Federal officials confirm botulism outbreak in Klamath Refuges, with 20,000 birds dead so far

On August 13, Outdoor living reported a suspected outbreak of avian botulism in the Klamath Basin National Wildlife Refuge Complex on the Oregon-California border. Biologists with the California Waterfowl Association had found about 500 dead birds, mostly ducks and other waterfowl, in the Tule Lake NWR, and they suspected that avian influenza might also play a role.

The botulism outbreak has now been confirmed by the U.S. Fish and Wildlife Service, and sanctuary managers fear they could be dealing with dual outbreaks of avian botulism and High Path Avian Influenza. The death toll at the Refuge Complex currently stands at about 20,000 birds, according to Jefferson Public Radio.

USFWS biologist John Vrandenburg told the Oregon-based news outlet Friday that sanctuary staff have been finding about 500 dead birds a day at Tule Lake NWR since the outbreak began in mid-August. Many of them were pintails, green-winged teals and other ducks that showed telltale signs of botulismcaused by a natural toxin that thrives in periods of low, stagnant water.

Similar deaths have occurred there in the past. In 2020, the NWR Complex experienced the worst botulism outbreak in the reserve’s history, with an estimated 60,000 birds lost.

Vrandenburg said recent water releases at Lower Klamath and Tule Lake NWRs have helped stem the losses they’ve seen so far. Those releases began Aug. 17, after Ducks Unlimited and the CWA appealed to to the Bureau of Reclamation and other water users to send more water from upstream to the system.

According to the refuge’s managers, they are better prepared to deal with botulism outbreaks after the experience they had four years ago, and there is now a bird rescue hospital at the NWR Complex. Jefferson Public RadioBut due to concerns about HPAI, which can be transmitted to humans and was identified at Tule Lake NWR in July, they have not yet been able to treat any birds there.

“We are well versed in dealing with botulism. This is a new pressure that we have never had to deal with before,” Vrandenburg told the Source weeklyreferring to HPAI.

Jefferson Public Radio reports that authorities are still waiting for more test results, but that the samples they have sent so far have only tested positive for botulism.

In an email statement to Outdoor living, A USFWS spokesman said that refuge managers appreciate the Bureau of Reclamation’s move to send more water to the Tule Lake and Lower Klamath NWRs. This is widely seen as the best way to mitigate the current outbreak, as it helps to mask the bacteria in the soil that cause botulism. Higher water levels also help prevent birds from congregating and accelerating the spread of both diseases.

“One of the most valuable tools to address an outbreak of botulism in birds is a sustained inflow to displace standing water,” the spokesperson said. “While it may take time, this inflow should reduce the impact of botulism.”

Read more: A Pacific waterfowl oasis is out of water. These duck hunters are footing the bill for more

But these water releases depend on complicated agreements between the Bureau of Reclamation, which manages the dams in the upper Klamath, and other water users. These include tribal peoples, ranchers and irrigators. The Bureau of Reclamation must also consider the health of endangered Chinook salmon and other fish and wildlife species that live in the greater Klamath River Basin. And because of all the competing demands for water from the Klamath River, the Lower Klamath Refuge Complex doesn’t always get enough water when ducks and other migratory birds need it most.

Established in 1908, the Lower Klamath Refuge Complex became the first waterfowl refuge in the United States and remains an important stopover for about 80 percent of all waterfowl that migrates through the Pacific Flyway. In 2022, however, after a summer of severe drought, the Lower Klamath and Tule Lake NWRs ran out of water and were closed to public bird hunting. Some wetlands there dried up completely.