How do you solve a problem like migration?

This post was initially published on the Science Borealis blog on April 27th, 2020. Check out their blog for more great science stories, published every Monday!

An ornithological pedicure: taking a claw clipping from a western bluebird for stable isotope analysis. Photo credit: Catherine Dale.

I can feel the rapid thrumming of the bluebird’s heart against my palm as I carefully manoeuvre its foot into position over a tiny Ziploc bag. I pick up my nail scissors and take a deep breath to steady my hand. I will only get one chance to make sure the miniscule claw clipping lands in the bag. If it doesn’t, I will have no chance of finding it…and no way to discover where this bird spent the winter.

Field biology often requires unusual skills. I have spent the last decade becoming an experienced bird pedicurist, because analyzing the chemical composition of tissues like claws and feathers is one method scientists use to determine the movements of migratory animals.

Unfortunately, this method suffers from the same drawback as many others: a lack of precision. As a result, many aspects of bird migration remain a mystery. But this spring, researchers at the Max Planck Institute of Animal Behaviour in Germany are entering the final testing phase of a new space-based tracking system, which they hope will revolutionize our understanding of animal movement.

The puzzle of migration

For Canadians across the country, the return of our migratory birds marks the beginning of spring. Each year, 2.6 billion birds cross the Canada-U.S. border, heading north to their breeding grounds.

Two thousand years ago, Aristotle believed the spring reappearance of barn swallows meant they were emerging from their winter hibernation at the bottom of ponds. Although we now understand more about animal migration, many questions remain – largely because it’s very difficult to track individual animals as they travel vast distances around the globe.

For many years, the only approach was to mark animals with bands or tags in the hopes of re-sighting them somewhere else. But the sheer number of animals that migrate makes seeing a marked individual again extremely unlikely.

A flock of shorebirds takes to the air at Oak/Plum Lake Important Bird Area, a migration stopover site in Manitoba. The mixed-species flock includes Wilson’s phalaropes, red-necked phalaropes, stilt sandpipers, pectoral sandpipers, dunlin, white-rumped sandpipers, and semipalmated sandpipers. Photo credit: Christian Artuso.

Putting the pieces together

In the 1990s, migration research took a leap forward when scientists realized the chemical composition of animal tissue reflected the place where it was grown. By analyzing the ratio of various isotopes in tissue (termed stable isotope analysis), researchers can roughly reconstruct an animal’s geographic history…which is why I found myself giving bluebird pedicures.

Scientists can also now track moving animals directly by fitting them with tags that record location. These tags can be divided into two broad categories. Archival tags, such as geolocators, record and store movement information. In order to find out where a tagged animal has been, researchers must recapture it and retrieve the tag.

Recapturing migratory animals often proves difficult, especially as many fail to return from migration. So when possible, researchers prefer to use tags that remotely transmit data to a receiver, eliminating the need to recover them.

But transmitting tags face a fundamental constraint: transmitting takes power, and the more power a tag requires, the larger it needs to be. Tags must weigh less than 5% of an animal’s body weight to avoid affecting its behaviour or survival. Considering that many migratory birds weigh less than 10 grams, making tags small enough for them to carry is a huge challenge.

A sanderling carrying a Motus nanotag. The tag’s long antenna is easily visible. Photo credit: Jessica Howell.

The amount of power required to transmit data depends largely on where the receivers are. Tags for ground-based tracking systems – with receivers located on the Earth’s surface – can be very small. For example, the nanotags used by the Motus Wildlife Tracking System range from 0.2 to 2.6 grams, and can even be carried by some large insects. However, the range over which ground-based systems can track individuals is limited. Animals carrying Motus tags can only be detected within approximately 15 km of a receiver.

In contrast, satellite tags send data to receivers on orbiting satellites. They can track movement at a much larger scale than ground-based systems, and have been used for years on big animals, such as seabirds and caribou. But most satellite tags are too heavy for small migratory birds.

The Icarus Initiative

In 2007, Martin Wikelski, the Director of the Max Planck Institute of Animal Behaviour in Germany, proposed a novel space-based system for tracking animals across the globe.

It took more than 10 years, and the cooperation of the Russian Space Agency (Roskosmos) and the German Aerospace Centre (DLR), for the system to become a reality. In March 2020, the International Cooperation for Animal Research Using Space (Icarus) entered its final testing phase. The first Icarus tags are waiting to be shipped to researchers, and the system will be available to the scientific community this fall.

“We wanted to build [a tracking system] specifically for wildlife,” Wikelski says of Icarus. “It’s built by the community, for the community.”

The International Space Station, pictured here in 2009 after a visit by the space shuttle Discovery to add additional solar panels. Photo credit: STS-119 Shuttle Crew and NASA.

Icarus tackles the trade-off between tag size and transmission distance in part by the simple expedient of moving the receiver closer. Conventional satellite tags transmit their data to Argos satellites, which orbit the poles at an altitude of 850 km. Icarus tags will transmit their data to a receiver on the International Space Station (ISS), orbiting at an average altitude of 400 km.

Data collected by Icarus will be stored in Movebank, a free online database accessible by the public.  The system will also incorporate a citizen science initiative: Animal Tracker. While Icarus tags tell scientists where an animal is, citizen scientists can provide information about what it’s doing there. Using the Animal Tracker app, people can follow tagged animals online, and anyone who spots those animals in the wild can submit their observations to the database.

Of course, like any tracking system, Icarus will have some limitations, at least initially. The first tags will weigh five grams, which – while smaller than many satellite tags – is still too heavy for most migratory birds. However, the design of a new generation of tags weighing only one gram is already underway.

Satellite coverage will also be an issue. The receiver on the ISS will be able to pick up signals from most of the Earth’s surface; however, high latitude regions in the north and south will not be covered. Eventually, Wikelski’s goal is to deploy dedicated Icarus satellites strategically to cover the entire globe.

But even with these limitations, scientists are eager to begin harnessing the power of Icarus to tackle some of the unsolved mysteries of migration. Dr. Kevin Fraser, an Assistant Professor in the Department of Biological Sciences at the University of Manitoba, is keenly awaiting his first shipment of tags. He and his graduate students plan to put them on saw-whet owls – and they are most interested in the birds that don’t come back in the spring.

Banding a saw-whet owl. Kevin Fraser’s lab hopes to use Icarus tags to track these small owls during migration. Photo credit: Kevin Fraser.

Fraser’s previous research has largely depended on archival tags, meaning tagged birds must be recaptured to determine where they went. Individuals that don’t return to the study sites to breed – those that die along the way, or the young birds that disperse to breed elsewhere – are lost data.

“Most of what we know about migration, we know from birds that have successfully migrated,” Fraser says. “We know much less about where survival might be limited, or what the juveniles are doing. But [with Icarus], for the first time, we will be able to track 100 gram birds (the smallest yet) in near real-time, without the bias of only focusing on survivors and adults.”

Solving the puzzle

With the sliver of claw safely stowed in a bag for later analysis, I’m ready to liberate my captive bluebird. I position its feet over my empty hand and release my hold. For a moment, it perches on my palm, apparently unaware of its freedom…then, in a flutter of wings, it’s gone.

Of the 450 bird species found in Canada, 78% spend at least part of the year outside our borders. This fall, four billion birds will cross our southern border to spend the winter in warmer climes. More than a billion of them will not return, succumbing to the dangers of the journey or the hazards of their wintering grounds.

Icarus offers us a unique window into the world of migratory birds, and a chance to improve their odds. If we know where they go and how they get there, we can begin to understand the perils they face – and perhaps develop solutions.

Technology in Fieldwork: Friend or Foe?

When I started doing fieldwork about 12 years ago, I didn’t use technology in the field. In fact, the only technology I had access to was an old flip phone that took photos so blurry I could barely tell if they were of plants or animals when I got back to the lab. I didn’t even pre-print my Excel data sheets and fill them in as I collected data. I just drew freehand columns in a Rite-in-the-Rain notebook and then spent hours afterwards trying to decipher my messy handwriting.

But over the last decade, technology has really boomed and it has changed the lives of field biologists everywhere. Take GPS, for instance. While hand-held GPS devices were certainly around 10 years ago, they tended to be clunky and slow, with limited functions – nowhere near as streamlined as current technology. In fact, they were often more trouble than they were worth. When I used to monitor roadside populations of wildflowers throughout the summer, I would simply remember where locations were based on landmarks, nearby street addresses, etc.

But now, I do my fieldwork using Collector, an mobile data collection app which allows me to take points instantly from my smartphone. If I were monitoring roadside wildflower populations now, I could just drop a point for a population, take a photo and attach it to the point and then navigate directly back to the point on follow up visits.
While GPS advances are very cool, the advent of iNaturalist is likely responsible for the greatest change to my life as a field biologist. According to their website, iNaturalist “is a lot of different things, but at its core, [it’s] an online social network of people sharing biodiversity information to help each other learn about nature. It’s also a crowdsourced species identification system and an organism occurrence recording tool. You can use it to record your own observations, get help with identifications, collaborate with others to collect this kind of information for a common purpose, or access the observational data collected by iNaturalist users” iNaturalist.

That explanation is much more eloquent than my description of iNaturalist, which can be summed up as, “a crazy-cool identification app that must be magic!”
When I was learning how to identify plants during my Undergraduate degree, I didn’t have access to anything like iNaturalist. To figure out what something was, I would excitedly bust out my plant bible, Newcomb’s Guide to Wildflowers, and open the book to the first page. Then I would carefully examine the features of the plant I was trying to ID. I would check if the leaves were alternate or opposite, determine whether the leaf edges were serrated, and then classify the radial symmetry of the flower. This information would lead me to a page number; with great anticipation I would flip to that page and quickly scan the images and descriptions. Inevitably, one of two reactions would follow: heart-beating excitement when my eyes stopped at a sketch that looked just like the flower in front of me…or sheer disappointment when nothing matched. In the second case, the next step was to flip back to the first page and take another look at the plant in front of me to try to figure out where I went wrong. Perhaps I miscounted the petals, or maybe the leaves were whorled, rather than opposite? It sometimes took a whole lot of trial and error, but eventually I almost always arrived at the right answer. And it was those mistakes that really made me remember the identity of the plant long after.

It is with some hesitation that I admit this, but I mostly use iNaturalist to identify things now. I just snap a photo of something in nature – be it a plant, an animal or a fungus – and iNaturalist gives me its best guess at the identity. It only takes a couple of seconds and it’s incredibly accurate. (Hence, magic app!) iNaturalist is such an exciting concept. In fact, I recently was part of a class visit at a Nature Reserve which involved a scavenger hunt as part of the tour. One of the species the students needed to find was Sensitive Fern, but this species is only really found in one small area, so it was easily missed by the students. To help them out, I pulled out my phone. I pointed to a specimen on the ground beside me and took a photo. Below is what iNaturalist came up with:

We proceeded to try the app on about a dozen more species of plants (even just the bark of trees!) and it was bang on every time. The entire grade 7 class was hooked on the app after that.

I love iNaturalist and all that it stands for. It intrigues people, it helps them learn about nature, and it fosters a curiosity about the natural world around us. It even helps collect important data about rare species and Species-at-Risk that monitoring biologists may miss. However, even though iNaturalist is useful in so many ways, it left me feeling very conflicted.

I can’t deny that iNaturalist has also made me a less engaged (or maybe a lazier) field biologist. To be clear, I don’t mean I am worse at my job now, by any means. In fact, I am probably more efficient. That being said, I don’t notice the things I used to notice about plants. I snap a photo and the answer is right in front of my eyes. I don’t spend 5 minutes flipping through the pages of field guides attempting to identify an unknown specimen. Moreover, when I do use iNaturalist, I often quickly forget the identity of the species – because I haven’t spent those long minutes working for my answer.
So, as I wind down this field season and think forward, I vow to reach for the book and not the phone next spring when I spot a new species or can’t recall what something is.

That being said, I think there is certainly a place for both technology and more traditional approaches as well. For those getting started, or in time sensitive situations, perhaps iNaturalist is the way to go. But maybe for those looking to thoroughly and deeply understand nature, the old school approach may be more suitable. Either way, I will continue to promote iNaturalist like the “crazy-cool magical app” it is, in hopes that more folks learn about, and begin to care about the natural world around us.

Do you use technology to do your fieldwork? Has the role of technology changed over the past few years? I would love to hear about your experiences! Leave a comment below and tell me – is technology a friend or a foe in your fieldwork?