From the Spring 2026 concern of Dwelling Chook journal. Subscribe now.
A Nice Horned Owl quietly sits in her dim-lit quarantine crate within the clinic of The Raptor Heart on the College of Minnesota in St. Paul, staring off into house following her consumption examination. Discovered in the course of the street simply exterior of the Twin Cities in April 2022, the owl was presumed to have hit her head after being side-swiped by a automobile. She appeared completely regular, in any other case—actually not contaminated with a raptor-killing virus.
So it was a shock to Dr. Dana Franzen-Klein, the middle’s medical director, when check outcomes for extremely pathogenic avian influenza, or HPAI, got here again constructive on the owl.
“I’d by no means seen [an HPAI infection] that gentle earlier than,” says Franzen-Klein. “She didn’t have any of the extreme indicators, like seizures.”
The Nice Horned Owl made a full restoration, from her accidents and HPAI, inside a number of weeks. However most raptors admitted to the middle that 12 months, on the peak of the 2022 North American HPAI outbreak, didn’t share this owl’s lucky destiny. Out of the 213 admitted raptors that examined constructive for HPAI that 12 months, she was the only real survivor.
Nonetheless, new analysis suggests extra wild raptors could also be surviving the illness than beforehand thought. A examine led by employees at The Raptor Heart and printed in February 2025 within the journal Scientific Reviews discovered that 23% of examined raptors in Minnesota carried antibodies in opposition to HPAI. Of these birds, 70% had antibodies particular to the H5N1 pressure that has ravaged North America in the previous couple of years.
Antibodies point out that the hen had caught the illness up to now and survived it, boosting its immune system in opposition to reinfection. Franzen-Klein says antibodies for avian influenza had beforehand not often been detected in raptors. Earlier than this examine, many researchers had assumed most birds had been dying from H5N1, however the Nice Horned Owl’s survival gave veterinarians pause.
“Her story was what spawned this complete undertaking,” says Dr. Kelsey Rayment, a former middle veterinarian who spearheaded the antibody examine. “As a result of we had been like … ‘If one may survive right here, may there be others surviving on the market?’”
Avian influenza has existed in numerous types world wide because the 1800s, rising and falling with hen migration as contaminated birds carry the virus throughout continents. In recent times, the illness has brought on quite a few mass die-offs of untamed birds—from Snow Geese in Pennsylvania to Widespread Cranes in Germany—and unfold to mammals like purple foxes in North America. About 20,000 HPAI circumstances in birds and mammals have been confirmed in the USA since 2022.
Firstly of the outbreak in Minnesota in 2022, The Raptor Heart’s veterinarians took on an onslaught of HPAI-ridden sufferers. On the time, the vets thought most or all of those birds had been unlikely to make it. Franzen-Klein dealt with many of the HPAI sufferers that 12 months, and he or she says many had been gravely ailing, stumbling about and having seizures. HPAI causes irritation within the mind, and in lots of circumstances, placing the hen to sleep was the one humane choice.
“It’s very, very exhausting to take care of that,” says Franzen-Klein, “and see birds struggling.”
Rayment joined the triage staff on the middle close to the tail finish of the spring 2022 peak. She and different veterinarians puzzled if there have been milder circumstances that by no means reached the clinic.
“We’re solely seeing actually sick birds,” she says.
So Rayment began the undertaking to gather blood samples from middle sufferers and a choice of wild raptors captured for analysis and banding at Hawk Ridge Chook Observatory in Duluth, Minnesota, about two hours’ drive north of the Twin Cities. After analyzing the samples, her staff made the surprising discovery of flu antibodies in lots of birds.
Rayment was notably impressed by the big proportion of Bald Eagles that had antibodies, with 54% of examined eagles displaying antibodies to H5N1 HPAI, and 15% to different avian influenza strains. To Rayment, these numbers present simply what number of raptors had been surviving the illness.
“While you are available in and also you’re seeing all these birds actually sick and dying,” Rayment says, “the truth that we had been in a position to see that some had survived was slightly little bit of hope for the longer term resilience of the inhabitants.”
Since then, the variety of constructive circumstances of the illness has declined, though HPAI reappears in birds and mammals each fall by means of early spring. The Raptor Heart noticed 213 confirmed constructive circumstances in 2022, however solely 10 in 2023 and 14 in 2024. Fourteen circumstances in 2025 have been confirmed constructive, whereas 20 extra are within the technique of affirmation at an off-site lab.
Rayment and Franzen-Klein agreed that antibodies could also be one contributor within the lowered variety of sick raptors displaying up on the middle.
“It’s doubtless that there’s now extra immunity within the raptor populations, contributing to the decline in circumstances,” Rayment says, “which we may see within the antibodies detected on this examine.”
The 2022 North American HPAI outbreak was notably nasty when in comparison with earlier outbreaks.
“That is the one outbreak, at the very least in recent times, that has brought on this stage of morbidity and mortality in wildlife species,” says Dr. Sara Childs-Sanford, director of the Janet L. Swanson Wildlife Hospital at Cornell College. “We don’t sometimes see raptors being affected to this stage.”
The H5N1 pressure of HPAI additionally has a novel endurance, having hung round for a number of years. Earlier HPAI outbreaks have blossomed throughout migration season earlier than disappearing as soon as birds unfold out for breeding. H5N1, nonetheless, is on its technique to changing into an endemic virus—just like the frequent chilly in people, solely far more lethal.
Neil Paprocki was a PhD scholar on the College of Idaho when HPAI swept the continent in 2022. He estimates that greater than 1 / 4 of North America’s Tough-legged Hawk inhabitants could have died at the beginning of the outbreak.
Paprocki tracked 71 Tough-legged Hawks with GPS gadgets all through the outbreak. He remembers watching GPS-tagged hawks go down like flies within the few months that the virus was at its peak. Every time a tagged roughleg went down, native sport wardens had been despatched to recuperate the our bodies and check for the reason for demise.
“I suspected after a pair birds what was occurring, nevertheless it was simply actually overwhelming seeing hen after hen go down,” Paprocki says. “It was very complicated, irritating, scary.”
Between March 2022 and March 2023, 29 of the tracked hawks died or had been presumed useless. Of these, 11 deaths had been confirmed to be from HPAI, and one other 9 had been doubtless, although unconfirmed, HPAI circumstances. The general 47% mortality fee in 2022 was far increased than the conventional vary of annual deaths—between 3% and 17%—that Paprocki had noticed whereas finding out roughlegs in earlier years.
Since 2022, nonetheless, HPAI-related mortality amongst Tough-legged Hawks has dramatically fallen. Paprocki solely noticed one H5N1 mortality in his examine cohort in 2024, and none in 2025. He believes this lower could also be because of the virus itself rising weaker.
“If the virus was as virulent because it was [in 2022], a few of these youthful birds may nonetheless be getting uncovered to the virus and have fairly excessive mortality charges,” says Paprocki, who’s now a postdoctoral researcher on the Cornell Lab of Ornithology. “We all know the virus remains to be on the market, nevertheless it doesn’t appear to be on the market on the stage that it was in 2022.”
Researchers at The Raptor Heart in Minnesota are nonetheless grappling with a slew of recent questions on HPAI.
“We don’t precisely know why some people survive an infection and a few don’t,” Franzen-Klein says.
The Raptor Heart is constant to diligently gather blood samples and check for antibodies in clinic sufferers and in Hawk Ridge’s banded birds.
“It’s actually exhausting to say what’s going to occur sooner or later,” says Franzen-Klein, “as a result of this virus may change in a manner the place it makes birds sick once more and we now have one other main die-off.”
As for the feisty Nice Horned Owl that earned the title of sole survivor in the course of the peak of the HPAI outbreak in spring 2022, she was banded after recuperation at The Raptor Heart and launched in a public park in Could 2022 close to the place she was initially discovered. Her band has not been recovered since.
“Hopefully,” says Franzen-Klein, “which means she’s nonetheless doing nicely.”
