The Science of Birds - Avian Navigation: How Birds Find Their Way

Episode Date: January 18, 2026

👕 Bird Merch —  Get yourself some bird shirts!~~~This is Episode 128. How does a bird travel thousands of miles across the globe only to return to the exact same backyard or nest site year after year? This episode explores the fascinating science behind avian navigation. Learn the difference between simple orientation and "true navigation," uncovering how birds reach specific destinations they have never even visited before.The discussion dives into the bird’s "map-and-compass" toolkit, highlighting a range of incredible adaptations. From internal biological clocks and genetic blueprints to the ability to "see" magnetic fields through quantum physics, the episode breaks down how birds interpret the world around them. Whether they are tracking the sun, the stars, or even atmospheric scents, birds take a multi-sensory approach to get from one place to another.Finally, the episode examines the role of experience versus instinct, explaining how juvenile birds navigate their first solo journeys and how seasoned adults build complex mental maps of the planet.Link to this episode on the Science of Birds websiteSupport the show

By what means, do you suppose, would a person in ancient Egypt or ancient Greece send a text message to their friends to flake out on their dinner plans at the last minute? I mean, there were no smartphones, no landlines, there was no internet, there wasn't even the telegraph. But there were plenty of pigeons. There were special pigeons bred for the purpose of carrying messages from one place to another. We call them homing pigeons. Before the telephone and telegraph, a homing pigeon was sometimes the fastest way to send a message, in the form of a little note or strip of microfilm fastened to the bird's legs.

A homing pigeon has the uncanny ability to find its way home after being displaced to some other location, even if that location is over a thousand miles away. So let's say you've got a pigeon who was born and raised in London. His name is Humphrey Plunkett. You carry Humphrey with you in a cute little pigeon carrier all the way to Warsaw, Poland, a distance of about 900 miles or 1,400 kilometers. To send a message back to London from Warsaw, you just attach it to the bird, toss him into the sky and yell,

Fly home, Humphrey, fly! And off he goes. A few days later, Humphrey arrives and the message is received. you have successfully flaked on your dinner plans. And you know, this gives me an idea. The next time I go backpacking in the wilderness, I could leave the emergency GPS beacon behind and just take a homing pigeon instead.

It's a low-tech safety solution that doesn't require batteries. And bonus, I've got a little hiking buddy riding in my pack. So if I slip and break a leg or something, I just release my pigeon and it flaps away, all the way back to my mom's house with a note that says, Hi, Mom, how are you? Good, I hope. Anyway, I wish I could have told you this in person, but I would like my casket to be made of mahogany,

lined with velvet preferably, and it should have some nice gold-plated handles. And I also want a big fancy funeral. Spare no expense! P.S., please take good care of the pigeon. Don't forget, her favorite treats are blueberries and Cheetos. This homing behavior and the ability to navigate long distances isn't unique to pigeons. All birds are able to find their way around in their local

area, and many of them can make their way back to a specific spot after being hundreds or thousands of miles away for months at a time. So that hummingbird buzzing around in your backyard, or if you're in the UK, let's say, it might be a common chif-chaff or a Eurasian black cap. That might be the same individual bird that was there last summer. During its absence in the winter, it was far away to the south, having all sorts of little adventures. How do they do it? How can these small creatures fly from one side of the earth to the other, and, amazingly, end up exactly where they intended?

Hello and welcome. This is the Science of Birds. I am your host, Ivan Philipson. The Science of Birds podcast is a light-hearted exploration of bird biology for lifelong learner. This episode, which is number 128, is all about the adaptations birds have for finding their way, how they navigate on journeys both near and far. As we'll discuss, birds have more than one trick up their sleeve, more than one tool in the toolbox when it comes to navigation.

An individual bird has multiple anatomical, physiological adaptations that help it get to where it needs to go. Originally, I wanted to make this episode all about the phenomenon of vagrancy in birds, where individuals get off course and end up as vagrants in places far outside their normal ranges. But I thought it would be good for us all to have some background knowledge on avian navigation first. I'll do an episode on vagrancy in the near future. But for now, how about we just go ahead and get into it and talk about avian navigation. As humans living in the 21st century, many of us might take it for granted that we can almost always pinpoint our exact location anywhere on Earth. We have things like Google Maps, powered by GPS transmitters in our phones, and so on.

But this is totally like science fiction or like magic compared to how things were before, let's say, the 1820s. It wasn't that long ago that it could be a serious challenge, to figure out how to get somewhere or to figure out where exactly you are at the moment. The easy part to figure out, relatively speaking, is latitude, how far north or south you are. Humans have, for thousands of years, measured the height of the sun at noon

or the north star at night above the horizon. That kind of information would allow sailors, pirates, and other travelers to tell exactly how far north or south they were. Knowing your position on the west-to-east axis is another story. Because the earth spins, the sky constantly changes, making it impossible to use just the stars or sun to tell east from west. Unless that is, you know the time.

To figure out your longitude, how far west or east you are, with any accuracy, you need to know both the time at your current location and the time at a fixed point like your home city. You have to know what these times are simultaneously at the same moment. Only when humans invented accurate clocks in the 1700s did this become possible. Birds have had to solve these same challenges. They did it through evolution. We did it through technology.

Now, before we go further, we should probably talk about the difference between navigation and orientation. Orientation is knowing where you are, that is, your relative or absolute position and which direction you're facing right now, this very moment. Like, I'm standing on the shore of this lake, facing northeast, and I'm five miles from that mountain peak. That's my orientation. Orientation is a stationary state. Navigation, on the other hand, is a process. It's a process of getting from point A to B, planning, choosing a route, and moving along that route. Orientation, knowing your position and which way you're facing is an essential part of navigation.

What we call true navigation is the ability to return to a known location from a place you've never visited before, using only local information. And research has shown us that birds are indeed capable of true navigation. For example, there's research that's been done with white-crowned sparrows here in North America. Researchers captured sparrows on their

wintering grounds in the western U.S. Then the birds were packaged up and flown to the east coast for release. The following winter, a bunch of those sparrows had made their way back to the exact same spot where they were originally captured. This shows a high level of fidelity to a specific winter range. In another study on white-crowned sparrows, some were captured in the west during their southward migration, so before they even made it to their winter range. When these sparrows were released on the east coast, the experienced adults immediately

began correcting their flight paths toward their correct winter range, to the west. But the inexperienced juvenile sparrows just kept flying south in the same direction they would have if they were still on the west coast. So this suggests that true navigation capability is, at least in part, based on experience. Relocation studies like this using other species have found similar behaviors. With some exceptions, sure, but this is the general pattern. To understand navigation in birds, we can use a map and compass model. In the map and compass model, there is a two-step process.

First, the bird uses its map sense to determine its current position relative to its goal, and then it uses a compass sense to maintain, the correct heading to that goal. Birds have multiple ways of sensing their compass direction, and we'll talk about those in a few minutes. The compass part is relatively well understood by ornithologists. The sensory basis of the map, however, is still a bit more mysterious. It's something scientists are still trying to figure out.

One of the leading theories is that birds possess a mental grid based on environmental gradients that vary predictably across space, such as latitude and longitude. By comparing the local values of these gradients at a displaced location, with the remembered values of their home or their goal, birds can figure out their position. Now, that's at a large spatial scale, like across a continent or across an entire hemisphere.

But some ornithologists think that birds also have what's called a mosaic map. which is what they use when they're close to home or near a familiar location. This mosaic map is a mental representation of prominent landscape features, such as mountains, rivers, and lakes, in relation to each other and the birds' home. Mental maps in birds, at whatever spatial scale, aren't something birds are born with. They build maps in their minds over time, through experience. Okay, so those are really. some of the basic ideas to lay the foundation of our understanding. Next, let's talk about the

navigation instincts that birds inherit from their parents. As I mentioned, many birds rely on their life experience, in other words, learning to build their mental maps. But genetics also plays a big role in navigation. This is particularly important for young birds about to undertake their first ever long-distance migration. Think about a juvenile bobolink, which is a songbird species in the New World Blackbird family. Bobbolinks breed in the grasslands of northern North America, but they spend the winter way down in Central South America. Our little Bobalink hatched out of an egg a few months ago. Mom and dad took care of it for a little while after it fledged, but then they were like, good luck, have a nice life. And they left their offspring to fendom.

for themselves. It's now autumn, and the naive juvenile bird needs to fly south to escape the harsh winter. It needs to find the ancestral winter home of its people down in South America. But without the guidance from any adults, how does it know where to go? This is where genetics comes in. Bobelinks and many other birds are born with an instinct described as a clock and compass or vector navigation mechanism. This system involves two innate senses. First, there's a sense of direction. This is a genetically programmed migratory direction that serves as the compass. The bird knows which direction it needs to fly to reach its winter range for the first time.

Second, there's a sense of time, an internal biological clock that works on a yearly cycle. The clock tells the young Babelink how long it needs to fly. the duration of the journey, 15 days, for example, or whatever. By combining its sense of direction and time, our bird is able to reach its winter home even without any prior knowledge of the destination. And that is just crazy. It's wild. There is information coded in the bird's genes that tell it how to get to a specific place over 6,000 miles or 10,000 kilometers away.

Without any prior experience to draw on, juvenile birds only have this clock and compass instinct to rely on. That instinct is a sort of program that works only if the young bird sets out on its first journey from the general location where, for countless generations, its ancestors have been born. If you hatched out of an egg in British Columbia, Canada, you will have clock and compass instincts that are adapted for that specific location. Because remember what happened to those juvenile white-crowned sparrows, they were experimentally relocated from their normal migration route on the west coast to the other side of the continent. When they were released, their instinctual programming

told them to keep flying in the same direction for the same duration. But because the starting point was off by thousands of miles, the juvenile birds were never going to end up in the right wintering area. They had no way to correct their course. The Eurasian black cap, Sylvia Atrocapola, has been used as a sort of model organism by researchers studying the genetic basis of a juvenile songbird's migration instincts. The black cap is a warbler-like species in the family Silveity, and it's found in Eurasia and Africa. Different populations of black caps in Europe occupy distantly separated winter ranges. One population might winter in the western Mediterranean region, while another population flies down to a region in sub-Saharan Africa.

One thing researchers did was they paired up birds from two such populations, bred them in captivity, and then monitored the migration behavior of the resulting juvenile birds, the hybrid offspring. Well, the hybrids just followed their genetic program when it was time to migrate. The direction and duration of their migratory behavior was intermediate between those of the two source populations, between the parents. So left to their hybrid instincts, they would end up somewhere halfway between the Western Mediterranean and Sub-Saharan Africa. As one more example, let's consider the common kuku, Ku Kluxculus Kanoris. And, FYI, I'm going to be doing a full episode on the Kuku family, Kukuladi, very soon.

Anyway, like so many of its brethren, the common kuku is an obligate brood parasite. A female kuku lays her egg in the nest of another. species, she sneaks away and lets the other birds raise her chick. But the common cuckoo is a long distance migrant. Even though every cuckoo is raised by some other bird species, the cuckus all end up migrating to the winter range of their parents. In other words, the cuckus don't follow their host parents or learn anything from them with regards to migration. Juvenile common cuckus have a genetically programmed clock and compass instinct that allows them to fly thousands of miles

and end up in the right spot. Okay, let's say a young bird like a common cuckoo or a bobble link successfully completes its first long-distance migration to its non-breeding winter range. Hooray! First, it probably learned some of the landmarks and other environmental cues along the journey, and that will help it navigate the route next year.

Second, the bird is going to imprint on its non-breeding home, its winter range. Again, remembering local landmarks and all of that. So genetically programmed instincts are what got the bird where it needed to go the first time, but now it can start to learn and accumulate experience. Experience becomes increasingly important in seasoned adult birds. And it seems there's also evidence that birds might inherit directions for the return. journey in the spring. If so, that would complement and reinforce whatever they learned on their first journey. Because these innate migration behaviors are genetic, that means their adaptations

forged through natural selection over many generations. And it means these behaviors can change if environmental conditions change. Birds can at least potentially evolve shifting their migration routes and locations and other behaviors. Remember that with humans, one of the essential inventions that leveled up our navigation ability was the clock, an accurate clock. For a bird to navigate, it also needs a clock. Birds have an internal circadian clock that regulates their daily activities on a roughly 24-hour cycle, even when they're in constant light or constant darkness. Humans have something like this too. The biological timer in birds is much more complex than the human version because birds have multiple clocks in their

bodies that can act as independent pacemakers. The timers are located in several places, the pineal gland, which sits on top of the brain, the retina of the eye, and the supra-chaismatic nucleus of the hypothalamus, which is a region of the brain. The way these avian clocks are calibrated and how they interact is complex. They reset every day by external cues. While the light-dark cycle is the most powerful cue, birds can also synchronize their clocks through social interactions, sound, and other things. At least some of the clocks are also on genetic feedback loops. On a molecular level, the clock operates through negative feedback loops where specific clock genes make proteins that eventually build up and shut off their own production in a cycle that

takes, you guessed it, roughly 24 hours. I should also point out that birds have internal clocks operating on two timescales, the daily scale and the yearly scale. The daily clock runs on a cycle of course 24 hours. It manages a bird's basic day-to-day habits, such as when to wake up, when to eat, and when to sleep. The yearly clock, tracks the passage of the seasons on a cycle of approximately one year. This long-term clock signals major life events, telling the bird exactly when it's time to start migrating, begin molting, get ready for breeding,

and when it's time to shop for their Halloween decorations. To get the best deals, smart birds buy all of their Halloween stuff on like November 1st, because everything's on sale. The spookiest decorations, at least from a bird's perspective, are the black cats. especially the feral ones. So we're using the map and compass model to understand bird navigation, right? Let's talk about the compass. Birds have not one, not two, but, depending on how you look at it,

as many as four ways of determining compass direction. First, there's the sun compass. Birds use the sun's location, its direction, where it is in the sky, and they compensate for the sun's movement using their internal sense. circadian clock. A bird makes a mental calculation from the sun's direction called its azimuth and the time. With these two pieces of information, the bird can determine true north at any time of day. So if the bird's internal clock says it's morning time, the bird knows the sun is in the east, and if it needs to fly south, it keeps the sun on its left. Or at noon,

the bird knows the sun is in the south, so to fly south it would fly directly toward the sun. Researchers have run experiments where they screwed up the internal clocks of birds like homing pigeons. The birds were kept indoors with artificial light, and the day and night cycle was offset, thrown off by like six hours. Then when those pigeons are exposed to the real sun, they fly in the wrong direction because they didn't know the real time. Many birds make their long migratory journeys by flying at night.

Nocturnal migrants like this make use of another type of compass, the star compass. Birds learn the rotation of the night sky to determine a north-south axis. You know, you've probably seen those long exposure photos of the stars making concentric circular streaks in the sky, all of them centered on the north star. Well, birds do that. They observe the rotation of the stars, and that tells them which way is north. So, as far as I understand, birds don't memorize particular constellations or star maps. It's really all about the rotation of the stars.

Birds also use polarized light as another compass. What is polarized light? Well, for most light sources, the beams or rays of light are shooting outward in all directions. It's a big mishmash. but when light gets polarized, all or most of the rays are moving parallel to each other in the same direction. Humans can only see polarized light while wearing particular sunglasses, but birds have a natural ability to see it. They perceive the angle of polarized light directly.

In nature, sunlight becomes polarized when it hits the Earth's atmosphere and scatters off gas molecules. This creates a predictable map of polarized. light across the entire sky, even if the sun is hidden behind a cloud or it just dipped below the horizon. Birds don't just see brightness. We think they see a pattern of lines across the sky, and this pattern tells them exactly where the sun is located, even on a cloudy day. Two of the ways birds use polarized light include one to calibrate their internal magnetic compass, which we'll get to in a moment. Birds use polarized light. light cues near the horizon, especially during sunrise and sunset, to reset or recalibrate their

internal magnetic compass. And two, many birds that migrate at night begin their journeys shortly after sunset. So they use polarized light patterns at this time to determine their initial heading and then they try to stay on course through the night. Calibration is necessary because the Earth's magnetic field shifts over time and it varies by location. Birds use polarized light as their primary calibration tool to keep their other senses accurate. Okay, so birds use the sun, the stars, and polarized light to determine direction. And yes, the final compass has to do with the planet's magnetic field. In general terms, a magnetic field is a sort of invisible map of force that flows in

and continuous loops from a magnet's north pole to its south pole. We humans visualize this by making diagrams with field lines, which are packed most densely at the poles to show where the magnetic strength is most intense. On a global scale, Earth acts like a giant bar magnet, with these field lines stretching into space to form a protective shield around the planet. The lines radiate out from the poles.

birds are able to sense magnetic fields somehow. We'll talk more about that in a moment. However they do it, birds can sense the dip or angle of the Earth's magnetic field lines at a given location relative to the Earth, rather than just figuring out North versus South. So birds are able to extract the direction as well as other location info out of the magnetic field. So birds, some of them anyway, have this amazing superpower. to see magnetic fields. It's called magnetoreception.

It seems that this process involves a special protein called cryptochrome located in a bird's retina. Here's how that might work. And I have to warn you, there's some quantum physics involved. Maybe you already have a decent understanding of quantum physics. But me? Well, let's just say that I've watched the Marvel Ant-Man movies. So that means I basically know nothing about quantum physics.

Anyway, in a bird, when blue light hits the eye, it excites electrons within the cryptochrome molecules, creating what are called radical pairs of electrons. Earth's magnetic field is very weak, but it's strong enough to influence the spin of these electrons at a quantum level before they return to a stable state. This is a chemical reaction, and it's thought to create a visual pattern or a sort of shadow on the bird's retina, allowing the bird to literally see the Earth's magnetic field lines overlaid on its normal vision. And that's pretty cool. However, I want to point out that, yes, this is the leading scientific theory for how birds sense direction using magnetic fields.

But I don't think it's been accepted across the board as a solved mystery. There's still some debate about it. In any case, there is some compelling evidence supporting the eye-based magnetic compass. Hopefully, with more research, we'll get closer to understanding how this all works in birds. We've covered the various compasses birds use.

Now let's talk about the map. A bird's mental map is something it develops over time through experience. As I mentioned earlier, scientists are less certain about how this part works. So keep that in mind. The scientific challenge lies in identifying the sensory cues that create a bird's map sense. There are two leading hypotheses, the magnetic map and the olfactory map.

But these hypotheses are not mutually exclusive. It could be that both are correct to some extent. First up, we have the magnetic map. While the eyes provide a magnetic compass, it's the beak that seems to beak that seems to be involved in the magnetic map. There are tiny particles in the upper layers of the bill, and they're made of a mineral called magnetite. The exact physical structure at the cellular level here is still unknown, and it's an area of ongoing research. In any case, the magnetite-based receptors, or whatever, that are in the beak, are connected to the brain via the trigeminal

nerve, and it seems that's fairly certain. It's likely that they sense magnetic intensive. It's likely that they sense magnetic intensity helping birds determine their latitude, because the intensity of the Earth's magnetic field varies across latitude, generally being strongest at the poles and weakest at the equator. Also, some landforms like iron-rich mountains create their own magnetic fields. These too could be added to a bird's mental map. Again, the map is based on experience. Unlike the innate compass sense, the navigational map is something a bird has to learn and remember. Now let's consider the alternative or complementary idea of the olfactory map, the one that has to do with the bird's sense of smell. Because, like Gandalf the wizard says, if in doubt, always follow your nose.

The olfactory navigation hypothesis offers the idea that birds use stable gradients of atmospheric odors to form their navigational map. Smells wafting on the wind. Good smells like maybe a meadow full of springtime flowers, as well as bad smells, like the foul vapors spewing forth from an Arby's restaurant. Remember from the podcast episode I did on seabirds that many of those birds have a keen olfactory sense. They create mental maps by learning odor gradients to pinpoint their home colonies. There was this study from 2015 on lesser black-backed gulls that gave us some strong evidence for the old factory map hypothesis. In this experiment, researchers captured adult gulls migrating from northern Europe to Africa. The birds were then surgically treated, and personally I'm not all that

thrilled about that part, but yeah, one group of gulls had their olfactory nerves cut, and another had a branch of the trigeminal nerves cut. Remember that the trigeminal nerve is associated with the magnetite-based beak system. And then there was a control group of gulls. gulls whose nerves were left intact. Okay, so you've got one group that can't smell, you've got another group that can't use its beak to detect magnetism, and then the third is the control. All of the gulls were then displaced 620 miles or 1,000 kilometers

west of their normal migratory pathway. So what happened? Well, the intact control birds and the gulls with severed trigeminal nerves successfully compensated for the displacement. They were able to orient back towards their population-specific migratory corridor. But the gulls with severed olfactory nerves were unable to compensate.

They maintained a clear southerly migratory direction but failed to correct for the westward displacement. So at least for these lesser black-backed gulls, airborne olfactory information was essential for true navigation when they were displaced far outside their familiar migration route. In addition to magnetic information and smells, some birds might even use sound for their mental maps,

because it turns out that some birds can hear infrasound at super low frequencies that humans can't hear. Low frequency sounds from oceans or mountain ranges can travel thousands of miles. So these sounds might work as acoustic beacons or landmarks for long-desquencies. travel. There are many amazing things about birds, and one of them is this ability to successfully navigate vast distances, including to places that they've never even been. This behavior is orchestrated by an innate genetically programmed system that integrates internal biological clocks with external environmental cues. Birds pick up on those cues using pretty much

all their senses, sight, smell, hearing, and magneto reception. Many birds begin their lives with innate navigation skills, and then through experience they improve those skills. They have these detailed mental maps, crisscrossed, I imagine, with magnetic lines and odor gradients, and filled with landmarks. Birds remember key landmarks like mountain ranges, coastlines, large lakes, and who knows, maybe human-made things like cities, amusement parks, IKEA stores, and the Great Walls. wall of China. This topic, navigation in birds, is fairly complex. I've done my best to explain it as I understand it, and I really hope it makes sense to you. Many questions remain, and ornithologists continue to do research on navigation in birds. For example, as I mentioned, figuring out longitude is way more difficult to determine than latitude. Birds clearly have solved this,

but scientists don't know exactly how. Do birds use celestial cues like the sun and stars combined with internal clocks to determine longitude? Or do they use magnetic intensity or olfactory cues or what? Another big question is whether the mental map of birds is unimodal, as in there's just one cue for everything, bimodal, so there are different cues for latitude and longitude, or redundant, multiple key.

cues providing overlapping data. We just don't know. But we do know that there are multiple ways for all of this to go very wrong. Birds are amazing navigators for sure, but many of them still get lost and they end up in weird places. That's the phenomenon of vagrancy, and we'll cover that in an upcoming episode. Thank you for listening to episode 128 of the science of birds. I don't know, I find this stuff fascinating, and I hope you do too. It's amazing to see how non-human animals have evolved senses that are just so different from ours. It kind of makes you wonder what else is possible. As always, I offer my deep gratitude to all of you who support this show as members of my Patreon community.

You are amazing and thank you so much. The freshest cohort of generous people to become members includes Rosa, Mark Forrester, Jill Marquitt, Jennifer B, Jason Hall, Scott Barron, Michelle, Carolyn Stan Lee Hanson, Valwise, Nancy Archer, and Alexey Hobbs. Welcome to all of you and thank you for the support. And forgive me if I mispronounced your name. If you are listening right now and you're not yet a member, you can check out my Patreon page over at patreon.com slash science of birds. you'll also find a link in the show notes in your podcast app. You can shoot me an email if you have something you'd like to share with me, a birding story, or perhaps you want to explain quantum physics to me in three sentences or less.

In any case, my email address is Ivan at Scienceofbirds.com. Again, this is episode 128. You can check out the show notes for the episode along with some photos of birds I talked about today on the science of birds website, scienceofbirds.com. And don't forget to check out bird merch, my online store over at birdmerch.com. I'm Ivan Philipson, and True Fact About Me, when I was about nine years old, an uncle of mine gave me a baby snapping turtle. As you might know, I was all about reptiles and amphibians as a kid, so I was really stoked. So there I was with this tiny turtle.

I named him Jupiter. Jupiter was pretty chill at first, even though he liked to escape from his aquarium. him. But he just got bigger and bigger and bigger. I was pretty young, so I never really learned to properly handle him. His tendency to snap, as is the nature of a snapping turtle, was intimidating. I was kind of scared of him, even though I loved him. Snapping turtles are not native to California where I lived, so releasing him into the wild was not going to work. And that's not a good idea anyway. Luckily, I found a guy who was highly knowledgeable about reptiles, and he adopted Jupiter, and we all lived happily ever after. So there you go. Thanks again for listening. I hope you

have a great day. Peace.