Tiny Trackers Are Revealing the Secret Lives of Tens of Thousands of Birds

Well before ornithologist Lucas Berrigan embraced technology to find out where birds travel around the world, he started bird-watching around his home. At around 10 years old, anytime he heard a new call in Nova Scotia, he’d search out the bird. At 14, he went to a remote station on Bon Portage Island, just off the southwest coast of Nova Scotia, to learn how to band birds. At 15, he was hired for a seasonal job on the island conducting a bird census route each morning and banding the animals. For college, he stayed close to home and attended Acadia University, where he majored in biology. He remained there for a master’s in 2016 and studied the behavior of Swainson’s thrushes, using a wildlife tracking system called Motus, which launched in 2014. He found that the birds often made short flights close to sunset, possibly to calibrate their celestial compass, and credits that discovery to Motus.

Motus, which is Latin for movement or motion, is an international network that uses automated radio telemetry to track small flying animals. The system, which is run by Birds Canada, is made up of three components: tags, receiving stations and a centralized database that can be accessed online.

Field researchers put tiny solar- or battery-powered radio transmitters on birds, bats and even flying insects like dragonflies and butterflies. The tags weigh as little as 1/200th of an ounce, and they are only put on if they weigh less than 3 percent of any animal’s body weight—so they don’t cause harm. Each tag costs about $250, so they are much less expensive than satellite tags, which Berrigan says often cost somewhere between $2,000 and $10,000. Those more expensive tags have the benefit of being able to load their information to satellites over a broad geographic area—while radio tags need nearby receiver stations with antennas to upload data. But compared to heavier satellite tags, the radio tags can go on smaller animals. Since 2014, researchers working with Motus have tagged almost 50,000 animals of nearly 400 species. When one of those animals flies by a receiver station that has an antenna, that individual’s location is recorded.

Motus has put up more than 2,000 receivers in 34 countries around the globe. The receivers cost between $3,000 and $15,000, according to Berrigan, and can detect animals up to nine miles away, though the range depends on terrain—as features like mountains can get in the way. The receivers either store the recorded data on a device, or, if they have Wi-Fi or cell service, upload the data to servers where it gets processed.

Anyone can access that data on the system’s dashboard. The public can see when any individual bird passes by a certain research station on a given day, or the route that it flies over time between receiver stations. Researchers can access more granular-level data, which they can use to write scientific papers on animal migration. So far, Motus has been incorporated into more than 200 studies. Researchers have used it to discover, for example, that only about 40 percent of fledgling barn swallows in southern Ontario survive to migrate. And Smithsonian researchers used Motus to reveal that some Kirtland’s warblers in Michigan made previously unknown long-distance flights during mating season. As the wildlife tracking system expands, it is changing what can be discovered about birds, bats and insects—all while connecting researchers and building community. “Motus is basically a platform for not only science and technology, but it’s an outreach program as well,” says Berrigan. “The main goal is to be a global research network to deliver critical information to help conserve small flying animals.”

Berrigan, who joined Birds Canada in 2018 after he completed his master’s degree, is now the Atlantic regional program coordinator and technology specialist for Motus. He works with researchers and developers, and helps guide the direction the program takes with technology. We called him up to find out more about the growing wildlife tracking system and what is next for it.

Can you tell me about some of the coolest finds from Motus?

I like looking at individual tracks that are nice and complete, because, oftentimes, you’ll only get a few detections for a single animal. In looking at roost networks of bank swallows in Ontario you can identify that, “Oh, some bank swallows at night are actually going to different roosts from where their babies are,” and the adults will often trade off. We don’t know why, but they will sort of wander around and travel a hundred or more kilometers to a different place between nights.

It’s some weird stuff that we’re seeing. We call it the new frontier of research almost, because we’ve never been able to look at movement of these animals individually before. We’re just seeing these behaviors that it never was possible to look at.

And then round-trip migrations I find the most interesting to see. Like nighthawks that traveled down to Central America and back.

There’s also a publication at Smithsonian which summarized a paper that I was on, looking at the departure timing of animals about to start migration. It showed that most birds, of the many different species that we looked at, are starting within this roughly one-hour window after sunset. It falls in line with a lot of theory around this subject, because we think that birds are calibrating their compass around that time, looking at the polarized light of sunset, for instance. With Motus data, it’s really easy to tell when a bird is making a flight, because the signal strength from a tag all of a sudden increases [when the bird is flying].

Why is Motus important?

We know a lot about bird breeding sites. We know a lot about bird wintering grounds. But we don’t know a lot about migration, what birds are doing during that final frontier of their life cycle. Research shows that there’s an almost 15 times higher chance of mortality during the migratory period. [Editor’s note: And this 2024 study shows it may be as high as 20 times greater in some species.]

We’re at this critical stage where we’ve lost a third of the birds in North America over the past 50 years. Climate change is only accelerating at this point, and habitat loss is increasing at the same time. We need to start yesterday, really, to understand how migration is being affected. And before we can say how climate change is impacting birds, we need to know the baseline of how birds behave to begin with.

Motus helps do that by allowing us to study these small animals. It’s the only real tool that lets us do that on large scale and with so many different species.

You mentioned that big stat on bird declines, that North America has lost a third of its population since the ’70s. Can Motus help stem this decline in any way?

Yeah, so the question would be: How can Motus be used as a conservation tool? We need to figure out what are causing these declines now. We have a pretty good sense of a number of things, like human habitation encroaching on important habitats, insects declining and also climate change making migration a little more dangerous. But we still don’t really know well where those critical points are within migration that are the most impactful.

We have theories on it, but we don’t have evidence really yet. That’s where Motus helps a lot.

One thing that I was working with in my master’s, and others have as well with different species, is looking at decision-making when birds meet migratory barriers. Migratory barriers occur when birds have to cross an ocean, or a bay, or something like that. If you look at when birds hit the southern end of Nova Scotia, they have a choice. They can either fly across the Gulf of Maine to go farther south or fly up north a couple hundred kilometers and cross a land-based route or a much shorter ocean crossing. We don’t really know which individuals are doing one route or the other. We suspect young birds are more likely to take a safer route because they’re less experienced, but we’re not really sure.

The other part, too, is: How do birds behave around urban environments? Do they avoid these environments or are they attracted by them? There’s some evidence that they are attracted by them, based on radar studies, but radar doesn’t allow you to track individual animals.

Then finally, another important application that Motus has been used for is looking at what are the important stopover sites for animals. These are spots during migration where animals spend their most time, not necessarily flying, but resting, or feeding and seeking shelter. For shorebirds, this has been a big focus, looking at those foraging habitats—coastal regions that are most important to them. And we’re just starting to look at stopover decisions songbirds make as well. Songbirds probably stopover in a much broader area, because their habitat is more widely distributed, so it’s much more difficult to identify those areas that are most important to them.

Again, we could use Motus to see where birds tend to concentrate most of their time or slow down the most during that migratory pathway. When you have 50,000 animals tagged, that gives you a lot of data to work with.

What about, along those same lines, real-time conservation decisions? Could Motus, for example, help with letting buildings know in big cities when they should turn off their lights at night so they don’t confuse migrating birds?

We’re not there yet. That is certainly an idea that has been tossed around. It’s similar to the idea of shutting off wind turbines when there’s a big movement of animals. If something like that was ever to come into effect, it would really work best in combination with other technologies like satellite tracking of individuals, using radar, or using acoustic recording units that track or that detect nocturnal flight calls.

I think right now, radar is the primary use case for those sorts of things, but there’s still a lot of improvement to be made to all these technologies. The main difficulty is combining models. That’s what’s taking a lot of time, but it is in the works. We’ll hopefully have something like that someday.

You have 2,000 receiver stations in 34 countries with more than 2,400 collaborators now. What are your ultimate goals for the network in terms of numbers, maybe even by 2030?

We are expecting something like a doubling of that number by 2030. A lot of what we need is to figure out how to fill in those major gaps within the network. At this point, we’ve got a lot of the easy spots, where we have people who are ready and willing to provide the work and the money needed to put in stations.

Now, we’re focusing more on the areas where it’s more difficult to do that. That’s in Canada’s north, in the mountain ranges—the Rockies and Andes, and a lot of Latin America. There are other regions that we’re not focusing on as much, but we have collaborators in Europe and in Australia. We support them where there’s a need, but generally, our ambitions mainly lie in the Americas.

The Motus Wildlife Tracking System

Do you have a next big step that you’re looking to do with Motus?

We want to have a research tool for offshore wind monitoring. It’s not well understood how birds interact with offshore wind turbines. This is mainly being done to create collision risk models for at-risk species, to assess where and when those species are most vulnerable. Think piping plover, roseate tern, rufa red knot.

There has been some work done on that already, and we’re going further with that. We’re working with technology partners and the U.S. government to help make it an easier tool to work with for industry.

And we’re really excited for our expansion up in Canada. We’re putting up 300 stations in the next five years within Canada, which is a huge undertaking. Working with Indigenous groups in northern Canada has been a focus of mine the past couple of years, to help build the capacity within the communities to be able to monitor animals within their region. We’re giving them some training tools for how to deploy tags as well.

What advice would you give to folks who want to be involved with Motus in some way?

We often get requests from folks asking this sort of thing. There’s definitely a few ways they can get involved, and it depends ultimately on where their skills are, where their time is, what they have to offer.

For one, knowing where we can put stations is always helpful. We might not put a station on your property, for instance, or where you tell us, but we want to know as many places as possible, so we have a lot to work with.

If you want to get involved with research in some way, we have all the Motus networks split up into coordination regions, and people can get in touch with the local coordinator. That’s at motus.org/collaborative.

Then there’s donating. Housing a station costs money. If you want to host a station somewhere in your region, you can contact the local collaborator and offer a donation, or just donate directly to Birds Canada, and we’ll gladly use those funds for putting up a station or putting on more tags.

Motus is a really valuable tool for schools, museums and zoos to get a sense of what’s passing over their communities. We’ve worked with several different institutions to help put stations on their buildings for that reason. And we have events to talk with community members about where their interests lie in terms of birds, so that we make sure that we put out transmitters on animals that matter to them. And anybody can see what animals are flying through on our website.

There’s also an education platform that we put together a few years ago with a few exercises for teachers to use, a bunch of teacher materials. That can be found on motus.org/education. It walks through different things about how Motus works and how you can use it for conservation.