Birds, mammals in Lake Tahoe area dying from avian flu

Wildlife—birds and some mammals—in the greater Lake Tahoe area are dying from avian flu, the virus that is decimating the poultry industry.

However, no one knows exactly how many wild animals have died from highly pathogenic avian influenza or HPAI. That’s because animals die every year from a variety of causes without their deaths ever being recorded or investigated.

State agencies, and some cities and counties, collect data when people report a dead animal, with testing coming afterward. More populated areas tend to have the highest number of cases because more people are making reports.

“A tiny fraction of what happens in the landscape is reported to us,” Nate LaHue, wildlife veterinarian with Nevada Department of Wildlife, said. Even so, he added, “Any bird that preys on waterfowl is potentially at risk.”

In 2022-23, the first season of this avian flu outbreak, the California Department of Fish and Wildlife had nine detections of the virus in birds in the Lake Tahoe area, with two being in South Lake Tahoe; two detections in 2023-24, with one of those in the city limits; and no submissions for 2024-25 as of mid-March.

Birds like this one at Fallen Leaf Lake could be susceptible to contracting avian flu. (Image: Kathryn Reed)

Since 2022, CDFW has reported 15 local detections in mammals, with two raccoons in South Lake Tahoe contracting the virus that first year.

Statewide, CDFW reported 367 cases of avian flu in wild birds in 2022-23, with detections in 11 wild mammals; in 2023-24 119 wild bird detections, with one mammal;  2024-through mid-March 2025 241 wild birds, three mammals.

“Avian influenza viruses naturally occur in waterfowl and shorebirds,” explained Krysta Rogers, CDFW senior environmental scientist. “Over history these viruses naturally circulate. Water is important in transmission. Even if they are not getting sick from it, they can shed the virus in bodily fluids—feces and saliva—and if another bird ingests it, they could get sick.”

Her department is responsible for all wildlife in California. The H5N1 strain is what has Rogers and her colleagues throughout the country worried.

“It has changed in that it can infect a diversity of wild bird species, and mammal species and has a high mortality rate, whereas in the past that did not happen,” she said.

The Nevada side of the basin has not recorded a single avian flu case since the outbreak started three years ago.

“We are certainly concerned about its effect on wildlife,” NDOW’s LaHue said of avian flu. “I would say where we receive most reports is mostly raptors because raptors are highly susceptible because they are in contact with waterfowl with consumption.”

Detections are close by—in the Carson Valley, Washoe Valley and Reno.

“There really is not much we can do about it other than cross fingers and hope through waterfowl migration and movement that birds adapt to it,” LaHue said.

While the U.S. Forest Service is the largest land owner in the basin, it is in the business of protecting habitat for animals, not the actual animals. At this point the Lake Tahoe Basin Management Unit has nothing to do with avian flu.

If those in the animal world find protected species declining in alarming numbers, that is when habitat policy changes could be warranted. We aren’t there yet.

The California Tahoe Conservancy does some wildlife breeding monitoring, but is not actively involved with avian flu detections.

“The Conservancy monitors wildlife breeding activity in relation to land management projects such as forestry and meadow restoration projects. Surveys are completed for threatened, endangered, or otherwise sensitive wildlife species that have the potential to occur within project boundaries,” Chris Carney, spokesperson for CTC, said. “The Conservancy does monitor one peregrine falcon nest in collaboration with TRPA and other partner efforts to monitor peregrine breeding activity in the Lake Tahoe Basin.”

Peregrine falcons and other raptors like bald eagles and ospreys could find their numbers declining if they were to eat an infected shorebird—which is what many raptors like to dine on.

In early 2025, Nevada reported a great horned owl and golden eagle tested  positive for HPAI. The state has also seen the virus in a single sage grouse, a group of quail, and Cooper’s hawks.

Both state wildlife officials said this version of avian flu is similar to the Covid virus is that it mutates, changes, but is always present. For the animals, though, there is no vaccination or other preventative measures that can be taken.

“It is likely here to stay in some version,” Rogers said of the avian flu virus.

Note: A version of this story first appeared in Tahoe In Depth.