The Science of Birds - Cranes

Episode Date: March 26, 2023

This is Episode 73. It’s all about birds in the avian family Gruidae… the cranes.These tall birds are charismatic and super interesting. It’s going to be fun to do a deep dive into all things crane today.Humans around the world have celebrated cranes for thousands of years, for their graceful beauty and their exuberant courtship dances. Across many cultures, cranes have inspired paintings, songs, dances, legends, martial arts, heavy construction machinery apparently, and the most iconic animal design in the fine art of origami.It’s spring in the Northern Hemisphere right now, and that means that in many parts of the world, cranes are on the move. They’re migrating north. Along the way, they stop to rest and refuel at certain staging areas. Hundreds or thousands of cranes can end up at a single staging area or stopover and this can be a wonderful sight to see for birders and other nature lovers.There are a bunch of crane festivals around this time every year. It’s a rare thing for any kind of bird to get so much attention and adoration like this. Cranes are just that special.So how about we have our own little crane festival today. Let’s get to know these amazing birds. Links of InterestSandhill Cranes and Colts [VIDEO]Crane TrustInternational Crane FoundationWhooping Crane dancing [VIDEO]Common Crane courtship [VIDEO]  ~~ Leave me a review using Podchaser ~~Link to this episode on the Science of Birds website Support the show

Okay, I've got my notes here, and I didn't have much time to prepare, so I'm just going to wing it using my notes. I wrote these up late last night after some hastily performed Google searches. Let's start with some fun facts about cranes. Everybody loves fun facts, right? Fun fact number one. Cranes were invented by the ancient Greeks. They were originally powered by people or animals such as donkeys. cranes began to be powered by steam engines in the 19th century.

Hmm, okay. Invented? I don't know if people can invent birds, but that's what it says here. Well, here's fun fact number two. There are many different kinds of cranes. Okay, here we go. Now that sounds more like it. There are mobile cranes, floating cranes, crawler cranes, rough terrain cranes, and many others. Crawler cranes?

Like it crawls on the ground. ground? Can you, can you picture a bird crawling? Anyway, our third fun fact is that cranes are dangerous. Every year there are approximately 43 crane-related deaths in the United States and a similar number of deaths in the UK. Really? Crane-related deaths? I had no idea. Do they use their beaks, their claws? Oh, wait. You know what? This is embarrassing. Forget all of that. That was about cranes the machines. I guess Google didn't know I was searching for facts about cranes, the birds. Let's blame Google for this. Getting rid of my notes. But to be fair, cranes, the machines used in construction, are named after cranes

the birds, with their long necks stretching toward the sky. It's true. And it's probably safe to say that the number of humans killed every year by cranes, the birds, is approximately zero. These birds are nothing to be afraid of, thankfully. Quite the opposite, in fact. Humans around the world have celebrated cranes for thousands of years, for their graceful beauty and their exuberant courtship dances. Across many cultures, cranes have inspired paintings, songs, dances, legends, martial arts, heavy construction machinery, apparently, and the most iconic animal design in the fine art of

origami. 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 is episode 73. It's all about birds in the avian family, Gruidi, the Cranes.

These tall birds are charismatic and super interesting. It's going to be fun to do a deep dive into all things crane today. Now, you might recall that I recently did a podcast episode on the Great Blue Heron, a common North American bird species. Many herons are long-necked, lanky waterbirds that look superficially anyway like cranes. Storks too fall into this category. But cranes, herons, and storks belong to three different families. They're only distantly related.

Many of the similarities we see among birds in these families have more to do with what they eat and where they live than with their shared ancestry. For example, long legs are great for striding around in grass or wading around in water while hunting for fish or small animals or aquatic invertebrates. Long legs evolved more or less independently in the cranes, herons, and storks. Okay, so cranes are not close relatives of herons or storks. Enough said. Anyway, it's spring in the northern hemisphere right now, and that means in many many parts of the world, cranes are on the move. They're migrating north. Along the way,

they stop to rest and refuel at certain staging areas or stopover areas. Hundreds or thousands of cranes can end up at a single staging area or stopover, and this can be a wonderful sight to see for birders and other nature lovers. There are a bunch of crane festivals around this time every year. It's a rare thing for any kind of bird. get so much attention and adoration like this. Cranes are just that special. For example, there's the Othello Crane Festival in central Washington State. That's going on right now, more or less, as this podcast episode goes live. The festival happens every year about this time. It's a celebration of the Sandhill Crane. The pothole wetlands and fields near the town of Othello

form an important staging area for Sand Hill cranes, as the birds make their way north to Alaska. So how about we have our own little crane festival today? Let's get to know these amazing birds. What are the distinguishing physical features of birds in the family Gruidi? As I think we all know, cranes have long necks and long. long legs. They're elegant looking birds. The body sandwiched between the neck and the legs is ovoid and streamlined. The large wings of cranes are broad and rounded. In general, these birds are strong flyers. They have to be in order to survive their long migrations. For example,

the Demazelle crane, Anthropoides Virgo, flies over the Himalayas on migration, between its winter range in India and where it breeds in Central Asia. To cross the mountains, these birds fly at altitudes up to 26,000 feet, which is over 7,900 meters. Broad wings give cranes lots of aerodynamic lift for making epic journeys like that. Many crane species have what looks like a fluffy tail, a puff of fancy feathers at the back end. But this mass of feathers, called a bustle is not actually the tail. The bustle is formed from elongated feathers on the wing that fall close to the midline of the bird's body. I suspect some of the upper tail-covered feathers are involved too, but I'm not sure about that. In any case, the bustle covers up the real tail

beneath, which is really quite stubby. Cranes can raise or lower their bustle feathers, like when they fluff them up during courtship displays. Technically, we would say the bird erects its feathers. The blue crane of southern Africa has taken this to an extreme. When its wings are folded, this bird has what looks like a long, elegant tail that drags on the ground. But surprise, this isn't the real tail. It's a sort of pseudo-tail formed by flight feathers of the inner wing called secondaries and tertials. Blue cranes use their fancy ornamental wing feathers to impress other members of their

species. A crane in flight keeps its long neck outstretched. Herons, on the other hand, typically fold their necks into an S shape. So it's pretty easy to tell these two types of bird apart when you see them flying. Storks also fly with their necks sticking out in front. However, storks generally have shorter, thicker necks than cranes. Storks are just chunkier birds overall, and their bills are proportionally larger than those of cranes. Crane bills are all pretty much the same across the species. The bill is long, straight, and stout. It's a general-purpose tool for a bird that eats a wide variety of food items,

both plants and animals. In terms of size, all cranes are large compared to most birds. In fact, the tallest flying bird in the world is a crane. The Saris Crane, Antigone Antigone. This bird stands up to six feet tall, that's 1.8 meters. Beak to tail, the Saris Crane is about 5.3 feet long, or 1.64 meters. It has a wingspan of over 8 feet, about 2.5 meters. The smallest crane species is the Demoiselle Crane,

you know, the one that flies at an altitude of 26,000 feet up over the Himalayas. Those guys have body lengths of only 3.3 feet, or about one meter. The word demoiselle comes from French and originally meant a young unmarried woman. But I'm not sure about my pronunciation. Let's see how the internet translator robot says demoiselle. Demoiselle. Right. Yeah, that's what I said.

Demoiselle. Demozele. Close enough. This word is closely related to the word damsel. like those gals in romantic medieval stories who always seem to be in distress for some reason. Regarding this particular crane species, a naturalist in the 18th century wrote, quote, This bird is called demoiselle by reason of certain ways of acting that it has,

wherein it seems to imitate the gestures of a woman who affects a grace in her walking, abasances, and dancing. end quote her obeisances huh moving on to look at the plumages of cranes in general these birds are gray or white with some accents of black but most have jazzy splashes of red color on their heads the gray crowned and black crowned cranes in africa are exceptions to the rule they are quite a bit more colorful than your standard issue crane their wings display a bold common nation of white, black, golden yellow, and a dark, rusty red. But it's the crown of the crowned cranes that really sets these birds apart. This feature is kind of hard to describe in words, so I'll put a photo in the show notes on the Science of Birds website. But growing out from the back of the head is a dense spray of hair-like golden feathers. They radiate out in all directions from a single point, like an exploding firework. And to me, these feathers also look

a lot like porcupine quills. In any case, the two crowned crane species are stunningly beautiful birds. Interestingly, at least two crane species use mud to change the color of their feathers. The common crane and sandhill crane scoop up iron-rich mud in their bills, then work it into the feathers on their backs. Those feathers, which are naturally gray, end up being stained a modeled, rusty brown color. Cranes only do this during the breeding season, so ornithologists think the mud is used as camouflage, because it makes a crane sitting on its nest less visible to predators. Pretty cool, huh? Now, recall that most crane species have some red color on their heads. The only two that don't have any red are the Demoiselle crane and the blue crane. The latter two species are closely related,

being the only members of the genus Anthropoides. Every other species has at least a small patch of bare, bright red, or pink skin on their heads. The Saris crane has the most red. Its head is almost entirely red and the color extends down the neckaways. This red facial skin of cranes isn't what you'd call smooth. Rinkling. or bumpy aren't really the right words to describe it either. If you look closely at it, the skin is bunched up into hundreds of little, I don't know what to call them, tubercles, finger-like projections. The effect is that the skin has a fuzzy, velvety appearance. To me, it looks like a swanky shag carpet. Cranes actually have some control over the intensity and amount of red skin

they show. By contracting and relaxing tiny muscles, a crane can change the color and level of engorgement of its skin. Why do you suppose this would be a useful trick? If you answered, for communication, you are correct. It's sort of how humans blush, right? Capillaries in our faces fill with blood in certain social situations. Our cheeks turn red. You know, like when I see a stranger at a cafe and they're smiling at me and waving, then I smile and wave back, thinking I might have just made a new friend? Hooray, somebody wants to be my friend, at last. But then I realized that, no, the stranger was just waving at someone standing slightly to my left and behind me. My blushing face in this awkward situation communicates to the world that I feel like an idiot

it for thinking I finally made a friend. The red skin of a crane is a communication signal to other cranes. The skin expands and gets brighter during certain stressful or exciting situations. Like when the crane makes a threat display, while it's dancing, during mating, or when it has to answer tough questions in a job interview. Your resume is certainly impressive, Mr. Crane, but there's a just one more thing. You've neglected to mention that you spent three years in the state prison. Yes, we ran a background check. You shouldn't be surprised. Would you like to explain to us how we

can trust someone like you? Someone who stole an ice cream truck and used it as a front to sell bootleg Air Jordan sneakers to teenagers? The shag carpet of bare skin on the crane's face grows bright red. When it comes to the pattern of facial skin and plumage coloration of cranes, we don't see differences between the sexes. Males and females look pretty much the same. In other words, there's no dimorphism or dichromatism in these birds. Now, how about the sounds that cranes make? What are their voices like? Some people have described them as haunting resonant cries. They've also been called melodic and beautiful, or they've been likened to the sounds of trumpets, bugles, or clarinets.

Interestingly, the calls of cranes are very similar across the species. Let's have a listen to some, shall we? Here's a common crane, which has the scientific name, Grus Grus, recorded in Sweden. Yeah, I'd say haunting and resonant are good words to describe that amazing call. Again, that was a common crane. Here's a couple sandhill cranes in Yellowstone National Park, calling to each other as they do a flyby. On the other side of the world, let's listen to some Demoiselle cranes.

Demoiselle. Right, that's what I said, Demoiselle. These birds were recorded in India in their winter habitat. You can almost hear the way that they imitate the gestures of a wild. woman who affects a grace in her walking, obeisances, and dancing. I hope you can hear the similar tonality of these calls from different crane species. Now, here's something really cool about how cranes generate these haunting sounds. The trachea, or windpipe, of most crane species, is super long. It's coiled up like a garden hose in the bird's chest. Not only that, but the

trachea is actually embedded in the breastbone, the sternum. In some species, the bony rings of the trachea are actually fused to the sternum. So what is the purpose of this anatomical oddity? I should point out that swans and a couple other types of birds also have long, coiled tracheas. The effect is similar in all of these birds. It gives them the superpower of making loud, penetrating calls that carry a long distance. Maybe you remember me mentioning this in episode five of the podcast. I talked about a songbird in the bird of paradise family called the trumpet manucode.

That bird has a trachea that's more than twice the length of its entire body. Anyway, the extent that the trachea permeates the sternum bone in cranes varies by species. The gray and black crowned cranes don't have much of a variety. this going on. They represent the simple, more primitive anatomical arrangement. And side note, crowned cranes can also make low-pitched booming calls unlike the sounds of other cranes. But the common crane and whooping crane have taken this arrangement to the extreme. Their long tracheas make a couple loops inside the breastbone. It seems that relatively small vocal sounds in cranes are transmitted to the large breastbone, the sternum, which then transmits the sound to the system of

air sacs inside the bird's body. Researchers studying this phenomenon concluded that the way sound is transmitted and amplified in the body of a crane is not so much like a trombone, but more like a violin. There are many resonating sound frequencies happening all at once. And get this. One way that these researchers figured this out was by having cranes inhale helium gas. They wanted to see if the mix of resonating tones changed when the birds were full of helium. You know, like when you get a party balloon, suck in some helium, and you sound like this. And so, my fellow Americans, ask not what your country can do for you? Ask what you can do for your country. My fellow citizens of the world, Ask not what America will do for you, but what you will do for America.

I think I got that quote right. Eh, more or less. So this tracheal coiling thing allows cranes to make some loud and lovely noises. Noises like this one. That one was kind of in your face, wasn't it? Those were whooping cranes. Would you describe that call as whooping? Sounds more like a violin to me. Anyway, here's another recording of whooping cranes. Gruidi is the name of the Crane family.

The origin of this name is the word grus, G-R-U-S, Grus. I'm Groot. No, not Groot, Grus. That's also the name of a genus, right? Grus, like the Whooping Crane's scientific name, Grus Americana. This comes from the Latin word for crane. Tracing it back further in history, we come to the Proto-Indo-European word, Gur-Gur. That's G-E-H-R times two.

Gur-Gur means to cry hoarsely, so you can see how that might apply to cranes, with their distinct, throaty calls. If you want more fun with word origins, how about this? The words congruence and pedigree both have elements that trace back to gruce to the Latin word for crane. Congruance, pedigree. Also, the word cranberry was originally cranberry. Early European settlers in America thought the plant looked vaguely like a common crane. So the next time you're sipping on some vodka cranberry cocktails with your friends, you can drop that fun fact into the conversation. Hey, you guys, you know what these drinks should really be called? Vodka

crane berry. When you proceed to tell them why, your friends will be super impressed, guaranteed. There's only one species in the family Gruidi that doesn't have the word crane in its name, and that is the Brolga, Antigone Rubicunda. This bird lives only in Australia and on the island of New Guinea. Back in the day, it was called the Australian crane. Well, that's what European colonists called it. But way back in the day, one of this bird's original names given by Aboriginal people was Boralga, B-U-R-R-R-A-L-G-A. In honor of this traditional name, the Australian Crane's name was officially changed to Brolga in 1926. Brolga has a nice ring to it. I'll add that to my list of possible baby names if I ever have a daughter. Brolga Philipson.

Moving on. Earlier, I talked about how cranes are not close relatives of herons or storks. So what other birds out there are the closest relatives of cranes? Well, cranes belong to a major branch of the avian tree of life called Gruiformes. That's the taxonomic order Gruiformes. Gruidi is one family in the order Gruiformis. There are several other families in this order. The one most closely related to the Crane family is Aramidae. Aramidae is a family of one.

It contains just one living species, the Limpkin. The Limpkin is a long-legged, long-beaked waterbird that lives in the neotropics, and it loves to eat apple snails. I recently had fun watching some Limpkins hunting for snails in a wetland reserve in Buenos Aires, Argentina. I actually posted a video of one on my Instagram, so check that out. My handle on Instagram is at Science of Birds. The next closest family to the cranes is that of the trumpeters. The family, sophiaidae, contains just three trumpeter species.

These tropical, vaguely chicken-like birds live in the Amazon basin. But let's return our focus to the crane family, Gruidi. This family contains six genera, and there are 15 species divided among those genera. That's right, there are only 15 crane species in the world. Maybe you've seen one or two, or ten. To me, it's always a special occasion when I see a crane. I've been lucky enough to see five species so far. So that means my life is now 33.333% complete.

I hope to see at least a few more Gruids in my life. That's Gruids, Birds in the Family Gruidi. Not to be confused with Druids. I'm probably not going to go out of my way to find any ancient Celtic wizards, even though seeing one of those guys can also be a special occasion. The 15 crane species are distributed around the world. East Asia is the number one hotspot for crane diversity. You can find eight species there.

Examples include the hooded crane and the elegant red-crowned crane. The latter species, Grus Japonensis, is famous for its courtship dancing behavior in the snowy landscapes of northern Japan on the island of Hokkaido. Africa is another crane hotspot, with five species living there year-round and another one that visits in winter. Australia has two species, the Brolga and Saris Crane. North America, likewise, has just two species, the Sandhill Crane and the Whooping Crane. These cranes are not that closely related, since they belong to different genera. Sandhills are in the genus Antigone, while whoopers are in the genus Grus.

Of the two species in North America, you're much more likely to come across a sandhill crane. Recent population estimates for those guys is about 700,000. This is actually the most abundant crane species in the world. The whooping crane, on the other hand, is the rarest crane species in the world. As of 2022, there were only about 550 of them in the wild, and another 130 or so in captivity. Over in Europe, the most common species is, well, it's the common crane, good old grous gruce. It seems members of this family are found on all the continents, doesn't it? But what's missing?

If you've been paying attention, you will have noticed I didn't mention South America. That's because cranes are, strangely, missing from the continent of South America. Ornithologists have no idea why. This is just one of those unsolved avian mysteries. But there's one last continent we haven't talked about. Surely you know of what I speak. It's that virtually lifeless place where few birds dare to tread. It's all cold and white and stuff.

Yes, I'm talking about my old nemesis, Antarctica. There are no cranes in Antarctica, and there's no mystery about why that is. But all of that was about the global distribution of cranes. Let's talk about crane migration now. One thing these birds are known for is the spectacle they create during their northward migrations. When thousands of large, beautiful birds gather in a field making strange, raucous noises, they're bound to attract the attention of humans. Things get really interesting when the cranes do some courtship dancing on these migratory stopovers.

The Hula Valley in Israel is a perfect example of a place where thousands of cranes stop on their migratory journeys. In this case, we're talking about common cranes. Most of them are moving between Africa and Europe along the Black Sea Mediterranean Flyway. But some common cranes will spend their entire winter in Israel. That's as far south as they feel the need to go. A similar situation exists in the United States at Bosque Del Apache National Wildlife Refuge in New Mexico. This is a famous migratory stopover and wintering site

for sandhill cranes and lots of waterfowl. Thousands of sandhill cranes spend the winter on the flood plains of Bosque de la Pache. Migratory behavior varies among crane species. Some, like the Demoiselle Crane, are highly migratory. They fly thousands of miles every year between their wintering and breeding grounds. Other crane species are non-migratory or sedentary. They hang out in the same place year-round.

For example, the Demoiselle Crane's close cousin, the Blue Crane, lives in Southern Africa all year. The Blue Crane is actually the national bird of South Africa. Other species that are pretty much non-migratory are the waddled crane and the two crowned cranes. These birds might move around a bit over the seasons in search of water or greener pastures, but they aren't technically migratory. A few species, like the Saris crane, have some populations that migrate and others that don't. Okay, we haven't really talked about the habitats of cranes, have we? These are birds of open spaces, wetlands, meadows, grasslands, savannas, tundra, and croplands.

Wet habitats are generally the best. Most of the 15 species build their nests in shallow wetlands. The Siberian crane, leukogenes, leukogenes, is, of all the gruids, the most water-loving. This bird nests, forages, and roosts in wetlands of various. kinds. In contrast, the blue crane is an example of a species that prefers drier upland grasslands. So if the ancient Greeks did not invent cranes, where did these birds come from? What do we know about their evolutionary history? Although the fossil record for cranes is far from complete, scientists think these birds originated in the northern parts of the old world. The earliest evidence of crane-like

birds is from about 25 to 30 million years ago in the oligocene epoch. But those early ancestors of cranes were more like modern-day rails or coots. Rails and coots are in the family Raleigh, and Raleigh is also within the order Gruiformis. So rails and cranes aren't as different as you might think. That's why when you flip through the pages of most modern bird field guides, which are organized taxonomically, you'll see rails and cranes listed close together. I mean, you can kind of imagine that if you grabbed a rail and stretched it out a bit, hypothetically, of course, don't try this at home, kids, if you stretch out a rail, you end up with something that looks a lot like a crane. The proto-cranes of the oligocene had

stubbier beaks and legs than their modern counterparts. But then as grassland ecosystems spread around the world in the oligocene and the Miocene epic that followed, this group of birds evolved longer and longer legs. Long legs are pretty useful for strutting around in grasslands and marshy places. Genetic evidence from DNA suggests that by the late oligocene there were two primary lineages of cranes. One of them gave us the two crowned crane species. The other lineage diversified into all other crane species that we have today. As I take a little pause here to refill my trusty coffee mug, I'd like to ask you a favor. If you've been enjoying this podcast, maybe even binging the episodes, as I know some of my listeners have done, please consider telling a friend or two about the

show. That would be just glorious. If you think your friends would enjoy the Science of Birds podcast, let them know that it exists and point them in the right direction. Maybe you could suggest one of your favorite episodes. Word of mouth like this is a fantastic way for a podcast to find more fans. So thanks for that. Now, pardon me while I pour some scalding hot coffee down my throat. And then we'll get back to the show. Cranes in general are in trouble. Around the world, they've been hammered by the destruction of their wetland and grassland habitats. They have been, and in some places, continue to be, hunted for food, for sport, and for their feathers.

Two-thirds of the world's crane species are seriously threatened. According to the International Union for the Conservation of Nature, the IUCN, seven crane species are in the vulnerable category. Two are endangered and one is critically endangered. The Siberian crane is the species with the sad distinction of being critically endangered. There are only a few thousand of these birds left. They breed in the Arctic tundra of Siberia, but it's in their wintering habitats where they face the biggest threats. Recall that the Siberian crane is the species that depends most heavily on wetland habitats. Well, in China, the enormous three gorges dam and many other hydroelectric projects have destroyed much of those habitats. As a result, there's a good

chance this crane species will go extinct in the next century. The two crane species that are endangered, according to the IUCN, are the gray-crowned crane and the whooping crane. The Whooping crane is not only the rarest crane in the world, it's also one of the rarest birds in North America. In 1941, there were only about two dozen whooping cranes left in the world. Hunting and habitat loss had almost wiped the species out. Thankfully, intense conservation efforts for over 50 years have increased the total population significantly. But as I mentioned earlier, it's still less than 1,000 birds. The full whooping crane story is too long for me to tell you right now.

I'll have to dedicate an entire episode to that species at some point. Now, if you're like me, you're feeling inspired to help cranes after learning about them today. If you're in the U.S. and you'd like to support a local conservation effort, consider making a donation to the Crane Trust based in Nebraska. The mission of the Crane Trust is, quote, through land management, scientific research, and education, our mission is to protect and maintain the physical, hydrological, and biological integrity of the Big Bend area of the Platte River so that it continues to function as a life support system for whooping cranes,

sandhill cranes, and other migratory bird species. End quote. Oh, wow, that was one long sentence. It was a little hard to get through without taking a breath. I'll put a link to the Crane Trust in the show notes. Or you can help cranes at a more global scale by making a donation to the International Crane Foundation, headquartered in Wisconsin.

This organization is celebrating its 50th anniversary this year. The International Crane Foundation has been a key player in the conservation of all 15 crane species around the world since 1973. I'll also put a link to this organization in the show notes. the foundation actually has a mascot. Her name is Hope, and she's a seven-foot-tall Muppet in the form of a whooping crane. Like a Muppet for real, since Hope was created by the Jim Henson Company. She's the crane version of Big Bird from Sesame Street. Hope goes around to birding festivals and whatnot and spreads the word about crane conservation, and that is just

great. But remember in the beginning of the episode when I said cranes are nothing to be afraid of? That's true, mostly, but I gotta say I'm kind of concerned about this giant Muppet. I mean, I'm already terrified of Big Bird. Do we really need another one of these things running around? Did anyone stop to think before unleashing Hope the seven-foot monster of a Muppet crane on the world? Another thing that sets cranes apart from herons and storks is their diet. Cranes are omnivores, eating a wide variety of plant material as well as small animals. Herons and storks, however, are strictly carnivorous.

On the veggie menu for cranes are things like berries, fruit, leaves, nuts, roots, and tubers. Animal-based food items include rodents, lizards, small birds, fish, insects, aquatic invertebrates, and bird eggs. Cranes are opportunistic feeders, and what they end up eating on any given day depends on the season and what habitat they happen to be in. The bill of a crane is perfectly constructed for snatching up small animals like mice, but also for plucking leaves, probing for clams, and digging up roots. For crane species that migrate long distances, their summer and winter diets can be quite different. The whooping cranes' summer diet, for example, includes things like snails, aquatic tubers, grasshoppers, mice, frogs, and minnows.

But for the whooper population that spends the winter on the Texas coast, they eat a ton of blue crabs and clams. as well as several kinds of shrimp, crayfish, and snakes. Their diet is especially carnivorous at this time of year. Many crane species depend on waste grains from agricultural crops in the winter. Sandhill cranes, for example, flock to harvested fields of corn, barley, and wheat in the non-breeding season, and also during migration. Likewise for black-necked cranes that spend the winter in Tibet. They gather in Highland valleys to gorge on waste cereal grains, mostly wheat and barley.

In Spain, the common crane has a mostly herbivorous diet in winter. The oak woodlands and fields of Spain provide the birds with acorns, leaves, and cereal grains. If so many cranes depend on our leftover cultivated grains in winter, what did they eat before humans came along. Well, they probably would have eaten the seeds of wild grasses and other plants in grasslands, meadows, and wetlands. But such habitats have, unfortunately, been mostly replaced by large-scale agriculture. As for the predators of cranes, these birds are large enough and aggressive enough that most predators steer clear of them. They're probably not worth the effort. But the largest raptors, like the Golden Eagle, can still pose a threat to adult cranes.

Crane eggs, chicks, and juveniles are much more vulnerable, however. They sometimes fall victim to foxes, minks, raccoons, coyotes, dingoes, and other critters of that nature. When cranes pair up to breed, they form monogamous bonds that last a lifetime. Only if one member of the pair dies will the other seek a new mate. Or occasionally, a pair will divorce if their attempts at breeding keep failing. These are long-lived birds, so they mature a bit slowly. Young cranes are about two or three years old when they first pair up, but they might be four or five years old before their first actual attempt at nesting.

Although a bonded pair will stick together for life and they'll raise brood after brood together, there can be some degree of infidelity in cranes, a little hanky-panky on the side. For example, a 2006 study published in the journal The Condor looked at breeding behavior in a sandhill crane population in Wisconsin. The researchers used data from DNA to determine who the genetic parents were for 45 crane chicks. It turned out that up to 11% of the chicks were the result of an extra pair fertilization. An extra pair fertilization is when one of the two adults raising a chick is not genetically related to that chick. For example, the female might sneak away to mate with a male on the side while her bonded male partner is sitting on their nest. Female Sandhill cranes can store sperm for days, so she can

lay an egg later that was fertilized by the rando male she made it with. To my knowledge, there hasn't been much research on the extent of extra pair fertilization in other crane species. Anyway, cranes form and maintain their pair bonds using elaborate courtship displays. These spectacular dances have delighted and inspired us humans for thousands of years. Displays are usually more frequent in younger birds that have yet to mate. Bonded pairs perform ritualized displays less often, but they still dance for each other on occasion, while they're in their winter flock, during migration, or on the breeding territory.

This behavior reinforces their existing bond. Here's a great description of dancing in the world. a pair of whooping cranes. This comes from a report written by Robert Porter Allen in 1952. Quote, suddenly one bird began bowing his head and flapping his wings. At the same time, he leaped stiffly into the air, an amazing bounce on stiffened legs that carried him nearly three feet off the ground. In the air, he threw his head back so that the bill pointed skyward, neck arched over his back. Throughout this leap, the great wings were constantly flapping, their long black flight feathers in striking contrast to the dazzling white

of the rest of the plumage. The second bird was facing the first individual when he reached the ground after completing the initial bounce. This second bird ran forward a few steps, pumping her head up and down and flapping her wings. Then both birds leaped into the air, wings flapping, necks doubled up over their backs, legs thrust downward stiffly. Again they leap, bouncing as if on pogo sticks. On the ground, they ran towards each other, bowing and spreading their huge wings. Then another leap.

The climax was almost frantic, both birds leaping two and three times in succession. Quickly, it was all over, after about four minutes, and an extended period of preening followed. End quote. I'll see if I can find a video of this amazing display, and I'll put a link in the show notes.

Other crane species have similarly complex dance moves like these. When a few cranes in a flock start dancing, the behavior can be contagious. Pretty soon dozens or hundreds of cranes might get all ramped up, jumping and flapping energetically. But why do cranes mate for life and go through all this fancy dancing stuff? What evolutionary advantages do they gain with these behaviors? I came across one hypothesis that seems pretty reasonable. Birds that breed in high latitudes, like in the Arctic, have a pretty brief window of time to build their nests,

incubate eggs, and raise chicks, because summer don't last too long in the far north. Imagine if cranes had to find new mates every spring. They'd have to spend a lot of energy and time in courtship every year. But if you're a crane and you've already found your soulmate, you can get right down to the business of laying eggs when you reach your breeding territory. So, being monogamous for life might be an adaptation that saves time and energy for birds with short breeding seasons.

That's an interesting idea, an interesting hypothesis. Breeding pairs of cranes are territorial. The pair establishes their territory and then they build a nest. Most species nest on the ground, building a mound out of vegetation. Two eggs per clutch is the norm. However, the two crowned crane species will often lay three or four eggs per clutch. The male and female share in the work of building the nest, incubating the eggs, and raising the chicks. Crane chicks are what ornithologists call nidifugus.

This means the newborn birds leave the nest soon after they. hatch. I've talked about precocial chicks before. Precocial chicks are born with their eyes open, they can walk, are covered with fuzzy down, and in some cases they can feed themselves not long after hatching. Well, a nidifagus chick is simply a precocial chick that busts out of its egg, hops over the rim of its nest, and never looks back. All nidifugus chicks are precocial, but not all precocial chicks are nidifugus. You dig? So there's a fun and weird ornithological word for you, nidifugus, N-I-D-I-F-U-G-O-U-S. Sounds sort of like a spell in Harry Potter, doesn't it? Like you aim your wand at a large egg and shout, Nidifugus! There's some swirly, magicy sparkles,

and, ta-da, a lanky bird hatches out of the egg. What? I don't know. Some kind of whimsical escapade, I suppose. Back in the real world, crane chicks have their own special name. We call them Colts, C-O-L-T-S. That's right, Colts, as in the same thing we call young male horses. Apparently, crane chicks got this name because, being precocial slash nidifugus little buggers, they start running around on their long legs within 24 hours after hatching. So I guess someone thought the chicks look like little horses running around? I don't know.

What I do know is that crane colts are 100% adorable. Oh, Lordy, they're gangly, they're full of wide-eyed innocence, and they're covered in fuzzy golden-brown down feathers. In my opinion, way cuter than any old horse. Mom and dad feed their colts for a month or more. more before the young birds learn how to find food on their own. But juvenile cranes might keep begging for scraps from their parents until they're nine months old or so. In the autumn, the crane family will migrate south together.

Well, that's true for the species that migrate, anyway. Young cranes have to learn their migration routes. Their brains are not pre-programmed with flight instructions, as in many other types of migratory birds. The crane usually becomes completely independent of its parents after about a year. For migratory species, this happens after the return north to where the crane was born last year. Crane lifespans are relatively long. They can survive 20 to 50 years in the wild. For example, the oldest wild sandhill crane was at least 37 years old.

As with so many other birds, cranes in captivity tend to live longer. than those in the wild. The oldest crane on record, that I know of, was a captive Siberian crane that lived 83 years. In traditional Japanese culture, the crane is a mystical symbol of good luck and long life. Legends claimed cranes can live a thousand years. Yes, these birds do live a long time, but a thousand years is a bit of a stretch. Looking 1,000 years into the future, though, what do we imagine will be the fate of the world's cranes? Individual birds may not live that long, but what about species? Will the Siberian crane, gray-crowned crane, and whooping crane still be with us a thousand years from now? I sure hope so. That wraps up our episode on

the family Gruidi. Cranes are pretty cool, aren't they? I hope that. I hope that we're you found this episode reasonably enjoyable, at least slightly more enjoyable than whatever else you could have been doing with this time. Seriously, though, I appreciate you being here. Thanks for learning about birds with me. And we should all thank my supporters on Patreon, since their financial support of this show is a big part of what keeps it all going. My patrons have helped me so much. I'd like to offer my obeisance and deep gratitude to my newest patrons. Christine Williams and Mike Melchin.

Welcome and thank you guys. If you are interested in becoming a patron to support the podcast, you can check out my Patreon page over at patreon.com slash science of birds. And if you have something you'd like to share with me, please shoot me an email. Maybe you have some deep thoughts about the podcast. Or you'd like to tell me a story about an embarrassing situation that made your facial skin turn red. Whatever it might be, my email address is Ivan at scienceofbirds.com. You can peruse the show notes for this episode, which is number 73, on the science of birds website, scienceofbirds.com.

I'm Ivan Philipson. Thanks for being here, and I hope you'll join me on the next episode. Cheers.