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[00:00] Hi, my name is Anaga. I am from Canada. You are listening to Sleep Tight Science. Did you know that flamingos are not born pink? What? Every pink flamingo you have ever seen in a zoo, in a nature documentary, on a birthday card, started life as a gray, white chick. The pink comes entirely from their food, and if they stop eating the right things, they fade. Hello, friends, and welcome back to Sleep Tight Science, a bedtime show that answers your questions about science. Have you ever seen a flamingo and thought, that can't be a real animal? The color alone is almost too much. That particular shade of pink, standing in the water, reflected back up from the surface. It looks like something someone painted. And then there's the leg. Just the one, tucked up, perfectly balanced, apparently asleep. Flamingos are real, of course, and almost everything about them turns out to be more interesting than it looks. They eat with their heads upside down. They raise their chicks in flocks so large, a single crash, that's a shared nursery, can hold thousands of chicks at once, and a parent can still find its own baby by voice alone. They choose to live in lakes so salty or so hot that most animals can't survive there for more than a few minutes. And they start life white and turn pink one meal at a time. In this episode, we are going to find out how all of that works. Before we start, here are some words to listen for. Carotenoid, the pigment found in certain foods that gives flamingos their color. You say it like this, carotenoid. It's the same family of pigment that makes carrots orange and tomatoes red. Alkaline, the chemical opposite of acidic. Water that is highly alkaline is called caustic, and it can burn skin on contact. Filter feeder, an animal that eats by filtering tiny food particles out of large amounts of water. Flamboyance, the official name for a group of flamingos. And keratin, the protein that builds hair, nails, hooves, and rhino horns. We met it in our rhinoceros episode. It also turns up tonight. In a place you might not expect. A quiet thank you to Onaga in Canada for introducing our show. And to all of you who keep sending in your questions and ideas. You help us decide where to go next. Take a slow deep breath in. And let's get started. Let's start with the pink, because it really is the first question. Why is a flamingo pink? The answer starts with food. Flamingos eat algae, brine shrimp, and other tiny organisms that live in shallow, salty water. These food sources are rich in carotenoids, that pigment family we mentioned, and when a flamingo digests them, its body doesn't flush the pigment out. It deposits it into the feathers, into the skin, into the legs. The more carotenoids in the diet, the deeper and richer the pink. A flamingo eating well in the right habitat, with the right food, goes a deep, almost shocking coral. A flamingo on a poor diet fades. In zoos, flamingos are fed carotenoid supplements, specifically to maintain their color, because without them, the birds would gradually turn white. Flamingos hatch with a different color. Flamingos hatch covered in soft gray-white down. No pink at all. The color takes years to develop fully, as the diet gradually builds up pigment in the growing feathers. But the process starts earlier than you might think, because of something called crop milk. Both flamingo parents produce crop milk, a reddish liquid made in glands in the upper digestive tract. It's thick, rich in fat and protein, and it's the only thing a flamingo chick eats for the first few weeks of its life. It also contains carotenoids, which means the coloring begins almost from the first meal. Producing crop milk costs the parents a great deal. Adults that are feeding chicks actually lose some of their own color in the process, the pigment going to the chick instead. A pale parent flamingo is often a parent working very hard. Then there's the beak. A flamingo's beak has a sharp, downward kink in the middle, a distinctive bent shape unlike almost any other bird. This is not a design quirk. It's the entire point. Flamingos feed with their heads upside down, beaks submerged, and that sharp downward bend is precisely what makes the posture work. Hold your hand flat, then bend your fingers sharply downward at the knuckle. That angle is roughly what the flamingo's beak does. So that when the head tips over, the beak sits level on the water's surface. Inside the beak, things get even more interesting. The upper jaw moves while the lower jaw stays fixed. The opposite of how almost every other vertebrae's jaw works. Including yours. Along the inside edges of both jaws, run rows of fine comb-like plates called la mili. And this is where keratin comes back. Those plates are made of keratin, the same protein as your fingernails and a rhino's horn. They act as a sieve, trapping tiny food particles, while water is pumped out. The tongue moves back and forth up to four times per second, driving water through the filter. The whole system is extraordinarily efficient, pulling food from water that looks, to almost any other animal, like it has nothing in it worth eating. There are six species of flamingo living today. The Greater Flamingo is the largest and most widespread, found across Africa, Southern Europe and parts of Asia, standing up to 1.2 meters tall and weighing up to 3.5 kilograms. At the other end of the range is the Andean Flamingo, which lives on high-altitude salt lakes in South America, sometimes above 4,000 meters, higher than many mountains where people live. All of them pink, all of them built for water that most creatures wouldn't touch. So now we know what a flamingo is made of. Let's find out where it lives and why. Flamingos are drawn to some of the most extreme aquatic environments on Earth. Highly saline lakes, where the water is saltier than the ocean. Alkaline lakes, where the chemistry of the water is so caustic, it can blister the skin of most animals on contact. Shallow coastal lagoons baking in equatorial sun. These are not places most creatures choose. Flamingos choose them specifically, and the reason is straightforward. Hardly anything else can follow them in. Lake Natron in Tanzania is the most striking example. The water is so alkaline, loaded with sodium carbonate from volcanic minerals in the lake bed that prolonged exposure can irritate or damage skin. Surface temperatures can reach 60 degrees Celsius, about 140 degrees Fahrenheit. The lake is a deep, rust-red color from the salt-tolerant algae that thrives there, and it looks genuinely like somewhere nothing should live. Nearly 3 million lesser flamingos breed there. It is the largest flamingo colony on Earth. The extreme conditions are the whole point. Crocodiles can't tolerate the water chemistry. Most predators avoid the shore. By nesting somewhere actively hostile to everything else, flamingos have found a kind of safety that no amount of camouflage or speed could provide. They brought the harsh environment with them in a way. They became the thing that thrives where others can't. Now, about that leg. The one leg question is one of the most asked questions in biology classrooms, and scientists have been studying it for years. The leading explanation is thermoregulation, heat management. A flamingo's legs have no insulating feathers and sit in cold water for most of the day. By tucking one leg up close to the warm body, the bird cuts in half the surface area losing heat to the water. Studies have found flamingos stand on one leg significantly more often in cooler temperatures, which supports this explanation well. Standing this way costs them almost nothing. A flamingo's leg bones lock into position when it is standing, meaning no muscle tension is required to stay upright. They can sleep on one leg, completely relaxed, with no more effort than you need to lie in bed. The leg isn't gripping. It's simply locked. When you look at a flamingo standing motionless on one leg in cold water, it is not performing a balancing act. It is just very efficiently warm. Flamingos are one of the most social birds on earth. A group, the flamboyants, can range from a few dozen to several million individuals. They breed in colonies, nest side by side, and raise chicks in enormous shared crashes, supervised by a small number of adults, while the parents go to feed. A single crash can hold thousands of chicks, and yet when a parent returns, it finds its own chick in that crowd by call alone. Each chick has a unique voice, and the parent knows it from the first day after hatching. In a crash of 10,000 chicks, the right one answers. Flamingos mate for a season, and many return to the same partner the following year. They build cone-shaped mud nests, raised above the waterline, and lay exactly one egg. Both parents incubate it for about four weeks. Both produce crop milk. Both, for a while, go a little pale. One last thing, and it surprises almost everyone. Flamingos are fast. In the air, a flamingo can reach 60 kilometers per hour, about 37 miles per hour. They travel between feeding sites overnight. Sometimes covering enormous distances. Navigating using visual landmarks, the sun, and possibly the stars. A flock lifting off a lake at dusk, thousands of birds all turning together, all that pink catching the last light, is one of the great sites this planet has to offer. Most people only ever see them standing still. Did you know the word flamingo comes from the Spanish and Portuguese word flamenco, meaning fire or flame? It was the color that named them, that burning, sun-setting pink that stopped early explorers in their tracks. The flamenco dance from southern Spain is named for the same word, and some historians think the dramatic arm movements of the dance were inspired by the birds themselves. Sweep your arms up slowly, and you can almost see it. Did you know that what looks like a flamingo's backward bending knee is actually its ankle? The real knee is hidden up near the body, tucked under the feathers where you can't see it. What bends the wrong way in the middle of the leg is the ankle joint. The foot is the long thin section below it. A flamingo is essentially walking around permanently on tiptoe, on legs that are mostly ankle. Did you know the greater flamingo is one of the longest lived birds on earth? In the wild, flamingos regularly live for 30 to 40 years. In captivity, with a reliable food supply and no predators, individuals have reached their late 70s and beyond. There was a flamingo at a zoo in Adelaide, Australia named Greater, who lived to be at least 83 years old. He arrived at the zoo in 1933. Think about how much the world changed in the time he was alive. Did you know that flamingos must run across the surface of the water to take off? They need a runway, sometimes sprinting for several meters, feet slapping the water, wings beating, before they get enough speed to lift off. Landing works the same way in reverse. It is not graceful. It is, however, extremely entertaining to watch. Did you know flamingo tongues were considered a delicacy in ancient Rome? They were served at banquets as a luxury dish. Here's a wave to some of our question askers. Ada, age 7, Mara, age 8, and Luella, age 12, sisters from Horace, North Dakota. Adam Salguero, from Málaga, Spain. Bronx, age 6. Liam, 9 years old. Nico DiCamillo, 6 years old in Gross Point Woods, Michigan. Ezra, 5 years old in Alberta. Alexis, 8 years old in Caines, Australia. Aidan, 7 years old from Melbourne, Australia. Casey, 8 years old. And Ekal, 11 years old from Arizona. Thank you for asking questions that spark our curiosity and keep us learning. To submit your questions, ask your parents to help you write us a note to the email address in our episode notes. You can also visit our website and send a message that way. Also, don't forget to leave us a review. It helps other people find our show. In this episode, we learned that flamingos are born gray-white and earn their color one meal at a time. Carotenoid pigments from algae and brine shrimp depositing slowly into feathers and skin, building that impossible pink from the inside out. We learned how the beak works with its sharp downward kink and its row of keratin filter plates pumping water in and out four times a second to catch food too small to see. We met the crop milk and learned that a parent flamingo working hard to feed its chick goes a little pale in the process. We visited Lake Nitrin and found three million flamingos living in water that would burn most animals on contact. We solved the one leg mystery. We discovered that the knee bends the wrong way, except it doesn't because it isn't a knee. And we learned that a group of flamingos is called a flamboyance, which was always going to be the best fact. As your eyes grow heavy, let your mind travel across the ocean, across the equator, all the way to the edge of a lake that glows rust red in the early morning light. The sun is just coming up. The air is warm and sharp with salt. And as far as you can see in every direction, flamingos are standing in the shallows. Thousands of them. Hundreds of thousands. Every shade of pink the sky has ever been at sunset, all of it reflected back up from the water below. Some have one leg tucked up. Some are feeding. Heads tipped over, beaks just below the surface. Somewhere in the middle of it all, a crash of chicks is waking up. Gray-white and noisy. Each one with a voice its parents already know by heart. This is Lake Natron. Almost nothing can live here. We're glad you spent this time with us. From Sheryl and Clark, Good night. Sleep tight. If you're still here, thank you. Making something your child wants to listen to at the end of the day is the thing we care about most. If Sleep Tight Science has become part of your family's bedtime, Sleep Tight Premium removes the ads and adds a little extra science. There's a free trial link in the show notes. And if you have a moment for a rating or a short review, it helps other families find us. We're grateful for every one. Thank you.