries. Made from the nests of edible-nest swiftlets—usually Aerodramus fuciphagus (formerly Collocalia fuciphaga) or Aerodramus maximus (formerly Collocalia maxima)—it can be either savory or sweet. Savory soup is made with chicken broth and contains pieces of nest, bits of chicken breast, mushrooms, quail eggs, and sometimes ham. Sweet bird’s nest soup is a simple recipe using nest, rock sugar, and water.
Edible birds’ nests have a rubbery texture and don’t appeal to many palates; however, they are thought to be very nutritious and to have aphrodisiac properties. Nutritional analysis reveals a high protein content and variable amounts of minerals.
Edible nests
Edible-nest swiftlets nest communally in caves, building nests high above the ground. During nest building, the birds’ salivary glands become enlarged and produce thick ropey sticky saliva that hardens quickly when exposed to air. Over a period of weeks, swiftlets gradually construct a cup-shaped nest about the size of a human ear. Nests may be white, golden, black, or red: white nests are very clean and contain nothing but saliva; black nests contain plant parts and feathers; red are believed to contain blood from the birds’ salivary glands, but the colour may actually come from insects that they have eaten, or minerals leaching from the cave wall.
Harvesting edible nests
Harvesting edible birds’ nests is dangerous work that requires climbing to great heights in dark caves and prying the nests off the cave wall. Deaths and injuries are not uncommon.
If the first nest is destroyed or harvested before the birds lay eggs, the birds will rebuild—traditionally, the people of Southeast Asia have harvested the nests of edible-nest swiftlets after the birds have built the first nest but before there are eggs or hatchlings. A second harvest is carried out after fledglings have left the second nest.
Today, some swiftlets are farmed, using wooden structures that mimic cave conditions. So-called “house nests” are cheaper but have the same nutritional value as cave nests.
Threats to edible-nest swiftlets
Today, edible birds’ nests are one of the most expensive foods on Earth—packaged bird’s nest costs more than $150 US for just a hundred grams, and a bowl of bird’s nest soup in a restaurant will cost $60 or more. High prices result from the difficulty of obtaining nests and the high demand for the product. Because the nests command such a high price, there is increasing incentive for harvesters to take too many nests and even to take nests with young birds in them. In some places, edible-nest swiftlet populations have declined precipitously, although they are not threatened globally.
Dangers of bird’s nest soup
Bird’s nest soup is very nutritious and it certainly is a novelty to westerner’s who enjoy trying new things, but is it worth it? Those who eat it should be aware of a few caveats:
• Edible birds’ nests are one of the most common causes of anaphylactic food-related allergic reactions in East Asian children.
• Commercial birds’ nests, especially the highly prized varieties, are often adulterated with karaya gum (a tree extract), red seaweed, or a variety of fungus.
• Birds’ nests may absorb toxic metals from the walls of caves.
• The increasing value of edible birds’ nests is resulting not only in overexploitation of the swiftlets, but also corruption and violence in the industry. Those who control the caves guard them carefully and unwary trespassers are sometimes seriously injured or killed.
