The Science of Birds - Where Does Bird's Nest Soup Come From?

Episode Date: April 14, 2023

This episode—which is Number 74—is all about edible bird’s nests and Bird’s Nest Soup.Edible bird nests are a traditional delicacy in east Asia. Especially in China. For centuries, wealthy Chinese people have consumed edible bird nests. Usually in the form of bird’s nest soup.Throughout much of recent history, this dish has been one of the most expensive foods in the world.No wonder people have called edible bird nests the “caviar of the east,” or “white gold.”Perhaps the primary reason people spend ungodly amounts of money on bird’s nest soup is because of its medicinal properties. Well… It’s supposed medicinal properties, anyway.In traditional Chinese medicine, it’s believed that the benefits you can get from eating these nests include: a prolonged life, increased attractiveness, increased libido, brain health, bone strength, no more diabetes, no more cancer, a stronger immune system, more energy, better looking skin, and better circulation.Wow.  So basically, it sounds like an edible bird’s nest is a cure-all—a panacea. That’s pretty impressive! But is it true?And where do these nests come from? What do they look like?In today's episode, we'll get into all of that. We’ll talk about which birds make these amazing nests, and how they do it.We’ll also look at the way people harvest edible bird’s nests, the global industry for this product, and some ethical concerns. Links of InterestSalivating for a New Nest [VIDEO]The Swiftlet Tribe, Collocaliini~~ Leave me a review using Podchaser ~~Link to this episode on the Science of Birds website Support the show

People eat all sorts of weird animal body parts and animal products. We guzzle milk and blood from animals. We cook up their brains, their eyeballs, and sometimes even their testicles. Ew! Heck, we can't get enough of honey. And fundamentally, honey is just bee barf. Tasty, tasty, bee barf. But one of the most bizarre animal products that humans

eat is bird nests. Not just any old nest, mind you, but those of some very special little birds. We'll talk about them in a few minutes. Edible bird nests, or E.B.Ns, as they're called by those in the know, are a traditional delicacy in East Asia, especially in China. For centuries, wealthy Chinese people have consumed edible bird nests, usually in the form of birds, nest. soup. Throughout much of recent history, this dish has been one of the most expensive foods in the world. No wonder people have called edible bird nests the caviar of the east, or white gold. Perhaps the primary reason people spend ungodly amounts of money on birds' nest soup is because of its medicinal properties. Well, it's supposed medicinal properties anyway. In traditional

Chinese medicine, it's believed that the benefits you can get from eating these nests include a prolonged life, increased attractiveness, increased libido, brain health, bone strength, no more diabetes, no more cancer, a stronger immune system, more energy, better looking skin, and better circulation. Wow. So basically, it sounds like an edible bird's nest is a cure-all, a panacea. That's pretty impressive. But is it true? And where did these nests come from? What do they look like? Well, if you hear me say nest and you picture a cute little bowl-shaped thing made of brown twigs and some leaves, yeah, no, that's not right at all. The nest we're talking about is creamy white and it's made of pure bird saliva.

Hello and welcome. This is the Science of Birds. I am your host, Ivan Philipson. The Science of Birds podcast is a lighthearted exploration of bird biology for lifelong learners. This episode, which is number 74, is all about edible birds' nests and birds' nest soup. We'll talk about which birds make these amazing nests and how they do it. We'll also look at the way people harvest edible bird nests and the global industry for this product and some ethical concerns.

The things we care about the most here are birds, right? So first, let's talk about the birds themselves. Swiftlets are the birds that make edible nests. These are small, brown, or gray birds that are found in tropical and subtropical regions in the eastern hemisphere, in the old world. Swiftlets have narrow pointed wings, which make them fast and highly maneuverable in flight. Their wide mouths are perfect for catching insects on the wing. These birds are aerial insectivores.

There are about 40 species, and they're all members of the avian family, Apodidi. This is the Swift family. Apodity contains 112 species in all, and, as you might expect, I plan to do an entire episode on this family at some point. Swiftlets make up one distinct lineage within the family Apodidi. This lineage has a name. It's the Colocoleonai tribe within the sub-family Apodini. That's right, there are more taxonomic sub-divisions than just good old kingdom phylum class order, family genus, and species. Here we're talking about a family, a podidi, being subdivided into sub-famil, and those sub-families can be further divided into tribes.

Four genera are in the tribe Kolokhalionae. These are erodramus, hydrochois, colloquia, and shouted DeNapis. Take all this with a grain of salt, though, because there still seems to be some disagreement among ornithologists about swift-lit taxonomy. In any case, by taking the name swift and tacking on the suffix let at the end, ornithologists have acknowledged that swiftlets are both diminutive in size and, let's be honest, adorable in appearance. Because as we all know, any animal with a name that ends in let is objectively cute. Piglets and toadlets, for example. These creatures are cute by anyone's standards.

Extreme cuteness among birds is achieved by piculets, ocklets, and owletlette-knit night jars. Within the family Apodody, the award for champion of cuteness goes to the pygmy swiftlet, Colokalia troglotetes. This tiny bird from the Philippines weighs just 0.19 ounces, or 5.4 grams. That's about the same weight as a single sheet of standard printer paper. Swiflets in general, roost and nest in caves. They live in colonies that are often made up of thousands of individuals. One of the coolest things about swiftlets, besides the whole edible nest thing,

is the fact that many of them use echolocation. You probably know that echolocation is the detection of objects in the environment using reflected sound. Bats and dolphins are famous for their echolocation superpowers. Echolocation works beautifully for bats because these animals are nocturnal hunters and many of them live in caves. Well, swiftlets live in caves too. Eyesight is no good in the pitch black of a deep cave. As an adaptation, many swiftlets have evolved the ability to find their way around using a simple form of echolocation. They make clicking sounds, and those sounds bounce off the cave walls and back to the bird's ears.

This allows the swiftlets to judge distances between themselves and objects in their surroundings. This is another excellent example of convergent evolution among animals. Two very distantly related critters, bats, and swiftlets have independently evolved the sensory ability of echolocation because they share a similar habitat and lifestyle. Not all swiftlet species can echolocate. And among those that can, there's some variation in their abilities. The species with the most finely tuned echolocation systems tend to live way back in the darkest depths of caves. Other swiftlet species with relatively weak echolocation abilities live nearer to the mouth of a cave,

where there is at least a little light. Swiftlets make their nests in caves, but as you can imagine, there aren't many raw materials for building nests in a cave. And there are no tree branches or similar platforms upon which to construct a nest. Not very many, anyway. So swiftlets, through millions of years of natural selection,

have come up with an ingenious solution to the lack of nest-building material. They make their little nests entirely out of their own saliva, out of their spit. A swift-lit nest is in the Adherent Cup category, which I talked about briefly in episode 49 of the podcast. That episode was all about nests. Adherent cup nests are glued to a vertical surface by something sticky, like mud or saliva. swallows which look sort of like swifts but are only their distant cousins use mud as the sticky stuff

some swifts also use mud in their nests but most swiftlets use nothing but spit if we imagine how this whole thing evolved we can look to other members of the family apodidae many non swiftlet swifts build their adherent cups out of twigs, bits of plant material, feathers, et cetera. But somewhere way back in the evolutionary history of the Swift family, the birds started using saliva as a glue to hold all of this stuff together. Over countless generations, the saliva became a secretion that turns into a hard, strong material after drying out in the air, very much like super glue. I should mention that sticky saliva isn't unique to swifts and swiftlets.

The Canada J, for example, makes a wad of seeds and spit and then sticks it to a tree or a rock. Later in the winter months, the J will remember where it placed this little food cache. The bird's saliva acts like glue to keep the cache in place. So in deep, dark caves, swiftlets gained the ability to make nests without sticks or or any other material besides their own saliva. The two species most relevant to our story today are the white nest swiftlet, erodramus fusophagus, and the black nest swiftlet, erodramus maximus.

Another common name for the white nest swiftlet is edible nest swiftlet. The male swiftlet in these species seems to be the one most involved in making the nest. Scientists discovered that the salivary glands in the mouths of swiftlets, the glands beneath the tongue, grow larger during the breeding season, and these glands are more conspicuous in males than in females. In any case, it takes one to two months to construct the nest. It's anchored against a vertical face of the cliff wall. The birds make thick strands of gelatinous, sticky spit and weave these into a little half-cup structure. It ends up a sort of semi-translucent off-white color. One or two tiny white eggs are laid in the nest. As the swiftlet chicks grow, bits of bird poop, feathers, and insects accumulate in the nest.

But now, let's have a closer look at this bird spit. How similar is it to the saliva pulling up in your mouth right now as you think about eating a few corn dogs for lunch? Human saliva is made of 99.5% water. The rest is a bit of mucus and some other fun stuff like enzymes. But in the case of swift-lit saliva, water is only a minor component. Swift-lit spit is only about 10% water. Most of it, about 85%, is made of glycoprotein molecules, which are a combination of proteins and carbohydrates.

Another word for this slimy glycoprotein substance is one you might be familiar with, mucus. That's right, swiftlet nests are made of mostly mucus. It's gross enough to talk about eating something made of spit, but mucus, yick! That's way grosser, right? But hold up, before we get all judgmental about what food items are gross or not gross, we should remember what milk is. Many of us, myself included, are probably guilty of having enjoyed a cold glass of milk or two. Or at least we've used milk as an ingredient in our cooking. Mammalian milk, like the stuff that does a body good, got milk and all that,

Mammal milk evolved as a substance that oozes out of sweat glands. So cow's milk is really just fatty, protein-rich sweat. Bird spit, cow sweat, bison testicles, monkey brains, like in the movie Indiana Jones and the Temple of Doom, what people enjoy eating is a matter of personal taste, I guess. These things are subjective. That said, I think we can all agree that there's one so-called food item that's objectively disgusting and should be eradicated from the face of the earth. I'm talking, of course, about that candy store abomination, black licorice. Ew!

People have been collecting swift-lit nests from caves across Southeast Asia for hundreds of years. It's dangerous business since it involves climbing high, often slippery cliff walls in dark places. Entire communities and traditional ways of life have grown up around productive swift-lit nesting caves. For example, in the Philippines, there's a municipality called El Nido. In Spanish, that translates as literally the nest. Limestone cliffs are riddled with caves. Harvesters, known as Bousiadores, have, for many generations, been making treacherous climbing expeditions into caves to collect swiftlet nests.

You know, it must be super frustrating for the little swiflets when, after all their hard work, the nest they just finished gets plucked off the cave wall by a human. I mean, the reason these birds nest in what they thought was an inaccessible place is probably to avoid predators, to avoid being messed with. Then along come some meddling, spelunking primates wearing t-shirts, and then there goes the neighborhood. At least in some regions, nests are harvested twice during the breeding season. First, the nests are taken immediately after the birds finish making them, but before the eggs are laid. A pair of swiftlets can often make a second nest in the same season if their first one was appropriated by greedy primates. So the second harvest occurs a few months later, after the swiftlets make a second nest and raise their chicks to fledging.

Using ropes and rickety ladders to climb into natural caves is the traditional method of harvesting edible birds' nests. The difficulty and danger of this work is one reason these nests. are so expensive. But in the last several decades, there's been a big cultural change. Swiftlets are now being farmed in many places across Southeast Asia. Yes, you heard me right, swiftlets are being farmed. People figured out how to make buildings out of concrete that swiftlets find attractive, or they convert pre-existing buildings. These are located near the ocean, usually, since that's where swiftlets normally would look for caves. The concrete houses have openings on the top and or sides,

but the inside is mostly a dark open space, like a cave. The real trick to luring in the birds is to play recordings of their calls. Would-be swiftlet farmers blast the calls from speakers attached to the building. If all goes according to plan, the birds eventually set up a colony. They then construct their little spit-slash-mucous nests, and then the farmers start harvesting. The nests can't just be sent off to market as is, though. Not before they get some serious, meticulous cleaning. All those bits of feces, feathers, bugs, and God knows what else need to be removed.

Armies of factory workers are involved in this nest. cleaning and packaging process. It's crazy stuff. All of this is fine, right? I mean, I can't imagine there would be any ethical concerns when we have a wild animal product that sells for enormous amounts of money. Humans have a long track record of acting responsibly and of self-regulating in these situations. Except that we don't, I mean, just ask whales, elephants, tigers, and bluefin tuna how things have gone for them. So yeah, in some regions, the harvest of swift-lit nests has led to dramatic population declines for the birds. These declines are attributed to significant reductions in the numbers of swift-lit

nestlings that fledge each year in caves where nests are harvested. By taking newly constructed nests, harvesters interrupt the breeding cycle of swiftlets. Yes, the birds will often make a second nest, but research has shown that the birds, in that case, have lower reproductive success. But from the data I could find, swiftlets that make edible nests seem to be doing sort of okay, at least at the global scale.

Traditional harvesting of their nests for hundreds of years hasn't pushed any of the species to the brink of extinction. The white nest swiftlet, a.k.a. the edible nest swiftlet, for example, is in the least concern category as determined by the International Union for the Conservation of Nature. So maybe, just maybe, this is one example of humans actually using sustainable harvest practices. I want to believe that. And I do know that there have been some local governments and multinational organizations in Southeast Asia working to set standards for sustainability in this industry. The relatively recent practice of farming swiftlets

might actually increase the populations of these birds. Those concrete structures are providing more nesting habitats. Mo habitat, mo birds, right? Well, maybe. I'm not aware of any research that shows any swiftlet population increases resulting from the explosion of the farming practice. In any case, there's a lot of the farming practice. are now hundreds of thousands of these so-called swift-lit hotels spread across Southeast Asia.

Some scientists are concerned that swift-lit farming at this scale could also have some negative ecological consequences, both predictable and unforeseen. For example, if swift-lit populations increase unnaturally, that might increase competition for local resources among these birds. And will farming practices bring multiple swift-lit species together that wouldn't, under natural conditions, ever co-mingle? If so, this could lead to unnatural levels of interspecies hybridization, and, well, who knows what else. Some researchers have also voiced concerns about public health. We know all too well about the dangers of zoonotic diseases, those that spread from animals to humans. Inviting thousands of swiftlets into large buildings, then having people harvest and clean their nests,

well, that might cause some problems. Who knows? This is all so new that we just don't know. There hasn't been enough scientific research yet on the consequences of swiftlet farming. Also, I want to point out that the practice is sometimes called swiftlet ranching, which Swiftlet ranching, yeah, I think that's hilarious. All right, let's pretend you're someone who couldn't care less how hard those little swiftlets worked on their nest. It doesn't matter to you that there might be negative consequences to the large-scale harvest of edible birds' nests.

You've got a fat wad of cash in your pocket and you're hungry for some delicious bird mucus soup. What are the actual ingredients of this mysterious, expensive dish? A dish that can easily cost you more than $100 for a single serving. Well, as you might expect, there are many recipes out there. Here are the ingredients in one traditional Chinese recipe. 50 grams of edible birds' nest, one liter of chicken or pork broth, two teaspoons of cornstarch, two teaspoons of water, one egg white, salt and white pepper to taste, chopped green onions for garnish.

Some other recipes are for a sweet dessert-like version, with ingredients such as the following. One bird's nest. Four cups water, half cup rock sugar, half teaspoon ginger, one quarter teaspoon cinnamon, one quarter teaspoon cloves, and one pound of top quality black licorice. Oh, wow. I guess, I guess I won't be trying that one. Yuck. Actually, I haven't eaten any version of bird's nest soup. The impression I've gotten is that the nest itself, in all its mucusy glory, doesn't taste like much. After being rehydrated and cooked, it's just a mass of musilaginous slime. But the savory version of the soup in that first recipe sounds like it would taste pretty good to me.

But even if I could brush the ethical concerns aside, I don't think I'd should. shell out 100 bucks for a bowl of what is just a pretty basic mid-grade Chinese soup. But wait! What if you're simultaneously suffering from cancer, diabetes, bad skin, weak bones, a low level of attractiveness, and a stupid brain? Well, first off, I'm sorry. Second, isn't birds' nest soup supposed to be a wonder cure for everything that ails you? According to some practitioners of traditional Chinese medicine, yes. But is there scientific evidence to support any of the claimed health benefits of edible bird's nests? Eh, maybe a tiny bit, a smidge. But in general, there's very little evidence that these nests are good for you. They probably won't cure any of your

many physical ailments. Again, I'm sorry. Maybe go see a doctor or something. And edible birds' nests aren't even all that nutritious, not enough to justify their ridiculously high prices anyway. So I'd say don't waste your money. Take that fat wad of cash and go buy something truly useful. Like a portable karaoke machine or a lava lamp. I don't know. According to several resources I came across, the global industry for edible birds' nests is worth about $5 billion. The nests are harvested across Southeast Asia, in Indonesia, Malaysia, the Philippines, Thailand, Vietnam, etc.

But the major buyers and consumers are people in China and the U.S. These nests, the caviar of the east, are said to be worth their weight in gold. Okay, so I just looked up the current price of gold. It's about $66,000 U.S. dollars per kilogram. Wow. One kilo of edible bird's nest, at its most expensive, costs about $10,000. So, no, these nests are not worth their weight in gold. But dang, they are still.

super expensive. The actual cost of a nest depends on its quality or grade and its shape and its color. The standard white nests might cost $2,000 per kilogram, but there are these red nests that can fetch up to that maximum amount of $10,000 per kilo. What's the deal with red swiftlet nests? Red nests, also called blood nests, are relatively rare in nature. Their color has nothing to do with blood. Instead, it results from the way nitrogen vapors in the cave react with the mucus-slash-glycoprotein in the nests. And where do those nitrogen vapors come from, you ask? They're given off by steaming piles of bird and bat poop.

So people will pay up to five times more for red nests that have absorbed the nitrogen gases released by feces. Awesome. Not only is there no additional nutritional or health benefit to these red nests, those stinky nitrogen compounds can actually be dangerous to one's health. Nitrites and nitrates in edible birds' nests are associated with carcinogens. Rather than curing cancer, birds' nest soup made from red nests might actually cause cancer. But hey, who cares about all that, because I guess many people still think that the red nests are somehow way better. They still pay a premium price for them. And that's why some criminally minded dudes have resorted to making counterfeit red nests.

I mean, all you got to do is soak a boring old white nest in some red dye and bam, 10,000 bucks per kilogram, baby! Sounds like a great racket to me. In response to counterfeiting and the dangers of carcinogens, Chinese authorities have cracked down on the import of edible birds' nests, EBNs. There are now all sorts of high-tech ways to test the authenticity and safety of swift-lit nests. Lab tests, microchips, DNA, probably some lasers, and all that sort of stuff. Prices for EBNs have come down in recent years.

that's a reflection of the shift away from the traditional labor-intensive harvest in caves to large-scale farming in concrete buildings. And as the prices drop, the traditional practices are becoming less and less lucrative, less appealing to younger generations. So that way of life is disappearing. In China, the combination of a growing middle class and cheaper swift-lit nests means the demand for this strange natural resource is higher than ever. Who knows what the future of this industry will look like? I just hope that the swiftlets will be okay. Okay at the individual bird level, the population level, and the species level.

Oh, and the tribe level, too, I guess. I'll leave you with some reviews of edible bird's nest soup being sold on Amazon.com. This particular product is called Golden Swallow Nest. But remember that Swiftlets are in the Swift family, a podidi. Swifts are not swallows. Not even close. The makers of Golden Swallow Nest soup should have called me up before naming their product. I would have set them straight with a lesson in bird taxonomy.

Anyway, there are eight small bottles of soup in a box, and the whole thing sells for the dirt cheap price of $68 U.S. dollars. Looking at the topmost five-star reviews on Amazon, one of them says, good. And a second review reads, good. Oh, and here's another person who left a review that is, by comparison, a veritable novel. They wrote, Very Good. So there you have it, folks.

The people have spoken. Bird's Nest Soup is good. All right, my friends, episode 74 is in the can. I really hope you enjoyed it. I've wanted to learn more about this topic myself, so it was great to have the extra motivation to research it and make a podcast episode about it. I've had some major upheavals in my personal life lately.

So more than ever, I want to give a huge thank you to all of you who support my work through Patreon. on. Slowly but surely, the support of my patrons is moving me towards making a real living out of the science of birds. I put a ton of work into this show, so I deeply appreciate all the help. And here's a shout out to my newest cohort of awesome patrons. And forgive me if I butcher your name. Lee Walker Smith, Tarek Teckman, Marla Poore, Susan Brewer, Noel Labet Comas, Elaine Lavin Pule Horbelt

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of the Science of Birds is easy and fun Just check out my Patreon page over at Patreon.com Science of Birds I hope you'll consider becoming a supporter

I should remind you you of the fact that one could, if one were so inclined, contact me using electronic mail. Perhaps to share something with me, thoughts about the podcast, or maybe a favorite recipe that uses black licorice as the main ingredient. That's disgusting, but in any case, I can be reached at the following address, Ivan at scienceofbirds.com. You can check out the show notes for this episode, which is number 74 on the Science of Birds website, Scienceof Birds.com. I'm Ivan Philipson, and I wish you a very happy day. Peace.