Tracking the Wood Thrush with Motus
You may have noticed a tower and antennas on the side of the visitor center and education building. This isn’t so the staff can watch their favorite soap operas and game shows, it is for scientific research. Two-thirds of all songbirds in North America, along with many other animals like butterflies, dragonflies, and bats, are migratory, and many migratory species are undergoing serious population declines. Studying migratory animals is difficult because it is hard to follow them for their entire journey, but knowing their migration routes and the hazards they face is critical for their conservation. Technological advancements, most notably the miniaturization of tracking devices, have made it possible to record the movements of migrants throughout their annual cycle. One of the most recent advances is the Motus tracking system (Motus is the Latin word for movement). The Motus system is a network of receiving stations that are tuned to a common transmitter frequency, allowing for any animal wearing a Motus tag to be detected by any station. Thus, researchers are able to remotely gather data on such information as migratory routes, length of stopover along the way, migration speed, and wintering locations. There are currently over 2,000 stations around the world, and over 47,000 individual animals of 375 species have been tagged.
Reflection Riding Motus Station
My project is looking at Wood Thrushes, which have been undergoing significant population declines and have been declared a species of concern by TWRA. Specifically, I am interested in how urbanization may be affecting their migration. The Reflection Riding station represents an urban site, and I have a second station at the Paint Rock Forest Research Station in NE Alabama, which represents a non-urban site. If any of the thrushes I tag pass within 5 miles of a Motus station, it will get detected, and the system will notify me. Similarly, if someone else’s tagged animal passes within range their data will get recorded. The tags I am using weigh about half a gram, which is only 1% percent of a Wood Thrush’s body weight. To catch the thrushes, I listen for singing or calling birds and then set up a net nearby. I then place a Wood Thrush decoy near the net and broadcast Wood Thrush songs and calls. Birds coming to check out who the intruder is fly into the net and get caught. I then attach the tag to the bird’s lower back using an elastic harness, and the bird is released unharmed.
To gather finer-scale data (e.g. Do thrushes in an urban environment have to move more to find food?), I use a hand-held receiver. I sweep the antenna and look at the signal strength; the closer the signal is to 0, the closer I am to the bird. I can also use the map feature to get a more visual idea of where the bird is; the blue dots indicate signal pulses from the tag.
So far, neither the Reflection Riding Station nor the Paint Rock Station has had any detections. The Tennessee River Gorge Trust has a station that has been active since last year, and they have had 5 detections; a Common Tern, a Sora, a Cerulean Warbler, a Swainson’s Thrush, and a Wood Thrush. I was able to tag 3 Wood Thrushes last spring, all of which were transient, meaning they stayed just a few days and then migrated elsewhere, and so far, those birds have not been picked up by other Motus stations. I have not tagged any thrushes this year because there haven’t been any Wood Thrushes at Reflection Riding since April, which is very unusual. I will try tagging more birds during fall migration, and I am optimistic that the data I gather from this project will help guide the management of Wood Thrushes and other migratory species.
Left Image: Wood Thrush fitted with a Motus tag.
Right Image: Inside the Motus Receiver.
To add to the value of the station, Reflection Riding and I want to use it as an educational tool to teach visitors about the importance of bird migration and the conservation of migratory species. To help achieve that goal, Reflection Riding contracted UTC art student Gus Gaston to create a mural that describes aspects of bird migration and what the Motus project is about. So the next time you visit Reflection Riding, I hope you will look at the wonderful mural Gus made, and think about ways you might help protect migratory birds!
