The Science of Birds - How Bird Feathers Get Their Colors

Episode Date: July 21, 2022

This episode—which is Number 56— is all about the colors of birds.The diversity of color in bird plumages is one of the things we love most about these animals.But bird plumages are impressive not only when they display vibrant colors plucked from the rainbow. Thousands of species aren’t what we’d call colorful, but they do have gorgeous, intricately patterned feathers in combinations of black, brown, and white.Today, we’re looking at how feathers get their colors, from white to subtle earth tones to scintillating displays of wild iridescence.~~ Leave me a review using Podchaser ~~Links of InterestSponsor Link: Sign up through wren.co/birds to make a difference in the climate crisis, and Wren will plant 10 extra trees in your name!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, guided exploration of bird biology for lifelong learners. This episode, which is number 56, is a. all about the colors of birds. The diversity of color in bird plumages is one of the things we love most about these animals. Because let's be honest with ourselves, if every bird was a quote unquote little brown bird, we humans would probably be slightly less interested in them,

don't you think? I'll admit that I'm a total sucker for colorful birds. At my core, I love and respect all birds, even the drab little buggers. But show me an orange-breasted bunting in Mexico or a Gouldian finch in Australia, and I freak out like a teenage girl at a Beatles concert, or a Justin Bieber concert, I don't know, whatever the kids are excited about these days. But bird plumages are impressive not only when they display vibrant colors plucked from the rainbow. Thousands of species aren't what we'd call colorful, but they do have gorgeous, intricately patterned feathers in combinations of black, brown, and white. Today, we're looking at how feathers get their colors, from white to subtle earth tones to scintillating displays of wild iridescence.

Before we dive into things like feather pigments and keratin and all that, let's slow down to first ask, what exactly is color? You probably know the answer, but it's always good to review. Color is fundamentally important to humans. Among animals, we have pretty decent color vision. That's probably because color has been useful to us throughout our evolution as a species. Having the ability to distinguish colors helped our ancestors find food, like fruits. Color vision also helped us avoid some dangers, like stinging insects or venomous snakes. Today, our deep-rooted, primitive attraction to bright colors is reflected all around us in our artificial environments. For example, just take a stroll through the toy section in your local Walmart. The kaleidoscopic

display of color is almost blinding, isn't it? Human kids apparently have a hardwired attraction to rich colors, and toy companies have been capitalizing on it for ages. Some of us adults may find the overload of color in the toy section bordering on nauseating, but we too are hardwired to love colors. Because ogling colorful birds in a tropical woodland isn't all that different from shopping for toys. Many of us birders have the same acquisitive mentality kids have with their action figures or dolls. Gotta collect them all! And some birders will throw a tantrum when they don't get the bird they want.

But hey, I still haven't answered the question of what color is. It starts with the sun. The ultimate natural source of color on Earth is sunlight. The sun is blasting out all sorts of waves from the electromagnetic spectrum. These travel at the speed of light to reach Earth. The waves that humans see as color represent only a narrow band of the overall electromagnetic spectrum. Visible light is what we call the collection of wavelengths between about 390 nanometers and 700 nanometers. These are all the colors of the rainbow.

Red, orange, yellow, green, blue, indigo, and violet, Roy G. Biv and whatnot. Each color of light has a narrow and specific band of wavelengths. Blue, for example, has relatively small waves, between 490 and 450 nanometers. When wavelengths of all the rainbow's colors are mixed together, we perceive that as white. Black, on the other hand, is the absence of all colors. Humans detect the colors in visible light using specialized cells in our eyes called cones. We have three different types of cone cells in our retinas, and each is tuned to pick up a specific range of wavelengths. When we say visible light, we mean visible specifically to certain

bipedal apes of the species Homo sapiens. There's no rule that says other animals see this exact same range of colors. If you listened to my podcast episode on Bird Vision, you might remember that birds have not three but four different types of color-sensitive cone cells in their eyes. One type of bird cone cell is specialized for detecting wavelengths in the ultraviolet part of the spectrum, UV. So birds can see UV colors that are invisible to us humans, and that is just so cool. The fact that birds have these four types of cones is a big deal. Compared to us, it's as though birds have added an extra dimension of color. They have amazing eyesight.

They see not only a wider range of light wavelengths, they can also single out colors in the rainbow that we can't even imagine. So for birds, instead of just plain old Roy G. Bivv, maybe they have an acronym like Leroy G. Bivington the 3rd. Consider Atlantic puffins. These chunky little seabirds have colorful, bills that sport bands of orange and yellow. They're pretty jazzy. If we could see things through the eyes of a puffin, however, their beaks would be even more colorful. That's because to a bird,

some of those bands glow in the ultraviolet part of the spectrum, with a color we might think of as cyan green. And that color is invisible to humans. For a puffin, having a super colorful bill like this probably helps it attract a mate. Ornithologists have found hundreds of other examples of bird species with feathers or ornaments that light up in UV wavelengths of light. So we should keep in mind that birds are colorful for each other, not for us. Most birds probably couldn't care less about humans, and they might appreciate it if we just stop staring at them all the time. Bird plumages, skin, and bills reflect colors that fall within the range of wavelengths that other birds can see using their special four-cone visual system.

That said, birds also have predators to deal with, some of which are mammals. So bird feather colors also have to help with predator avoidance. We'll talk more about the functions of bird coloration in a moment. Okay, no more rambling. Here it is. Color is something perceived by an animal when light of certain wavelengths reaches cone cells in the eyes, and then signals from those cells are interpreted in the brain as red, blue, eggplant, tangerine, seafone, or whatever. So, color is something that really exists only in the mind, the mind of a person, a bird, or whoever. If there's no observer, there's no

color. That's a trippy philosophical idea, isn't it? Like if a bird of paradise displays its feathers in a forest, and no one is around to see it, does it have any color? To understand color in birds, we need to understand how birds see the world. We just talked a little bit about that, and as I mentioned, I did an entire episode on bird vision. That was way back in episode seven. It's also important that we understand why birds are colored the way they are. What are the functions of color in birds? First off, there's predator avoidance.

That's a technical way of saying not ending up as lunch for a bloodthirsty carnivore. One useful adaptation birds have here is to be camouflaged. There are tons of examples of birds having wonderfully crissue. cryptic coloration, so that they practically disappear against the background. This is true for many owls, night jars, pheasants, potus, shorebirds, tree creepers, sparrows, and so on. These guys usually have combinations of brown, gray, white, and black feathers with spotted or streaked patterns. But there's another form of camouflage called countershading. This is where feathers on the bird's upper surface are dark-colored, while the underside of the body is white, or at least relatively

pale. Think penguins, puffins, gulls, and sandpipers. This coloration makes a bird camouflaged when viewed above against a background of dark water or a forest canopy. Likewise, when viewed from below, against the sky or sunlit water, the bird is harder to see. A second function of feather coloration is species recognition. It's helpful for a bird to be able to quickly spot other members of its own species, if for no other reason than to find a compatible mate. Imagine you're in a crowded cocktail bar, full of birds. I know, sounds like a good time. It's a diverse gathering with birds of many species. For example, some storks are hanging out over there by the jukebox. There's a few hornbills playing pool, and a group of buntings are doing

jello shots over at the bar. Let's say you are a black-backed dwarf kingfisher. You're sitting at a table by yourself, hoping to maybe meet a nice bird tonight. Ultimately, you'd like to find someone to help you raise a few chicks. So you don't want to waste your time chatting up birds of the wrong species. As a black-backed dwarf kingfisher, however, there are few other bird species that would be even half as colorful as you. Your species has a unique combination of neon, purple, orange, blue, and yellow feathers. Since you arrived over an hour ago, there haven't been any prospects for you in the crowd. But then, through the door walks a radiantly colored vision of beauty. There's no question you're looking at another black-backed dwarf kingfisher. That plumage is unmistakable. You toss back the

last of your drink and go over to say hello. Black-backed dwarf kingfishers are among the many bird species in which males and females are equally colorful. So it's reasonable to hypothesize that these species have flashy colors so they can spot each other easily across a crowded room. Or, more realistically, among the trees in a forest, something like that. The other major functions of bird coloration also have to do with recognition. There's age class and sex recognition. The underlying principle here is the same. One of the biggest motivations in a bird's life is to make babies. In its quest to find a suitable mate, it doesn't want to waste its time courting another bird that's too young or of the wrong sex.

This is probably why many bird species have distinct plumages when they're immature. Immature brown pelicans, for example, are, well, brown, uniformly so. Adults, on the other hand, have colorful feathers and skin on their heads and neck. Even their eye color is different. And think about the bald eagle. Immature bald eagles don't get that clean white head until they're sexually mature at about five years old. Plumage differences between the sexes are helpful for recognizing

who you can mate with if you want to have some chicks. Even when we humans can't tell male and female birds apart, they don't seem to have any trouble with it. Research on what birds see in the UV wavelengths has revealed that many species we write off. as sexually monochromatic are actually dichromatic. In other words, there are plumage color differences between the sexes, but only birds can see them. The barn swallow is one such bird. To us, male and females look pretty much identical. They're monochromatic. But researchers

have shown that, in the ultraviolet part of the spectrum, these little birds actually have feathers on their heads, throats, and bellies that are colored differently between the sexes. And finally, the one function of color and bird feathers that many of us probably think of first is mate attraction. I did a podcast episode on sexual selection, and we talked a lot about this. Birds in a vast number of species use colorful feathers and skin to win the hearts of the opposite sex. Usually it's the male who has the brightest colors and females choose the flashiest males to mate with. But sometimes it's the other way around. So to recap, the colors of birds help them do things like avoid predators, identify members of their own species, avoid the mistake of

trying to mate with a bird that's too young or of the wrong sex, and impress members of the opposite sex. This seems like a good spot to pause for a moment to tell you about the sponsor for this episode. I know you care about birds, and if you're like me, you're worried about the negative impacts of climate change on birds. There are ways we can reduce our carbon footprints to fight climate change. For example, I chose to become a vegetarian, but there's a tool I want to tell you about,

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and tell Wren the Science of Bird sent you Wren will plant 10 extra trees in your name and you know who likes trees that's right, birds and let's get back to talking about them Before we go further let's quickly review the basic structure of a feather. If you want more detail, you can listen to the entire episode I did on Feather Structure, Episode 13.

Picture a lovely flight feather from a bird's wing. First, there's the shaft running up the middle. Then you have the flat, blade-like part of the feather that extends outward from the shaft. This is the vein. If we zoom and enhance a section of the vein, we see that it's made of small branches attached to the shaft. These are called barbs. The barbs run in parallel, side by side.

Zooming in even further, we find that each barb has its own little branches coming off the sides. Those are the barbules. And that's all you really need to remember for today. There's a central shaft, the branches coming off it are called barbs, and the tiny branches coming off of each barb are called barbules. The entire feather is built from the protein carotin. This is the same stuff that your hair and fingernails are made of. Keratin on its own is mostly transparent.

Only when pigments are added to keratin does it get some color. And speaking of color, let's finally get down to brass tacks and look at how feathers get their wonderful hues and nice. patterns. As with that age-old pastime of skinning cats, there's more than one way to color a bird. And by more than one, I mean two. There are two primary mechanisms by which feathers get their color. I'll be referring to feathers mostly, but a lot of this stuff also applies to skin and beaks.

The first mechanism is using pigments. Pigmentation is pretty intuitive, right? You've got a colored powder or liquid. You add it to something else, and bam, you're done. For example, you can add some green food coloring to your jello shots. Or if you're like me when I was in my early 20s, you can use dye to turn your hair purple, and bonus, scandalize your grandparents at the same time.

Okay, those were actually examples of dyes, which I suppose are not quite the same thing as pigments in terms of chemistry and all that. But who cares? You get the idea. So what are pigments, really, and how do they work? Well, recall that different wavelengths of visible light give us different colors. A pigment is a molecule that absorbs certain wavelengths of light and reflects or scatters the other wavelengths. The latter reach our eyes and we perceive them as colors. For example, a certain pigment might absorb all the wavelengths of light except yellow. The light with yellow wavelengths escapes the pigment and then travels to our eyes.

What we see then is the color yellow. In a bird feather, light passes through the outer layer of colorless, transparent keratin. Then the light hits and interacts with a bunch of pigment granules, which absorb some of the wavelengths and reflect others. And I should point out that all of this is happening at the level of molecules, molecular bonds, and atoms. There are several classes of pigments that we find in the feathers and skin of birds. Two of them are the most common, the most widespread among all birds. These are the melanins and the carotenoids. Melanine pigments are found in many animals, including humans. They're molecules that usually produce darker earth tones,

like black, brown, or tan colors. Melanin is what gives human skin and hair its color. Higher concentrations of melanin gives you darker tones. We manufacture our own melanin in our cells, and so do birds. In birds and other vertebrates, there are two major types of melanin. U-Melanin, the word starts with the letters E-U, produces black, gray, and dark brown colors. Phae-Melanin, this word starts with P-H-E-O. Phae-Melan makes earthy, light brown, orange, and yellow colors. There are different molecular flavors of both U-Melanin and Phaelan, and each unique molecular structure makes a different color.

The specialized cells in a bird that make melanin are called melanocytes. To me, a melanocyte looks sort of like a microscopic octopus, with dendrites that look like tentacles. Melanacite cells are clustered in the skin of birds and around growing feathers. A melanocyte is a little melanin factory. It packages its pigment molecule properties, using little bundles called melanosomes. Melanosomes shapes vary across different types of birds.

Some are spherical. Some are flat like pancakes, others are sort of sausage or rod shaped. Melanacite cells use their dendrite tentacles to deposit melanosomes wherever pigment is needed to produce color in a feather. You following so far? We've got cells called melanocytes. melanocytes. Melanocytes make melanosomes, and melanosomes are filled with melanin pigments. How melanin is distributed in a bird's plumage determines what colors and patterns you get.

Melanin concentrations can vary from feather to feather, and they can vary from place to place within a single feather. The pattern of melanosomes laid down in a growing feather can be amazingly complex. You've probably noticed how a single feather can have beautiful patterns of spots and stripes. One of the most extreme examples of this within-feather pigment patterning can be seen in the feathers of the male great argus, argusianus argus. This is a species in the pheasant family that lives in Southeast Asia. The male great argus has elegant, grayish-brown feathers with complex patterns of spots, squiggles, and circles. He uses these fancy feathers to impress females, of course.

I'll put a photo of some great argus feathers in the show notes on the Science of Birds' website. They're unreal. Besides creating color and patterns, melanin has a couple other important functions in birds. Just like in humans, melanin in the skin provides protection from ultraviolet radiation. Also, melanin is often highly concentrated in parts of the feather that experience a lot of wear and tear. That's because feather keratin that's heavily infused with melanin is more resistant to wear and abrasion than plain old vanilla keratin. This is why so many birds have black wing tips or black flight feathers. Those parts of the wing need to be extra tough, and melanin helps

with that. All right, so that was melanin. Now we come to the other widespread class of pigments in birds, the carotenoids. I've talked about these pigments more than once on the podcast. Carotenoids are what give many birds their orange, yellow, and red colors, sometimes even purple. Picture the bright orange colors of Baltimore and Bullock's Orioles, or the pink of a flamingo. An important different between carotenoids and melanins is that birds get carotenoids from what they eat. They can't make their own carotenoids the way they make their own melanins. The ultimate source of carotenoids in nature is certain cyanobacteria, plants, and fungi. Animals have to eat these things in order to get carotenoids.

Birds get these pigments from eating fruits and berries, or from slurping up cyanobacteria directly, or from eating invertebrates that already have carotenoids in their bodies because of what they ate. There are hundreds of different carotenoid molecules out there in nature. Ornithologists have found dozens in the bodies of birds. In their cells, birds often modify the molecular structures of carotenoids they get in their diet. Now, besides melanins and carotenoids, there are a few other less common classes of pigments in birds. The first of these is the porphyrens. Porphyrin is spelled P-O-R-P-H-Y-R-I-N.

Porferin pigments are made in the cells of birds like owls, pigeons, busters, grouse, and members of many other families. However, ornithologists aren't quite sure what porphyrens do for these birds, since the pigments rarely add much noticeable color. Noticable to humans anyway. One interesting thing is about porphyrens is that they're fluorescent in ultraviolet light. So I'm guessing that porphyrins are present in some of those feathers with colors that only other birds can see. Some of the most spectacular porphyrens are made by birds called turakos. These are the 23 species in the family Musofagody, all of which are found in sub-Saharan Africa. Many Turikos are brightly colored, gorgeous birds. One weird trick they use for being so colorful is making special porphyrin pigments.

Remember those stupid clickbait ads on the internet back in the day? Lose your belly fat in 10 days with this one weird trick. Man, I used to spend a lot of time and money clicking on those ads. And I still have belly fat. Oh well, live and learn, I guess. Anyway, Turikos probably have more than one weird trick for being such awesome birds. But we're talking about porphyrens. A porforin pigment unique to the Turaco family is called Turacin. This gives feathers a velvety crimson or maroon color. Another porforin found only in Turacos is Turrico Verden. This one is green. That's important because, as far as I know, Turaco Verden is the only green pigment found in birds. I'll put a couple photos of Turikos in the show notes on the website, so you can see just how beautiful these birds are.

Yet another class of pigments is the Sataka-Fulvins. That word begins with P-S-I-T-A. So if you know a little about bird taxonomy, you might guess that Sataka-Fulvins have something to do with parrots. And you would be right! Only birds in the order of... cetacaformis have these special pigments. These are the parrots, macaws, cockatoos, lorries, budgies, etc. Sitaka fulvins produce the bright reds, oranges, and yellows of parrots. An important difference here is that these colors have nothing to do with what parrots eat. Carotenoids have to be eaten, but sitacopholvins are made in the cells of parrots. There's a couple other relatively rare pigments in the avian world,

but I think it's time to move on to look at the second mechanism by which birds get their colors. The second mechanism is called structural color. This is where the physical structures of feathers produce colors by bending light. The physics of color produced by pigments, occurs at the scale of molecules and atoms, as I mentioned. But the processes of structural color are happening at a larger scale. We're talking about melanosomes and keratin structures with dimensions on the order of hundreds of nanometers.

You might remember that this is more or less the same scale as the wavelengths for visible light. Microscopic structures in feathers interact with light, causing it to do one of several things. One, light can reflect off of layers of shiny keratin. Two, light can also pass through transparent layers of keratin. And three, light can get absorbed by pigments such as melanin. Perhaps the simplest form of structural color in birds is white. Imagine a willow tarmigan, lagapus-lagopus.

If you're in the UK, you'd probably call this bird a red grouse. Well, in winter, these buggers are almost pure white. They're perfectly camouflaged against fluffy white snow. Feathers on birds like this are white because beneath the glossy keratin surface, there are countless microscopic air bubbles trapped in a matrix of keratin. White light enters the feather and then all of the wavelengths get scattered by the air bubbles, sort of chaotically in all directions. These waves then come back out of the feather and are seen as white. So white is one form of structural color.

Then we have iridescence. Iridescent colors are the ones that make us go ooh and ah. They have a metallic sheen and they change from one hue to another depending on the way light hits them. Just picture a male Indian pea fowl, aka the familiar peacock. He's spreading his train of amazing blue, green, and gold feathers in an enormous fan. This bird is all about iridescence. There are many other types of birds that display iridescent feathers, including hummingbirds, sunbirds, ducks, pigeons, starlings, pheasants, and birds of paradise.

Iridescence has apparently evolved independently many times in birds. To explain iridescence, I need to find iridescence, I need to First set the stage by describing the nanostructures involved. We are going to zoom in on a feather to look at the inside of a single barbule. The outside layer is made of smooth, transparent keratin. It's like plexiglass or clear acrylic. Below the surface, inside the barbule, there's a thin layer of melanosomes, arranged in orderly rows. We can picture these as rod-shaped melanosomes,

but remember that melanosomes can have different shapes. Going deeper into the barbule, there's another layer of keratin, followed by another layer of melanosomes. Below those are even more layers with the same structure. This is sort of like a layer cake, or a quadruple-decker sandwich, but feathers are nowhere near as tasty, which you probably know if you've ever tried to eat hair or fingernails. So we've got our not-so-tasty layers of keratin and geometrically arranged melanosomes. Then here comes some pure white light from Mr. Sun. The light hits the first outer layer of keratin.

Some of the waves are immediately reflected, while the rest pass through into the barbule. Light of some wavelengths gets absorbed by the melanin and is never seen again by man or bird. As the remaining light penetrating the feather hits each deeper layer of keratin, some waves are reflected while some pass through. The waves that are bounced back out of the feather will have traveled different distances if they reflected off of different keratin layers. When those waves line up on their way to the eye of an observer, they can do one of two things. If the peaks and troughs of the light waves align perfectly, they reinforce each other.

creating a super bright color of that particular wavelength. Alternatively, if the peaks and troughs are misaligned, the waves might cancel each other out. The resulting color, in that case, is less bright and might even appear black. A key feature of iridescence is that the color or hue changes with the angle it's viewed from. In a bird feather, different wavelengths of visible light are bent at slightly different angles by those thin layers of keratin. At one angle the feather might look blue, at another angle it's green or purple.

And, of course, at some angles, you don't see much color at all, do you? Iridescent feathers can appear almost black when they're placed between you, the observer, and the light source. This phenomenon is obvious when you observe a male hummingbird. Males of many hummingbird species have brilliantly iridescent patches of feathers on their throat. The technical name for this patch is the gregor. Gorgit, G-O-R-G-E-T. Male hummingbirds seem to find perverse pleasure in frustrating human photographers. Naturally, the photographer wants to get a shot where the hummer's brightly colored

gorget is on full display. But the cheeky little Hummer keeps looking away, making sure that its gorget looks dull and black from the human's perspective. Hummingbirds are possibly the most diversely colored of all birds. Iridescence is there one weird trick for achieving this distinction. A recently published study in the journal Communications Biology found that the range of colors in the hummingbird family matches or even exceeds the range of colors found in all other birds combined.

That is just incredible. Okay, we're still talking about structural color, right? We've got white and we've got iridescence. but there's also non-iridescent structural color. These colors are usually some shade of blue, so they're also referred to as structural blues. Here you want to picture something like a bluebird, Blue J, Kingfisher, Blue Tit, or Fairy Wren.

These birds aren't iridescent, but their blue colors are the result of nanostructures in their feathers. In this case, all the exciting, light-bending action is in the barbs, not in the barbules as with iridescence. The barb of a structurally blue feather has three primary layers, an outer layer of transparent keratin, a spongy layer of air bubbles and keratin, and a base layer of melanin. White light first passes through the outer layer of keratin. Blue light gets bent by the spongy layer and then shoots back out. The other longer wavelengths are not bent, so they pass all the way down to the dark and spooky layer of melanin.

Those wavelengths of light are trapped in the dungeon of melanin forever. Unlike iridescent color, structural blue colors are not as dependent on viewing angle. They're pretty consistent, except for when the feather gets between the observer and the light source. In that situation, again, the feather can look rather dull, dark instead of blue. For birds to be blue like this, natural selection had to come up with these nanometer scale structures inside the feathers. Because here's the thing. Blue pigments are rare in nature. Blue pigment molecules are either super large, unstable, or even toxic. They just don't work well inside the cells of animals. So if you see a bird with some nice blue feathers, you can be

certain that there's no pigment involved, other than melanin. It's all just a trick of the light as it gets bent by microscopic structures in the feathers. We've covered the two mechanisms for how birds get their colors, pigments and structures. But this isn't one of those either-or scenarios. It's not like how you get either heads or tails in a coin. Toss. Birds often use a combination of pigments and structural colors in their plumages. Green colors are almost always made this way. The much-loved Budger-A-Gar of Australia, Malopsatacus, aka the Budgie, is a great example here. If you've never seen a wild budger agar, I bet you've at least seen them at the pet store. Or maybe you've even had one as a

pet. I had one when I was a kid back in the 80s. His name was Buddy. May he rest in peace. The plumage of wild budgies is mostly yellow and lime green. We can look once again at the microscopic structure of the feather barbs to understand how the green color of budgies is produced. There are three layers involved. First, there's a layer of yellow carotenoid pigment. Second, there's a spongy layer of keratin and air bubbles below the yellow layer. Last, there's a layer of dark melanin way down there in the dungeon. The outer layer of pigment reflects light in the yellow part of the spectrum. And you know now that the combination of the spongy and melanin layers beneath

should give off a blue color, a structural blue. What ends up reaching the eye of the beholder is a combination of blue and yellow light. And we perceive that as a nice, saturated, budgy green. So that, my friends, is how we get the seemingly limitless palette of colors we see among all the birds of the world, with pigmentation, structural color, and combinations of the two. That wraps up episode 56. I hope you enjoyed listening and that you learned a thing or two. The next time you're looking at a bird, see if you can guess which of these processes are involved in making its color.

Thanks to all my supporters on Patreon for helping to make the science of birds more sustainable. Your ongoing support is really helping a lot here. And I want to welcome my newest patrons, Mark Deaton, Kalin Mooney, Emily Kim, and Keyword Kiwi. Thanks so much to all of you for your generous support. If you are listening right now and you're hoping I'll produce many more episodes like this into the future, consider becoming a supporter to help make that happen. 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, or maybe one weird trick you use for losing belly fat. But I'm not going to give you my credit card. Fool me once, shame on you. Wait, how does it go? There's an old saying in Tennessee. I know it's in Texas, probably in Tennessee, that says, fool me once.

Shame on you. It fooled me. We can't get fooled again. Ah, yes. Thanks, George. In any case, my email address is Ivan at Scienceofbirds.com. You can check out some pretty pictures of birds in the show notes for this episode, which is number 56, on the Science of Birds website,

scienceofbirds.com. This is Ivan Philipson, wishing you nothing but joy and contentment. Cheers.