A new study using the largest network of microphones to track birds in the United States is providing crucial insights for managing and restoring fire-prone forests across California's Sierra Nevada region.
The research, published March 11 in Frontiers in Ecology and the Environment, demonstrates how emerging bioacoustics technology can enhance wildlife monitoring and forest management.
The study, led by researchers at the Cornell Lab of Ornithology's K. Lisa Yang Center for Conservation Bioacoustics and the University of Wisconsin, analyzed more than 700,000 hours of audio recordings from more than 1,600 sites spanning approximately 6 million acres of Sierra Nevada forest.
"The amount of coverage allows us to draw really powerful inferences about what's happening with species across many different locations," said lead author Kristin Brunk, a postdoctoral research associate at the Yang Center.
The team focused on 10 important bird species, including spotted owls and woodpeckers, that can provide information about the forest's health. To identify birds from the recordings, the team used BirdNET, a machine-learning algorithm developed by researchers at the Yang Center and at Chemnitz University of Technology in Germany. They then related these findings to fire frequency and forest characteristics, such as canopy cover, canopy height and the number of trees per hectare - variables that managers commonly use in fire management decisions.
"We designed our analysis to bridge the gap between research and practical application," said co-author Connor Wood, a researcher at the Yang Center. "By focusing on metrics that forest managers already use, we've made it easier for them to incorporate our findings into their decision-making processes.
"We were able to take bird diversity data and relate it to the forest conditions that are most relevant to managers," Wood said, "helping them balance often competing objectives, such as managing high and growing risk of large fires and conserving biodiversity; to me that is really powerful."
This information is particularly valuable now, as forest managers face tough decisions about preventing destructive wildfires while protecting wildlife. The study creates detailed maps showing where different birds are likely to live, helping managers make better-informed decisions about where to thin forests or conduct controlled burns.
"Within the Sierra Nevada, I think this is really going to enhance the way that forest management works," Brunk said. "Not only do we have this highly detailed model, but we also have the ability to keep iteratively refitting these models and making them better over time."
The researchers emphasize that their research could serve as a model for other regions facing similar conservation challenges. "It's sort of a blueprint for how monitoring bird songs and calls can inform management," Brunk said. "I'm really hoping that we'll hear from other researchers who are trying to do similar things."
Acoustic monitoring with microphone arrays is a cost-effective solution for monitoring birds compared to traditional survey methods, Brunk said. "If you think about what the cost would have been to get that amount of information by having biologists counting birds across the landscape, the cost effectiveness can't really be matched," she said.
Looking ahead, the research team is already using these findings to project how different species might respond to various climate-change and forest-restoration activities.
Said Wood: "By combining new technologies with practical management needs, we're creating tools that can help protect both forests and wildlife during a time of rapid environmental change."
The research was conducted in collaboration with the U.S. Forest Service, the University of Wisconsin, Madison; Oregon State University; the University of California, Merced; and Chemnitz University of Technology.
Kathi Borgmann is communications manager for the Cornell Lab of Ornithology.
