The Science of Birds - Tracking Methods: How We Know Where Birds Go

Episode Date: September 14, 2023

This is Episode 82. It's all about the ways that scientists track the movements of individual birds.The focus of today’s episode is not so much about the behaviors of birds, but about the technologies used by researchers to study bird behavior—the methods used to reveal the movements of birds.And our focus will be on the tracking of individual birds. There are other methods scientists use to record the mass movements of birds, like using radar to track flocks of migrants. But today we’re looking at techniques that can reveal the unique paths taken by an individual bird—a sandpiper, a hawk, albatross, pheasant, penguin, or whoever. Links of Interest Motus   ~~ Leave me a review using Podchaser ~~Link to this episode on the Science of Birds website Support the show

As I'm recording this, autumn is just around the corner in the northern hemisphere. For me, that means it's almost time to put my fuzzy sweaters back into heavy rotation and to start drinking gallons of hot herbal tea, which I guess if we're not pronouncing the letter H, I should say ot herbal tea. And autumn is also a time when I look wistfully out the window day after day. at the rain-drenched city of Portland, Oregon, thinking about the past and the future. But for countless birds around the world, this is a season to move, to relocate. Some will make epic migratory journeys of thousands of miles.

Others will travel only a few tens of miles. Some birds migrate up or down in the vertical dimension, along the slopes of mountains. Many birds move into habitats different from the ones where they spend the summer. Meanwhile, other birds might just hunker down where they are, staying in more or less the same location all year long. All spring and summer, we get to know certain birds in our backyards and our local parks. In North America, familiar species include American Robin, ruby-throated, and Anna's hummingbirds,

Baltimore Oriole and broad-winged hawk. In Europe, the songs of nightingales and cuckus are familiar in the warm months. We recognize these birds at the species level, but sometimes we even get to know individual birds. But sadly, many of them disappear from our backyards during the winter. We miss them terribly and pine for them. Months go by. Then, as if by magic or in answer to our prayers, the little buggers reappear the following spring. How can we figure out where our birds go and what sorts of mischief they get up to while they're away? Well, scientists have been keenly interested in such questions for hundreds of years. By tracking the movements of individual birds, hardworking scientists have been able to address questions related to things like,

just to name a few examples, migration routes, the consistency of movement patterns made by individuals, where birds make pit stops on their migratory journeys, what habitats they use during the non-breeding season, their home range sizes, and the effectiveness of our conservation actions. Questions like these are super important. But until recently, they were often very difficult or impossible for anyone to answer. If, like me, you're curious about the comings and goings of birds, I have good news for you. It turns out we live in a golden age. A golden age of what, you ask? Well, some would say this is the golden age of superhero movies, or the golden age of gluten-free bread, or the golden age of having too many toothpaste varieties to choose from and

all of them do pretty much the exact same thing. But no, what I'm talking about is the golden age of tracking birds. 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 learners. This episode, which is number 82, is all about the ways that scientists track the movements of individual birds. You might recall that I already did a podcast episode on bird migration.

That was episode four. Check it out if you haven't already. The focus of today's episode is not so. much about the behaviors of birds, but about the technologies used by researchers to study bird behavior, the methods used to reveal the movements of birds. And our focus will be on the tracking of individual birds. There are other methods scientists used to record the mass movements of birds, like using radar to track flocks of migrants. But today we're looking at techniques that can reveal the unique paths taken by an individual bird. A sandpiper, a hawk, albatross, pheasant, penguin, or whoever.

Like, let's say I have a particular orange-crowned warbler in my backyard. I've named him Dr. Octopus. Or sometimes I call him Doc O'C. for short. You know, because he's an orange-crowned warbler, O.C. O.C. O.C. O.C. O. That's ridiculous, I know, but this is how my brain works. sorry. Anyway, me and Dr. Octopus, we had a fun summer together. He ate bugs and sang his little trilling song and raised a brood of chicks with his lady friend. Meanwhile, I enjoyed listening to his song while I sat in my lawn chair eating vegan hot dogs and chugging mountain dew.

But then, one day in August, Doc Ock was nowhere to be seen or heard. He was gone. Where did he go? I wonder what sort of habitats he uses when he's not in my yard. And does he miss me as much as I miss him? Would it kill him to send me a text message now and then? Did I get ghosted by a bird? For tracking very small birds like my little orange-crowned warbler friend, there are some amazing technologies that have been developed in the last decade or so. These take advantage of advances in things like satellite technology, hardware miniaturization, battery efficiency, solar power data storage, and so on.

The field of bird and wildlife tracking has been moving forward by leaps and bounds. The golden age of tracking birds is getting even more golden. Things are advancing so fast that maybe by the time I publish this podcast episode, a few days from now, most of what I say here will be embarrassingly out of date. Let's hope not. The first real scientific method invented for tracking individual birds was bird banding. Or what you would call bird ringing, if you live in the UK and some parts of Europe. In the late 1800s and early 1900s, ornithologists began to attach little aluminum bands to

the legs of birds. And well over 100 years later, this is still a popular and useful tracking method today. I won't go into a ton of detail on this method right now, because I plan to do an entire podcast episode on banding slash ringing in the future. But the basic idea is this. Each metal band, or these days, some are made of colored plastic, each band is imprinted with a unique number. So it acts like an ID card for the bird wearing it. When a banded bird is recaptured at a later date, and maybe at another location,

it's possible for researchers to get an idea of what that bird has been up to. And when this kind of recapture data is collected for a large enough set of individuals from a particular bird species, it can help us understand trends in the movement behavior of that species. Since 1960, over 77 million individual birds have been banded in North America alone. That's over a million birds a year, on average. Now, maybe you're thinking, ooh, I got to get in on that action. I'm going to go catch a bunch of cute little birds and slap some bands on their legs. I'll hold them and pet them and give them. And give them, them names? Believe me, I know that sounds like a fun time. I mean, I would love to put a band

on Dr. Octopus, the Orange Crown Warbler, the next time I see him, so I could keep tabs on him. But the federal governments of the U.S. and Canada regulate bird banding and other types of marking. Not just anyone can do it. Banding requires a special permit, likewise in the U.K. and probably many other countries. Such regulation is a good thing, for several reasons, not the least of which is that catching and handling birds is stressful on them.

In any case, of all the tracking methods we'll look at today, banding is probably the most basic and intuitive. You catch a bird, you put a band on it, you let it go, and then with any luck you recapture that same bird somewhere else, and now you have some data on the bird's movement. And if you're super extra lucky, you might recapture the same bird multiple times.

I should mention that when it comes to capturing and recapturing birds, one of the most common devices used in banding and other tracking studies is the mist net. This is a fairly large, finely woven net that's not easy for birds to see when it's set up in a forest or wherever. Birds will fly right into the mist net and get tangled up until a human comes along to free them. For some types of birds, and in some types of scientific or conservation projects, other kinds of ID tags might be used, in addition to or instead of leg bands.

California condors, for example, are marked with wing tags with ID numbers that human observers can read from a distance. If you're an oranthologist or conservation biologist who wants to start a bird tracking project, you'll have to consider the pros and cons of each method. A big pro for the banding method is that it's cheap. The bands or tags themselves don't cost much. But one con of this method is that it's labor intensive. For it to work, you have to recapture the banded birds, right? And when we talk about recapturing birds, well, earlier I said, with any luck you recapture your

banded bird. Recapture is not a matter of when, but if. The rate of recapture varies from species to species and from location to location. But in general, the chance of recapturing a banded bird is somewhere between 1% and 20%. Most of those 77 million, you know, birds that got bands on their legs in the last 60 years were never seen again after their initial capture. So it's a numbers game. You have to band lots and lots of birds if you have any hope of recapturing a few down the road. Despite the long odds, banding continues to be a valuable technique for studying bird movements, especially because it's so cheap. Sure, it's labor intensive, but I'm guessing that cheap labor isn't hard to come by for these projects.

Some people will work for free or for a pittance when they know they'll get to handle adorable birds as part of the deal. I should point out that every tracking method I'm talking about today requires birds to be captured at least once. So even when researchers are depending on more sophisticated tracking technologies, they often still put ID bands or tags on the birds they catch. Because why not, right? You've got the bird in hand. If the electronic gizmo you attach to the bird ends up failing or running out of battery juice, simple leg bands might still come in handy down the road. Leg bands don't run out of batteries. And speaking of batteries, the rest of the tracking methods I'll be describing today

rely on electronic devices that need a power source. These devices have batteries, or in some cases they run on solar power. First up, we have radio telemetry. This one has been around since about the 1960s. Radio telemetry was the first method that allowed researchers to track birds remotely, rather than having to recapture them to collect data. Tracking birds using radio telemetry requires a transmitter, an antenna, and a receiver. The transmitter is the radio tag attached to the bird, and it emits a signal.

The signal has a very high frequency, so this method is sometimes called VHF radio telemetry. A handheld directional antenna carried by a person picks up the radio signal and sends it to the receiver. The receiver is a little box that usually looks sort of like a walkie-talkie. The maximum distance for picking up signals from radio tags on birds varies, but it's usually less than a few kilometers. A scientist can use the strength of the radio signal to determine the bird's location using two methods. homing or triangulation. Homing involves walking or driving around with the antenna until the bird is located. The closer the antenna-wielding scientist gets to the bird,

the louder the beeps or pings that come from the receiver. Each tag emits a radio signal at a particular frequency. The person holding the antenna and the receiver system first has to tune in to the frequency of their bird of interest. Sort of like when I turn the dial of my car radio to my favorite radio station, KBRB, K-B-B-B-B-Burb. It's all birds, birds, 24-7. I especially like it when the talk show host interviews birds. So, Mr. Bluejay, what challenges have you faced in your career and how? How did you overcome them?

I see. That sounds like it was a very stressful experience. And are you and the cat still friends? Or did you go your separate ways after the incident? Actually, I just looked it up and KBRB, K-B-K-B-B-B-B-Burb, is a real radio station. It's in Ainsworth, Nebraska. Its programming includes shows like Morning Livestock and Hot Barn Report. But sadly, they've got nothing about birds, it seems.

That's a shame. Seems like a lost opportunity there with a name like K-berb. Okay, enough of that. So, in radio telemetry, there's homing, and then there's strangulation. I mean, triangulation. Not to be confused with strangulation. Triangulation requires the scientist to detect the direction of the signal from three different locations. With these three bearings, it's possible to sort of connect the dots to determine the bird's location on a map. Radio telemetry is considered one of the less expensive methods for tracking birds.

A single radio tag might cost $200 U.S. dollars. Yes, that's way more than the cost of those little metal or plastic leg bands, but it's significantly cheaper than some of the devices we'll talk about in a moment. Radio tags like this can also be very small. They have just a tiny bit of circuitry and a battery encapsulated in a plastic housing and a wire antenna that sticks out. The smallest of these devices weigh less than half a gram, and for comparison, a one inch by one inch Lego block

weighs about a half a gram. So does one raisin. The smallest tags like this are suitable for, attaching to medium-sized songbirds. Tags can be attached with glue, with a little backpack harness system, or as a sort of necklace. There are also radio tags in the form of leg bands, neck bands, and even some that are implanted under the skin. Tags, at least the ones on the outside of a bird's body, are often designed to biodegrade and

fall off after a while. ideally as soon as the research project is complete. Small tag size is important. There's a rule of thumb in bird tracking that says a tag or other such device should not weigh more than 3 to 5% of the bird's body weight. Anything heavier than that would be a burden on the bird, and could therefore change the bird's behavior or reduce its chances of survival. The average American weighs about 180 pounds.

Let's say I wanted to track the movements of an average American by gluing a radio tag to their back. If I stick to the 5% rule, the largest tag I could use would weigh about as much as a one-gallon jug of milk. Do you think that having a jug of milk glued to your back would have no effect on your behavior? It kind of seems like it would be a burden. I mean, just sitting down on the couch to watch Netflix would be awkward, not to mention trying to do yoga or play basketball. Small tag size is a good thing when tracking birds, in general. However, the smaller a radio tag is,

the weaker its signal and the shorter its battery life. So these are some of the trade-offs. The smallest tags might emit signals for only a few days or at most a couple weeks before their batteries give out. Most batteries last a few months or less, so this approach isn't great for long-term studies. Another challenge in using the radio telemetry method is that it's labor-intensive.

Running around with an antenna trying to get a fix on a bird day after day is a ton of work. I've never tracked a bird, but years ago I helped some biologist friends use radio telemetry to track black bears in one case and a green rat snake on another occasion. I can tell you it wasn't easy. Fun, for sure, but not easy.

These days, some researchers are using aerial drones to help get location data for birds with radio tags. A big enough drone can carry an antenna and record data or transmit data back to a receiver on the ground. This can save a lot of legwork, since a scientist can simply fly the drone around with a remote control, rather than having to walk or drive all over the place to locate a signal. A drone flying high above the ground might also be able to pick up radio signals from tagged birds over greater distances, compared to a person with an antenna standing on the ground.

Radio telemetry is limited to studies where scientists can get fairly close to their bird, subjects, because remember that the radio signals from the tags can only be detected within a distance of a few kilometers. I'll give you one example of a radio telemetry study, so you can get an idea of how labor-intensive tracking birds this way can be. A group of researchers in Greece conducted a study of gyps fulvas, the Eurasian griffon, also known as the Griffin Vulture. Their work was published in 2021 in the Journal of Zoology. The primary goal of the study was to figure out the spatial extent of home ranges in these vultures on the island of Crete. A home range is the area that an animal travels around in as it goes about its normal daily business, like

searching for food, searching for mates, and so on. This study ran for 10 years. In that time, data was collected from 27 tagged Eurasian griffins. Each bird was tracked, on average, for about 13 months. The researchers went out every 10 days or so and spent one to three days each time searching for vultures across rough terrain in the mountains. When a bird couldn't be located on foot, a pilot was paid to fly around in a small plane

with an antenna and a receiver to pick up the signal of the lost bird. The scientists in this study ended up spending a total of 1,615 days in the field, and they recorded 4,420 radio telemetry data points. That's an enormous amount of time and effort. But hey, guess what? It was worth it! Because the researchers achieved their goal.

They determined that the average home range size, for the vultures was 1,560 square kilometers plus or minus 140 square kilometers. This kind of information should be super helpful in any conservation efforts to protect griffin vultures on the island of Crete. So that was radio telemetry. Our next major tracking method is satellite telemetry. Satellite telemetry works by using orbiting satellites that communicate with transmitter tags attached to birds. In some cases, the satellites receive signals from the tags, and in other cases, it's the other way around.

The tag picks up signals sent by the satellites. There are two primary clusters of satellites used for this kind of research. GPS and Argos. We're all familiar with GPS, the global positioning system. These are the satellites that communicate with our phones, our cars, our airplanes, and so on. But you might not have heard of Argos. Argos is an acronym that stands for Advanced Research and Global Observation Satellite. The big advantage offered by both of these satellite telemetry systems is that they can

provide exact location data for birds. They automatically record where on earth a bird was at a specific time. In some cases, birds can be tracked in real time. A researcher looks on their computer and they can see where one of their tracked birds is at that very moment. GPS and Argos work differently to calculate the location of a tagged bird. With GPS, three or more satellites must send signals to the tag for an accurate location to be determined. The satellites use strangulation, I mean triangulation, geez, triangulation to calculate the location of the GPS tag. Argos tags, on the other hand, are sort of like radio tags

in that they emit a signal. The signal is received by a single Argos satellite. As the satellite drifts in orbit, it picks up multiple signals from the tag. This data is then processed to work out where the tagged bird is located. So other than the way they calculate location, what's the difference between GPS and Argos? Are there advantages to using one system over the other? Yes, indeed. There are some pros and cons for each system. The main pro for using GPS is that it's more accurate. Under the right conditions, the location of a bird can be pinpointed using GPS down to less than 30 meters. Argos is not as

reliable. Locations recorded by an Argos system can have an error of more than 250 meters. Another strike against Argos is that the satellites of this system are in orbit over the Earth's polar regions. So location data from Argos is more reliable at high latitudes, but might not be so great for tracking birds in equatorial regions. So does Argos suck? Why would anyone use it? Because the tags used by that system are lightweight. compared to most GPS tags.

An Argos tag can weigh as little as two grams. Relatively small birds can be tagged using the Argos system. All Argos tags transmit the data they collect, so fairly small birds can be tracked remotely this way. GPS tags that transmit remote data like this are heavier. The lightest of them still weighs about four grams. If you're following the 5% rule, that means the smallest bird you can track using GPS transmitters would be a bird that weighs no less than 80 grams, which is about 3 ounces.

So we're talking maybe a well-fed European starling, a Virginia rail, or a BlueJay, like that one that got interviewed on KBRB radio. But there are also GPS tags that don't transmit data. They just store their data on board. That means a researcher needs to recapture the bird wearing one of these tags in order to retrieve the data. And recapture is always a challenge. But the advantage of these archival tags, that's what they're called archival tags, is that they're the cheapest and lightest of all the GPS tags.

The smallest archival tags weigh only one gram. That's the same weight as a $1 bill or a paper card. clip. And as technology advances, it's likely that satellite tags, of all kinds, will get smaller and lighter. And hopefully cheaper. Because, yeah, right now these things ain't cheap. A typical satellite tag costs thousands of dollars. That's right, one tag costs thousands of dollars. So a scientist has to scrounge up some serious cash if they want to conduct a study on bird movement that uses satellite telemetry. So you can imagine the shock and frustration of some researchers in 2019

who witnessed a group of Australian magpies figure out how to remove their GPS tags. The goal of the study had been to understand the bird's movements and their social dynamics. If you don't know what an Australian magpie looks like, it's sort of like a crow with a black and white paint job and a dusty blue bill. But this bird is not closely related to crows or ravens. It's not in the family Corvody. It's in an entirely different family, Artamadee. Anyway, the researchers caught

five magpies and attached fancy new GPS trackers to them with tiny harnesses. But just a few hours after the birds were fitted with their trackers, almost all of them had helped each other remove the devices. Australian magpies are known to be super smart, but this was actually an unexpected and amazing discovery. The magpies were being altruistic. They cooperated and used problem-solving to break free of their GPS backpacks. This is one of the few documented cases of rescue behavior among birds. Yeah, so those scientists had spent a ton of money buying GPS tags,

only to have the cheeky magpies yank them off pretty much immediately. Unfortunately, the researchers couldn't carry out their study as originally planned. The magpies weren't having it. But the researchers were able to make lemonade out of lemons, I guess, because they went ahead and published a paper about the remarkable behavior they had witnessed in their magpies. So, with satellite telemetry, there are these two systems, GPS and Argos. But there's actually a new system being developed.

It's called the Icarus Initiative, I-C-A-R-U-S, which stands for international cooperation for animal research using space. Also, like Icarus, the young man from Greek mythology, who, like a dumb-dum, ignored the warnings of his father and flew too close to the sun using his artificial wings. The Icarus satellite system is the first one specifically built for tracking animals. This system was originally installed on the International Space Station. It was a joint effort between German and Russian scientists. But, unfortunately, Icarus got the plug pulled in March of 2022. Can you think of why that happened at that time?

Well, in February of 2022, there was this thing called the Russian invasion of Ukraine. No more cooperation with the Russians after that. But the good news is that the Icarus Initiative has continued moving forward even without the support from Russia. The receiving antenna is now installed on a tiny low-orbit satellite called a cube set. It's a 10-centimeter cube, about the width of an average human hand, and a couple more Icarus cube-sats are supposed to be launched in the next few years.

This satellite telemetry system seems to have a lot of promise for studying birds. But even the smallest, lightest GPS, Argos, or Icarus tags today are still too big to use with small passerine birds. And that's kind of a problem, because most of the bird species on Earth are small passerines. So how about we move on now to talk about some tracking methods that can be used for itsy-bitsy birds, like small songbirds and even hummingbirds. Today, here where I live, the sun rose at 6.42 a.m. and it will set at 7.31 p.m. The date is September 10th. With that information alone, and with some fancy computer calculations,

you should be able to figure out my approximate geographic location. Yes, I know I already told you I live in Portland, Oregon, but let's pretend I hadn't. You could use the combination of day length and the date to determine where I am. because the time of sunrise and sunset on a given day of the year varies from location to location in a predictable pattern. That's why we can get an accurate answer when we ask Google something like, Hey Google, what time will the sun rise on July 17, 2024 in Istanbul, Turkey?

In Istanbul on July 17, 2024, the sun will rise at 547 a.m. So the duration of daylight on a given date provides us with an important clue about geographic location. And this brings us to the tracking method called light-level geolocation. The tags used in this method rely on a different kind of technology, not radio signals or satellites. The tag, in this case, called a light-level geolocator, has a tiny light sensor and an internal clock. While attached to a bird, the geolocator records how much daylight hits the sensor over the course of time. This data is then stored on board. Once downloaded and processed, the data gives researchers the latitude and longitude of where their tagged bird was located on each day that data was collected.

That's pretty clever, isn't it? The main advantage of using the light-level geolocation method to track birds is that the tags, the geolocators, can be very light weight. We're talking 0.3 to 0.5 grams. This is in the range that's okay to use for small songbirds, like warblers, finches, and sparrows. The reason these devices can be so tiny is that the circuitry involved in recording light levels

doesn't need much electricity. So geolocators have super small batteries and they can keep working for a long time. They can record data for months or even years in some cases. The light-level geolocator opened up many new opportunities for scientists to study the long-distance movements

of small birds. These geolocators are also fairly inexpensive. Each of them costs less than $200 U.S. dollars. But there have to be some downsides, right? And yes, there are. Just like with banding and archival satellite tags, birds wearing light-level geolocators have to be recaptured. The data stored on the geolocator is useless until it gets manually downloaded.

Another major con for light-level geolocators is that the location data they provide isn't all that actually. accurate. These devices provide more of a ballpark estimate of where the bird was before being recaptured. In other words, this method is nowhere near as accurate as GPS data or even Argus data. But wait, there's more. More potential disadvantages, that is. What if the light level geolocator gets covered up? Like, what if the bird is sitting in the shade, even on a bright sunny day? Yeah, this can be a problem. The data can get messed up when a bird with a geolocator hangs out during the day in the deep shade of a forest, for example. Or when it loiteres around in a dingy dive bar at two in the

afternoon, drinking cheap beer and telling war stories to anyone who'll listen. Did you know that one time there was a snake? A huge snake was trying to eat the eggs in my nest. I was like, oh no, you don't. Don't do it, Snake. I went over there and I pecked that thing so hard, I pecked it real good in the face. The snake, it still ate, it ate all my eggs, but I sure made it think twice before it did.

Stupid snake. Also, is there an Australian magpie in here? I need someone to help me get this backpack off. It feels like I'm dragging a milk jug around or something. Despite its shortcomings, light-level geolocation has still been a useful tool for scientists to get a better sense of where birds go over the course of months or years. As one example, a study on Kurtland's Warbler that used this method was published in 2017

in the Journal of Avian Biology. Kurtland's Warbler, Setaferga Kurtlandii, is an endangered species in North America. I've talked about it before on the podcast. Well, in this 2017 study, the researchers wanted to better understand the full annual cycle of Kurtland's warbler. Plenty of data already existed for where the species breeds in the Great Lakes region. But these researchers wanted to learn more about where the warblers go in the non-breeding season. The scientists attached light-level geolocators to 84 adult male kirtland's warblers over two breeding seasons. The devices each weighed a bit more than half a gram.

That's about as much as a raisin, remember? After a couple years, the researchers were able to get usable data out of 27 geolocators from the birds they recaptured. The data revealed that all of these male Kirtland's warbler, went to the Caribbean for the winter. They spent about six months down there. About two-thirds of them ended up hanging out in the central Bahamas. Now, prior to this 2017 study, it was already known that this species winters in the Caribbean. So that wasn't a new discovery, but this tracking data provided more detail on the birds' movements over the course of a year. It showed that the birds make a big loop during their full annual cycle. In the fall, their migration route

south was more to the east, but in the spring their route was in the west. The researchers were also able to locate where the warblers made major stopovers during migration to rest and refuel. So this study is an example of how light-level geolocation can help scientists track the full annual cycle of a small passerine bird. This is especially important information to have when you're dealing with an endangered species like Kurtland's warbler. Before light-level geolocation technology was developed, it would have been pretty much impossible to get

this kind of movement data for such a small bird. We have one more tracking method to talk about today. This one is the newest and, in my opinion, one of the most exciting. It's called the modus wildlife tracking system. Modus, M-O-T-U-S, is the Latin word for movement. This system got up and running a little over 10 years ago. It uses the age-old technology of radio telemetry. Boring! No, wait, wait, it's way cooler than you think. because there's a twist. The twist is that this is an automated system.

Birds wearing radio tags are detected automatically by modus stations. A station is basically an antenna connected to a computer that records data. The whole contraption needs a power source, and it either stands alone on its own tower or it's attached to a previously existing tall structure like a cell phone tower or building. The current cost to set up a station is between $3,000 and $10,000 U.S. dollars. Annual maintenance of a station varies widely from only $100 up to $5,000.

Today, there are over 1,800 modus stations scattered across 34 countries. Most of them are in North, Central, and South America, as well as Europe and Australia. The array of modus stations is most dense in the eastern part of North America, because that's where the project got started. But hopefully, the network of stations will continue to expand rapidly in the coming years. The more of these modus stations there are out there, the more powerful this system becomes for tracking birds and other critters. Any bird with a modus tag can be detected by any modus station.

Each tag emits a unique ID number. Tags can be detected up to 12 miles away, which is 19 kilometers. With this automated approach, it's no longer necessary for scientists to run around through the woods or the swamp or wherever waving their handheld antennas, desperately hoping to detect some faint pings from their radio-tagged birds. Unlike that traditional version of radio telemetry, the modus system requires a lot less labor-intensive fieldwork. And birds traveling long distances can be detected automatically by multiple stations along their route. That sort of data would be nearly

impossible to get using the traditional approach. Modus is also highly collaborative. All the tracking data feeds into a centralized database and is available to any scientist. In fact, the data is available to anyone, you, me, your grandma, even that 11-year-old bully that terrorizes young kids in your neighborhood. He, too, can access all the bird tracking data on the modus website. The website and database are managed by the nonprofit organization, Birds Canada. Another beautiful thing is that modus tags are super lightweight. After all, they're just radio tags. Some are as light as 0.2 grams. They're great for slapping onto birds as small as kinglets, hummingbirds, you name it.

These tags are so small, they can even be safely attached to some butterflies, dragonflies, and bees. To date, at least 300 bird species have been tracked using the Modus system. Just to name a few recent examples from the Western Hemisphere, modus was used to study the annual cycle of the rusty blackbird, the nomadic wanderings of snow buntings in winter, the use of a key migration stopover site by gray-cheeked thrushes, and the migratory behavior of semi-palmated sandpipers. A study conducted in Western Europe involved not one but ten songbird species.

These included birds like Eurasian black cap, Greater White Throat, Dunnock, European Robin, and Garden Warbler. Modus location data were collected for an impressive 259 tagged birds on their autumn migrations along the edge of the North Sea. The goal of the study was to look at which species tended to fly offshore, over water during their southbound journeys. Anyway, I could go on and on with more examples, but I think you get the idea. As I said, anyone can access modus data. So if I go to modus.org and explore the data, I see that the nearest modus station to me is the one installed at the Ankeny Hill Nature Center.

That's about 60 miles south of here in the central Willamette Valley. The station was erected about a year ago. Looking at the website, I can see that the Ankeny Hill station has already detected six individual birds from three species, American Robin, Swainson's Thrush, and Dunlin. I can see the path of each individual bird as it was detected at other stations in the Modus network. This is super cool, you guys. I encourage you to go to modus.org and poke around. It's amazing that this kind of data is freely accessible. We should all feel lucky to live in this golden age of bird tracking.

Scientists who want to study bird movements have this wonderful assortment of methods at their disposal. To quickly review, we have banding slash ringing, which is cheap but labor-intensive and requires recapture. Radio telemetry is also labor-intensive in a different way, and it's still semi-cheap. It allows data to be collected remotely over short distances. Satellite telemetry comes in several flavors. In general, this approach provides much more detail on the movements of birds all across the planet. But it's expensive and in some cases requires recapture. Light-level geolocation is relatively cheap and allows small passerine birds to be tracked over large distances.

But it's not very accurate, and yes, it requires recapture. And finally, there's the modus system, which allows birds of any size to be tracked automatically over potentially vast distances. It's fairly cheap and not very labor intensive. For now, the main limitation of this approach is that the network of modus stations is still unevenly distributed across the globe. but hopefully that will improve in the near future. A scientist starting a new bird tracking project has to consider the trade-offs among these methods, the cost, the labor, geographic range, weight limitations, and other factors.

As I said, maybe this episode will soon be out of date because some of these technologies are moving fast and who knows what new technologies and methods are on the horizon. For example, people are working on integrating bird and wildlife tracking with the 5G cell phone network. Unlike modus stations, cell phone towers are already distributed all over the planet. So it seems like there's a lot of potential there. I mean, the federal government is already using 5G towers to track its human citizens, right? Following our every move and controlling our minds with energy beams?

So why not use the towers to track birds, too? Future technology may also allow tags on birds to interact with each other. Like maybe a tag could record data on which other tagged birds are nearby. That would be amazing. We could learn a lot about the social behaviors of birds and about the interactions between different species and so on. And the tags of the future might be able to collect a wider range of data, from birds. Not just their location, but also things like body temperature, heart rate,

oxygen levels, stress levels, vocalizations, and who knows what else. Tiny cameras could even be attached to birds. I know most of this is already possible using heavy sensors attached to beefy birds like eagles, cranes, and geese. But with the ever-increasing miniaturization of our gadgetry, I'm imagining this becoming possible for little birds like warblers, finches, nut hatches, and hummingbirds. I'm excited to see how all this incredible technology will help us discover new things about birds in the years to come. I hope you are excited too. And that, my friends, is a wrap on episode. 82. I suspect a fair number of you listening right now are researchers who have actually used

one or more of these tracking methods on birds. I hope you feel I explained them correctly and did them justice. In any case, I learned a lot as I researched this episode and I just think this stuff is so cool. Thank you as always to my lovely supporters on Patreon. You are to me as a battery is to a GPS tag. You keep me going. And welcome to my newest patrons. Rob Palin, Christy Richter Duff, Danny Jawa, Christina Miley, Ross Conover, Michael Stover, and Sam Silver-Jerlinga. Thank you all so much for joining my community and helping me make this podcast possible. If you are not yet a patron of the Science of Birds, but you're interested in your interest, in lending some support, you can check out my Patreon page over 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, a comment, an anecdote that involves a bird, a conspiracy theory that involves the 5G cell phone network, or the silly name you came up with for your BFF backyard bird. In any case, my email address is Ivan at scienceofbirds.com. You can find the show notes for this episode, which is number 82, on the Science of Birds website, scienceofbirds.com. I'm Ivan Philipson, and I hope you're having an excellent day. Peace.