Science & Nature
Bird Flu Toll Continues to Rise in Chicago. Are Massive Die-Offs the New Normal?
A dead merganser, seen on the Chicago lakefront, Feb. 1, 2025. (Patty Wetli / WTTW News)
Michele DiBernardo has started carrying garbage bags and rubber gloves in her coat pockets during her morning walks along the Chicago lakefront. Just in case she comes across more dead birds.
Over the weekend, DiBernardo collected six dead mergansers — a type of migratory duck — at Oak Street Beach, after seeing multiple reports on social media of hundreds of dead birds washing up on beaches all along the lakeshore, likely suffering from bird flu.
“I was like, ‘Well, I’m seven minutes from the beach.’ I felt like I had to act,” DiBernardo said.
An experienced rescuer with Chicago Bird Collision Monitors, DiBernardo is no stranger to encountering injured, sick or dead birds. But the current outbreak of avian influenza is like nothing she’s ever experienced, she said.
“This is just bad, it’s just heartbreaking, because there’s so many (sick birds),” she said. “I’m not hearing anything at all other than there’s nothing to be done.”
‘Unique and Devastating’
A group of dead mergansers on Chicago’s lakefront. (Courtesy of Chicago Bird Collision Monitors)
Avian influenza has been circulating in wild birds since the late 1990s, with some strains deadlier than others. The latest strain, H5N1, which broke out in 2021-22, is what’s known as “highly pathogenic” or HPAI for short, meaning it causes severe disease and has high mortality rates.
Where a 2015 outbreak was largely contained among waterfowl, which have long been identified as reservoirs for avian influenza, this strain of H5N1 has been “unique and devastating” in the scope of its spread and the variety of species involved, said Dr. Stephany Lewis, director of the wildlife medical clinic at the University of Illinois Urbana-Champaign.
“What we’re seeing that’s so different is a wider number of bird species — our raptors and scavengers like hawks, owls, eagles,” Lewis said.
Some of these species — like owls — don’t even feed on ducks, but are likely getting sick from eating the rats that eat the infected birds, she noted.
The danger posed to other birds was, in fact, what compelled DiBernardo to remove the dead mergansers from the Chicago shoreline.
Though it felt like an insult to toss the ducks in a trash bin — securely tied up in a plastic bag — the alternative of leaving the carcasses out to be picked over by scavengers seemed an even worse option, she said.
“I love birds and I don’t want the crows and seagulls and hawks and owls to get sick,” DiBernardo said.
The number of affected mammalian species has also mushroomed, according to Lewis.
In addition to expected scavengers like foxes and raccoons, in a startling development, herds of cattle have been infected. Cats are known to be particularly vulnerable, and marine mammals — including dolphins off the U.S. coasts and even a sea lion at Lincoln Park Zoo — have also succumbed, she said.
“It’s really far-reaching,” Lewis said of the outbreak. “And it doesn’t seem to be going away. It’s not behaving the way it normally does.”
Massively Underreported Toll
Dead geese, in December 2024, in the first wave of bird flu die-offs. (Courtesy of Chicago Bird Collision Monitors)
The virulence of this particular strain has led to the loss of some 150 million poultry birds in the U.S. alone, according to the Centers for Disease Control.
While those deaths have mostly occurred out of sight — reaching the broader public consciousness only when egg prices began to rise — the loss of wild birds has hit close to home for Chicagoans and it’s been highly visible, including a large die-off in late December.
“We are a very important place for migratory birds, so we’re face to face with something you think might only be in agricultural areas,” said Annette Prince, director of Chicago Bird Collision Monitors. “We’re seeing the toll avian flu is taking.”
The CDC has recorded 11,000 “detections” of the virus in wild birds since the 2022 outbreak was identified. According to the Illinois Department of Natural Resources, there have been 144 reported incidents in Illinois since Dec. 3, 2024.
Both those numbers are likely “massively underreported,” Lewis said.
For starters, there’s no way of knowing how many dead wild birds are never found, she said. And then there’s the fact that this epidemic has overwhelmed already underfunded and under-resourced agencies at the federal, state and local levels.
There isn’t enough capacity, Lewis said, to investigate every report of a sick or dead bird or to test them to confirm the virus.
According to Prince, large die-offs of 10 or more birds have been reported to authorities, but the carcasses have been left to rot in place.
“The question is, whose responsibility is it?” she asked. “There isn’t anyone tasked with doing this.”
For its part, the Chicago Park District said it deployed staff to beaches and lagoons after being contacted over the weekend about the lakefront “mortality event.”
“The district is addressing the removal and disposal of carcasses from park property,” Michele Lemons, Park District spokesperson, told WTTW News via email. “Residents can assist by reporting any sick or deceased birds to 311.”
What Chicagoans are experiencing is a small taste of the frustration and helplessness poultry farmers have been feeling as they’ve lost all of their birds to a seemingly unstoppable virus. The situation has been labeled unprecedented by some epidemiologists, and there’s no sense of how the virus might continue to mutate or why it seems to be gaining steam rather than petering out.
There’s no treatment and the disease is so contagious that once it’s detected, euthanasia of an entire poultry flock is the only available course of action.
Infected wild birds aren’t even given that humane option, Prince noted.
Wildlife rehabbers have been directed to halt admission of any waterfowl patients, out of concern for other animals in their care and to guard against potential spread of the virus among the birds’ human handlers.
In some cases, that’s meant injured birds not suffering from avian influenza are going without treatment.
“We had a goose that had a fishing line injury, that goose couldn’t get helped,” said Prince.
Long Way Until Spring
A sick merganser, found on a beach in Wilmette. (Courtesy of Chicago Bird Collision Monitors)
While there’s been much handwringing about whether avian influenza could mutate to the point of human-to-human spread — at this point, exposure to infected animals has been the only cause of disease in humans — wildlife professionals and advocates are equally worried that the virus could infect even more species, including songbirds. And that this year’s high level of mortality could represent a new normal.
“It’s not the future I want to see,” said Prince.
Bird populations have already declined dramatically due to factors such as habitat loss, pesticides and building collisions. Now tack on large-scale deaths from the virus, and “you worry about species that aren’t so resilient,” Lewis said.
Take the California condor.
The condor became extinct in the wild in 1987 when all remaining wild individuals were captured as part of a conservation effort to save the species. Today, there are 347 condors living in the wild and 214 in captivity — a success to be sure, but the species is still endangered — so when 20 of them died of suspected bird flu, alarm bells rang.
Because of the condor’s status, in 2023 the U.S. Fish and Wildlife Service, in collaboration with the U.S. Department of Agriculture, decided to approve, on an emergency basis, use of a vaccine previously not allowed in the U.S. So far it appears to be effective.
Could a vaccine be used to protect other populations of birds, both wild and domesticated?
It’s a topic that’s provoked heated debate among veterinarians, farmers and economists.
It’s almost impossible to envision a scenario where inoculating wild birds would be remotely feasible — outside of small, highly localized and heavily monitored groups like the condor, Lewis said.
As for vaccinating poultry flocks, there are trade implications, among other issues, driving policy: Other countries won’t allow the import of meat from vaccinated poultry because the birds could have been harboring the virus without getting sick.
In the absence of any short- or long-term solutions, it’s just a waiting game for warmer weather, which typically causes the virus’ impact to subside.
“The idea that the virus is going to survive as long as we have cold temperatures … it’s a long way to spring,” said Prince.
The Basics of Avian Influenza
Goldeneye ducks are another popular winter visitor in Chicago. (gjohnston photo / iStock)
Though the CDC says the current risk to humans from H5N1 remains low, influenza viruses are known for their adaptability and mutations.
Here’s what to know about how it spreads, how to protect yourself and your pets, and what to do if you come across a sick or dead bird.
How does it spread?
The virus is contained in the feces, mucous and other secretions of infected birds. It spreads by entering nasal passages, the mouth or eyes.
Wild birds spread it by dropping their poop — this is how a dolphin might become infected off the East Coast, for example.
It enters poultry flocks either because wild birds mix with the farm animals (say, on a “free range” farm) or because other animals such as rodents (rats or mice) or barnyard cats might be moving between the two populations, tracking feces on their feet.
The mobility of animals like mice and cats is another way the virus might move into the human environment, according to Dr. Carol Cardona, a specialist in avian health and a professor in veterinary and biomedical sciences at the University of Minnesota.
“We thought mice were resistant but now we’ve seen H5 breaks all the rules,” Cardona said during a recent media briefing. “I think that’s an important species because (mice) simply infiltrates everything in our human lives and can transmit to a variety of species.”
Why are there flare-ups?
The movement of migratory birds, particularly waterfowl, usually sparks seasonal outbreaks, typically as they spend winters in their southern ranges. And “south” for a lot of these birds means south of the Arctic.
In the central valley of California, the waterfowl population will balloon from 600,000 resident birds to more than 8 million, according to Dr. Maurice Pitesky of the University of California-Davis Veterinary School of Medicine.
Because a lot of the wetlands where ducks and geese would hang out have been destroyed, these birds use “sub-optimal” habitat like dairy lagoons, flooded rice fields, just ponding from rain, in many instances near farms, Pitesky said.
Migratory waterfowl also tend to congregate in tight quarters — in Chicago they might cluster, for example, on non-frozen sections of lakes and ponds, making it easier for the virus to move from bird to bird.
The virus also likes cold weather, so it’s a perfect storm of conditions leading to winter outbreaks.
How can I protect myself and/or my pets?
The first step is to avoid close contact with wild waterfowl, according to Dr. Stephany Lewis at the University of Illinois.
So now might be a good time to stop feeding geese and ducks, or attempting to pet them.
Cats, which are extremely vulnerable to H5N1, should be kept indoors, Lewis said, and dogs should be kept on a leash.
The Chicago Park District is urging “residents to follow park rules by keeping dogs leashed and avoiding any contact with bird remains.” Lewis added that people should keep their dogs from nosing into any bird poop.
Michele DiBernardo said the first thing she did as she picked up dead ducks from Oak Street Beach was to warn dog owners about the danger and ask them to leash their pets. “I actually had two people thank me. Normally people yell at me when I tell them to put their dog on a leash,” she said.
What should I do if I see a sick or dead bird?
First, know how to identify the clinical signs of avian influenza, which are typically neurologic, Lewis said.
Symptoms include tremors, difficulty standing, lethargy and cloudy eyes.
“They’re just not moving at all or their head is spinning around, they’re just stuck, unable to move,” is how DiBernardo described it. “It’s just heartbreaking to see.”
In some instances, a volunteer with Chicago Bird Collision Monitors might be able to fetch the bird and take it to the lone wildlife rehabber willing to perform euthanasia. Members of the public shouldn’t attempt to handle sick birds, IDNR said.
The city of Chicago is asking people to call 311, and people can contact IDNR if they see more than five dead birds.
To dispose of a dead bird yourself, follow guidelines from the Illinois Department of Public Health, which include using disposable rubber gloves, wearing an N95 mask and placing the bird in a doubled plastic bag.
Is there anything I can do to help the birds?
Support researchers, support wildlife biologists, support wildlife rehabbers, Lewis said.
Support birds in general by bird-proofing windows to reduce window collisions, she added, and keep cats indoors — not to protect the cat but to safeguard birds. “Cats are just devastating to our songbirds,” Lewis said.
And push to limit the use of rodenticides, specifically anticoagulants, which unintentionally kill the raptors and scavengers that feed on poisoned rats.
Contact Patty Wetli: @pattywetli | (773) 509-5623 | [email protected]
