The Science of Birds - Bird Bones: The Avian Skeleton

Episode Date: January 30, 2023

This episode—which is Number 69—is all about the avian skeleton. Bird bones.So this is an episode about some basic anatomy of birds.Bird bones and the avian skeleton are elegant, strong, and rigid.  Let’s put on our x-ray goggles, and peer inside the body of a bird, to see what’s going on with all those beautiful bones...Links of InterestCranial kinesis in the skull of a Hyacinth Macaw [VIDEO]~~ Leave me a review using Podchaser ~~Link to this episode on the Science of Birds websiteSupport the show

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 69, is all about. about the avian skeleton, bird bones. So this is an episode about some basic anatomy of birds. I've done a few episodes in this category before, like the one where I talked about

eggs, the one about bird vision, and a couple episodes on feathers. We have quite a few more anatomical topics to cover in the future. Muscles, the respiratory system, digestive system, and so on. But today, it's bones, bones, bones. But before we jump in, I want to own up to a couple mistakes I made recently, a couple boo-boos. First, there was a scientific study I mentioned in episode 67. That episode is titled, Awesome Things We Learned About Birds in 2022. The study had to do with great busters in Spain eating plants to self-medicate.

Well, a colleague of mine pointed out that this study has some serious flaws. The researchers didn't really have the data to back up their claims. I should have caught that, and I'm sorry I didn't. The second boo-boo I made was in the last episode, episode 68, which was all about hornbills. At the very end of the episode, in the outro, I made a joke about the mutualistic relationship between the Egyptian plover and the Nile crocodile. Even though I was joking, I was basically perpetuating an old myth. The myth being that the plover gets into the open mouth of the crocodile and picks bits of meat from between the reptiles' teeth.

Apparently, there's no real evidence that this happens. There is no mutualistic relationship between those two species. I apologize for suggesting that there is. Sometimes I just need to slow down when I'm writing my podcast scripts. I need to double and triple check my facts. And that is what I usually do. But I'm far from perfect. Every once in a while I get a fact wrong and it might slip through the cracks.

Even though the Science of Birds is a lighthearted podcast, and I make stupid jokes here and there, you can trust that I'm doing my best to give you the most accurate scientific information I can. That's really important to me. So I went back to episodes 67 and 68 and, using the powers of modern digital technology, I deleted those two errors. They've been expunged. It's like they never happened. This way, future generations of children listening to the science of birds won't be led astray by my sloppy mistakes.

Anyway, we can move on to the fun stuff now. Let's put on our X-ray goggles and peer inside the body of a bird to see what's going on with all those beautiful bones. We begin. by considering the basic features of bird bones and of the avian skeleton. Actually, let's back up and ask the question, why do animals like birds, crocodiles, and humans even have skeletons? I mean, besides the obvious answer, that they're great for scaring little kids on Halloween. The skeletal system, which is made up of bones and cartilage, has several functions.

First off, the skeleton gives an animal its shape and provides attachment points for muscles, so it allows for movement. Bones also protect many internal organs, and they make blood cells, and they store minerals like calcium. Vertebrate animals like birds have an internal skeleton, but some other types of animals have skeletons on the outside of their bodies. The exoskeletons of insects and crustaceans are great examples. The first vertebrate animals were vaguely fish-like creatures that lived in the ocean

about 520 million years ago. Those little dudes had a very basic internal backbone. Internal skeletons and fish continued to evolve for millions of years, becoming stronger and more elaborate. Some of those fish, with the help of their supportive skeletons, eventually crawled out of the water and evolved into land-dwelling beasts. That began sometime between 400 and 350 million years ago. Fast forward to today, and we have several groups of terrestrial vertebrates, birds, mammals, reptiles, and amphibians.

The skeletons of these diverse critters have many things in common, shared features they inherited from their ancestor, an adventurous fish that dragged itself out of the water onto dry land. Scientists have been able to piece together this long evolutionary story because vertebrates have bones and bones make great fossils. The skeleton of a dead animal decays more slowly than its squishy bits. That's because bones are hard and made of minerals. Now, at this point, you might be thinking, bones are hard? Seriously, are you kidding me, Ivan? You're talking to us like this is a fourth grade science lesson or something.

Maybe you're worried I'm about to bust out some plastic dinosaur toys to use as a visual aid. But this is a podcast, so that wouldn't work. But what if I pull out an acoustic guitar? Maybe I'm going to say, settle down class and gather around because it's time for teacher to sing you the vertebrate evolution song. Yay! Actually, that would probably be pretty awesome.

But alas, I'm not going to sing for you today. Sorry. Up to this point, I've just been trying to set the backdrop for what's going on with bird bones as we see them today. They didn't materialize out of thin air. The skeleton of a modern bird is the end product of over 500 million years of fine-tuning through natural selection. So, yeah, bones make great fossils. The fossil record gives us a pretty good idea of the evolutionary progression the avian skeleton went through,

starting with the theropod dinosaur ancestors of birds and ending with the birds of today. That progression involved a couple major trends. First, there was a gradual reduction in the number of bones and in bone size. Many bones also became fused, forming unique skeletal elements. Ooh, there's another idea to put on my list of possible band names, the skeletal elements. Anyway, the second trend was that the bones became more and more hollow. We'll come back to look at hollow bones and fused bones in a moment. As theropod dinosaurs evolved into the first birds,

many of these changes in the skeleton happened at the same time that the body sizes of these animals were getting smaller and smaller. What was driving all this dramatic change? It was super slow, of course, happening over millions of years, generation after generation. But the driving force, many scientists think, was natural selection for the ability to fly. When you study the anatomy of a bird, pretty much every structure you see looks the way it does and works the way it does because flying is hard.

Flying is an extreme way of getting around, one that requires many special adaptations. All of the approximately 11,000 bird species on earth are the descendants of a single ancestor that could fly. So the skeletons of all birds, even flightless ones like kiwis, ostriches, and penguins have been shaped strongly by the extreme demands of flight. The basic architecture of the bird's skeleton we see today was inherited from that flying ancestor long ago. Every bird has a beak, a flexible neck, wings, some fused vertebrae in its backbone, sturdy legs, and a stubby tail. And I mean, the tail bones are stubby. We're not talking about tail feathers, since we all know that those can be extremely long in some species. In general, the avian skeleton is made of strong,

stiff bones that have relatively low volume. But there are two special features of the avian skeleton that we need to talk about. First, we've got those hollow bones. The technical way to say this is pneumatic bones. That's spelled P-N-E-U-M-A-T-I-C. Numatic bones are filled with air spaces. If you cut one cross-section, it would look sort of like a tube. Some pneumatic bones are so tube-like that humans have been making flutes out of them since the Stone Age. For example, archaeologists discovered a flute made from the radius bone of a griffin vulture in Germany. Dating to about 40,000 years ago, this is one of the oldest musical instruments ever found. But the inside of bird bones aren't filled with just air. There are all these little rods made of bone that crisscrossed the

inside of each pneumatic bone. They give strength to the bone, acting like the trusses or struts humans use in architecture. The technical name for these struts is trabeculae, trabeculae. The singular form of the word is trabecula, as in trabecula, named, of course, after the world-famous vampire and game show host Alex Trebek. No, that's not true? I'm being told that's not true. Alex Trebek, was apparently not a vampire. Well, in any case, rest in peace, Mr. Trebek. But about these trabeculae, some are shaped more like rods, others are more plate-like. These structures are not unique to birds.

For example, at this very moment, you have a bunch of trabeculae inside each end of the femur bone in your leg. In humans, the spaces between the trabeculae are filled with bone marrow. But in birds, those spaces are filled with air. It gets more interesting, though, when we see that the air spaces in many bird bones are directly connected to the bird's lungs or to air sacks. Now, I haven't really talked about air sacks in birds, but at some point I'll do an entire episode on the respiratory system, and we'll get into all of that. For now, just imagine these air sacks as a series of balloons that connect to the lungs and take up space in a bird's body. Among other things, these sacks are involved in the exchange of oxygen and carbon dioxide during breathing. Some air sacks have small extensions called diverticula that connect directly to the hollow spaces in the bones.

These tubes, the diverticula, are like little fingers reaching into the inside of the humorous bone and the wing, as well as into the vertebrae, sternum, ribs, and femur. Not all birds have pneumatic bones. flightless birds and some birds that do a lot of diving have bones that are pretty much solid. For example, penguins and loons have solid bones. Other diving birds like cormorants, grebes, and puffins have bones that are hollow but still heavier than those of most other birds. Paleontologists studying fossils have figured out that hollow bones evolved way before there were ever any flying birds.

Going back to about 240 million years ago, the theropod dinosaur ancestor of all birds appears to have had hollow bones. Theropods are critters like velociraptor and Tyrannosaurus and all their cousins. 240 million years ago, no theropod had evolved the ability to fly. So why did some of them have pneumatic bones? It seems scientists don't have a complete answer yet. Still, there is some evidence that non-avian dinosaurs had hollow bones for several good reasons, not just because they lightened the load.

For example, theropod dinosaurs may have breathed using a combination of lungs and air sacks the way birds do today. This is a high-octane, highly efficient respiratory system, and hollow bones are an integral part of that system. And or it could be that hollow bones evolved in dinosaurs because their structure made them surprisingly strong for their weight. This brings us to the idea that pneumatization in bird bones, even today, may have more to do with strength and with breathing than with saving weight.

Having strong bones and a supercharged respiratory system are still major advantages for a flying animal, without a doubt. So maybe those were the features of hollow bones that made them an important prerequisite for flight. adaptations already found in dinosaurs that helped pave the way for the evolution of flying birds. But here's the thing. Contrary to what your middle school science teacher told you, the human brain doesn't use only 10% of its full capacity. That's a common misconception. In the case of my brain, for example, I'd say I use about 3% of its capacity.

But more to the point, and also contrary to what your middle school science, teacher told you, a bird's skeleton contributes pretty much the same proportionally to its total body weight that a mammal's skeleton does. Put another way, let's say you've got a cottontail rabbit that weighs three pounds and an osprey that also weighs three pounds. That's about 1.36 kilograms. We expect the rabbit and the osprey to have skeletons that weigh more or less the same, somewhere between 6 and 8% of their total body weight. So birds don't really have lightweight skeletons, at least not when we compare them to mammals in this way.

Sure, some of those hollow, aka pneumatic bones, are fairly graceful and light. But at the same time, the leg bones of many birds are actually pretty hefty. They're often heavier than the corresponding leg bones of similarly sized mammals. birds need robust leg bones because they put all their weight on just two limbs, rather than spreading it out on four as in most mammals. In any case, comparisons like these, like the Who Has the Heavest Skeleton Contest, aren't easy for scientists to make, at least not in living animals.

So we're talking broad generalizations here, based largely on research from several decades ago. Maybe more research will add new twists. For example, there was this study published in 2010 by Dr. Elizabeth Dumont. She measured the density of the same three bones from the skeletons of a bunch of birds, bats, and rodents. Her data set included 39 rodent species, 34 bat species, and 96 bird species from across 20 families. Dr. Dumont discovered that, in this contest, birds win the trance.

trophy for having the densest bones. Bats took second place, and the rodents all had to go home in shame, having received only a participation award. Why are the results of this study interesting? Because they help explain why bird skeletons aren't as lightweight as you'd expect. The denser a bone is, the heavier it is. And the denser a bone is the stronger and stiffer it is relative to its own weight. So even if a bird's skeleton might look all flimsy and delicate, it can still be tougher and more rigid than the skeleton of a bat or a shameful rodent. This is kind of like me. I may look flimsy and delicate, but I'm actually tough to work with and have very poor flexibility. Okay, that was a lot of jibber-jabber about hollow bones. Moving on to the second special feature of the avian skeleton,

and that feature is fusion. Birds have several major regions in their skeleton where multiple bones have fused to become one bone. I'll point out these fused regions as we work our way through the skeleton in a few moments. But just remember that fusion is an adaptation that makes parts of the skeleton even more rigid. Rigid bird bones fused into a rigid skeleton

provide great support for all that pecking, flapping, jumping, and landing on hard surfaces. But there's a trade-off. Compared to mammals, the bodies of birds aren't very flexible. Birds have less mobility. The way birds get around this limitation, to some extent, is by having long, sexy necks. Bird necks are, in most species, highly flexible. And speaking of necks, how about we take a little tour of the avian skeleton now? We'll start with the head and neck and work our way down from there. The bones of a bird or of any other vertebrate can be divided into two major parts, the axial skeleton and the appendicular skeleton.

The axial skeleton forms the central axis of the bird. like the axis of the earth running from the north pole to the south pole. When a common raven flies through the sky doing acrobatic barrel rolls, it too is spinning around a central axis. Its axial skeleton, which is composed of the skull, neck, backbone, and ribs. A bird's beak, or bill, is an extension of its skull. It has a core of bone and an outer layer of tough keratin protein. The upper and lower beak connect to the rest of the skull at several joints.

This arrangement allows the upper and lower jaws to move independently of the rest of the skull. The fancy term for this ability is cranial kinesis. Some types of birds, such as parrots, have really obvious cranial kinesis when they raise their upper beak. You know, like when you try to hold your friend's pet parrot, everything seems cool at first. You're like, who's a pretty bird? You are. Yes, you are. But nah, the parrot isn't having it. Out of nowhere, it bites you on the face. There's blood everywhere and you're left with a nasty cut and a bruise from that strong, sharp beak. Congratulations. You've just experienced firsthand the wonder that is cranial kinesis. Humans don't have cranial kinesis. We can move only our lower jaws. But even with that limitation, some of

us flap our jaws a little too much. You know what I'm saying? It's probably for the best that we can't move our upper jaws too. The part of the skull that contains the eyes and brain and whatnot is called the cranium. It's formed from a bunch of smaller bones that become fused by the time a bird reaches full adulthood. This fusion can take one to several years, depending on the bird species. In contrast, the skull of an adult human still shows suture lines where the various parts join, sort of like a jigsaw puzzle. But adult bird skulls are so completely fused that we can't see any suture lines. A fused skull like this is extra strong. Birds need strong skulls because they go around hammering on things with their bills. Bird eyes are

enormous relative to the size of their skulls. The eye sockets, what scientists call the orbits, take up a lot of real estate in the skull. These holes are so deep that they almost meet in the middle. In many birds, only a paper-thin wall of bone separates the two eye sockets. Bird eyes also have something called a sclerotic ring. Attached to the outer surface of the eye, actually embedded in a layer of tough tissue called the sclera, is a ring of tiny bones.

The sclerotic ring helps to support the eye by providing extra tension and rigidity. Mammal skulls don't have these eye bones, these sclerotic rings. But most other vertebrate skulls do, including those of fish, amphibians, reptiles, and the non-avian dinosaurs from back in the day. Moving along to the backbone, the vertebral column,

we can think of this as having five sections. Now, before I start talking about the vertebral column, I want to address the fact that, more than once on this podcast, I've pronounced vertebrae as vertebre. That's because, in general, when you have a scientific word ending with the vowels A-E, you pronounce them as a long E, like the word algae, or like the many bird families I've talked about on the podcast. Most recently, it was the Hornbill family, Bucerota D. Anyway, vertebrae is the way normal human beings say it, so I'll stick with that. I guess. The first section of the vertebral column is the neck. This is composed of the cervical

vertebrae. Almost every mammal species in the world has just seven bones in their neck. Seven cervical vertebrae. I have seven. The mole digging around in my garden has seven, and even a giraffe has just seven cervical vertebrae. But the number of neck bones in birds is wildly different among different groups. Parrots, for example, have 10 cervical vertebrae, while swans have 26, but most species have between 13 and 15 vertebrae in their necks. But here's something weird. You'd think that if the number of cervical vertebrae is so variable in birds, the birds with longer necks should have more vertebrae. Seems logical, right? But that's not always how it works in birds. There's not a strong association or correlation between neck length and the number of bones in the neck.

Some birds with short necks have more cervical vertebrae than other birds that have long necks. Ah, the marvelous mysteries of nature! But we can say that birds of all kinds have highly flexible necks. They can whip their little heads around in all directions, which is very useful when you have a beak instead of hands. Birds can even look straight behind themselves, no problem. That's why a bird can swivel its head around to spot a birder, sneaking up from behind with their binoculars to get a closer look. The bird is like, I see you, human ape creature. Your attempts at subterfuge have failed. I will now defecate in your general direction and take to the sky, denying you the pleasure of looking upon my

glorious form. So the first section of the vertebral column was the neck. The second section is the thoracic vertebrae. This is a group of between 5 and 10 fused vertebrae that connect with the ribs. The vertebrae and ribs together form the rib cage, which protects the heart, liver, lungs, and thoracic air sacs. The place where the ribs come together on a bird's chest is called the sternum. Most birds have a large ridge or blade-like bone sticking out of the sternum. This is the keel, otherwise known as the carina. Birds are the only living animals that have this special anatomical feature.

The keel is where the massive flight muscles attach, such as the pecs, the pectoralis muscles. The larger the keel jutting out of a bird's sternum, the larger the flight muscles that attach to it. So the birds with the strongest flying ability tend to have the largest keels. So guess which type of bird has the largest keel, relative to body size.

Let me rephrase that, in honor of Alex Trebek. This type of bird, renowned for its flying ability and aerial acrobatics, has the largest keel relative to body size. Remember to phrase your answer in the form of a question. You answered, what is ostrich? No, I'm sorry. You could not have been more wrong.

The correct answer is hummingbird. Hummingbirds have the largest keels of any bird relative to their body size. As for ostriches and many other flightless birds, they have a flat sternum. They don't even have a keel. No flight, no need for large flight muscles, no need for a keel. Moving along to the third section of the vertebral column. This is a special structure, unique to birds and the non-avian dinosaurs. It's called the Sinsacrum, S-Y-N-S-A-C-R-U-M.

This is a big, fused mass of vertebrae. The Sinsacrum includes some thoracic vertebrae and all the lumbar and sacral vertebrae. It also includes the first few caudal vertebrae. The Sinsacrum is a strong, rigid structure that helps a bird fly, hop, land on tree branches, etc. Section number four is made up of the remaining caudal vertebrae. The word coddle, C-A-U-D-A-L, refers to the tail. This short section of the vertebral column has between five and eight freely moving bones. But birds don't have a bony tail, right?

Well, at least not one we can see, like the tails of cats, monkeys, and lizards. Nevertheless, that stubby, hidden tail in birds is plenty wiggly. Birds can shake their tail feathers, in part thanks to their unfused caudal vertebrae. The fifth and final section is basically the tip of the tail. The last five or six caudal vertebrae have become fused into a single nubbin of a bone called the Pigea style, P-Y-G-O-S-T-Y-L-L-E, Pigea-Sty-Sty. Not to be confused with tiger style in Kung Fu, and definitely not to be confused with Gangnam style. Remember Gangnam Style? Sure you do.

That video on YouTube has 4.6 billion views, but it came out like 10 years ago. So I guess if you're less than 10 years old, you might have no idea what I'm talking about. Well, it doesn't matter because the Pigea style is way more interesting. This small, adorable bone is where the tail feathers attach. And it's those feathers, technically known as the rectracies, that we think of as a bird's tail. Okay, super quick review. For the axial skeleton, we've got the skull, followed by the cervical vertebrae, the thoracic vertebrae, the synsacrum, the caudal vertebrae, and the pygastyle. The appendicular skeleton has to be able to.

to do with the appendages. It includes the pectoral girdle, pelvic girdle, wings, and legs. The pectoral girdle supports the wings. The bones involved are the coracoids, the scapulas, i.e. shoulder blades, and the clavicles. But not just any old clavicles, mind you, because we have another unique skeletal feature here, found only in birds. The right and left clavicles, what we call collar bones, are fused in birds. The single bone they form is the furcula, aka the wishbone. This bone has a special place in my heart. Because I talked about the furcula in the first few sentences of the very first episode of the Science of Birds podcast. Maybe you've gone back and listened to it. It's about dinosaurs and stuff. So that's the pectoral

girdle. The pelvic girdle includes several hip bones and these are fused to the synsacrum. You can see there's lots of fusion going on in a bird's skeleton. I should point out that all these fused bones used to be free to move around in the ancient ancestors of birds, many millions of years ago. Okay, let's have a look at the actual appendages now, starting with one of the key features of the avian skeleton, the wings. From the shoulder and moving outward, the first bone of the arm slash wing is the most comically gifted bone of all,

the humorous. Except that humorous in this case is spelled H-U-M-E-R-U-S, not H-U-M-O-R-U-S. This is also the thickest of the wing bones. It's round in cross-section, making it very tube-like. Back in the 80s, we might have said it was totally tubular.

This shape makes the humorous bone very strong. Next, we have the radius and ulna bones. Together, these form the forearm. Nothing too shocking there. So far, these bones are pretty much elongated versions of what's going on in your own arm. But then it starts to get more interesting when we move further outward to the bird's hand bones. A whole lot of bone fusion has happened in the avian hand over the long history of the wing's evolution. The three claw-tipped fingers that were present in theropod dinosaurs and archaeopteryx, and all those

dudes, have been heavily modified in the modern bird hand. Some bones were lost and others became fused. Between the wrist and knuckles, there's the carpal metacarpus. This bone is the fusion of the carpal and metacarpal bones. The bones of three fingers are still visible in the bird's hand. They're reduced and heavily modified, of course, but two fingers are out at the wingtip, and the third is in the thumb position. The latter bone is called the allula, spelled A-L-U-L-A.

Three to six small feathers attached to the alula. This bone and those feathers help regulate airflow over the bird's wing at slow flying speeds. The bird wing, when we compare it to the human arm, the forelim of any other vertebrate, is a fascinating example of homology. Biologists use this word to mean a similarity that reflects a common evolutionary origin. All land-dwelling vertebrates had an amphibian-like ancestor way back around 400 million years ago, and that ancestor had a front leg with a humorous, radius, ulna, some wrist bones, and five fingers. Today, the wing of a bird, wing of a bat, flipper of a dolphin, front leg of a wolverine, and arm of a gorilla all have, more or less, the same basic architecture.

We say that these are homologous structures. They're similar because they're just modified versions of the front limb that terrestrial vertebrates all inherited from a single ancestor. Pretty cool, right? So what's left? The legs, of course. Homology applies to bird legs, too. They have many similarities with human legs. But birds, as you may know, walk around on their tippy toes. So the thing that looks like a backwards knee in the bird leg is actually equivalent to your ankle. The thickest bone in a bird's leg is the femur. It's relatively short, though. The true knee of a bird, the joint between the femur and the lower leg bones, is tucked up close to its body, so that in many species, you can't see it. The lower leg bones are the fibula and tibiotarsis. Then below, the ankle

joint is a bone called the tarso-metatarsis. It's like the carpomedicarpus in the bird's wing. The tarso-metatarsis is basically the fusion of several foot bones. It's the equivalent of your foot between your ankle and where your toes begin. Oftentimes, the tarso-metatarsis is the only part of the leg we can actually see sticking out from the body feathers. If you look at a diagram of a bird's external anatomy, in the first pages of your bird field guide, let's say, you'll often see the stick-like leg labeled as tarsis. But technically, I guess, it should be labeled tarso-metatarsus. Maybe that's too much of a mouthful? Birders ain't got no time to say tarso-metatarder sauce or what have you.

We get right to the point. Just call it tarsis and move on. at last we come to the avian foot the toes and such i might do a short podcast episode on bird feet at some point so i won't steal my own thunder here i'll just keep this concise Most birds have four toes. The standard tow arrangement is three facing forward and one facing backward. Like what you see in your typical backyard songbird. The toe, the digit facing backward, is called the halix, H-A-L-L-U-X. This is the equivalent of the big toe in a human's foot.

And just like that, we're just like that, we. we've explored the avian skeleton from the beak down to the toes. We've learned a bunch of wacky terms, like trabecula, diverticula, sclerotic ring, and tarso-metatarsis. As usual, there's much more detail we could get into, but I think we've done a good enough job for today. Bird bones and the avian skeleton are elegant, strong, and rigid, and they're fascinating, in part because of their similarities to our own anatomy. but also because of their highly divergent unique features, such as pneumatic bones penetrated by air sacs

and fused bones like the Sinsacrum and Furcula. I'm passionate about birds, and I know you are too. Otherwise, you probably wouldn't tolerate me flapping my jaw like this about bird bones. You and I love birds, and by learning about their skeletons, we get to know them from the inside out. Thanks a lot for hanging out with me today to talk about spooky skeletons.

I really hope you had fun and found the episode informative. A big much thanks to all my lovely supporters on Patreon. I have so much gratitude for all of your help. It's seriously amazing. The latest additions to my Patreon community are Nancy Campbell, Penny Thompson, Alec, and H. fist bumps and high-fives to all of you and thank you, thank you. You too can support this podcast by becoming a patron. It's almost as easy as spelling archaeopteryx. Just check out my Patreon page at patreon.com slash science of birds.

You can also shoot me an email if you have something you'd like to share with me. An insightful comment about the podcast, perhaps. Or you want me to know what percentage of your brain capacity you use. If it's more than 3% you've got me beat. In any case, my email address is Ivan at scienceofbirds.com. You can check out the show notes for this episode, which is number 69, on the Science of Birds website, scienceofbirds.com. This is Ivan Philipson, and I hope you're having a lovely day.

Peace.