A global antenna array is the next frontier in migration science


Lewis’s Woodpecker is one of the avian gems of the West. He has a ruby ​​red face and emerald feathers draped over his back like a cape with a silver hood. In summer, it dives and circles above the forests west of the Great Plains, performing aerobatics while chasing flying insects. Wintering in the forests of the far west and southwest, it aggressively defends caches of stored nuts from pirate Acorn Woodpeckers. As captivating as it is, however, there’s still a lot we don’t know about the bird’s movements and biology, or what has caused its population to drop by about half since the 1960s.

To figure out what’s causing the losses, scientists at MPG Ranch, a conservation research group in western Montana, are tracking Lewis’s woodpeckers with a simple and increasingly popular technology. Since 2019 they have attached radio transmitters to birds breeding in the Bitterroot Valley. When a tagged bird passes within a dozen miles of one of 13 receiving stations in the 96-mile-long valley, its identity is automatically registered at the antenna location, revealing its movements on its breeding grounds. Individuals tagged in the Bitterroot also sent signals to tracking stations in southwestern Oregon, providing new information about where the birds go in winter. According to MPG Ranch biologist William Blake, the technology paints a more complete picture of the woodpeckers’ annual movements and helps determine where they might encounter problems due to logging, wildfires or other threats, and so where to focus conservation efforts.

Lewis’s Woodpecker is one of hundreds of species that scientists are monitoring remotely with the Motus Wildlife Tracking System, which went online in 2015. Named after the Latin word for movement, Motus uses networks of automated radio receiving stations to detect marked animals over large distances. . Today, some 1,500 receiving stations are active worldwide. Scientists have tagged more than 34,000 animals, from birds and bats to butterflies and bumblebees.

The Motus network is overseen by a team from the non-profit organization Birds Canada, including longtime migration scientist Stu Mackenzie, who helped launch the system with researchers from Acadia University in the early 2010s. While scientists have used radio telemetry to track animals since the 1960s, recent advances in technology have ushered in miniature tags weighing as little as a coffee bean. These tags can be attached to songbirds as small as the Canada warbler or the gray-cheeked thrush, and even to smaller insects. In addition to studying their movements, scientists can analyze beacon data to glean details like when a bird is active, when it sleeps and when it takes flight.

In the past, scientists had to track radio-tagged animals with cumbersome portable antennas, tracking them across the landscape to get within signal range. Now, with Motus, a large community of collaborators has assembled a global network of low-cost, fixed radio receivers that can passively pick up signals from any nearby tagged animal.

“You can put a Motus station on just about anything,” Mackenzie says. Many are self-contained towers. But they have also been attached to telephone poles, weather stations, ships, lighthouses, high school rooftops and, near Tucson, Arizona, an idle windmill. A point common to all these locations: a clear view of the sky, to better capture the signals.

When a bird passes a receiving station, a computer records and stores the unique radio identifier of its beacon. Many stations upload this data directly to the Motus database housed at the National Bird Data Center Canada in Ontario. This centralized database is the latest innovation behind the success of Motus. It connects all the antennas around the world and makes information freely accessible to researchers and the public on motus.org.

Each tracking technology has its pros and cons. GPS beacons, deployed since the mid-1980s, are the most geographically accurate, but they are cumbersome and expensive. Geolocators, half-gram sensors that estimate location from light intensity, emerged in the early 2000s, allowing researchers to track songbirds for the first time. But they also have a catch: you have to recapture a bird to retrieve the data stored on the gadget, and the majority of birds are never recaptured.

With Motus, there is no need to spend days or weeks in the field trying to catch previously marked birds. In addition, the system collects data in real time. “I can sit in my office at a university or at an Audubon facility, and the data comes to me,” says Cristina Francois, former manager of Audubon’s Appleton-Whittell Research Ranch, who erected a station in Arizona in March.

The main limitation of Motus is the number and density of stations. Receivers range from as far north as the Northwest Territories of Canada south to the southern tip of Chile, but most are concentrated in the eastern regions of Canada and the United States. -United. There are significantly fewer in South America, where many migratory birds winter. “The actual range of a Motus station is quite small compared to the vastness of the landscape,” says Mackenzie. “There are many gaps in the network.

When the structures are far apart, scientists are forced to make educated guesses about the routes taken by the birds. So they took a strategic approach in placing certain stations to get the most out of their Motus money. A chain of four stations spanning the Isthmus of Panama, for example, could detect almost any tagged animal flying above land through the narrow corridor, revealing which birds follow this route between North America and the United States. ‘South America.

Motus is complementary, not competitive, with other tracking tools, says Mackenzie: “We want all of these technologies to work together to solve the problems we face.” It’s a big challenge. During their annual cycles, migratory birds face habitat destruction, pesticides, predators, extreme weather conditions and many other threats to their survival. Knowing the location of birds – the flight path of an endangered species or the preferred flocking areas – is integral to safeguarding them throughout the year.

Motus data can help show decision-makers how to prioritize funding and target areas for protection. For example, many grassland birds from North America winter in the Chihuahuan Desert in the southwestern United States and northern Mexico. But farms and ranches take precedence over valuable habitats. The new Motus Station at Appleton-Whittell Research Ranch is part of a project led by the Bird Conservancy of the Rockies (BCR) to study how declining species like Grasshopper Sparrow are using the remaining grasslands of Chihuahua. “Which ones are most important for conservation efforts to best meet the needs of these birds?” says Matt Webb, a BCR avian ecologist. Motus will help him find out.

The network lends itself well to conservation because it is collaborative in design. While MPG Ranch’s Blake uses stations dotted around the Bitterroot Valley to study Lewis’s Peaks, they also pick up any tagged animals that come close enough, for example, bank swallows and golden eagles tracked by other researchers. “In some cases, [the scientists behind] a project can benefit from the actions of dozens or hundreds of people who maintain the stations on their behalf, often without their knowledge,” says Mackenzie. “Everyone is working together for this common goal of understanding migratory animals as much as possible and ultimately conserving them.”

This approach also reflects a trend in conservation science. Data repositories such as Cornell Lab of Ornithology’s eBird, Audubon’s Migratory Bird Initiative, and Max Planck Institute of Animal Behavior’s Movebank all embrace open, community-based science and rely on data sharing. “The breadth of the questions we ask about migratory birds is so great that if you don’t collaborate across institutions, across political boundaries, you’ll never get the answers you need,” says Bill DeLuca, a migration manager. conservationist with Audubon’s Migratory Bird Initiative who helps Audubon Centers set up Motus stations. So far, 13 Audubon Nature Centers host Motus stations, filling important gaps in the network. Audubon also supports stations in South Carolina, the Great Lakes, northern Yucatan, Colombia, and elsewhere.

Blake feels the urgency to build partnerships. Lewis’s woodpeckers are doing well on their Montana breeding grounds, so they must encounter threats elsewhere in their life cycle that explain the decline in numbers. As coordinator of MPG Ranch’s Intermountain West Collaborative Motus project, he works with researchers across the West to install dozens of stations there. They will allow him to answer questions essential to the survival of the woodpecker and will help his colleagues to ensure that other species also thrive.


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