Tracking the Mysteries of Migration: The Motus Wildlife Tracking System & The Chasing Melody Project

by Chris Fox, Land Stewardship Director

As the sun slowly peeks over the horizon, the orange and pink rays of light illuminate the wooded hills that surround the Beanblossom Creek valley at the Sam Shine Foundation Preserve. A layer of fog that had formed over the fields and wetlands is slowly beginning to lift as the air warms on this early June morning. The peaceful scene brings back fond memories of vacations spent in the foothills of the Great Smoky Mountains. As I gaze at the rising sun while listening intently to the birdsong welcoming the new day, I take a deep breath of the fresh morning air and fully immerse myself in the moment. Looking around at our crew, I catch a glimpse of a yawn from one of the interns which as it often tends to do causes a chain reaction of yawns among the group. I try as I might to resist but alas give into the reflex as I rub my eyes still trying to chase away the sleep. For a night owl like myself, morning comes early but sleep can wait for it is a glorious time to be out in the field. Despite the early start, spirits are high and there is much excitement among our crew which is a mix of Sycamore and Indiana Department of Natural Resources personnel of varying degrees of experience. For many in our group this will be a first but for others this is familiar territory. For me, it is familiar and one of those full circle kind of moments. One of those moments that takes you back to a time in your past that is now connected to the present.

A mother wood thrush feeds her babies at the Sam Shine Foundation Preserve. Photo by Wyatt Downey

Today we are in search of perhaps the most beautiful songster of our woodlands and forests, the wood thrush (Hylocichla mustelina). There are of course many beautiful bird songs but it is hard to think of one that is more beautiful than the ethereal “ee-oh-lay” song that echoes through our woodlands. Like any musical masterpiece, if you listen closely to the three-part song, it has many subtle intricacies from the soft introductory notes to the complex trills as the song reaches its crescendo. This talented songster can even perform a “duet” by itself singing two notes simultaneously. I can just imagine the ovenbirds with their simple and harsh “teacher, teacher, teacher” song feeling a bit embarrassed and annoyed by the overachieving wood thrush opus. Despite its well-known song, much is unknown about the migration and conservation needs across the range of this beautiful bird. Steep declines in the last 50 years has put the wood thrush on the USFWS’ Birds of Conservation Concern list. Indiana forests are important to this species since nearly 4% of the entire population nests in our home state.

The Chasing Melody Project

In a first of its kind program named Chasing Melody, Indiana Audubon and the Indiana DNR are partnering with international partners in the first full scale tracking project of wood thrushes from every part of their life-cycle, including both breeding and non-breeding ranges.

Our crew this morning is being led by Allisyn Gillet, State Ornithologist with Indiana DNR. After a briefing with Allisyn, we gather the mist nets, poles, tags and banding gear as we head toward the forested hills listening for that flute-like song where our summer interns, Lindsey Levine and Wyatt Downey, had previously scouted and flagged a potential wood thrush nest. As we approach the area, we listen for that unmistakable song but the woods are fairly quiet on this warm morning except for the constant drone of a red-eyed vireo and the occasional call of a distant yellow-billed cuckoo. Then we spot the nest and to our surprise a female wood thrush is sitting on it. We quickly get to work setting up the mist nests and preparing the banding and tagging gear.

Seeing the wood thrush nest reminds me of one of my first field research positions during graduate school where I was tasked with locating and monitoring the nests of several neotropical migratory songbirds to determine if they were reproductively successful. This research was led by the late Dr. Donald Whitehead, a mentor to me and many budding birders and researchers alike. One of our target species was the wood thrush which quickly became a favorite of mine not only for its melodious song but also because of the understated beauty of the bird itself. Through my research experience, I developed a deep appreciation for the challenges these birds faced on their breeding grounds. The declines we saw then in the 90’s was alarming and unfortunately for many birds those numbers have not improved. In fact, the outlook has worsened for many once familiar species. The warning Rachel Carson gave in 1962 with her groundbreaking book, Silent Spring, has proved quite prophetic. Each year, I wait with great anticipation hoping that our springs will not be silent and that our forests will be filled with the enchanting song of the wood thrush.

Our objective this morning is to locate and catch several wood thrush in order to attach a miniaturized radio transmitter which will allow researchers to track its movement. These transmitters or tags as they are often called can weigh as little as 0.15 gram and can be affixed to birds, bats, and even insects. Each tag emits a slightly different radio signal allowing animals to be tracked individually by using a receiver that can be hand held or stationary on a tower similar to a TV antenna. After the mist nests are set we play a wood thrush call from a device to try and lure one of the pair into the nets. Moments later we have our first wood thrush in hand and begin the meticulous process of attaching this small transmitter to her ever so gently. As I watch the transmitter harness being adjusted and fitted to female, I think about my first experience attaching transmitters to birds. I was working for the Smithsonian Institute and we were stationed on Cat Island in the Bahamas studying the Kirtland’s warbler which was Federally Endangered at the time. I had used radio telemetry in the past but this was the first time I was able to use radio telemetry on a migratory bird. To imagine a small bird flying thousands of miles with a small electronic device on its back was hard for me to believe. As we attached the transmitters to the birds in the Bahamas I wondered what threats it would face on its journey crossing the over the ocean to the mainland and then north to Michigan. What route would it take? Where would it stop? Will it even make it? All these questions crossed my mind as we released these birds. I distinctly remember looking out the plane window as I flew back to the U.S. and wondering where the birds were and if they survived their journey. What a thrill it was to find these same birds again in Michigan. One of the highlights of my career has been getting to hold the same individual bird on its wintering ground in the Bahamas and on the breeding ground in Michigan. And this was made possible by the advances in science and equipment like the tags and Motus network. In fact, the Kirtland’s warblers we tagged were detected in Florida and Georgia on their journey north and that helped to piece together their migration route. We were able to detect these birds due to the increasing number of Motus towers being built.

The Motus Wildlife Tracking System

The word motus comes from Latin. Translated, it means motion, but can also mean progress or change. The name is appropriate since this company uses technology that is changing the way we track animal movement. The Motus Wildlife Tracking System is an international collaborative network of researchers that use automated radio telemetry to simultaneously track hundreds of individuals of numerous species of birds, bats, and even insects. The system enables a community of researchers, educators, organizations, and citizens to undertake impactful research and education on the ecology and conservation of migratory animals. When compared to other technologies, automated radio telemetry currently allows researchers to track the smallest animals possible, with high temporal and geographic precision, over great distances. Earlier this year, Sycamore and the Indiana DNR along with help from generous donors, interns and volunteers installed a new Motus tower at our Sam Shine Foundation Preserve. This new station is part of a network of towers throughout not only Indiana but the world. Currently, there are 1,904 Motus wildlife tracking systems operating in 34 countries. So far, 358 species and over 44,000 individuals have been tracked using this technology. In the Hoosier state, we currently have 20 towers installed and have over 150 unique individuals detected representing at least 10 different species. One of the longest running tagged birds that was detected by a tower in Indiana belongs to a common nighthawk that was originally tagged in Montana on July 14, 2021 and detected 785 days (2.15 years) later by the Hovey Lake tower on September 7, 2023 before heading south to Panama.

Our new Motus wildlife tracking system radio telemetry tower at the Sam Shine Foundation Preserve in partnership with Indiana DNR is tracking the migration of the wood thrush and other threatened species. Photos by Chris Fox

Our efforts to tag wood thrush in Indiana are actually part of an international project which aims to deploy tags on upwards of 600 wood thrush between 2024-2025 in breeding states throughout the U.S., as well as six non-breeding countries in Latin America (Mexico, Belize, Guatemala, Honduras, Nicaragua, and Costa Rica). Data gathered will assist managers in targeting habitat management along migratory pathways and allow us to learn which corridors to add for management protection. The information gathered will provide clearer ties from breeding to non-breeding grounds which allows for strengthened partnerships between North American and Latin American conservation partners.

In 2019, ornithologists across North America, led by Ken Rosenberg, wrote a landmark article that was published in the journal Science that quantified the net loss of 2.9 billion birds, or 29 percent, in North America since 1970. For many species, the causes of the population declines are unclear. Habitat removal and landscape-level changes have been substantial in the last 50 years. Additionally, habitat loss and land-use changes are occurring on stopover sites during migration and on wintering grounds. Threats like outdoor and feral cats, window collisions, and pesticides continue to increase at a pace that birds cannot match. For many species, there is much we still don’t know, like migration timing, routes, and departure dates. We know much less about species survival on wintering grounds or during migration, which could be affecting populations of migratory birds significantly. Using Motus to track birds locally to assess survival or long-distance migration can help to fill these knowledge gaps. Taken as a whole, this data can inform us more about what conservation actions need to occur and at which stages of a bird’s annual cycle. Full annual cycle conservation means working to protect migratory birds throughout their annual cycle, which includes four general phases: breeding, spring and fall migrations, and nonbreeding/wintering. Many of us in the U.S. likely see the birds who breed here as “our” birds, but about half of all birds in North America migrate to the tropics for up to eight months of the year. We are simply hosting them for a few months while they benefit from seasonal abundance of resources like insects and breeding habitat. Because these birds are beyond our borders for most of the year and face different threats to their survival during migration or on their wintering grounds, conservation agencies and organizations across the hemisphere must be strategic about partnerships and projects that will help fill knowledge gaps on our shared and often declining migratory bird populations.

As we release the female we have appropriately named Melody, I can’t help but wonder what her future holds. What migratory path will she take? What will she face on her journey? Will she encounter obstacles or storms? Will she stay on course and make it to her destination? Will she return back to this place next year? Thanks to this new technology we might just be able to answer some of those questions. The information gathered over the next few years could help fill in the informational gaps and provide a better understanding of the conservation needs of this iconic species of our forests. As I watch Melody fly off to a nearby sycamore tree, it dawns on me that maybe our life’s journey is a bit like a bird’s journey. Full of starts and stops, detours and times we face obstacles and storms. Even sometimes possibly being blown off course. But, like our fine feathered friends, we persevere. Driven by a desire to survive and thrive. Always adapting and improvising to overcome what we face. Maybe the unknown of what our wood thrush might face on her journey and the unknown we might face shouldn’t frighten us so. Maybe part of the beauty of this bird and life in general lies in that unknown.

This article is from the Summer 2024 issue of The Twig, “The Habitat Issue.” Read the issue at sycamorelandtrust.org/twig.