TILLAMOOK STATE FOREST, Ore. — Oregon forestry officials are turning to new technology in an effort to better monitor and protect two threatened bird species—the northern spotted owl and the marbled murrelet—across the state’s vast forestlands.
The Oregon Department of Forestry (ODF) is responsible for ensuring compliance with both state and federal endangered species laws. A key part of that effort involves surveying where these species live and developing strategies to preserve and improve their habitat.
Traditionally, biologists have relied on “call-back” surveys to locate northern spotted owls. The method involves broadcasting owl calls in the forest and listening for a response, following protocols approved by the U.S. Fish and Wildlife Service, the federal agency that administers the Endangered Species Act.
“Right now, we use call-back surveys to determine where spotted owls are,” said Mike Davis, a state forest biologist with ODF. “As the name implies, we go out in the forest and broadcast owl calls and wait for them to respond.”
But the method comes with challenges. Surveys are typically conducted at night and often only once per location. Contract biologists conducting the work must navigate dark, rugged terrain, frequently in poor weather conditions.
“It is not easy work nor a fun experience some nights,” Davis said.
In recent years, another complication has emerged: the spread of barred owls, an invasive species that is displacing northern spotted owls from their traditional habitats.
“The barred owls are basically bullying the northern spotted owls out of their preferred habitat,” Davis said. “We are seeing spotted owls at atypical higher elevations now and calling back less and less because that call alerts barred owls to their location.”
These limitations have prompted ODF to explore alternative survey methods. Since 2022, the agency has been testing Autonomous Recording Units, or ARUs—devices that can capture environmental sounds over extended periods without requiring a human presence.
“ARUs have many advantages,” Davis said. “They can be left out in the field several weeks or more, set up and retrieved anytime, record multiple species, and can be analyzed back in the office.”
Roughly the size of a trail camera, ARUs are equipped with microphones, batteries, and removable memory cards. Once retrieved, the recordings are processed using specialized software that converts sounds into visual spectrograms, allowing researchers to identify species based on unique call patterns.
ODF officials believe the technology could also significantly reduce costs. The agency currently spends about $2 million annually on northern spotted owl surveys and an additional $500,000 on marbled murrelet monitoring.
“ARUs with rechargeable batteries, memory cards and software are coming in at about $600 to $700 per device,” said Corey Grinnell, Biological Support Unit Manager for ODF’s State Forest Division.
The agency currently has 23 units in operation and plans to expand their use. However, broader adoption depends on final approval of survey protocols by federal regulators.
“We are waiting for the USFWS to approve a final protocol for using ARUs,” Grinnell said. “Once that happens, we can integrate them more into our management plans.”
The shift in monitoring techniques comes as ODF prepares for a broader transition to a new Habitat Conservation Plan, or HCP, expected to be approved later this year by the National Oceanic and Atmospheric Administration Fisheries and the USFWS. The plan would provide a 70-year framework for managing 17 terrestrial and aquatic species while allowing continued forest operations.
“The entire point of the HCP is to keep this working forest working,” Grinnell said.
Officials say combining improved technology with long-term planning will help balance environmental protection with economic and community benefits.
State forests are legally required to provide a mix of social, economic, and environmental value, including wildlife habitat, clean water, timber revenue, and recreational opportunities.
“Our goal is to create healthy, productive forests and high-quality habitat for native fish and wildlife,” Grinnell said. “To do that, we embrace cutting-edge technology to improve our data in the most cost-effective way. ARUs are one tool to help us make the best management decisions.”
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