The Science of Birds - Owls

Episode Date: December 16, 2023

This episode—which is number 88—is all about owls. Owls are fascinating birds that have captured our imaginations since the dawn of humankind. They have amazing camouflage that allows them to blend in with their surroundings, and they have several other avian superpowers that set them apart from all other birds. Owls are divided into two families—Tytonidae and Strigidae—and we'll be discussing both of them today.Links of InterestOwl Notes–Denver Holt Shares the Short eared Owl's Courtship Flight [VIDEO]Long-whiskered Owlet (Xenoglaux loweryi) [VIDEO]The silent flight of an owl [VIDEO]Pellet.comWhat an Owl Knows [BOOK]~~ Leave me a review using Podchaser ~~Link to this episode on the Science of Birds website Support the show

I'm going to share an embarrassing personal story with you. Several years ago, I was in Southern Oregon leading a birding tour. It was a warm day in early summer. My group and I were walking through a beautiful forest at the edge of a wet meadow. We were actively birding, looking at every direction with our binoculars, trying to find all the birds we could in the area. We were seeing species like willow flycatcher, yellow warbler, song sparrow, and western Tanager. Suddenly, one person in the group called my name as they were peering intensely through

their binoculars at something. They said to me, I see a bird, I think, way up there on the hillside, in the Douglas fir trees. I think it's an owl. The other folks in the group had seemed only half interested until that magic word was uttered, owl. We all snapped to attention and started scrutinizing the far hillside with our binoculars. I saw something. It was at least a quarter mile away, but there was something gray and

modeled catching a little light between the branches of some large conifers. I made a snap decision and said, okay, guys, we have an owl, we have an owl. I tried not to be too frantic as I set up my spotting scope. I said, this is a big deal, guys, I think it's a great gray owl. And that would be a big deal. The great gray owl, Strick's nebulosa, is often hard to find, and it's a highly sought-after species among birders. So there I was. I got the scope aimed at the distant bird, focused it hastily, and asked people to take a look. Everyone was bubbling with excitement. My heart was racing, I was grinning, feeling proud of myself for being such a fabulous and talented, and while we're at it, ruggedly handsome, birding guide.

Each person in the group stepped up, squinted through the scope's viewfinder, then let the next person have a go. They were saying things like, oh, is that it? I guess I see it. It's so far away. The excitement was, for some reason, quickly dissipating. I found out why when I could finally take a serious look through the scope myself. And what did I see? Was it a great gray owl in all its glory? Nope. It wasn't any kind of owl. It wasn't even a bird. It was a sunlit patch of gray tree bark. Its outline was vaguely owl-shaped, framed as it was by the dark green boughs of fir trees.

I felt stupid. I had to admit my mistake and apologize to everyone. But I laughed at myself, and we all had a nice chuckle. And then, no one in the group would look me in the eye for the rest of the trip, and then afterward they each gave me only a one-star review. Worst guide ever. No, just kidding. Everyone was actually really kind and understanding. We all make mistakes, right? Well, I've been careful not to make that kind of mistake again.

I learned some lessons that day. As far as I know, I've never again mistaken. identified an inanimate object as a bird, at least not out loud to a group while on the job as a guide. Sometimes the power of suggestion is strong. That first person said they saw an owl, and so when I looked, my brain was primed to see an owl. So I did. We have to be careful about this sort of thing. Anyway, my little story highlights a couple of things about owls. The first is the fact of their amazing camouflage. Owls often really do look like just a random patch of gnarly tree bark. You wouldn't mistake a flamingo for tree bark, would you? Or mistake tree bark for a flamingo?

Of course not, but that sort of thing does happen with owls. The other thing my story highlights is how much people love owls. Anytime we're able to see an owl while out birding, it's an exciting experience. There's just something about these birds. Many, like the Great Gray Owl, are elusive. Throughout history, people of different cultures have variously considered owls, mysterious, benevolent, evil, wise, stupid, lucky, or unlucky. But one thing, owls definitely are amazing. Biologically, they have several avian superpowers that set them apart from all other birds in the world. 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 88. It's all about owls. Usually, when I make an episode about a group of birds, I'm talking about a single bird family, but owls are divided into two families, and we'll be discussing both of them today. That way, we're covering all the owl species of the world. I predict this

will be a popular episode, since owls are among the most loved birds. They've captured our imaginations since the dawn of humankind. For example, there's an ancient image of an owl that was drawn by a person's finger tracing in the mud of a cave wall in France. It dates to about 36,000 years ago. And of course, owls show up all over the place in modern pop culture. There's the male delivering owls of Harry Potter, the character owl in Winnie the Pooh, the mechanical owl named Bubo in the 1981 movie Clash of the Titans,

and the book series called The Guardians of Gahoul, where the main characters are all owls. And let's not forget Woodsy Owl. Here's Woodsey in a public service announcement from the 1970s. Woodsy is running around with a bunch of kids. Hi, I'm Woodsy Owl. In order to try and stop pollution, we need more help. So, help Woodsey spread the word.

Come on. Never be a dirty bird. No matter where you go, you can let some people know to. Give a hoot. Don't pollute. Never be a dirty bird. In the city or in the woods, help keep America looking good. That's right, kids, never be a dirty bird. Do what Woodsy Owl says, or else. Fictional owls are fine and all, but they don't tell us much about the lives of real owls. We can thank all the scientists who've worked hard to help us understand the biology of owls, and scientists are still learning new things about these hard-to-find birds.

In the quest to find elusive owls, researchers use several techniques. They attract owls by mimicking their calls or playing recorded owl vocalizations. They scour forests for trace evidence of owls like whitewash from feces or regurgitated owl pellets. In some cases, dogs have been specially trained to find owls. And now there are technologies that allow for passive acoustic monitoring. A researcher can leave a device in the forest, or wherever, and it automatically records the sounds of owls, which can later be identified to species by artificial intelligence algorithms.

Among non-scientists, owls are an obsession for some birders. The name for going out to search specifically for owls is called owling. However, if you look up the word owling in the Merriam-Webster dictionary, its definition is given as The Act of Smuggling Wool or Sheep Out of England. So if you and your buddies plan to go out owling one night, just to make sure everyone in the group is clear about the goal. Are you looking for nocturnal birds, or are you smuggling sheep out of England? So owls are so popular they have their own subcategory within the activity of birds. birding. You can't really say that about too many other groups of birds. I mean, you don't hear

about woodpeckering, vulturing, or finching, do you? Now, having said that, when I checked the dictionary, I came across some words that suggest there are other birding subcategories. I had no idea. Examples include parroting, ducking, swallowing, and railing. Anyway, I'm sure those are all delightful activities, especially railing, but today we're talking about owls. And I hope you're ready because this is going to be a long episode, maybe the longest Science of Birds podcast episode so far. Prepare to enter the mysterious world of the owls. Beginning with the key,

features of owls. We all know the basic iconic silhouette of an owl. It has an ovoid or egg-shaped body, a short tail, and a big round head. There may or may not be a pair of quote-unquote horns on the head. We'll get to those in a moment. Owls have relatively large, rounded wings. They have low wing loading because their wings have a lot of surface area compared to their body weight. This allows owls to have a slow, buoyant flight. They glide with ease on their broad wings. Probably the most outstanding feature of owls is their eyes. Ask a four-year-old kid to draw an owl, and the one thing they're likely to include in their scribbling is a pair of big, staring eyes. Owl eyes are indeed very large, relative to the size of the bird. From the front, they appear to be shaped like a sphere,

just like human eyeballs. But owl eyes are actually shaped differently from ours. They're more tube-like. They extend back into the skull, taking up a lot of room in there. In fact, if you look into the earhole of a living owl, you can see the bulge of the eye intruding into the ear canal. It's pretty crazy.

The size and totally tubular shape of owl eyes prevent them from being able to rotate, so they're fixed in place. To compensate, owls have super-flexible necks. They have the famous superpower of being able to rotate their heads way more than humans can. Now, can an owl rotate its head 360 degrees all the way around? No, that's a myth. The full sweep of head rotation for an owl is about 270 degrees.

Still, that's much more than the maximum of 180 degrees that humans have. Owls have several adaptations that make this level of head spinning possible. The vertebrae and arteries in their necks have unique anatomies that prevent the blood vessels from getting pinched during head rotation. Without these adaptations, the owl would lose the blood supply to its brain whenever it swivels its head to see what's going on behind it. The inability to rotate the eyes is also the reason many owls make little bobbing or dancing motions with their heads. They're trying to get a better look at you or whoever. These exaggerated movements help an owl judge the distance and position of objects. When owls move their heads up

and down and side to side like that, they're using a phenomenon called parallax to judge the distance of things. Parallax is that thing where objects appear to move to a different extent depending on the observer's point of view. Head movements like this are not. not unique to owls, since other birds like raptors do it too. But the head dancing movements of owls are especially cute and funny. Young owls make some of the most dramatic head moves, including rotating their faces to be almost completely upside down. The large eyes of owls face directly forward.

This sets them apart from pretty much all other birds, and it makes owls look a bit human-like, since we too have forward-facing eyes. This arrangement gives owls and humans binocular vision. Compared to animals and birds with eyes on the sides of their heads, those of us with binocular vision have a superior sense of depth perception. We see in 3D. Now, we still need to ask the question, why do owls have such ginormous tube-shaped eyes that aren't able to rotate?

The answer is, so that owls can see better in low, light conditions. Bigger eyes allow more light to reach the retinas. And compared to humans and many other birds, the retinas of owls are packed with more rod cells. Rods are the light sensitive cells responsible for vision and low light conditions. They're great for detecting motion. They're highly sensitive to light, but don't distinguish colors very well. Owls also have color-sensitive cone cells in their eyes, but these birds probably see only a limited subset of colors compared to other birds. You might remember from the podcast episode I did on Bird Vision

that birds have special cone cells in their retinas that are sensitive to ultraviolet light, to UV. Well, there's some evidence that owls lack such UV detecting cone cells in their eyes. But there's also evidence that the rod cells in owl eyes may have picked up the slack in that department. Some of their rod cells may have evolved to detect UV light. Pretty cool, but more research is needed. Moving on. We'll talk about the ears of owls a little later, but first I want to look at those so-called horns. Of course, they aren't actually horns. That would be super cool, though,

like what if a bunch of owls had little devil horns? Technically, these protuberances are called plumorns, spelled P-L-U-M-I-C-O-R-N. That word translates as feather horn. They're not horns and they're not ears. They're just special tufts of feathers. Ornithologists aren't 100% sure why so many owl species have plumacorns. But it seems these ear-like tufts have a couple of functions. First, they work sort of like human eyebrows to express emotions, and attitudes. Second, plumacorns provide an owl with extra camouflage because they break up the otherwise rounded silhouette of the owl's head. And another possible function of plumacorns is species recognition. They help owls recognize each other as belonging to the same species.

At the other end of the body, we have the feet. Many owls have fuzzy feathers on their legs and toes. all of them have two toes that face forward and two that face backward. This toe arrangement is called zygodactyl. Other types of birds with zygodactyl feet are woodpeckers, parrots, and the osprey. But owls are different because they can swivel one of their rear toes forward so that there are actually three in front and only one in back. But when an owl is swooping down to grab a prey animal, it typically holds its feet forward in the zygodactal position, toes spread wide.

Armed with long, pointy talons, this makes the feet into wicked devices for capturing small animals. And it's with these strong feet and talons that an owl kills its prey. The bill is used for tearing prey apart. Owl beaks are short, curved, and hooked at the tip. They're oriented more or less downward. Okay, now let's see. consider the range of body sizes among owl species. The smallest owl in the world is the perfectly named Elf Owl, Microthenny Whitney Eye.

This tiny creature is only about five and a half inches or about 14 centimeters from beak to tail. That's smaller than a friggin' house sparrow. Elf owls live in the deserts of the southwest use. U.S. and down into the mountains of western Mexico. There are two other diminutive owl species that could also claim to be the smallest in the world, the Tamalipas pygmy owl and the long-whiskered owlet. But the elf owl weighs a bit less, so it wins the world record title. Then we have the big owls. The world's largest owl lives in northern China and Japan and in the far east of Russia. It's Blackistons Fish Owl, Katupa Blackestinai. This monstrous beast is 28 inches long,

which is about 71 centimeters. Its wingspan is over six feet, or about 1.9 meters. Females can weigh over 10 pounds. Now, I specified females there because female owls are often heavier than their male counterparts, up to 25 percent heavier in some species. So, Blackistan's fish owl is the largest owl. It is to owls what the Siberian tiger is to cats in the family Phelody. And coincidentally, Blackistan's fish owl lives in Siberia. Other very large owls, or VLOs, as we call them in the biz, include the Eurasian Eagle Owl, the Snowy Owl, and the Great Horned Owl. The Great Gray Owl, you know, the one I did not see that fateful day in Southern Oregon, that species too is a VLO.

But if you were to look at a cross-section of a great gray owl, you might be shocked to see that about 70% of the bird's volume is actually just feathers. Deep inside all that thick plumage is a scrawny little body with a thin neck. From the outside, we see this enormous, majestic owl. But it's a hoax. It's just a bunch of fluff, man. It's as though the 2.5 pound owl inside that looks like a gargoyle is wearing a big mascot costume,

like a Mickey Mouse costume. Oh, wait, no, like a Woodsy Owl costume, circa 1977. Hi, I'm Woodsy Owl. But seriously, all those feathers on a great gray owl serve as a thick layer of insulation. This bird spends lots of time in the frigid boreal forests of North America and Eurasia. I'll put a photo in the show notes of a stuffed, taxidermied great gray owl that shows the bird in cross-section. It's pretty wild. Also, side note, it seems to me like a better name for the great gray owl would be the great gray growl.

I'm just putting it out there. Let's look some more at the plumages of owls. First off, for every square inch of their skin, owls in general have more feathers than other birds. In other words, owl plumage is relatively dense. For example, let's compare the barred owl to a bald eagle. The eagle is way bigger with a body mass 10 times that of the owl. The total number of feathers on the eagle is about 7,000. But the barred owl has about 9,000. At least for some owls, a large proportion of their feathers are concentrated on the head. The circular flat faces of owls are packed densely with layer upon layer of feathers. Together, these feathers form the owl's

facial disc. This is an extremely important feature of owls, and I'll come back to it a little later. Pretty much every owl species is cryptically colored. Their modeled earth-tone plumages blend into their surroundings, making them camouflaged. Owls need camo, not only to run sneak attacks on their prey, but also to avoid being messed with when roosting. Nocturnal owls roost in the day. They don't want to be conspicuous to predators that might strike them when they're sleeping. So they operate in stealth mode. They close their eyes and assume the form of tree bark or a broken branch. Some owls, like the many screech owl species in the genus Megascops, have a habit of perching in the opening of a natural tree cavity. The

bird's body will often fill most of the hole. The feathers with all their streaks, barring, and spots blend in with the surrounding tree bark. All the little screech owl has to do is close its eyes and, like magic, poof! The bird becomes impressively camouflaged and practically disappears. The snowy owl, with its glowing white plumage, is an outlier among owls, but it too relies on camouflage. A snow-white bird can be hard to see in a snow-covered landscape. All other owl species have feathers that are some combination of brown, gray, and rusty red. Many also have small patches of white or black thrown into the mix.

Feathers that strongly reflect UV light might be important for certain owl species as a visual signal. For example, the white throat feathers of the Eurasia, Eagle Owl are highly reflective in the ultraviolet end of the spectrum. These owls show off their fluorescent white throat badges at dawn and dusk during territorial and courtship displays. There's evidence that male Eurasian eagle owls with the brightest throat badges are the most successful breeders. In general, there's not much sexual dichromatism among owls. In other words, the plumages of males and females look pretty much the same, at least to our human eyes. One exception is the snowy owl. The white plumage of

female snowies is peppered with lots of little black spots and bars. The male is much whiter overall. There are some other interesting features of owl feathers, and we'll come back to those a little later. But for now, let's address a frequently asked question about owls. Are owls smart. In Western culture, most of us grew up hearing about the wise old owl, or we've heard a person being described as wise as an owl. For example, I remember that classic tootsie roll lollipop commercial from the 1970s. This kid is going around asking different animals how many licks it takes to get to the tootsie roll center of a tootsie pop. Eventually, the kid is told he should talk to Mr. Owl, because Mr. Owl is the wisest of all animals.

Mr. Owl, how many licks does it take to get to the Tootsie Rolls Center of a Tootsie Park? A good question. Let's find out. One, two, three, three. If there's anything I can't stand, it's a smart owl. And just to make sure we know Mr. Owl is smart, in the commercial he's wearing glasses and a square college graduate. cap, complete with a tassel. Because that's what smart people do, right? They just hang out wearing their college graduation hats. I mean, I'm wearing one right now. So in Western society, we're told that owls are the smartest birds around. But people in some other cultures view owls differently. In India, for example, owls are more likely to be seen as lazy and stupid creatures.

If you call someone an Ulukhapata, you're accusing them of being an idiot. Ulukapata translates to son of an owl. So if you're someone who's fond of hurling insults at other people, now you have a fun, new addition to what I imagine is already an extensive repertoire of insults. The next time someone in the grocery store inadvertently blocks your path in the candy aisle, you can yell at them, Out of my way, you son of an owl! But are owls actually stupid?

Or are they smarter than other birds? Which is it? Well, let's consider relative brain size. Birds known to be super smart have a large brain compared to the size of their body. We're talking about birds like parrots and those in the family Corvody, crows, ravens, magpies, jays, etc. Even though these birds are rarely seen where, wearing glasses or graduation caps, they perform well on a variety of intelligence tests.

One part of the avian brain, the Nidopalium Cato Laterale is particularly well developed in parrots and corvids. This is analogous to the prefrontal cortex of mammals. The Nidopalium Cotolaterally is used for certain high-level cognitive tasks in birds. So what about owl brains? it turns out the relative size of owl brains is not as large as those of other birds that show high intelligence. I mean, there's not a lot of room left in their skulls after packing in those giant eyes, right? And when owls are put through batteries of intelligence tests, they perform no better than the average bird. Owls may not be stupid and lazy, but they don't seem to be especially smart

either. Perhaps the reason some human cultures associate owls with intelligence and wisdom is that they have those flat faces with large, forward-facing eyes. They look more human-like than other birds. Big round heads with big eyes. These features are shared with human children, so maybe our instincts can't help but make us think owls are smart like us. In any case, intelligence is a tricky thing to measure in non-human and human animals alike. There are many ways of being smart. Owls may not be book-smart and they may not crush the competition during intelligence tests in a lab, but we could say they're smart in other ways.

They're masters of stealth and survival and of navigating the gloomy nighttime world. And speaking of nighttime, Hollywood movies seem to think the only way to convince us the audience that a scene is happening at night is by playing the sound of a hooting owl. That was the classic great horned owl call that you hear in movies. And this brings us to the topic of owl vocalizations. The word owl comes from the ancient Indo-European word U-W-A-L, and that eventually evolved into Ool, in Old English, U-L-E. U-W-A-L-A-L-L, these words are phononyms. They're names based on the sounds, the vocalizations made by owls.

In my last podcast episode, I was talking about bird names that are eponyms. But bird names based on bird's songs or calls are called phononyms, and that begins with a pH. We could also say these names are Anamotopeic. Other examples of phononyms are chickadee, cuckoo, kitty wake, tohee, Bob White, and Phoebe. Fun stuff. Anyway, owl songs and calls are hardwired. They're not learned. Owls show a lot of individuality in their sounds

compared to many other animals. So researchers studying owls can use acoustic monitoring technology to not only identify owls at the species level, it's also possible to tell individual owls apart using only their vocalizations. Each owl species makes a lot more than one simple hooting sound. They each have a repertoire of calls that mean different things. Now, I hope you enjoy listening to owls

because we're about to hear a whole bunch of them. For those of us in North America, the following recording is the classic owl sound. It's the Great Horned Owl again, Bubo Virginianus. This individual was recorded on the Arizona-Mexico border. The long-eared owl, Azeo Otis, is found across North America and Eurasia. Here's one in Poland making a stereotypical hooting sound. The next sound was recorded at about 9.30 p.m. on a summer night in Nova Scotia, Canada.

It's an owl who is keen on getting a job as your new head chef. It seems to say, who cooks for you? Who cooks for you all? That, of course, is Strick's Varia, the Bard Owl. I'll play it again, see if you can hear it saying, Who cooks for you? Who cooks for you all? Interestingly, that Bard Owl recording was made by scientists using an autonomous recording device. Pretty cool. Jumping back over to Europe, we have a cousin of the Bard Owl.

Here is a tawny owl, Strick's Aluko. It's calling during a dark and stormy night in France. Jeez, that was kind of spooky, wasn't it? Why you got to be so scary, tawny owl? Well, now let's head down to South America. First up, we have a pair of Pacific Pygmy Owls in Peru. That's a lot of peas. We have a pair of Pacific Pygmy Owls in Peru.

Next is a burrowing owl in Bolivia. This one is making the Rasp call, which is used when a burrowing owl is distressed or when begging for food. Now in this next recording, listen to these birds duetting. No, those weren't cuckaburas in Australia. That was actually a couple of Puerto Rican owls, gymnasio nudipes. But speaking of cuckaburas, how about we go down to Australia to listen to some owls down under? Here are some barking owls, nine ox canivans.

I think you'll agree this species is well. named. This was recorded in Queensland, Australia. The next recording is also of barking owls, but this time in New Guinea. Not long ago, I was working in Madagascar. This next sound is one that I heard on several nights in the spiny forest ecosystem there. It's the white-browed owl, Atheni superciliaris. The recording has a low-frequency hum that I think is a generator. I tried to filter it out, but you can still kind of hear it.

Anyway, this is the white-browed owl in Madagascar. Near to Madagascar is the Comoros, a group of islands off the east coast of Africa. The following recording is of a duetting pair of Mayotte Scops owls in the Comoros. Those Mayotte Scops owls sound to me a little bit like French police sirens. All right, back here in the U.S. of A, we have the Western Screech Owl, Megascaps, Kenakotiae. And every time I see the genus Megascaps, I'm really tempted to say it like, Megascaps. Anyway, in this next recording made in Washington State, we can hear a couple of Western screech owls. One is making a double trill call.

It sounds a little like a bouncing ball. That might be the male. The softer, begging Winnie is likely the female. Also, listen for a couple of other owl species calling in this same recording. Besides the two western screech owls, there's a long-eared owl in the middle distance and a very distant great horned owl. Okay, here we go. Listen carefully.

I don't know. So, and... ...whoe... ...woulda... ...theirdered. ...and... ...theirc... ...and...

...you... ...the... ...and... ...the... ...the... ...and... You may have noticed that those vocalizations of the western screech owls weren't so screechy, were they? All owl species in the genus Megascops are called screech owls.

They make all sorts of sounds, including hoots, barks, and squeals. But not all screech owls screech. But you know who does screech? Listen to this next recording. That was a barn owl, Taito Alba, calling in France. It was making either an advertising call or a distress call. I remember hearing that sound when I was a kid in my backyard on dark nights. I thought, surely that screechy sound was coming from a screech owl.

But nope, it was a barn owl every time. It's time to talk about the diversity of owls, as well as their global distribution and their habitats. When I say owls, I mean all the birds belonging to two avian families, titanidae and strididae. Titanidae includes the barn owl and all of its close relatives. There are between 11 and 22 species in this family. The number depends on which official species checklist you're looking at. I plan to do a podcast episode focusing more on barn owls and the family titanity in the future. So today's episode is a bit more heavily weighted toward the family Strigody.

Strigidi is the family of birds ornithologists call the typical owls. Or, you know, what I would call your everyday garden variety, ordinary sort of owls, run-of-the-mill owls. They aren't all fancy like those titanity owls. There are between 190 and 235 species in the family Strygody. The Clements checklist, the one used by Ebert, has 224 species in this family. Together, the two families, titanity and Strygity, form the taxonomic order stridiformes. The root of the words Strygiformis and Strygidi

is the ancient Greek word Stricks. You might remember that Stricks is the modern-day genus of birds like the Great Grey Growl, Owl, and the Bard Owl. Strix means a screecher. It's probably a reference to the tawny owl of Europe, Stricks Aluko. Remember the spooky sound of the tawny owl?

In ancient Greek mythology, Stricks was a bird-like demon that fed on the flesh of humans. Stricks also liked to suck the blood of human babies. That makes sense. Listening to the creepy call of the tawny owl, I can imagine how ancient people thought there was a demonic creature lurking out there there in the dark, thirsting for the blood of infants. But it's pretty funny that, in reality, the creature was just a cute little fluffy owl. Owls resemble some other types of nocturnal birds, night jars, owlet night jars, potoos, and frog mouths.

But none of these are closely related to owls. The true closest relatives of owls are probably mouse birds and raptors, like cocks and eagles. Mousebirds, in case you haven't heard of them, are found in sub-Saharan Africa, and they belong to the family Kaliadi. There are only two genera within the family titanidae, but the family Strigidae has 23 genera. Of those 23, a few of them have a disproportionately large number of species. Otis, O-T-U-S, has 55 species. These are the Scops owls. They're distributed across Eurasia and Africa. The genus Ninox contains 37 species. Most of the birds in this genus are called Bubukes. You find them in Asia and Australasia.

Earlier we heard a representative of this group, the barking owl, Ninox connivans. Here's the sound of another owl in the genus Ninox. This is the Luzon Hawk Owl from the Philippines. That's a great sound, isn't it? Another species-rich genus is Glokidium, which is the genus of the pygmy owls. There are 26 of those little buggers spread across parts of north and South America, Eurasia and Africa. Then we have good old Stricks. This group of 22 species is known as the wood owls and their allies.

Representatives of the genus Stricks are found all over the world. However, they're absent from Australasia. So if we back up and consider owls in general, all the birds in the family's titanity and stridgety, you've probably figured out from the previous discussion that this is a cosmopolitan group of birds. They exist on every continent on earth, every single continent. That is to say, every single continent that isn't a white wasteland covered in ice and crawling with pesky penguins. Believe it or not, there are no owls in Antarctica. Even the snowy owl

has enough self-respect to keep its distance from Antarctica. Snowy owls are creatures of the far north, not the south. Owls of one species or another can be found in most of the world's terrestrial ecosystems. One species, the barn owl, has an enormous distribution that pretty much spans the globe. In fact, this is one of the world's most widely distributed bird species. Then again, some ornithological authorities argue that barn owl populations around the world represent not one, but three, or as many as five species. This is based on recent genetic evidence, and some bird checklists already reflect these taxonomic updates.

Another owl with an enormous geographic range is the short-eared owl, aezoflammius. It's widespread across North America, Eurasia, and Southern South America. There are a few regions in the world with a high, high concentration of owl species. These owl diversity hotspots include southeastern Brazil, southern Asia, and the arid southwest of North America. Owl species are scattered among many islands, too. For example, the multitude of boobook species in the genus Ninox are often confined to small islands here and there across Indonesia, the Philippines, and Southeast Asia. Just recently,

a new island-dwelling owl species was described by scientists. It's the Principae Scop's owl, Otis Bikajila. This owl lives on the island of Princepe off the western coast of Africa. It has perhaps the tiniest geographic range of any owl species. The Principae-Skops owl is found in only one patch of forest which has an area less than six square miles, or about 15 square kilometers. The owls most commonly observed in North America are the great horned owl, the barred owl, and eastern screech owl. Of course, these birds are usually identified by their sounds rather than by sight. South America's most commonly reported owls include the burrowing owl, tropical screech owl, and ferruginous pygmy owl. Just a few days ago, I saw my first

tropical screech owls. I was in a swamp in the country of Trinidad and Tobago. There was this adorable pair of tropical screech owls huddled side by side on a branch hanging over the water. It was fantastic. While we're talking about South America, I want to mention the lesser horned owl, bubo Magellanicus. It's found in the southern part of the continent and in the Andes as far north as Peru. This bird used to be considered a subspecies of the great horned owl, but recently it was upgraded to full species status. It's also called the Magellanic horned owl. Over in Europe, the most common owls are the tawny owl and little owl. The spotted owlet and ural owl are the most familiar species in Asia. Here's the call of the spotted owllet, recorded in

West Bengal, India. Two large owl species are the ones most frequently encountered in Africa, the spotted eagle owl and Varroes eagle owl. People in Australia are most likely to hear the southern or Australian boobook calling in the night. Its scientific name is Nynox boobook. Here's what it sounds like. from that sound you can see why this bird is called a boobook this is another example of a phononym right the name boobook comes from the bird's call another famous species in australia is the powerful owl nine ox strenua it's the largest owl on the continent and the largest representative of the genus How powerful is the powerful owl, you ask? It's so powerful that it routinely snatches mammals like koalas, possums, and sugar gliders from trees. It's an opportunistic hunter. So, if you live in

Australia, keep a close eye on your pet dog when the sun goes down. And your cat, too, and your small children. Weirdo alert. Weirdo alert. Yes, my friends, it's time to look at a weird species of owl, an oddball. Owls are sort of weird birds in general, and there were a few contenders for this episode's weirdo alert. But the species of interest today is the long-whiskered owlet, zinoglok's Lowry Eye. And that's Owlitt, not to be confused with Towelet. This is one of the smallest owls in the world, being basically the same size as its closest relative, the elf owl. It's found in only one small part of the Andes Mountains in Peru.

The long-whiskered owlet does indeed have long, wispy feathers, radiating outward from around its beak and its caramel-colored eyes. No other owl has feathers that look like this. I'll put a photo or two of this bizarre bird in the show notes for this episode on the Science of Birds website. Weird though it may be, the long-whiskered owlet is, got to say, pretty cute. This owl also has short wings and a short tail. At one point, some scientists speculated it might be flightless. But flight has since been observed in this species more recently.

Ornithologists from Louisiana State University discovered the Owlet in 1976, but for decades after its discovery, there were very few observations and scientists knew almost nothing about the long-whiskered outlet. One reason it's been so difficult to study is its habitat. These owlets live on steep slopes covered in dense, sopping wet cloud forest vegetation. It's not easy for people to get around in this mist- shrouded ecosystem, where everything is covered by thick mats of mosses, bermiliads, orchids, and ferns. The long-whiskered owlet is such a weirdo that it is the only species in the genus Xenoglux. That word comes from Greek and it means strange owl. The organization BirdLife International has flagged this species as vulnerable.

Scientists estimate the total population is between only 250 and 1,000 individuals. You probably won't be surprised to hear that the long-whiskered owllet is threatened by habitat destruction. Surrounding the small region of Peru where these birds live, forests are being cleared for timber and mining operations. There are some protected areas there now, so fingers crossed that this weird and wonderful little owl will be around. for the long term. I'll put a link to a YouTube video in the show notes so you can see one of these owlets chill in on a mossy tree branch.

Now, let's get back to looking at owls in general. In terms of habitat, we find owls in just about every conceivable terrestrial habitat on the planet, from sea level to over 15,000 feet, which is about 4,500 meters. Owls love forests of many kinds. of course, but there are also owls in grasslands, craggy mountain highlands, wetlands,

tundra, and deserts. There's even a species named the Desert Owl. Its scientific name is Strick's Hatteramai. This sand-colored cutie lives in the Middle East, from the Sinai Peninsula to the Arabian Peninsula. Some owl species are fairly comfortable in human environments, agricultural areas and the suburbs. And I'm looking at you, barn owl. Owls tend to be resident birds in all of these habitats across the world. They aren't all that migratory as a group. Now that said, some species are known to migrate, but these are usually what ornithologists call partial migrants. Their populations have different seasonal movement behavior across the species range. Some populations stay put, others migrate. Examples here include the short-eared owl,

long-eared owl, burrowing owl, and northern saw-wet owl. Snowy owls often migrate south in the winter to escape the frigid darkness of the Arctic tundra. Their migratory movements are more haphazard from year to year. In some winters, snowy owls migrate further south, where they might end up in populated areas. For example, in suburban or agricultural areas of the northern United States. When a snowy owl shows up, birders and even non-birders kind of lose their minds. They grab their cameras and binoculars and jump in their cars, racing off to see the rare and beautiful white bird. The mass movement of snowy owls into more southerly latitudes like this happens about every three to five years. These events are called eruptions.

Eruption is spelled I-R-R-U-P-T-I-O-N. I still haven't seen a snowy owl. So the next time there's an eruption of this species here in Oregon, I'll be one of the birders that loses their mind. I'll race off to wherever that bird is, breaking whatever laws I have to along the way. I'll shove kids and little old ladies out of the way just to get a sweet, sweet glimpse of that angelic white owl.

Let's take a moment now to consider the evolution of owls. If we resign ourselves to, nay, embrace the fact that this is going to be a long episode, I guess I might as well trace the evolution of owls all the way back to the beginning. The first life on Earth appeared around 3.7 billion years ago. Surprisingly, owls had not yet appeared in those early days. Okay, just kidding. Maybe we won't go all the way back. The oldest fossil we have for an owl that I know of comes from late in the Paleocene Epic. We're talking somewhere between 60 and 55 million years ago.

That fossil is from a bird named, and... This is kind of hard to pronounce. Ogagoptinx. Ogagoptinix. Something like that. Ogagoptinix wet mori. And this fossil was found in Colorado in the U.S. The fact that this bird,

Ogad, ogadigoptonics was identifiable as an owl, suggests that the origin of the owl lineage goes back to around the time of the big extinction that wiped out all of the non-avian dinosaurs. So we're talking around 65 million years ago. That means that owls and their cousins form one of the world's most ancient groups of land birds. This group, this large branch of the avian tree of life, or what scientists call a clade, has the name Afro-Avies. Afro because it appears to have originated on the continent of Africa. Besides the two owl families, Afro-Avies includes hawks, eagle,

kingfishers, woodpeckers, hornbills, toucans, and a handful of other excellent bird families. The other name for the Afro-Avies clade is the African land bird radiation. Not only is this probably my favorite branch of the avian tree, I also love that name, the African land bird radiation. I think I'm going to add that to my list of possible names for the rock band I'm going to start someday. Recent research using data from DNA has helped to sort out the evolutionary relationships among modern owls. One study published in 2020 in the journal The Ock sorted out the evolutionary tree for the family of typical owls, stridity. The analysis was based on genetic data from

owl DNA. The researchers ended up making a fair number of suggestions to revise the taxonomy of owls in this family. Because the story told by the DNA did not always jive with what the physical appearances of the owls had suggested. One pattern described in this 2020 study was that there are some owl species living on islands that have unique outward appearances, but at the genetic level they aren't all that special. Ornithologists had previously assigned each of these island owls to its own monotypic genus. Monotypic meaning that each genus contains just one species. For example, there's the giant Scops owl from the Philippines. The distinct plumage and size of this bird motivated ornithologists back in the day to place it in its own genus, Mimizuku. Its scientific

name was Mimizuku Gurnei. Then along comes this new DNA-based research in 2020, and the genetic data tells us that Mimizuku gurneyi really should be changed to Otis Guerni. And so it was. But I guess the main point here is that among all these owls in the family stridji, there are multiple cases of morphological convergence and differentiation through evolution. Some owls look really different on the outside, but genetically they're closely related to some other owls.

This is morphological differentiation. And the opposite situation happens in other owls. Some species look physically, morphologically similar, but at the genetic level, they're quite different. That's convergence. And it's at the genetic level that scientists can often unravel the true evolutionary relationships among birds and their evolutionary histories. So I guess it's true what my wise owl-like grandmas.

he said, it's what's on the inside that counts. As long as what's on the inside is a molecule called deoxyribonocleic acid, or DNA, it's formed from two strands that twist around each other in a shape called a double helix. DNA not only carries genetic information for the growth and functioning of an organism, it also carries information that can provide insights into that organism's evolutionary history. Just kidding. My grandparents didn't believe in evolution. Like most groups of birds, owls are far from immune to the ravages of humanity. Five species have already been driven to extinction in historical times. All of them were Strigids, members of the family Strigody, and all of them lived on remote islands.

For example, there was the Bermuda Sawwet Owl, and the Laughing Owl Laughing Owl of New Zealand. Of the 242 extant owl species in the family's titanity and Strigity, in other words the ones that are still with us, 63 are currently listed by the International Union for the Conservation of Nature as being threatened in some way. That means about 26% of the world's owl species are in trouble. 11 species are in the endangered category on the IUCN's red list, and three are critically endangered. Most of these species live on islands, but a couple are surviving in tiny habitat patches on continents. The primary threat, as usual, is habitat loss.

For example, the loss of large old trees and standing dead trees is a major problem for the many owl species that nest in cavities. Tree cavities have always been a limited resource for these birds. but humans have made them even scarcer. Now I want to highlight a few threatened owl species before we move on to other less depressing topics. First we have the spotted owl, Stricks Occidentalis, which lives in western North America.

The IUCN lists this species as near-threatened. But there are five subspecies of the spotted owl. One of these, the northern spotted owl, Strick's Occidentalis Karina, is near and dear to many nature lovers here in the Pacific Northwest, where I live. The estimate is that there are about 15,000 northern spotted owls remaining. This subspecies has been protected in the U.S. under the Endangered Species Act since 1990. This protection extends, in some cases, to the old-growth forest habitat of the spotted owl. Commercial logging companies and loggers haven't been very happy about that,

and the poor little northern spotted owl has been at the center of environmental battles and controversies for decades. Logging in old growth forests of the Pacific Northwest is still a big problem, but on top of that, the northern spotted owl has been dealing with another existential threat. Its cousin, the bard owl, Stricks Varia. Bard owls are native to eastern North America, but in recent decades, these guys have expanded their range into the Pacific Northwest and California. They've become an invasive species in these regions. Bard owls are bruisers. They're larger and more aggressive than spotted owls. The two species don't mix well. Bard owls out-compete the spotties, and the larger owls will sometimes

beat up or kill their smaller cousins. In any case, spotted owls are almost always the losers in conflicts with barred owls. And the controversies keep coming. Just recently, the U.S. Fish and Wildlife Service announced its plan to shoot 400,000 barred owls over the next 30 years in order to help save the spotted owl. Now, how do you feel about that, killing one owl species to save another? It's tricky, right? Another endangered species is Athenny Bluetai, a.k.a. The forest taulet. This bird lives in India in only a handful of, wait, no, sorry. Sorry, that's actually the forest alet, not taulet. My bad. Why do they got to make these words so similar? Anyway, this bird lives in India in a few small patches of open deciduous forest. But get this. The forest alet was first

described scientifically in 1873, but then no one saw it again for over 120 years. Everyone assumed it had to be extinct, but amazingly scientists rediscovered this bird in 1997. There are maybe only 1,000 forest outlets remaining today. Not great, but hey, 1,000 is still better than zero, better than being already extinct like we thought it was. The last example, of an endangered owl I have for you is Blackaston's Fish Owl. This is one of the world's rarest owls. And maybe you remember from earlier that this species is also the largest owl species. Blackestan's Fish Owl is found in northern China and Japan and in the far east of Siberia. Its habitat is old-growth forest along the banks of rivers. Rivers because, true to its name,

this fish owl really does eat mostly fish. Salmon, trout, catfish, and pike are some favorites. There are, at most, a few thousand of these majestic owls left. The primary cause of their decline is the loss of their riverine forest habitat. Blackistan's Fish Owl is the subject of a book by Jonathan Slat called Owls of the Eastern Ice, a quest to find and save the world's largest owl. I haven't read it yet, but people keep recommending it to me. It sounds like something I should check out.

Faux show. Owls are carnivores. They eat only the flesh of other animals. Owls eat so much meat that biologists call them hyper-carnavores. Examples of other hyper-carnavores out there include tigers, killer whales, crocodiles, and snakes. But the actual prey animals eaten by owls very widely amongst people. species. Pretty much any small animal on the planet is potential prey for one owl species or another. Owls use their piercing talons and the powerful grips of their feet to catch and

kill prey. They rip their food to shreds with their hooked bills. Small owl species eat mostly insects, whereas the largest owls usually concentrate their efforts on catching vertebrate prey. Some species are more specialized in their diets. like Blackistan's fish owl eating mostly fish. Fish are also the main thing on the menu for other owls in the genus Katupa and in the genus scotopelia. And let's not forget the terrifying tawny owl that specializes in sucking the blood of human babies. Titonid owls like the barn owl eat mostly small rodents, but they'll also eat birds, reptiles, other small vertebrates, and insects. Many owls are generalists.

when it comes to diet. The great-horned owl and its close cousin, the Eurasian Eagle Owl, are good examples. They eat all sorts of animal prey. For example, to name just a few items eaten by great-horned owls, ahem. Voles, ground squirrels, raccoons, domestic cats, porcupines, rabbits, bats, screech owls, short-eared owls, long-eared owls, northern bob whites, ring-necked pheasants, domestic chickens, ducks, coots, rails, pigeons, nestlings of red-tailed hawks and common ravens, earthworms, crayfish, scorpions, and spiders. Oh, and also fish amphibians and reptiles.

So, basically anything with a nervous system, I guess? And did you notice that great-horned owls eat other owls? The great-horned owl and the Eurasian eagle owl are predators that eat other avian predators. That's pretty hardcore. Now, for fun, let's also consider the diet of the desert owl, a species I mentioned earlier. These little buggers eat gerbils, shrews, hedgehogs, geckos, small birds like the desert lark and

house sparrow, beetles, grasshoppers, and scorpions. Now let's look at when and how owls forage. Owls are famous for being creatures of the night, right? For being nocturnal hunters. But by some estimates, only one-third of owl species are truly nocturnal. Many others are what biologists call crepuscular. Cropuscular birds and other animals are active in the dim light of evening and or early morning. The short-eared owl is a good example of a crepuscular species.

And then there are some owls that hunt mostly in the daytime. These include birds like the northern hawk owl and various species. species of pygmy owl in the genus Glokidium. Crepuscular and diurnal owls rely primarily on their sight to target prey. There was this study from 2018 published in the Journal of Avian Biology. It offered some evidence that iris color in owl eyes is correlated to when the birds are active. Owls that are strictly nocturnal tend to have dark-colored eyes, while diurnal species have lighter-colored eyes. Nocturnal owls with dark eyes include the spotted owl and barn owl.

Owls with light-colored eyes that hunt while the sun still up include the snowy owl and northern pygmy owl. There are many exceptions, but this eye-color thing is certainly interesting. The researchers in that study hypothesized that dark eyes in nocturnal owls would be less conspicuous to prey and therefore provide a bit of extra camouflage. Owls are all about camouflage. They're all about stealth. Owls are masters of the sneak attack. Besides having cryptically colored plumage, nocturnal owls have another way of going undetected by their prey.

They fly without making a sound. For example, let me play you a recording of a barn owl in flight. Okay, you ready? listen carefully. Here we go. Could you hear the barn owl flapping its wings or hear air rushing over the wings when the owl was gliding? No, you couldn't. I know you couldn't because there wasn't an actual recording at all. But that is what a flying barn owl would have sounded like, like nothing, like silence. The superpower of silent flight in owls comes from two small-scale structural features of their feathers.

First, the flight feathers have extra-long barbules that give the feathers a sort of velvety texture. So when the feathers rub against each other, they don't make noise from friction. Second, the flight feathers in the wing, what we call the remigies, these feathers have tiny tooth or comb-like projections on their leading edges.

These projections cut into the air, breaking it up into little pockets of turbulence. A serrated feather edge like this makes way less turbulence overall and therefore less noise than would a uniform feather edge. Oh, and nocturnal owls also flap more slowly during flight than other birds of prey. That's another way they can reduce the noise from both friction and air turbulence. silence. Silent flight is important to an owl for sneaking up on prey animals. But it's also important because it doesn't interfere with the owl's ability to hear. Nocturnal owls rely heavily on sound

to detect and zero in on their victims. We'll talk about owl ears and hearing in just a moment. But first, I want to point out what can happen to an owl when stealth fails. Obviously, if an owl's prey sees or hears it coming, the owl is likely to fail. But when an owl is just hanging out, roosting and resting with no ill intentions, it can still get in trouble if someone sees through its camouflage. Small bird species see owls as a threat, and they will mob owls. Recall that mobbing is an anti-preditor behavior where prey species cooperatively harass a predator. So imagine you are a northern pygmy owl. It's daytime and you're in the mood to perch on top of a tall fir tree and do a little singing,

some hooting, if you will. You cut loose with some high-pitched toots and you're feeling pretty proud of yourself. But then here comes a motley gang of small birds. They're screaming at you and flying around among the branches of your tree. This angry mob of birds includes some red-breasted nut hatches, mountain chickadees, and dark-eyed junkos. They're annoying as heck, but you just keep on tooting away. One way we bird enthusiasts can find owls while they're roosting in the daytime is to listen

for the sound of mobbing songbirds like this? Or, what if you're actually interested in the small songbirds themselves? You can imitate the repetitive whistle notes of a pygmy owl, and this will sometimes attract a mob. Suddenly, you're surrounded by a mixed flock of furious little birds. All right, back to owl ears and hearing. The concave face, possessed by many owl species, is a special adaptation. Owl faces are like satellite dishes that pick up auditory signals.

The technical name is facial disc, and it helps the bird to hear really well. The facial disc is formed by dense layers of stiff feathers. These collect sound waves and bounce them towards the ear holes. An owl can even move the feathers in its facial disc, changing the focal distance of its hearing. So that alone gives owl's excellent hearing. But wait, there's more! Owls that hunt in the dark have asymmetrical ear holes in their skulls. One hole is higher than the other.

This is in contrast to humans and pretty much all other animals. We have symmetrical ears, with both of them sitting on the same horizontal plane. The asymmetry of owl ears gives these birds the amazing ability to pinpoint the source of a sound in the up and down direction, not just in the left to right direction. In other words, owls can precisely locate a prey animal in terms of where it is in the horizontal dimension and in the vertical dimension. This means owls can catch small animals that are hiding under grass or leaves or snow, and some owls can hunt in total darkness.

They use hearing alone to catch their prey. You probably know all this stuff. it before, but still, it's really amazing to think about. And interestingly, those owls that hunt in the bright light of day, like the northern hawk owl and the various pygmy owl species, those birds have symmetrical ears, because they rely primarily on their eyes rather than their ears to locate and catch prey. Having successfully located, captured, and swallowed a prey animal, it's time for an owl to make a pellet. Yay!

Pellets are delightful little objects formed from some combination of compacted fur, bones, teeth, insect parts, and feathers. These are all the hard, indigestible parts of prey animals. Pellets are gray or brown. An owl barfs one up about ten hours or so after its last meal. Owls are famous for making pellets, but other birds are. make them too. Hawks, eagles, grouse, swifts, night jars, and a bunch of songbirds make pellets. Here's how an owl pellet is formed. The prey animal is swallowed and it moves down the owl's esophagus into the first chamber of the stomach, the proventriculus. This part of the stomach

secretes enzymes and acid to digest food. Next, the meal moves down into the second chamber of the stomach. The gizzard. The gizzard has walls lined with strong muscles. It contracts to break apart and grind up the food. The gizzard also squeezes the pasty, liquidy stuff that's been digested already further down the tube. But the crunchy, indigestible bits like bones and hair stay in the gizzard. They get squeezed by the muscular gizzard into the compact little miracle of nature that we call a pellet. Eventually, the pellet moves back up into the proventriculus, and finally, the owl hacks it up. While I was researching this stuff, I searched Google images by typing owl coughing up pellet. And, well, it was pretty funny, and also kind of gross.

Anyway, owl pellets are larger than those of many other birds. One reason is that the stomach acid in an owl's proventriculus is relatively weak. The acid isn't very good at dissolving bones, teeth, feathers, and that sort of stuff. Ornithologists have used owl pellets as a valuable source of data. They pick apart pellets in the lab, sorting out the tiny body parts to figure out what owls have been eating. And of course, kids in science classes have been dissecting owl pellets since, I think, the dawn of time. You can go on Amazon.com right now and buy yourself some owl pellets.

For real, a six-pack of barn owl pellets costs only $30. Sounds like the perfect stocking stuffer for Christmas. Or perhaps you could give your sweetheart a six-pack of owl pellets for your five-year anniversary. The possibilities are endless. Also, there's a real family-run business

based in Washington State called pellet.com. That's their whole thing, selling owl pellets. I'll put a link to the website in the show notes. And no, this episode is not sponsored by pellet.com, but that would have been a good idea. So, hey, folks at pellet.com, if you're listening, call me. And believe it or not, pellet.com has a competitor.

It's a business based here in Oregon, and it's called Oregon Owl Pellets. Man, and now I feel like I'm missing out on a major business opportunity. Everybody is out there getting rich selling owl pellets. But maybe it's not too late for me to get in on the pellet game. I could start a company called, I don't know, Ivan's owl pellet Emporium, or discount barn owl barf for you. When it comes to breeding, owls are generally monogamous, and both parents are involved in raising the chicks.

The breeding cycle begins with courtship. Owls show a variety of courtship behaviors. They hoot, fluff out their feathers and posture, preen each other, and feed each other. Some species make beautiful displays in flight. For example, the male short-eared owl performs a sky-dancing display to impress females. First, he makes a hooting courtship song while flying. high and fast. Then he drops rapidly into a stoop and claps his wings together beneath his body. These rapid wing claps make a staccato sound. It's pretty cool. I'll put a video of this

sky dancing display in the show notes so you can check that out. Many owl species are highly territorial, particularly during the breeding season. They defend their territory to keep other owls from stealing their resources. Resources like net, nest cavities and food. Male owls, and sometimes females, sing to maintain their territories. Singing usually suffices to deter any interloping owls, but a territory holder will attack if necessary. There's a big reason why nests are a limited resource for owls.

They can't make their own. That's right, owls don't make their own nests. They just use natural tree cavities, holes in rocky cliffs, depressions on the ground, etc. Or an owl or a pair of owls will hijack the nest of another bird. Great horned owls, for example, use the nests of birds like red-tailed hawks, ravens, and herons. For cavity nesting owls, an old woodpecker nest is often a great place to set up shop.

Elf owls in the Sonoran Desert are famous for using woodpecker holes carved into saguaro cactuses. Even more famous are the nests of burrowing owls. These little guys take up residents in burrows previously excavated by mammals, prairie dogs, badgers, armadillos, and so on. Burrowing owls decorate the entrances to their burrows with all sorts of goo gauze and gym cracks. Things like wads of grass or moss, bones, potatoes, corn cobs, or pieces of colored fabric. The owls are also fond of using mammal poop as a decoration. Cow poop, coyote poop, bison poop, whatever happens to be lying around on the prairie. Owl eggs are white, and in many species they're more rounded than the typical bird egg, more spherical.

Depending on the species, owls lay between two and nine eggs per clutch. Medium-sized owls that feed mostly on rodents are the ones that usually produce the largest clutches. The job of incubating the eggs falls to mom. She sits on the eggs and the male brings her food. He also defends the female and the chicks. Interestingly, most owls have what ornithologists call asynchronous hatching. This is where one egg hatches, then a day or two later the next one hatches, and so on. The result is that the owl chicks in a nest are of different ages. The older chicks are often dramatically larger than their younger siblings. After hatching as the chicks are growing,

the male continues to bring home the bacon for his family. Meanwhile, the female in species like the Great Grey Owl and Barn Owl keeps her nest tidy by eating the feces and pellets of her chicks. Ew! Gross, I know. But this is perfectly natural for owls, and keeping the nest clean is important. After eating the poo and pellets, the female may fly away from the nest and regurgitate all that stuff.

Newly hatched owl chicks are altricial. That means they're pretty much helpless and need to be fed by their parents. But unlike the altricial chicks of, say, a songbird, owl chicks are born wearing a fuzzy covering of down feathers. Because the eggs hatch at different times, because of asynchronous hatching, you end up with small, medium, and large chicks. There's a sibling hierarchy, and it's the older, larger chicks who tend to dominate the nest. We see similar hierarchies in some other types of birds, like hawks, seabirds, and herons. When the dad owl returns to his nest, the largest chick is more likely to draw attention with aggressive begging. Larger chicks, therefore, get fed more. In extreme cases,

the largest chick might even eat one of its smaller siblings. On the other hand, ornithologists have also observed what appears to be altruistic behavior among chicks in a nest. There are reports of the older, larger chicks giving food to their smaller siblings, in barn owls, for example. In breeding seasons where food is plentiful, all or most of the owl chicks might survive. But in lean years, only the largest chicks will probably make it. Owl chicks in many species piece out from the nest kind of early. Well before they can fly, the feisty chicks clamber out of the nest and onto nearby tree branches. They can't fly, but they can climb very well using their strong feet.

At this stage, the baby owls are often called branchers. They loiter around on branches begging to be fed. Both dad and mom are now making foraging runs to find food for their food for their fast-growing, demanding chicks. The chicks often spread out into the forest, making it harder for their parents to keep track of them. Branches are exposed and vulnerable to the elements and to predators. They defend themselves from predators by spreading their wings, biting, snapping their bills, hissing and kicking. It can be several months or more before all the chicks have fledged and they become totally independent. The breeding success.

of some or perhaps many owl species depends on the population dynamics of their prey. Snowy owl breeding success is famously linked with the boom and bust populations of lemmings on the Arctic tundra. Other owls similarly respond to year-to-year changes in the abundances of their food. Many adult owls, especially the larger species, don't have to worry too much about being eaten by predators. Their survival is more dependent on food, the weather, and disease. Small owls probably live between five and ten years. Larger species tend to live longer. The Great Horned Owl, for example, can live over 20 years in the wild and over 30 years in captivity.

Have you ever seen the animated TV series Futurama? It's one of my all-time favorite shows. It was created by Matt Graining, who also created The Simpsons. And fun fact, Matt Gaining is from Portland, Oregon, where I live. Anyway, there's this running gag in Futurama that involves owls. The show is set in the year 2999. By that time in the far future, owls have become pests in New York City, replacing rats and pigeons. Owls beg for scraps from people on the street, and they live in holes and walls and wall.

like rats. Owls are such a problem in the future that there are even owl exterminator businesses. Today, in the present, owls are loved by pretty much everyone, even though they're enigmatic and hard to find. They're basically the opposite of pests. Well, unless you're talking about barred owls in the western U.S., I guess. On that note, I'll leave you with an important question to ponder. Who cooks for you? Who cooks for you? Who cooks for you? you all. There you have it. The longest Science of Birds podcast episode yet.

Owls are just that cool. And I easily could have made this episode twice as long. As it is, I hope you enjoyed it and found some fun facts to increase your owl knowledge. If you want to learn more, you should definitely check out the recently published book What an Owl Knows by Jennifer Ackerman. It's really good. I'll put a link in the show notes. My work here making these podcast episodes benefits enormously from the support of my listeners.

Thank you to everyone on Patreon who is helping me to create these episodes. My newest patrons are Eric, Grant, Forrest Asaurus, Alicia, David A. and Steve W. Thanks so much to all of you and welcome to my Patreon community. If you are interested in becoming a patron, you can check out my Patreon page over at patreon.com slash science of birds. I also want to thank the many people who kindly let me use their bird sound recordings in this and all my episodes. Most of these sounds are from the Xenocanto website. Being able to include bird songs and calls really improves the educational value of this podcast.

If you have something you'd like to share with me, please go ahead and shoot me an email. Perhaps you have a friendly comment about the podcast, or you just want to tell me that I'm a son of an owl. I hope not, but in any case, my address is Ivan at Science of Birds.com. This again is episode 88. You can check out the show notes for the episode, along with some curated photos of species I talked about on the Science of Birds website, scienceofbirds.com. I'm Ivan Philipson. Thanks for going on an owl odyssey with me. today, and I'll catch you in the next episode.