Losing 20 birds is effectively akin to setting the recovery program back by 10 years.
Along the cliffs and canyons of the American West, a bird that once vanished from the wild is being asked to survive yet another human-era threat — this time, a virus. In the summer of 2023, veterinarians at three U.S. zoos administered an experimental bird flu vaccine to California condors, a species so imperiled that twenty-one deaths in Arizona this year erased what scientists measure as a decade of recovery. The trial is a quiet act of reckoning: a civilization that nearly destroyed these birds now racing to protect them with the most urgent tools it has.
- Avian influenza — the deadliest strain ever recorded in the U.S. — killed 21 free-flying condors in Arizona in 2023, threatening to unravel a 40-year effort to pull the species back from the edge of extinction.
- With fewer than 350 condors flying free worldwide, each individual death carries the weight of years; losing 21 in a single outbreak was calculated as erasing roughly a decade of painstaking recovery work.
- Wildlife officials fast-tracked an emergency-use vaccine — the first ever authorized for a bird species in the U.S. — testing it first on black vultures before administering two-dose regimens to condors at zoos in Los Angeles, San Diego, and Portland.
- Early results offer cautious hope: 60% of the ten vaccinated birds developed measurable antibodies, with no adverse reactions observed after 42 days of monitoring.
- Roughly two dozen vaccinated condors are planned for release into California and Arizona by year's end, while officials await further data before deciding whether to capture and vaccinate wild populations.
In the summer of 2023, veterinarians at three American zoos administered an experimental vaccine to California condors — birds with ten-foot wingspans whose entire species once numbered just twenty-two individuals. The trial was born from crisis: earlier that year, avian influenza swept through a wild flock in Arizona, killing twenty-one condors in weeks. Wildlife officials described the loss as equivalent to erasing a decade of recovery work.
The condor's history is a chronicle of human harm. Hunters, DDT, and lead ammunition drove the species to the brink. By the 1980s, only captive breeding programs kept it alive. The first zoo-bred birds were released in 1992, and today fewer than 350 condors fly free — genuine progress, but profound fragility.
When bird flu arrived in the U.S. in 2022, spreading from Europe, it devastated commercial poultry across 47 states and killed nearly 59 million birds. For the condor, the stakes were existential. The vaccine trial launched in July at the Los Angeles, San Diego, and Oregon zoos. After two injections and 42 days of monitoring, 60% of vaccinated birds developed protective antibodies and none showed adverse reactions. The condor became the only bird species in the country approved for the emergency-use vaccine.
"We're thankful that we're getting any immune response," said Ashleigh Blackford of the U.S. Fish and Wildlife Service. The plan is to release roughly two dozen vaccinated condors into the wild by year's end. For the Oregon Zoo's Dr. Carlos Sanchez, the intervention required careful deliberation; for the LA Zoo's chief veterinarian Dr. Dominique Keller, it was a career-defining moment.
For the Yurok Tribe of Northern California, the stakes reach beyond biology. The condor returned to tribal lands only in 2021, after a century-long absence, through major conservation efforts. Watching 21 birds die in Arizona shortly after that homecoming was, said wildlife director Tiana Williams-Claussen, "deeply impactful." In Yurok tradition, the condor is considered a being of spiritual significance — equal to or greater than humans. The vaccine trial is, for the tribe, a chance to protect not just a species, but a relationship.
In the summer of 2023, veterinarians at three American zoos administered an experimental vaccine to a handful of California condors—birds with wingspans that stretch ten feet across and a species so close to extinction that losing a single individual represents a measurable setback for the entire recovery effort. The trial was born from urgency. Earlier that year, avian influenza swept through a wild flock in Arizona, killing twenty-one condors in a matter of weeks. For a species that had been reduced to just twenty-two individuals in the 1980s and has spent four decades clawing back toward survival, that loss was catastrophic. Wildlife officials calculated it as equivalent to erasing a decade of painstaking recovery work.
The California condor's path to near-extinction is a chronicle of human harm. Hunters decimated the population during the Gold Rush in the mid-1800s. The pesticide DDT and lead ammunition finished what hunting had started. By the 1980s, the species existed only in captive breeding programs—a last-resort ark to prevent total loss. The first condors bred in zoos were released into the wild in 1992, and since then, the birds have been gradually reintroduced across habitats from the Pacific Northwest to Baja California. Today, fewer than 350 condors fly free, a number that represents genuine progress but also profound fragility.
When bird flu arrived in the United States in early 2022, spreading from Europe, wildlife officials recognized an existential threat to this fragile recovery. The strain proved to be the deadliest avian influenza ever recorded in the country. It devastated commercial poultry operations across forty-seven states, killing nearly fifty-nine million birds and costing the federal government more than six hundred sixty million dollars. The economic toll was staggering, but for the California condor, the stakes were different. A single outbreak could undo decades of work.
The vaccine trial began in July at the Los Angeles Zoo, the San Diego Zoo Safari Park, and the Oregon Zoo. Researchers first tested the emergency-use vaccine on black vultures to ensure safety before administering it to condors in managed care. The initial group received two injections—a first dose and a booster administered three weeks later—each consisting of half a milliliter. After forty-two days of monitoring, no adverse reactions occurred. The results were encouraging: sixty percent of the ten vaccinated birds developed measurable antibodies expected to provide protection against the virus. A second test group received a single, larger dose, with results still pending to inform decisions about vaccinating wild populations.
The California condor became the only bird species in the United States approved for this emergency-use vaccine, a distinction that reflects both the species' endangered status and the desperation of the moment. Ashleigh Blackford, the California condor coordinator for the U.S. Fish and Wildlife Service, acknowledged the modest success with measured optimism. "We're thankful that we're getting any immune response," she said. The plan is to release roughly two dozen vaccinated condors into the wild in California and Arizona by year's end, with decisions about capturing and vaccinating free-flying populations pending further data.
The decision to intervene was not made lightly. Dr. Carlos Sanchez, the Oregon Zoo's director of animal health, noted that veterinary intervention in wildlife management is not routine and required careful deliberation. Yet for Dr. Dominique Keller, the Los Angeles Zoo's chief veterinarian, participating in the trial represented a career highlight. "It was just so incredible to be the first one to hold the vaccine in my hand and actually give it to the first bird," she said. She hopes the condor study will pave the way for bird flu vaccines protecting other endangered species.
For the Yurok Tribe, whose ancestral lands in Northern California had been empty of condors since the late 1800s, the vaccine trial carries deep cultural weight. The condor returned to tribal territory in 2021 after major conservation efforts led by Tiana Williams-Claussen, the tribe's wildlife department director. Watching twenty-one birds die in Arizona just years after that return was, she said, "deeply impactful." The tribe is waiting to see whether the vaccine can prevent another such loss. The condor, in tribal tradition, is considered equal to or even superior to humans—a being whose survival matters not just biologically but spiritually. The vaccine trial represents a chance to protect that relationship.
Citas Notables
Losing 20 birds is effectively akin to setting the recovery program back by 10 years.— Dr. Hendrik Nollens, vice president of wildlife health for the San Diego Zoo Wildlife Alliance
It was just so incredible to be the first one to hold the vaccine in my hand and actually give it to the first bird.— Dr. Dominique Keller, Los Angeles Zoo chief veterinarian
La Conversación del Hearth Otra perspectiva de la historia
Why did this vaccine trial happen now, rather than years ago when the condor population was even more precarious?
The bird flu outbreak in Arizona this year was the trigger. Losing twenty-one birds at once threatened to erase a decade of recovery work. Wildlife officials realized they had to act fast or risk losing everything they'd built.
What does it mean that only sixty percent of the vaccinated birds developed antibodies?
It's partial protection, not a cure-all. But the officials were grateful to get any immune response at all. They're still testing a second group with a different dose to see if they can improve those numbers before vaccinating wild birds.
The condor was hunted nearly to extinction in the 1800s, then poisoned by DDT and lead ammunition. Now it's bird flu. Does the species just keep getting unlucky?
It's not luck—it's that the condor exists in a world shaped by human activity. Every threat it faces is something we created or introduced. The recovery effort is essentially humans trying to undo the damage humans caused.
Why does losing twenty-one birds equal ten years of recovery work?
Because the population is so small. Every individual matters enormously. When you're rebuilding from twenty-two birds in the 1980s to fewer than 350 today, each death represents a significant percentage of the total. The math of small populations is unforgiving.
What happens if the vaccine doesn't work well enough in the wild?
That's what they're waiting to find out. They're being cautious, gathering more data before they decide whether to capture free-flying condors and vaccinate them. If the vaccine fails, they'll have to find another way to protect the population—or accept that bird flu could devastate the species again.