06 Jan Following Our Kestrels: How Motus Tracking Helps Us See an Invisible World
If you’ve ever watched noticed kestrels in the grasslands here in San Diego or other parts of the US, you might have wondered if they are more plentiful during certain times of the year.
This year, our team is joining a global network of bird researchers using a tool called Motus to follow small birds on their travels. We’ll be heading out to the Salton Sea to place tiny radio and GPS tags on American Kestrels that use our region, and then listening for them as they move through the larger landscape.
Technology has a very special place in bird conservation research. It has massively enhanced our understanding what our kestrels need to survive in a changing world – and why that matters for conservation here in San Diego County and beyond.
From Beeps on a Receiver to a Global Network
In the 1960s, biologists started using VHF radio transmitters on raptors and other wildlife. Each bird wore a small backpack or tail-mounted antenna that sent out a simple “beep.” A researcher with a handheld antenna would walk or drive around, turning their receiver like a TV antenna to figure out where the signal was strongest.
It was painstaking and often limited to one bird at a time in a relatively small area.
Later, satellite and GPS tags changed everything. Tags could send location data to satellites, letting researchers follow birds across continents with surprising accuracy. Recent advances have made these devices smaller and lighter, so they can be used on more species and reveal fine-scale details of migration.
But satellite systems rely on Global Navigation Satellite Systems (GNSS). In conflict zones, those signals can be jammed or spoofed, which has started to affect wildlife tracking. Studies have shown that GNSS disruption in war zones can interfere with data from tagged animals.
During the war in Ukraine, researchers tracking Greater Spotted Eagles with GPS found that many birds changed their routes, took long detours, and spent more energy avoiding active conflict areas. The Guardian+1 That work is a powerful reminder that human conflicts ripple out into the lives of wild animals – and that tracking tech is only as stable as the systems it depends on.
That’s one reason why diverse tracking tools – including ground-based radio networks like Motus – are so important.
So What Is Motus?
The Motus Wildlife Tracking System is a worldwide network of automated radio receivers that listen for tiny tags on animals. Those tags emit a unique coded radio signal. When a tagged bird flies within range of a Motus station, the station logs the tag’s ID, date, and time. Motus Docs+1
Think of it as an enormous shared “listening system” for migration:
- Mini tags, big reach. Tags (often called NanoTags) are light enough for small birds and bats, some weighing just a fraction of a gram. Lotek |
- Fixed listening posts. Motus stations sit on ridgelines, coastlines, wetlands, and rooftops. With a clear view, they can detect tagged animals up to about 15–20 kilometers away. Motus
- Shared data. Researchers around the world use the same frequencies and shared database, so a kestrel tagged in California can be “heard” by a tower in another state or country.
In places like California, agencies are already exploring Motus as a way to understand how birds, bats, and even insects move through our landscapes and how climate and land-use change affect them. Wildlife Conservation Board
Our kestrel project is becoming part of that story.
Our Kestrel Project and the Salton Sea
Here at home, American Kestrels are struggling in many parts of their range. Nest box projects and careful monitoring help, but they only answer a few questions:
- Are pairs nesting?
- How many chicks fledge?
- Are boxes in good habitat?
What we don’t see easily is what happens when those birds leave the nest:
- Do our local kestrels stay in the county year-round or travel south?
- Do they depend on key stopover sites like the Salton Sea during migration or winter?
- How do weather, drought, or agricultural changes along their route affect them?
By tagging kestrels at the Salton Sea, we can start to connect those dots. The Salton Sea is a major stopover and wintering area for many birds. Understanding how kestrels use it helps us see how local conservation actions link to a much larger flyway.
When one of “our” birds passes a Motus tower – whether that’s along the coast, in the desert, or states away – we get a time-stamped data point. Over months and years, those points draw invisible highways in the sky.
What Motus Data Can Tell Us
For conservation, Motus data can answer questions that banding and casual sightings simply cannot.
Some of the insights we can gain:
- Migration routes and timingWe can see when kestrels leave breeding areas, how fast they travel, and which routes they favor. That tells us which landscapes matter most during the most demanding parts of their life cycle.
- Stopover “gas stations”Birds need safe places to rest and refuel. If we see many tagged kestrels using the same wetland, agricultural valley, or desert oasis, that site becomes a high-priority area for protection.
- Survival and riskGaps in detections can hint at where birds are running into trouble – collisions, habitat loss, or other pressures – especially when combined with other research.
- Response to changeAs climate, water management, and land use shift in California, long-term tracking reveals whether kestrels adjust routes, change timing, or stop using certain sites altogether.
For a small raptor that often hunts along roadsides and agricultural fields, these details matter. They help us design nest box placements, habitat projects, and outreach in ways that match how kestrels actually use the landscape, not how we imagine they might.
Why This Work Costs Real Money
Motus is collaborative and efficient, but it isn’t free.
Here are some of the basic costs involved in following a single small bird:
- Radio tags for the birdsCoded VHF “nanotags” typically cost on the order of $150–$225 per tag, depending on the model and lifespan, plus a one-time registration fee per tag so it’s recognized in the Motus system. Bay Soundings+1 When you add the capture equipment, permits, and field time needed to safely tag birds, each individual is a real investment.
- Motus receiving stationsA full station includes antennas, masts or towers, solar panels or power supply, receivers, and protective enclosures. Hardware alone can run into the thousands of dollars, and each site needs installation, maintenance, and occasional upgrades. DENIX+1
- Fieldwork and data analysisResearchers need to safely trap birds, fit tags, monitor nests, and later interpret the data. That means trained people in the field and at computers, along with travel, insurance, and all the quiet, behind-the-scenes costs that rarely make it into photos.
When you hear that “we’re tagging kestrels at the Salton Sea,” what that really means is:
- Someone donated or granted funds for tags.
- Someone helped cover the lodging and transportation, since government housing and vehicles are no longer an option in many scenarios.
- Someone supported the people in the middle of the nowhere in the wind and dust, carefully handling a feisty little falcon so it can carry that tag safely.
How Local Support Makes a Global Difference
Here’s the part that connects directly to you.
When our community invests in projects like this, we are doing more than buying gadgets. We are:
- Putting our region on the map of international bird research, quite literally. Each tagged kestrel that passes a Motus tower anywhere in North America carries a bit of San Diego County with it.
- Helping small raptors keep their place in the landscape. By understanding where kestrels succeed or struggle, we can better protect nest sites, hunting grounds, and crucial stopovers.
- Contributing to open, shared conservation science. Motus data feeds into a global system, so the lessons learned from “our” birds can inform protections for raptors and other migrants along the entire flyway. Motus Docs+1
In a world where satellite systems can be disrupted by war and global politics, investing in a robust, ground-based tracking network is also an investment in resilience. Motus doesn’t replace GPS or satellite tags, but it complements them and offers a powerful, collaborative way to keep learning from wildlife even when other systems are under strain. PMC
How You Can Help
As we prepare for our Salton Sea kestrel tagging work and expand our Motus involvement, we’re looking for community partners who want to be part of this story.
Ways you can support:
- Help sponsor a kestrel tag. A contribution toward a single nanotag, or part of one, directly funds a bird we can follow for months or even years.
- Support our Motus infrastructure. Gifts toward equipment and maintenance keep local towers listening for kestrels and other migrants passing through our skies.
- Share the story. When you talk to friends, schools, or local groups about our kestrel work and Motus tracking, you help build a community that understands why this research matters.
We can’t ask a kestrel where it has been. But with the right tools – and with your help – we can listen more carefully to the paths it takes and build a safer future along those routes.
If you’d like to help sponsor a tag, contribute to a research team, or learn more about our kestrel fieldwork, we’d love to talk with you. Want to sponsor a kestrel? Join in our fundraising efforts here