The Science of Birds - The Common Raven

Episode Date: November 7, 2022

This episode—which is Number 63—is about the Common Raven, Corvus corax. This species is also known as the Northern Raven.Few bird species in the world are as geographically widespread as the Common Raven. And few are as familiar and iconic. This is a really amazing bird.Ornithologists and other scientists have studied ravens extensively, so we know quite a lot about this species.Today, we’ll look at the basic traits of the Common Raven as well as its behavior, habitats, diet, reproduction, and more.Links of InterestBOOK: Mind of the Raven: Investigations and Adventures with Wolf-Birds [Amazon affiliate link]Two Species of Ravens Nevermore?Crow vs Raven in Size [YouTube video]~~ Leave me a review using Podchaser ~~Link to this episode on the Science of Birds websiteSupport the show

The Tower of London is a castle on the banks of the Thames River, originally constructed for William the Conqueror way back in the 11th century. The tower has, at various times, been a royal palace, a prison, and a place to carry out executions. Today, it's where the crown jewels are kept safe. It's also home to a small number of ravens. Legend has it that if those ravens were to ever leave the Tower of London, like if they were to just fly away one day, the tower would crumble into ruin,

and so would the British Empire. Wild Ravens have been visiting the Tower for hundreds of years. It seems they liked to lurk around to watch prisoners being executed. They were particularly fond of beheadings. Supposedly when Lady Jane Grey was executed by beheading, in 1554, some ravens swooped in and started pecking at the eyes of the queen's severed head. The ravens that you find at the tower today aren't wild. They are captive birds. At least six ravens have been kept at the tower since the late 1800s. Their wing feathers are clipped

so that they can't just take off whenever they get bored or restless. We don't want those Ravens to leave. You know, just in case that legend about the British Empire crumbling has any truth to it. Better safe than sorry, I guess. But, I mean, there isn't really a British Empire anymore, is there? That all ended in the late 90s. Maybe the job of the Ravens at the Tower of London now is to keep the United Kingdom from unraveling. Who knows? If you visit the Tower of London as a tourist, you won't see anyone get their head chopped off. Right, that's how the Ravens feel about it, too. You won't see executions, but you will, most likely, get to see the Ravens.

They're world-famous birds, and much loved by the people of London. In the gift shop at the Tower, you'll find Raven keychains, raven plush toys, raven mugs, and for all I know, Raven toilet paper, and raven toenail clippers. Ravens have, for thousands of years, played important roles in the cultural of not just the British Isles, but also the cultures of other European, Asian, Middle Eastern, and indigenous peoples across the northern hemisphere. These large, black, highly intelligent birds have long been seen as mysterious and ominous. Ravens are symbols of death, evil spirits, or the devil. Not too surprising, given their sooty color and tendency to eat

dead things. Ravens have also been seen as messengers between the living world and the spiritual world. But sometimes they've served as mundane mail carriers, like when they delivered messages back and forth in Game of Thrones. I live in the Pacific Northwest region of North America, where unfortunately we don't get our mail delivered by ravens. But the raven is a central character in the traditions of most Native American cultures here in the PNW. Raven is regarded as a trickster in many of their stories. But this bird is also said to have brought fire and light to humans after stealing these from the sun. Some stories tell how it was the raven who created the entire world.

Common ravens regularly fly over my yard here in Oregon. I'm always happy to see them. Sometimes they perch high in our Douglas fir trees and call to each other in their guttural voices. One call they make sounds to me and my wife like a chimpanzee screaming, so we affectionately call our local ravens sky apes. They sound like apes and they're smart like apes. That so many cultures around the world have legends and folk tales about ravens is a testament to the vast geographic range of this bird, and also to its mystique, charisma, and penchant for mischief.

But, hey, we aren't here today to discuss mythology or the cultural significance of Ravens, are we? No, we want just the cold, hard facts about these birds as they are in real life. We're here for the science. 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 63, is about the common raven, Corvus Korax.

This species is also known as the Northern Raven. Few bird species in the world are as geographically widespread as the common raven, and few are as familiar and iconic. This is a really amazing bird. Ornithologists and other scientists have studied ravens extensively, so we know quite a lot about this species. Today, we'll look at the basic traits of the common raven, as well as its behavior, habitats, diet, reproduction, and more.

Kicking things off with the basic traits. I assume you're pretty familiar with the general shape and color of these birds. You probably know what a raven looks like. But did you know that Corvus Corax is the world's largest perching bird? In other words, it's the largest species in the avian order Paseroformis. It's true. If by largest we mean heaviest, that is. The common raven is the heaviest passerine bird. It can weigh up to about 3.6 pounds, which is 1.625 kilograms.

That's heavier than a toaster or your average laptop computer. I should mention that a related species, the thick-billed raven, Corvus Kraserostris, is pretty much just as bulky as our common raven. Thick-billed ravens live in northeastern Africa, mostly in Ethiopia. Their beaks are relatively supersized and strongly arched on top, almost like the beak of a hornbill or something. The bill of the common raven isn't quite as massive, but it's still large and formidable.

It's chisel-shaped, with a hooked tip on the upper bill. Hair-like bristle feathers cover up to half of the bill's upper surface. They look like they were brushed forward toward the tip. On the neck below the bill, there are some long, shaggy feathers. These are called hackles. A raven can fluff up its hackles, erecting them so that they stick out, sort of like a beard. Males especially raise their hackles when they want to look tough in a dominance display. Likewise, a bird showing dominance can raise its ear tufts, which look like little horns.

These aren't actually ears or horns, of course. They're just small patches of feathers. Ravens hanging around in a group know things are about to get real when one of them decides to make a dominance display. Whoa, look out, everyone. This guy's suddenly got horns and a shaggy beard. I guess we should take him seriously? Beak to tail, the length of an adult common raven ranges from 23 to 27 inches, or 58 to 69 centimeters. The wingspan is between four and five feet, which is 120 to 150 centimeters. The large wings are well suited for soaring flight. Female and male ravens look pretty much the same, although females tend to be a bit smaller. And as for coloration, we all know that raven feathers are black, all over.

The bird's skin and eyes are black, too. They may not be colorful, but ravens are, in my mind. opinion, strikingly handsome birds. What's the difference between a raven and a crow? This question comes up a lot. Before I can answer, I should point out there are 44 bird species in the genus Corvus. Almost every one of them is either some kind of raven or crow. So we need to be more specific about which raven species and which crow species we're talking about. But since I live in North America, and I know many of you

listening right now, also live in North America, I'll assume the question is really, what's the difference between the common raven, Corvus Corax, and the American crow, Corvus Brachyrinkos. Telling these two critters apart is an identification challenge for many of us. First, there's the size difference. Remember that the crow is the bread box of bird sizes. It's the size standard. So we might ask, is it bigger than a crow? In this case, yes, it is bigger than a crow. The raven, that is.

Easily twice as big. The common raven is actually about as big as a red-tailed hawk. Then there are the relative sizes of the bill. The specific epithet of the American crow's scientific name, Brachy Rincois, is actually Greek for short bill. A common raven's bill is heftier, more chunky overall. It's usually as long or longer than the bird's head. And the raven's bill has a more distinctly hooked shape at the tip.

You can also tell these species apart when they fly overhead in a couple ways. American crows tend to flap pretty frequently, rarely soaring. Ravens spend a lot more time soaring. And raven wings make a whooshing sound in the way. flight. I'll play you an example in a few minutes. You won't hear that wing sound when a crow flies by. Another thing to look at when these birds are flying is the shape of the tail. The American crow has a rounded off or blunt tail tip. A common raven's tail is diamond or wedge shaped. The central tail feathers of the raven are longer than the outer feathers. You can often tell these birds apart

by their voices. Common ravens and American crows make distinct sounds. Crows make a higher-pitched, caw-ca-s sound like this. Raven calls are tonally similar, but lower-pitched. They croak rather than caw. Here are some ravens calling. So there you go. I hope that was helpful. You can tell crows. and ravens apart by their size, their bills, the way they fly, their tail shapes, and their voices. Let's talk a little about the basic behaviors of the common raven. These birds usually live alone or in pairs.

Bonded pairs stick together all year long. Non-breeding ravens are solitary. However, they often gather to feed around animal carcasses. Non-breeders will also spend their nights in communal roosts. A lot of the behaviors we observe in the common raven clearly reflect how smart these birds are. That's one of the biggest claims to fame for the common raven. It's high level of intelligence. More and more scientific evidence points to the fact that the common raven is not only one of the smartest birds on the planet,

it's one of the smartest animals, period. It rivals the intelligence of chimpanzees and orangutans. This assessment is based on a bunch of studies of ravens. These birds score high on a variety of cognitive skill tests. These skills include the ability to use tools, plan for the future, understand cause and effect, understand numbers, and solve problems in novel ways. If humans were to go extinct,

I'd bet on the common raven as a number, the animal most likely to replace us by evolving into the next highly intelligent, world-dominating species. I'm sure there are some science fiction stories out there already that explore this idea. These birds display a lot of social intelligence, too. They have complex social systems based on dominance hierarchies, friendships, and feuds with enemies. Ravens know each other as individuals. They can show empathy for each other. Ravens support their friends. For example, if a raven gets in a scuffle and ends up losing, his or her friends will comfort them. These birds hold grudges, too. They seem to have a sense of what a fair trade is. They aren't

too happy about it when they get cheated. For example, there was this study published in 2017 in the journal Animal Behavior. The researchers in this study worked with nine captive ravens. The birds were first taught a specific system of food exchange. In this system, a raven is given a piece of bread. The bird can choose to exchange the piece of bread with a researcher, getting a piece of cheese in return. And I should tell you that ravens are way more excited about cheese than a dumb old piece of bread. So the nine Ravens were taught that they can trade up, giving up their bread to the researcher, then the researcher hands them a piece of cheese. That's a fair trade. But in the actual experiment,

some researchers cheated the birds. Instead of giving the bird the cheese in exchange for bread, the researcher popped the cheese into her own mouth and ate it in front of the raven. I can imagine the researcher taunting the raven. Oops, where'd the cheese go? In my mouth, that's where? Wow, it's so good, too. You really should try some. Oh, but wait, there's no more cheese left, is there? Wah, wah. The raven stares at the researcher in astonished disbelief. What treachery. What villainy! This experiment was carried out with all the ravens. They were subjected to both fair and unfair exchanges, each with a specific person. The fascinating discovery in this study was that the ravens held

grudges against the humans who had cheated them. The birds could remember the faces of individual researchers. Up to a month after the experiment, Ravens were much less likely to take part in bread-for-cheese exchanges with the humans who had wronged them. Oh no, here comes Jenny. I'm not working with Jenny. Nope. She's a lying, cheese-stealing swindler. Fool me once, Jenny. Shame on you. I'd rather choke on this bread than give you the satisfaction. Another interesting behavior in Ravens and another potential sign of intelligence is that they like to play.

They're cheeky critters that like to goof around. Ravens tease each other and they tease other animals. For example, they grab the tails of predators like wolves and coyotes. Ravens roll around in the snow and some have been seen sliding down a snow-covered slope over and over playing like human kids. Common Ravens even seem to enjoy playing practical jokes. For example, more than one captive raven at the Tower of London

has freaked people out by pretending to be dead. And one source reported that ravens have peeled the warning labels off of barrels of toxic waste. Now that's a hilarious practical joke. A couple of humans come along. Hey, Fred, what do you suppose is in these rusty barrels with the green sludge leaking out? Beats me, but it can't be toxic waste, you know, because if it was, there'd be a warning label or something. I don't see no labels. I guess that means it's perfectly safe for us to dump it all out into the local water supply. Those ravens must have had a good laugh about that one.

No wonder the raven has such a reputation as a trickster. Common ravens are playful while flying too. They perform aerial acrobatics while riding the wind. They do barrel rolls and flips. These behaviors might not always qualify as, quote-unquote, playing, since they might be displays meant to impress potential mates. But Ravens also do these sorts of airborne tricks while flying alone. That suggests it might all be just for fun. One solitary bird was even seen flying upside down for at least a kilometer. Moving on to consider the sounds that the common raven makes. This bird has an extensive repertoire, including dozens of unique calls.

Most are guttural or sort of mechanical, in other words, not very musical. Ornithologists have figured out the meanings of about 20 raven calls. The functions of all the others are still a mystery. Of the vocal sounds we understand, some of their functions include advertisement of location, advertisement of territory occupancy, predator alarms, and comfort sounds. The latter, comfort sounds, are made by happy, recently fed nestlings, and by mated pairs as they snuggle and preen each other.

The calls and voices of common ravens vary from one geographic region to another. In other words, there are regional, dialects. Not surprising, given how widespread this species is across the northern hemisphere. Each raven also has its own unique voice and calls, so these birds can recognize each other individually by their calls. The common raven is also famous for its ability to mimic sounds. Captive ravens can learn to imitate human speech pretty well. I scoured YouTube to find you some good examples of mimicry in ravens. They're out there, but most of the audio recordings were low quality and wouldn't translate

well here on the podcast. Oh well. But here's a female common raven named Vanta that likes to say hello. But Vanta doesn't speak English. She speaks Spanish. That was seriously a raven. Here she is again saying, Ola. Now let's listen to some of the natural sounds made by wild ravens. Here are some ravens in France, calling while in flight. So those were French ravens. If we could translate those croaking calls, I wonder if they were saying,

Oh, ha, ha. Who knows? Here's a different type of call made by a raven in Germany. In this next recording, which is pretty amazing, you'll hear a raven in Sweden as it flies by. If you listen carefully, you can hear the wings beating against the air. Next up is one of the more mechanical sounds. Remember that I said I call my local ravens sky apes? Well, maybe you'll understand why after hearing this next recording.

Here's a raven in California making something like a chimpanzee or monkey sound. So those are just a few examples of what the common raven can do with its voice. But these birds are also skilled at non-vocal communication. They use physical gestures to communicate with each other. Researchers have found that ravens use their beaks to point at objects to direct the attention of another bird. This is analogous to how humans use their fingers to point at stuff. You know, like when a little kid accidentally drops their ice cream cone and starts crying,

and we all point and laugh. In another use of gestures, a raven will pick up an object in its beak and hold it up to show it to another raven. It's like, hey, look at this. Don't you wish you had one of these? That we know of, ravens are the only non-primate animals that use gestures in this way. And that is just amazing. I'm telling you, man, these birds are going to take over the world someday. Next up, we're going to look at the evolution, distribution, habitat, and conservation of the common raven. This species is a member of the family Corvody.

This family contains over 100 species, including birds. like jays, magpies, jackdaws, nutcrackers, crows, and ravens. I'll definitely do an entire episode on this family at some point. The family corvetee belongs within the avian order Pasariformes. Corvids are actually songbirds, and songbirds are a distinct evolutionary lineage within Pasariformis. So yes, the common raven is a big old songbird, the world's biggest songbird, in fact. This species appears to have originated millions of years ago, somewhere in Eurasia, in the old world.

By analyzing genetic information from the genome of the common raven, researchers have discovered some interesting geographic and evolutionary patterns. DNA sequences have been collected from common ravens across the northern hemisphere. It turns out that, at the genetic level, ravens in one part of the world are strikingly different from all the raveans. rest. The ravens living in the southwestern part of North America are highly divergent from the other common ravens. In fact, this lineage of southwestern or Californian birds is more closely related to an entirely different raven species. The Chihuahuan raven, Corvus

Crypto Lucas. Let me say that again. Common ravens in the southwest are more closely related to Chihuahuan ravens than they are to common ravens elsewhere in North America or Eurasia. Kind of confusing, right? And how is that even possible? Well, from the published research, my understanding is this. Researchers think that common ravens might have colonized North America twice. The first time was about two million years ago. The ravens that colonized the new world eventually became isolated from their old world relatives. Maybe it was the ice ages that caused this isolation. For at least a million years,

the ravens in North America evolved on their own path with no genetic link to the old world. It seems birds in the new world were evolving into a new species. Meanwhile, another raven population in the new world split off and evolved into another new species, the Chihuahuan raven. Now, I'd forgive you for imagining that the Chihuahuan raven is a tiny bug-eyed bird with an apple-shaped head and a nervous disposition.

But the real bird is nothing like the dog. This raven species looks, to the casual observer, a lot like our common raven. We have the Chihuahuan Desert here in North America, and that's where the Chihuahuan Raven lives. The dog and the desert are named after the Mexican sea. state of Chihuahua. Anyway, as the last glacial maximum of the ice ages ended about 15,000 years ago, more ravens from the old world crossed the Bering Land Bridge. They spread eastward into North America through Alaska. This was the second colonization event. An intriguing idea is that these ravens who arrived 15,000 years ago might have been following humans and or wolves as these

species spread into North America. The newly arrived common ravens from the old world were still genetically and behaviorally compatible enough with the new world common ravens that they could all mingle and reproduce. Before then, the two lineages had been diverging, evolving into separate species. But since the end of the Pleistocene 15,000 years ago, the two lineages have been slowly merging back into one. It just so happens that most of the common ravens in the southwestern part of North America represent the more ancient Californian lineage. They represent the first colonization event.

This is super cool stuff, you guys. It's actually one of the best examples we have for the process biologists call speciation reversal. This is when two lineages that have been evolving away from each other, breaking up to become two species, are like, never mind, who are we kidding? Let's get back together! Speciation reversal. But hey, let's not forget about the Chihuahuan Raven.

By 15,000 years ago, this species had evolved to be different enough that none of the common ravens wanted anything to do with it. The Chihuahuan raven maintains its distinction as a species. Now, biologists aren't 100% sure this is how it all went down. What I just described is a hypothesis, one possible explanation for the patterns found in the DNA of common and Chihuahuan ravens. In any case, today the common raven has a geographic distribution across Eurasia, northern Africa, and North America.

The reason this bird is so widespread is that it's a generalist, a generalist in terms of what it eats, and a generalist in terms of habitat. Speaking of habitats, you can find common ravens in deserts, mountains, rugged coastlines, grasslands, tundra, and several types of forest. This species is most strongly associated with wild places, far from cities. That said, ravens in some parts of the world live in farmlands and small towns.

And in recent decades, they've even moved into some urban areas, especially in Western North America and in Europe. Some ravens, smart birds that they are, have figured out that cities can provide reliable sources of food, water and nesting sites. Where these resources are abundant, the local population of common ravens can become unnaturally dense. So, on the one hand, ravens are creatures of remote wilderness. On the other hand, they sometimes gather in large numbers where humans have trashed the landscape. Like, especially where we've literally trashed the landscape, in places like garbage dumps. Oh boy, do ravens love garbage dumps.

I was once in the remote town of Nome, Alaska, and I encountered more ravens in one place than I had ever seen. There seemed to be hundreds of them. That place was on the outskirts of town at the Nome Landfill. There are an estimated 16 million common ravens in the world. As a species, it's not considered threatened or endangered. Common raven populations are even increasing in some regions. These increases may reflect the return of ravens to places where they had disappeared or declined before the mid-1900s.

For centuries leading up to that time, common ravens had been persecuted in North America and Europe. They were feared for superstitious reasons, and they lost a lot of their wilderness habitat, too. Ravens are still persecuted in some regions. These days, it's not so much because they're seen as a spooky symbol of evil or messengers sent from the devil or all that nonsense. Instead, it's often because they're seen as a threat to livestock, like newborn lambs or cows.

And sometimes government agencies in the U.S. have conducted programs to slaughter thousands of ravens because these birds are predators on other animals that are endangered. For example, common ravens eat baby desert tortoises, and they eat California condor eggs and nestlings. So yes, ravens are predators that can be a threat to these and other endangered species. It's an unfortunate reality, but, and I'm definitely not an expert on this complex issue, my understanding is that using lethal methods to control ravens is not the only option. There are creative, non-lethal ways to reduce the negative effects of ravens on other species.

The latter approach sounds way better to me. I mean, come on, it's not the raven's fault that animals like the desert tortoise and California Condor are endangered in the first place. It's the fault of people. So what do ravens eat besides cute baby tortoises? and the eyeballs of recently beheaded queens. The common raven has a wildly diverse, omnivorous diet. Like I said, it's a generalist. Animals are eaten alive or dead.

Ravens are both predators and scavengers. The flesh of mammals makes up a large portion of the diet in many raven populations. Often this is in the form of carrion ripped from the carcass of a deer, elk, or other large ungulate. but ravens will also actively hunt small mammals like rodents. Other animals in the diet include insects, reptiles, amphibians, fish carcasses, birds, and bird eggs. I took a photo of a common raven in Denali National Park in Alaska as it was holding an unbroken egg in its bill. I'll put that photo in the show notes for this episode on the Science of Birds website. The egg was tan-colored with dark-brown blotches and speckles.

It had been stolen from the nest of a willow tarmigan. I felt sorry for the tarmigan, but the raven sure looked pleased with itself. There was actually a raven nest nearby with chicks. So I guess that was one of those Circle of Life moments. Ravens do some other things that we humans might consider, uh, objectionable, even gruesome. For example, these birds have been known to snatch Arctic fox pups from their den. Ravens sometimes feast on the guts of another bird or a small mammal while the poor thing is still alive.

They like to eat cow placentas, and they'll also pluck out the eyes of newborn lambs. These birds are really into eating eyeballs, I guess. I don't know about you, but a lot of that sounds pretty horrific to me. But I remind myself that ravens are just trying to survive. Survive and if they're lucky, raise a few chicks. Their life is hard, and they're just following their instincts. On a lighter note, the common raven also eats some plant foods. These include fruits, berries, nuts, grains, and even some types of seaweed.

The robust bill of the raven works sort of like a Swiss army knife or a multi-tool. It works well for gathering and eating this wide assortment of food items. For example, the hook at the bill tip helps the raven rip pieces of meat off of its prey or off of a carcass. The lower bill, the lower mandible, has its own usefulness. It has a pointy tip, like a dagger. In snowy northern latitudes, common ravens often scavenge off of mammal carcasses that are frozen solid. it's not so easy to tear off pieces of frozen meat. But a raven can open its bill a little bit and then use its lower bill like an ice pick

to hammer into the frozen flesh. There's a bit more to discuss regarding the feeding habits of the common raven. These birds are certainly born with some instincts regarding what and how to eat. But they're highly intelligent and also have to learn. what is or isn't good to eat. Some of this they learn from their parents within the first few months, but otherwise they have to explore and learn on their own. Young Ravens are what biologists call neophyllic. That means they love new things. Young ravens are super curious, and they investigate just about every new thing they encounter in their world. These birds will

pick up objects in their bills and play around with them. Small rocks, sticks, leaves, used hypodermic needles, really just about anything lying around. Once a young raven becomes familiar with each of these items, it moves on to others. Eventually, the bird will figure out that some of these things qualify as tasty snacks. Those items will get a lot more attention in the future. This neophilic behavior helps young ravens learn about and adapt to their environment, they can take advantage of unique or novel food sources. Maybe this is one trait that helped the species become so widespread. As a raven gets older, however, it loses that childlike sense of wonder. It stops being so curious and eventually becomes neophobic. It becomes afraid of

anything new. It's much more set in its ways. A neophobic older raven, for example, doesn't want to upgrade to the latest iPhone. Its seven-year-old phone with the cracked screen works just fine, thank you. And an old raven probably thinks the music that kids are listening to these days is complete garbage. It's not even music. It's just a bunch of noise. But you know what is music to the ears of even a stubborn old raven? The howl of a wolf. many raven populations in wild northern places depend on large predators like wolves and mountain lions the predators kill big herbivores

then the ravens gather around to scavenge scraps of meat from the carcasses so ravens will fly in to investigate when they hear wolves howling and some of these birds will even investigate the sound of gunshots They've learned that humans too are predators of large game. Hunters leave behind steaming gut piles that are like a gourmet feast to a raven. Common ravens are so smart that they know the difference between the sound of a gunshot and other similarly loud sounds, like a car door slamming or an air horn. The birds are much more likely to swoop in to investigate a gunshot.

And there's actual scientific evidence for this. A researcher published these results in the prestigious journal Ecology back in 2005. Some people claim that common ravens will intentionally attract the attention of wolves and human hunters in order to lead them to prey like moose or caribou. I can picture a moose trying to hide in a snow-filled forest from a pack of wolves. Suddenly, two ravens perch in the branches just above the moose, and they start making a racket. The moose is like, Shh, shut up, shut up.

Shoo, get out of here. You little devils, you guys are literally going to get me killed. As far as I know, the evidence for this behavior in Ravens is only anecdotal. It has yet to be confirmed scientifically. Young non-breeding ravens will often forage together in loose groups. Some ornithologists call these crowds rather than flocks, since they're not as tightly coordinated as true flocks. These non-breeders tend to roost together overnight,

especially in winter. While roosting, they communicate about the locations of nearby food resources. So these communal roosting sites are hubs for information exchange. When morning comes, the crowd of young ravens flies off together toward the food resource. Let's say it's a wolf kill, and it's being guarded by a mated pair of mature ravens because the carcass is in their territory. But then here comes the rag-tag crowd of young ravens.

They overwhelm the pair of adults and chase them off. Strengthen numbers, yada, yada. Common ravens often stash bits of food in hidden locations so they can eat them later. This behavior is called caching, C-A-C-H-I-N-G. A raven has to be careful where it deposits a cash, because if other ravens are watching, they'll try to steal the food later.

A raven will sometimes just pretend to cash food if it knows another raven is watching. It bluffs to confuse the would-be thief. Or the first raven will come back later to move the food to a new, more secure location. These sorts of behaviors are evidence of high intelligence. After a raven digests all that delicious food, the insects, roadkill, garbage, cow placentas, or whatever, after digestion, the bird might cough up a pellet, you know, just like owls make pellets.

A raven pellet contains the indigestible bits from its meals, hair, feathers, maybe some seeds, bits of bone. Some researchers have found raven pellets full of gravel or plastic. And one raven even spit out a pellet that was just a wadded up handkerchief. What was going on there? Was the raven trying to do a magic trick or something? I've got nothing up my sleeve, ladies and gentlemen, nothing at all. Now let me just, just a sec. One moment.

And out of the bird's beak comes a blue handkerchief, all wet and gross. Presto. There are about 16 million common ravens flapping around out there in the world, doing barrel rolls in the sky and generally causing mischief. But that number is growing, right? Let's talk about how that's happening. It's time to look into the breeding behavior of ravens. This species is monogamous.

Common ravens pair up, and they tend to. to stay together for their entire lives. Or at least that's what we assume happens. It seems there isn't a lot of hard data to prove that these birds mate for life. And we also don't really know if monogamy in this species is purely social or is it also sexual? Because, as I've pointed out before, most songbirds that form monogamous pairs to raise a family aren't necessarily faithful to each other in the sexual sense. Paired males and females of many species mate with others on the side. These events are called extra pair copulations.

Do ravens in a bonded pair also mate with other birds outside of the pair? This has been documented a few times, but it seems ornithologists don't really know how frequently this happens. Probably not too often, but more research is needed. In any case, courtship between pairs of ravens can take place any time of year, but this behavior is strongest in autumn and winter. Once paired up, a couple interacts closely and frequently to reinforce their bond. They play together, and they preen each other.

They also join forces to display their dominance to other ravens. Each of the most dominant pairs eventually establishes a territory. The typical size of a territory varies from region to region, from about two square miles to over 15 square miles. That's five to 40 square kilometers. In landscapes where food and nest sites are plentiful, territories tend to be smaller. That's because more ravens can pack into the area and still get enough food or whatever else they need to be successful. A smaller territory works just fine in those situations. The pair of ravens holding the territory defended from intruders.

Their defensive behavior is most fierce during the breeding season. A territory holding couple are the top birds in the local dominance hierarchy. They're the king and queen of the social scene. Next in the hierarchy are pairs without a territory. Then it's pairs with only a casual relationship. And the lowest ranking birds are the non-bonded individuals. The Raven King and Queen want to keep their territory and all of their power. They may feel threatened by other couples that seem to be developing a strong bond.

So the dominant pair will often actively disrupt the courtship of those other couples, trying to get them to break up. Sounds to me like some kind of high school TV drama. I mean, if they made a coming-of-age show about the social lives of Ravens, I might actually watch that. But what would they call it? How about pretty little corvids? Or euphoria, but this time with birds? Or maybe Beverly Hills, 9021, oh, look, it's a bunch of ravens. I don't know. I'll have to give this some more thought. But how about we move on for now?

Nests. Common ravens nest in all sorts of places. Cliffs, trees, bests, buildings, bridges, power poles, you name it. In fact, some Cheeky Ravens have built their nests in deep space communication satellite dishes in California. The nest is constructed mostly by the female, but the male might help by bringing her some sticks. The sticks are piled up and then some are woven together to make a loose basket. The female then makes a cup on top using finer plant material. She lines the cup with soft things, like mammal fur, shredded bark, grass, or man-made material like paper.

One source I came across reported that, quote, an unpleasant odor often permeates the nest, end quote. What, unpleasant? You mean raven nests don't smell like peppermint or like fresh-baked brownies? I'm joking, of course, but now I'm actually morbidly intrigued. I kind of want to find a common raven nest so I can get a whiff of this notorious. odor for myself. In the name of science! Three to seven eggs per clutch are laid in the stinky stinky nest. The female does most of the

incubating. Meanwhile, the male raven stands guard. He also feeds his mate and will sometimes help incubate in cold weather when mom goes off to find food. The chicks are altricial. That means that when they hatch, they're blind, helpless, and mostly featherless. They're orange or pink. One biologist way back in the 1940s described common raven chicks as looking like grotesque gargoyles. Both parents feed the growing chicks. Mom and dad bring water to the chicks by carrying it in their beaks. The raven chicks fledge and leave the nest at about four to seven weeks old. They'll hang around with their parents for another few months. In their first summer, the young ravens leave home and gather into rowdy groups.

These teenagers roam around in their gangs looking for food and looking for trouble. Eventually, pears form and the gang breaks up. Common ravens breed for the first time when they're between two and four years old. In the wild, these birds probably live about 10 to 15 years. The oldest wild raven on record, though, was 22. captive ravens can live much longer. Some of those at the Tower of London, for example, have lived over 44 years. And that's a good thing because those birds have a big responsibility on their shoulders, don't they?

They need to stay alive and stay at the Tower of London. It's their job to keep the British Empire or whatever you want to call it from crumbling into oblivion. Well, my friend, that is what I've got to say about the common raven today. I hope you enjoyed listening and that you feel like you understand these magnificent sky apes a little better. As I mentioned in my last episode, I was recently working in Australia for a while. It was a fantastic experience, and I got to see countless, wonderful birds. But it's also great to be back home. Being gone for so long, I have to catch up on lots of shoutouts to my

new supporters on Patreon. So here we go. Thank you very much, Stacey Mitchell, Kayla Tebaldo, Sleeper Girl 541, Aspen, Molly A. Tanish, Deborah Tursky, Charlotte Van Vactor, Michael Nally, Mark Antoine Bouverage La Roche, Edward King, Karim A. Dieang, Amy S. Fenton, and Martin Bighauer. You guys rock. Again, thank you. If you, my bird-loving, friend, would like to be counted among the ranks of such fine individuals, you can become one of my supporters on Patreon. Just go check out my page at patreon.com slash science of birds. You can also send me an email if you have something you'd like to share with me. Maybe your thoughts about the podcast, or you want to tell me about some things that stir up your neophobia. What new things are you

afraid of? New flavors of potato chips? The new Taylor Swift album? New York? In any case, my email address is Ivan at Scienceofbirds.com. I do my best to answer every email I get, even though it might take me a while to get back to you. You can check out the show notes for this episode, which is number 63, on the Science of Birds website, Science of Birds.com. This is Ivan Philipson, wishing you a glorious day. Cheers. Thank you.