Engineering a Comeback: How Ducks Unlimited Science and Collaboration Offer Hope for Klamath Basin

U.S. Fish and Wildlife staff banding waterfowl on the Tule Lake and Lower Klamath National Wildlife Refuges during the 2025 season after new data and collaborative water management helped mitigate a botulism outbreak.

RANCHO CORDOVA, Calif. – Jan. 27, 2026 - After years of drought and poor wetland conditions, the 2025 season at Tule Lake and Lower Klamath national wildlife refuges marked an improvement for habitat recovery and waterfowl response in the Klamath Basin. Improved water management, strong collaboration among partners and data-driven decision-making supported migrating and breeding birds while reducing disease risk and setting the stage for continued recovery.

As part of Ducks Unlimited’s Klamath Basin Initiative, these improvements reflect a broader, long-term commitment to restoring wetlands, strengthening water management and supporting the wildlife and communities that depend on this landscape. The Initiative brings together partners, science and strategic investments to rebuild wetland systems across the Basin, and the progress seen this season at Tule Lake and Lower Klamath demonstrates the impact of that collaborative approach.

A Promising Spring, With More Work Ahead

Following a devastating botulism outbreak in 2024, last spring delivered encouraging signs across both refuges. According to John Vradenburg, supervisory biologist for the refuges, 2025 spring migration conditions were notably improved compared to recent years.

“The spring was really good,” Vradenburg said. “We had a good migration and saw a significant rebound of spring migrants. We’re still not where we should be in terms of long-term numbers, but going from zero to a quarter of a million birds was exciting.”

Lower Klamath, which had been dry for an extended period, needed time to respond. The prolonged drought delayed habitat recovery pushing nest initiation later into the season. However, the wet winter, a record snowpack and a great deal of community cooperation flooded 37,000 acres at Lower Klamath during the winter of 2024 - 2025, an extraordinary feat for a refuge that was nearly completely dry just two years ago.

Peak brood numbers occurred in late June and early July. While overall brood numbers were slightly lower than expected and densities were reduced, refuge production still exceeded expectations, Vradenburg said.

Preventing Botulism at Tule Lake

One of the most significant success stories of 2025 came from proactive water management at Tule Lake. Early in the summer, water levels began trending toward the elevations seen during the 2024 botulism outbreak, when refuge staff were picking up 100 to 200 dead birds a day, according to Vradenburg.

When staff recognized the early warning signs of botulism returning in 2025, they relied on improved data to quickly alert the Tulelake Irrigation District and the Bureau of Reclamation. In response, irrigation managers adjusted water operations, resulting in rapid habitat improvements that made a substantial difference for waterfowl.

“Those changes really helped,” Vradenburg said. “Counts dropped from 100 to 200 deceased birds a day to one or two a day, and weekly counts fell to 10 to 20 birds instead of the thousands we saw in 2024.”

By the time fall migration began, refuge water elevations had stabilized at safer levels.

“The proactive water management really helped stem the spread of botulism,” Vradenburg said. “It was a really good collaborative effort between all the players in the Klamath Basin.”

The coordinated response also benefited endangered Lost River and shortnose suckers, which were detected in Tule Lake units 1A and 1B. Tulelake Irrigation District was instrumental in managing stable wetland and farm field water supplies, reinforcing the shared goal of balancing ecological and agricultural needs on Tule Lake.

“The 2025 winter gave us the opportunity to manage our district and water supply more closely to ideal operations than we have been able to for quite a few years,” said Brad Kirby, manager of the Tulelake Irrigation District. “The results of the management efforts and collaboration speak for themselves, crops were produced and waterfowl, fish, and other wildlife were provided with habitat and protections sufficient to thrive.”

“Let’s have fish, ducks and farms. That’s what we’re trying to focus on,” Vradenburg said.

Using Data to Manage Against Disease

A key element in preventing another botulism outbreak was high-tech elevation data collected during the drought. Ducks Unlimited funded two aerial topographic survey flights while wetlands were completely dry, allowing managers to gather detailed elevation information. Additional surveying by DU was conducted while wetlands were flooded to refine the data.

DU engineers and Vradenburg then used those datasets to build a model identifying wetland areas most vulnerable to botulism under different water depths.
“We could show exactly what percentage of the wetland was at risk and how every inch of water made a difference,” Vradenburg said. “That gave us real numbers to share with the irrigation districts and helped communicate why operational changes mattered.”

The modeling effort proved critical.

“Without that data, we probably would have ended up with the same botulism issues we saw in 2024,” Vradenburg said. “The goal is to guide water management decisions so we’re not reacting to botulism, we’re managing against it.”

The approach reflects a broader shift in management philosophy.

“For DU, we often solve waterfowl habitat problems through on-the-ground engineering solutions,” said Jeff McCreary, director of operations for DU’s Western Region. “That kind of information gave everyone a much clearer picture of how water moves across the refuge and allows managers to be proactive instead of reactive, especially when it comes to disease risk and habitat quality. DU is proud to work with our partners to provide this support.”

Strong Production and Banding Success

Improved habitat conditions translated directly into on-the-ground success. Increased wetland availability supported more broods across the landscape, along with a noticeable increase in avian predators, a sign of a more functional and productive ecosystem.

Those conditions resulted in a strong banding season. Refuge staff banded approximately 8,000 ducks on the California side of the Klamath Basin and an additional 2,000 geese across California and Oregon.

“We saw almost every species in the Pacific Flyway represented in our banding totals,” Vradenburg said.

Species banded included gadwall, redhead, mallard, green-winged teal, northern shoveler, scaup, ruddy duck, hooded merganser, American wigeon, northern pintail and ring-necked duck.

One particularly encouraging trend is the return of diving ducks.

“In 2024, we saw the return of redheads, and last year they were the second most abundant duck we banded behind gadwalls,” Vradenburg said. “We also saw a higher variety of diving ducks, which is a strong indicator of the trajectory we’re on.”

In a landscape historically known for diving duck production, seeing those species refill their ecological niches is another important indicator of habitat quality.

“The return of diving ducks, the strong production numbers and the reduced botulism impacts all point to the same conclusion,” McCreary said. “When we manage water collaboratively and use the best available science, wetlands respond, and birds respond with them.”

Fall Conditions Improved, Despite Data Gaps

Heading into fall migration, habitat conditions remain improved, though still short of long-term goals.

The refuges had the most water on them since 2019, according to Vradenburg.

Early migrants such as northern pintail, green-winged teal and white-fronted geese arrived on schedule, though overall migration slowed due to weather conditions. Bird numbers were currently lower than expected, but monitoring last year was a challenge due to federal budget constraints.

Even so, observers were seeing cinnamon teal and other species late into fall, suggesting that fall migration is once again prolonged. Large numbers of diving ducks—estimated at more than a million—were observed on Upper Klamath Lake, along with substantial numbers of puddle ducks.

With additional water continuing to move onto the refuges, managers are optimistic for this winter and spring.

“As birds arrive, there are a lot of wetlands and a lot of food for them,” Vradenburg said.

Looking Ahead

The 2025 season demonstrated what’s possible when water returns to the landscape and partners work together across the Klamath Basin. While challenges remain and full recovery will take time, the response of wetlands and wildlife at Tule Lake and Lower Klamath offers renewed hope.

“Last year showed what can happen when science, collaboration and water all come together,” McCreary said. “DU’s Klamath Basin Initiative is implementing multiple near term Refuge infrastructure improvement projects, as well as longer term wetlands-based solutions that will benefit waterfowl, agriculture, endangered fish, and most importantly Klamath communities.  DU is delivering lasting benefits for the Klamath Basin by collaborating on mutually beneficial outcomes.”

To learn more about Ducks Unlimited’s work in this vital landscape, visit the Klamath Basin Initiative webpage.

Please visit the new DU Media Toolkit page for essential resources about Ducks Unlimited’s conservation mission.

Ducks Unlimited Inc. is the world's largest nonprofit organization dedicated to conserving North America's continually disappearing wetlands, grasslands and other waterfowl habitats. Established in 1937, Ducks Unlimited has restored or protected more than 19 million acres thanks to contributions from more than a million supporters across the continent. Guided by science, DU’s projects benefit waterfowl, wildlife and people in all 50 states. DU is growing its mission through a historic $3 billion Conservation For A Continent capital campaign. Learn more at www.ducks.org.
 
Media Contact:
Molly Jarone
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