BIRD'S NEST SOUP SWIFTLETS, THEIR NESTS AND NEST COLLECTORS

SWIFTLETS AND SWIFTS

Bird's nest soup

Swiftlets are the source of the nests used in bird’s nest soup. There are 28 species of swiftlets in the tribe Collocaliini, which is in the Apodinae subfamilies of swifts which are are in the order Apodiformes and the suborder Apodi. Apodiformes means “without feet.” Swifts do have feet but they are small ones and they are hardly of use them as swifts hunt, eat and even sleep on the fly.

Some swiftlets (Collocaliini) use echolocation calls (emitting sound waves and sensing their reflections to determine the location of objects). The calls are not used in capturing prey, as is the case with bats, but rather to find their way in dark roosting sites. There is a species of cave cricket (Rhapidophora oophaga) in Borneo that feeds on both the young and eggs of swiftlets. [Source: Alaine Camfield, Animal Diversity Web (ADW) /=]

Swifts are among the world’s fastest-flying birds. Their narrow, swept-back, scimitar-shaped wings allow them to not only flay fast, but also to make dramatic dives, acrobatic moves and dart around here and there. There are about 80 different swift species. They are found mostly in the tropics but can be also found in cold areas such as Alaska and Siberia. Many make long migration flights, some over long stretches of open ocean.

Most swifts are dark brown or sooty in color, have short legs and strong claws and stay aloft for months at a time They pursue food, mostly insects, in the air, mate there and presumably sleep there as well. Many swifts have wings that are so long they can not perch on the ground and legs that are so short they have difficultly taking off like other birds. Instead they have drop off from a branch, perch or a cliff side. Some species collect branches for their nest by biting off branch tips in mid flight.

Websites and Resources on Birds: ; Essays on Various Topics Related to Birds stanford.edu/group/stanfordbird ; Avibase avibase.bsc-eoc.org ; Avian Web avianweb.com/birdspecies ; Bird.com birds.com ; Birdlife International birdlife.org ; National Audubon Society birds.audubon.org ; Cornell Lab of Ornithology birds.cornell.edu ; Ornithology ornithology.com ; Websites and Resources on Animals: Animal Diversity Web animaldiversity.org ; BBC Earth bbcearth.com; A-Z-Animals.com a-z-animals.com; Live Science Animals livescience.com; Animal Info animalinfo.org ; World Wildlife Fund (WWF) worldwildlife.org the world’s largest independent conservation body; National Geographic National Geographic ; Endangered Animals (IUCN Red List of Threatened Species) iucnredlist.org

Swift Behavior

Swiftlet

Some species gather in colonies. For these there is a lot of social activity in the form of group flights and vocalizations that vary from long buzzy screams to short sharp chirps. Some species can fly at speeds of 170 kilometers per hour, cover 900 kilometers, collecting insects the whole way. Females swifts that mate in mid air fold out their wings while the male lands on her back. The couple glide together and sometimes plummet hundred of feet towards the earth intertwined.

Many swifts collect the prey they capture into food ball called bolus, and bring them back to their nests. Most of the time these balls contain swarming insects such termites, mayflies, aphids as winged ants, wasps and/or bees. Sometimes several hundred individuals from 60 different species can be found in a single bolus.

Some species of swift are able endure short periods of cool weather by entering a semitropic state with a lowered body temperature. Some swiftlets roost deep in caves in total darkness. These birds used echolocation like bats to navigate around. Non-echolocation swiftlets near the entrance of caves where there is enough light to see.

Swift Speed

Swifts sleeping or “roosting” in flight have been studied with radar. Observations show that they maintain an average speed of 20 mph, periodically flapping to maintain their speed and height. Studies of swift wings in wind tunnels shows that a speed of 20 mph gives the birds the maximum gliding time for the least amount of energy.

Swifts have been clocked going speeds of 60 mph. At high speeds they cock back their wings in a swept-back position. Wind tunnel studies indicate this position is more energy efficient at speeds over 40 mph as drag is reduced and enough lift is provided. When turning, spread wings are good at speed of 20 mph or lower but at speeds above 30 mph stiffened wings held closer the body keep the wings from being damaged by high forces and turbulent air.

These days, scientists are studying swifts for insights into aircraft wing development in part because they don’t flap their wings much when they glide or dive. Swift wings resemble long, thin, curved blades that taper off at the end sort of like a scythe. They gain added maneuverability by having an unusually larger proportion of their wings made up of the “hand” or wing tip bones. By changing the “wrist” angle between the “hand” and forelimb, the swift can change both the shape of the wing and its area, thereby maximizing their efficiency at various speeds.

Bird's Nest Soup

Bird's nest soup is a soup made from the nest of a kind of cave-dwelling swift. It is regarded as a delicacy, health booster, life prolonger and aphrodisiac in Asia, particularly in China and Hong Kong, and is said rejuvenate skin, clear up complexions, clean out the digestive track, and cure lung cancer. [Source: Eric Valli, National Geographic, January 1990; Roy Andries de Groot, Smithsonian]

The translucent, gelatinous material used to make the bird nest gives the soup richness and texture and was compared by an 18th century adventurer with the foam of wave crests. Chinese have made the nest material into a jelly mixed with spices or sweets as well as soup. The taste? One producer said, it was “sort of like a piece of paper.” The nest material has little flavor and generally is cooked with something else to be give it flavor.

Bird's nest soup was invented around 1750 by a Siam-based Chinese man named Hao Yieng who discovered the "wind-eating" swiflets and learned that their nests were soluble in water. In 1770, the King of Siam, granted Hao Yieng a monopoly on the bird nest trade. He promptly became rich. Later the Siamese took back control of the nests and a "corps of hereditary collectors" was established.

A kilogram of top quality bird's nests can go for $3,000 to $4,000, half the price of gold, and is the product of about 120 nests. A tureen of soup for four people of "Nest of Sea Swallows with Venomous Snake and Chrysanthemum Petals with Lemon grass Lotus Seeds in Soup"---with several drops of venom squeezed from the glands of a snake that pulled out a bag---can go for $100 or more in Hong Kong and is made from six nests.

Bird's Nest Swiftlets

nests

The nests used for the soup are made by three bird species: 1) the edible-nest or white-nest swiftlet; 2) Germain’s swiftlet; and 3) the black-nest swiftlet. These birds live primarily in large limestone caves on islands or near the sea in Southeast Asia. Sometimes called "sea swallows," the small swifts feed on flying insects and navigate through caves like bats using echolocation.

Both males and females participate in nest building. The sticky gelatinous noodle-like fibers used to make the nests are secreted by well-developed salivary glands in their mouth The glands enlarge during the breeding season. When the fibers harden they produce a glue that hold the nest together and keeps it attached to the cave. The incubation period for the eggs is 19 to 23 days. Young remain in the nest for an additional six to eight weeks.

The best nests come from swiftlets that live deep inside caves. These birds echoloccate with a series of high pitched clicks and rattles that increase in frequency from five a second in open spaces to twenty a second near walls. Distance is determined by amount of time it takes the sounds to bounce off the wall and return to the ear. Direction is determined by the minute difference between the time sound reaches each ear. The system is effective but crude compared to echolocation system of bats.

Swiftlet Nests

The nests are about the size and hardness of teacups; are essentially made from hardened saliva mixed with feathers, grass and twigs; and look like congealed strands of vermicelli. The noodle-like fibers are used to bond nesting materials together and attach the nest to a vertical walls of caves or cliffs or hollow tree nesting sites.

There are two kinds of nests: white nests made up mostly of saliva and black nests with plant materials and feathers mixed in. White nests are the most valuable. They are generally made by swiftlets that nest deep inside the caves and are ideally collected before a female lays her eggs. Generally the whiter and purer a nest is the more tasty and valuable it is. Black nests are also collected. These nests can not be eaten until they have been properly cleaned.

The edible-nest swiftlet often build their nest in the most inaccessible of places: on the roofs and upper walls of high caves and even overhangs. Other species build nests the in buildings and bridges and chimneys but not the edible-nest swiftlet. Sometimes the eggs and young of edible-nest swiftlets are placed in the nest of an other species, the uniform swiftlet, which lives in buildings. There are some claims that a third of nest form Indonesia are taken from swiftlets that have made their nests in buildings.

Making Swiftlet Nests

To make a nest a swiftlet moves its head back and forth like a weaving bobbin. David Attenborough wrote: “The bird starts by flying persistently in front of its chosen site and repeatedly dabbing the rock with its tongue, laying down a curved line of saliva which marks the lower edge of the nest-to-be. The saliva dries and hardens quickly and with repeated flights, the bird slowly builds up the low line into a low wall. As soon as this is big enough to cling to, the speed of construction accelerates and within a few days the wall has become a semicircular cup of creamy white interlacing string that is just big enough to hold the customary clutch of two eggs.”

The swiftlets are so small they don't have the strength to pick up nesting materials such as twigs and leaves from the ground like other birds. Instead they pick up pieces of feather, fragments of dried grass and other small things they find floating in the air and affix the to a surface their "sticky spittle.” Nests near the entrance to the caves have large amounts of feathers. Those that are deeper inside are made primarily of spittle, and are thus more desirable. .

The swifts can take up two months to build a nest. Ideally the nest is collected after fledglings have take wing rather than before eggs of hatched. That way there are more birds o create nests. After the nests are harvested they are soaked in water ti soften them up and a magnifying glass is used to pick out loose impurities like twigs and feathers. After being steamed or boiled the nest separate into long chewy strands. About half the material in protein. What health benefits might be found in the nests are believed to be lost during the cleaning process.

Bird's Nest Collectors

Nests are collected at Niah caves in Sarawak, Gomantong Cave in Sabah and the Phnag Nga Bay area in Thailand. At Gomantong Cave the nests are collected twice a year: once before the eggs are laid and again after the male has made a second nest and the fledglings are gone.

The nests are harvested by men that sometimes climb hundreds of feet up to roofs of flimsy bamboo and rattan ropes and scaffolding. The men use special knives and three-pronged tweezers — blessed by the cave spirits — to cut and pull the nests off the cave walls. To get to some caves they have to swim through underwater tunnels, shimmy down vines from cliff tops.

Collectors spend ay ear or more learning how to climbs the bamboo scaffolding. They often stay in the caves all day, in some cases feeding themselves on swiftlets eggs they collect. They are often watched while they work and sometimes searched to make sure they haven’t hidden any nests. The work is very dangerous. Some men climb among the bamboo at dizzying heights for decades with no mishaps. Others aren't so lucky, every year several nest gathers die or become seriously injured. The bamboo ropes deteriorate within a couple years. . How do you tell a good bamboo rope from a bad one. If it sounds hollow like cardboard it is no good.

Bird's nest gatherers who work on the rugged cliffs on the southern side of Java have to deal with strong tides and large waves blown up from Antarctica. The Blair brothers talked to one gatherer who misjudged the tides and got stuck inside a cave for 32 days. In the darkness he survived by eating bird's nest and grubs that eat the bird and bat dung on thee floor of the cave. [Source: "Ring of Fire" by Lawrence and Lorne Blair, Bantam Books, New York]

Endangered Bird’s Nest Swiftlets

The business is so lucrative and so many nests are collected before the swiftlets have a chance to lay their eggs, there are worries the swiftlets may become endangered. In some cases, birds have their nests snatched two or three times before they get a chance to lay eggs. In other cases poachers take the nests and toss the eggs or young birds to the ground. By one estimate, half a million eggs have been lost in one cave system in Sabah alone.

Poaching is difficult to control because the of the remote location of some of the caves. The laws on the books that regulate harvesting, poaching, selling, importing and exporting nests the laws are difficult to enforce.

Studies have indicated that populations of some swiftlet communities have declined as a result of poaching Some caves have only a third of the nests they once had. Some have abandoned completely because there are so few best it is unprofitable to collect them. By one estimate the overharvesting of nests and destruction of swiftlet habitats led to a decline in the number of birds by 73 percent in some areas between 1962 and 1990.

bird's nest harvesting

Image Sources: Wikimedia Commons

Text Sources: Animal Diversity Web animaldiversity.org ; National Geographic, Live Science, Natural History magazine, David Attenborough books, New York Times, Washington Post, Los Angeles Times, Smithsonian magazine, Discover magazine, The New Yorker, Time, Reuters, Associated Press, AFP, Lonely Planet Guides, Wikipedia, The Guardian, Top Secret Animal Attack Files website and various books and other publications.

Last updated February 2025