Bird Flu Outbreak Devastates Bay Area Wildlife

The fastest bird on Earth cannot outrun a virus. Neither, it turns out, can a two-ton elephant seal.

In the span of just three years, highly pathogenic avian influenza — the H5N1 strain of bird flu that has swept across continents, killing hundreds of millions of birds and tens of thousands of marine mammals — has arrived at the doorstep of the San Francisco Bay Area with devastating force. Peregrine falcons, once the triumphant comeback story of American conservation, are dying at rates not seen since the DDT crisis of the 1960s [1]. And in late February 2026, researchers confirmed that the virus had leapt to yet another beloved species: the northern elephant seals of Año Nuevo State Park, marking California's first confirmed detection of H5N1 in a marine mammal [2].

Together, these twin crises paint a picture of an ecosystem under siege — and a virus that shows no signs of slowing down.

The Falcon's Fall

For decades, the peregrine falcon has been the Bay Area's most celebrated conservation success story. Driven to the brink of extinction by the pesticide DDT in the 1960s, the species was nursed back from oblivion through a massive recovery effort led by falconers and wildlife biologists. Peregrines were removed from the federal endangered species list in 1999 and delisted in California in 2006 [1].

Now, that recovery is unraveling.

Research by UC Santa Cruz's Predatory Bird Research Group (PBRG), currently under peer review, has found that peregrine falcon populations across the greater San Francisco Bay Area have fallen by 65% in just three years [1]. The study, which spans monitoring territories from Point Reyes National Seashore in Marin County south to Salinas and east to Sacramento, documents a collapse that began in the winter of 2022 — precisely when highly pathogenic avian influenza was first detected in California wildlife [3].

"This decline rate is at least as deep as it was for DDT," said Zeka Glucs, director of the PBRG. "This is not only a local issue. This has happened globally." [1]

Source: UC Santa Cruz Predatory Bird Research Group / bioRxiv preprint

Data as of Feb 11, 2026CSV

The numbers tell a grim story. Within eight months of the H5N1 outbreak reaching the region, nest occupancy had dropped to 65.1%. By 2025, only 36.2% of historically occupied territories still had breeding pairs — a loss of nearly two-thirds of the population [4]. The California Department of Fish and Wildlife and the U.S. Department of Agriculture have confirmed 27 cases of highly pathogenic avian influenza in peregrine falcons within the study area alone [1].

Peregrines are uniquely vulnerable to bird flu for a cruel reason: they are predators of the very species most heavily affected by the virus. Hunting birds in midair — gulls, terns, sandpipers, ducks — peregrines preferentially target prey that appear weak or disoriented, which are precisely the symptoms of avian influenza infection [1]. The virus climbs the food chain through the falcon's own hunting instincts.

A Colony Under Threat

Five hundred miles of California coastline south of San Francisco's skyline, at the windswept point of Año Nuevo State Park north of Santa Cruz, another crisis was unfolding.

On February 19 and 20, 2026, researchers monitoring the park's world-famous northern elephant seal colony began noticing something wrong. Weaned pups — young seals recently separated from their mothers — were displaying abnormal respiratory and neurological signs: weakness, tremors, convulsions [2]. Within days, seals began dying.

By the time USDA's National Veterinary Services Laboratory confirmed H5N1 in seven weaned elephant seal pups on the evening of February 25, approximately 30 seals had already died — 29 of them recently weaned pups and one adult male [5][6].

"We are completely devastated that highly pathogenic avian influenza has reached this population," said Roxanne Beltran, a researcher at UC Santa Cruz who leads the university's long-running elephant seal monitoring program [7].

The speed of the disease was staggering. A wildlife veterinarian who performed necropsies on the dead seals noted that one deceased female pup "was in excellent nutritional condition," indicating the disease struck with overwhelming swiftness rather than slowly wearing the animals down [5]. Necropsy findings revealed watery chest fluid, severely swollen red-purple lungs, enlarged lymph nodes, swollen spleens, and dilated brain blood vessels — hallmarks of a virus that attacks both the respiratory and nervous systems [7].

Why This Colony Matters

The Año Nuevo elephant seal colony is not just another wildlife population. It is one of the most intensively studied marine mammal colonies in the world, with scientists having tracked more than 55,000 individually identified animals over six decades [5]. The colony is also a symbol of one of conservation's most improbable victories.

Northern elephant seals were hunted nearly to extinction in the 19th century for their blubber. By the early 1900s, as few as 100 animals survived [8]. Mexico granted them protected status in 1922, followed shortly by the United States. Today, all roughly 150,000 northern elephant seals alive are descended from that tiny remnant population [8].

At Año Nuevo, no seals were observed at all until 1955. The first pup was born there in 1961. By the 1994-95 breeding season, approximately 2,000 pups were being born on the mainland annually [8]. During the winter breeding season, about 5,000 seals crowd the beaches — though by the time the outbreak was detected in late February, many adults had already departed, leaving roughly 1,350 animals on site [6].

"That long-term individual-based data set gives us a really unparalleled opportunity to understand how this virus affects uniquely identifiable animals," Beltran said [5]. In other words, the very thing that makes this outbreak a tragedy for conservation also makes it an unprecedented opportunity for science.

The Vector: Seabirds as Silent Carriers

Researchers believe the virus reached the elephant seals through contact with infected seabirds. Brandt's cormorants, Western gulls, and brown pelicans — the most abundant birds at Año Nuevo Island, just offshore — are highly susceptible to H5N1 [7]. Dead seabirds positive for the virus have been found at Año Nuevo and other California coastal locations during the winters of both 2025 and 2026 [2].

The pathway is straightforward: infected seabirds shed the virus through feces and respiratory secretions, contaminating the beaches and waters where elephant seals haul out and rest. Young, recently weaned pups — still building their immune systems and spending extended periods on the beach before heading to sea — are especially exposed [7].

This same transmission route devastated marine mammal populations in South America beginning in 2022. Between January and October 2023, at least 24,000 South American sea lions died from H5N1 along the Pacific and Atlantic coasts of Peru, Chile, and Argentina [9]. Most alarmingly for the Año Nuevo researchers, H5N1 killed an estimated 70% of southern elephant seal pups born during the 2023 breeding season in Argentina's Patagonia region [9].

"Everyone was waiting for the other shoe to drop," said Christine Johnson, director of UC Davis' Institute for Pandemic Insights, regarding the virus's inevitable arrival in California's marine mammals [6].

The Response

California State Parks moved swiftly after confirmation of the outbreak, closing public access to seal viewing areas and canceling the park's popular guided elephant seal tours for the remainder of the 2026 season [2]. The Marine Mammal Center, the Bay Area's primary marine mammal rescue organization, paused hands-on elephant seal and harbor seal response operations to prevent potential spread through rescue activities [5].

Researchers at Año Nuevo shifted to strict biosecurity protocols, disinfecting all equipment and maintaining maximum distance from the animals. Daily monitoring was also implemented at Point Reyes National Seashore, another major marine mammal site north of San Francisco [7].

The California Department of Public Health urged the public to maintain at least a 150-yard distance from any marine mammals or birds, whether they appear sick or healthy, along the entire California coast [10].

Source: Compiled from KQED, Inside Climate News, Wikipedia / multiple research sources

Data as of Mar 8, 2026CSV

Human Risk: Low But Not Zero

While the wildlife crisis deepens, public health officials have been careful to emphasize that the risk of H5N1 to the general public remains very low. The virus does not spread easily to humans, and nearly all documented human cases have involved people with direct, sustained contact with infected animals — primarily poultry and dairy workers [11].

Still, the numbers have been climbing. As of February 2026, there have been 71 confirmed human cases of H5N1 bird flu in North America, with 38 of those in California — the most of any state [6]. Two people have died [6]. In the Bay Area specifically, a child in Alameda County was diagnosed with bird flu in November 2025 in a case that puzzled researchers because no source of exposure could be identified, followed by a child in San Francisco and an adult San Francisco resident who had had direct contact with wild birds [3].

Wastewater surveillance in San Francisco has shown no evidence of widespread H5N1 circulation in the human population [12], a reassuring sign even as the virus continues to expand its range in wildlife.

A Global Crisis Arrives Locally

The Bay Area's experience is a local chapter of what scientists describe as the worst avian influenza outbreak in recorded history. Since 2022, H5N1 has killed or led to the culling of more than 166 million domestic poultry in the United States alone [6]. The virus has been detected in more than 12,700 wild birds across 51 U.S. jurisdictions and has spread to over 1,000 dairy herds in 17 states [11]. Globally, it has infected species ranging from polar bears to cougars, and it has reached Antarctica, where it killed more than 50 skuas during the 2023-24 summer season [9][13].

Scientists warn that the virus is now entrenched in global wildlife populations in a way that makes eradication virtually impossible. Each new species it infects represents another reservoir, another opportunity for mutation, and another potential pathway toward a strain that could more readily infect humans.

"It's completely out of control," one researcher told BBC Science Focus, warning that 2026 could see further escalation [14].

What Comes Next

For the Bay Area's peregrine falcons, the future depends on whether surviving populations can rebuild in the face of ongoing viral pressure. Unlike the DDT crisis, which was resolved by banning the pesticide, there is no equivalent policy lever for a virus circulating freely in wild bird populations worldwide. The monitoring networks that once tracked the species' recovery will now need to track whether it can survive this new threat [1].

For Año Nuevo's elephant seals, there is cautious optimism mixed with dread. The outbreak struck after the peak of breeding season, meaning most adult females and their nursing pups had already departed, potentially limiting the damage to this year's cohort [5]. But with 1,350 seals still on the beach and the virus confirmed in their midst, the situation remains volatile.

Christine Johnson of UC Davis described the detection as "exceptionally rapid" — a sign that surveillance systems are working [7]. But speed of detection cannot compensate for the absence of a cure. There is no vaccine approved for wild elephant seals, no treatment protocol, and no way to quarantine thousands of animals on an open beach.

The researchers at Año Nuevo will continue to watch, count, and document — as they have for six decades. The data they collect in the coming weeks will determine whether this outbreak resembles the short-lived marine mammal events seen in Maine in 2022 and Washington state in 2023, or the catastrophic die-offs that devastated South American colonies [5].

The Bay Area's wildlife — its falcons stooping over the Golden Gate, its elephant seals thundering across the beaches of Año Nuevo — has long been a point of regional pride and identity. Bird flu is testing whether that heritage can endure the worst pandemic the animal kingdom has ever seen.