Swainson’s Hawks and the Fight to Save Migration
Each fall, Swainson’s Hawks take to the skies, swirling in tight flocks as they ride thermals south toward the tropics. From below, their migration looks effortless—just another seasonal rhythm, a pulse of the changing winds.
But their journey tells a different story. Swainson’s Hawks nearly disappeared, their survival hanging in the balance. Only a remarkable conservation effort—one of the greatest turnarounds in raptor history—brought them back. Watching them now, gliding overhead with purpose, is a reminder of what’s possible when people rally to protect the birds we love.
The Swainson’s Hawk Mystery
In the early 1990s, biologist Brian Woodbridge set out to answer a simple but crucial question: Where do Swainson’s Hawks go in winter?
At the time, little was known about their full migration route. Woodbridge and his team outfitted two hawks with satellite transmitters, a relatively new technology that allowed them to track the birds across continents.
One hawk followed the expected path—flying thousands of miles from California to the open grasslands of Argentina, where it settled into a routine of hunting insects, especially grasshoppers, its primary winter food source.
Everything seemed normal. Until the signal stopped moving.
A Disturbing Discovery
Woodbridge traveled to Argentina to investigate. What he found was devastating. The fields were littered with dead and dying Swainson’s Hawks—thousands of them.
The cause? Monocrotophos, a highly toxic organophosphate insecticide used to control grasshopper outbreaks. Farmers sprayed the fields, unintentionally setting off a deadly chain reaction.
Poisoned grasshoppers didn’t die immediately. Instead, they became sluggish—making them easy targets for Swainson’s Hawks. After consuming dozens, if not hundreds, of contaminated insects, the hawks suffered neuromuscular failure. Their wings, legs, and respiratory muscles locked up, leading to suffocation.
In a single season, at least 20,000 Swainson’s Hawks—nearly 5% of the global population—had perished. If nothing changed, the species could be pushed toward extinction within a few years.
A Conservation Turning Point
The discovery set off an international conservation effort. Scientists, governments, and conservation groups worked together to raise awareness and push for policy changes.
The result? Argentina banned monocrotophos for agricultural use, and farmers were provided with alternative insecticides that didn’t have the same devastating effects on wildlife.
This rapid response saved Swainson’s Hawks from a steep decline, making it one of the rare success stories in raptor conservation.
But the work didn’t stop there.
Today, long-term monitoring programs like Veracruz River of Raptors continue to play a crucial role in tracking migratory raptors, ensuring that threats—whether habitat loss, poisoning, or climate change—are detected before they become full-scale crises.
Witness the River of Raptors for Yourself
Each fall, millions of raptors, including Swainson’s Hawks, Broad-winged Hawks, and Turkey Vultures, pass through Veracruz, Mexico, in one of the largest bird migrations on the planet.
I’ll be there this year, leading a Veracruz and the River of Raptors Tour (September 25 – October 3, 2025), and I’d love for you to experience this incredible migration with me.
We’ll witness tens of thousands of hawks soaring overhead, explore Veracruz’s diverse landscapes, and meet the conservationists working to protect this migration.
Reserve your spot today, and let’s chase the birds together.