BAKER CITY, Ore. — Federal workers killed about 160 ravens this year in the sagebrush country east of Baker City in the final year of a four-year experiment designed to protect another bird, the sage grouse, from raven predation.

That’s about three times more ravens killed than in 2023.

Ravens eat sage grouse eggs and chicks, said Brian Ratliff, district wildlife biologist at the Oregon Department of Fish and Wildlife’s Baker City office.

Researchers have found that when raven population densities exceed a certain level, as they did in sage grouse habitat east of Baker City based on surveys from 2016-19, ravens pose a particular threat to sage grouse.

A 2017 report written by biologists from ODFW and the U.S. Fish and Wildlife Service listed predation by ravens as a significant threat to sage grouse.

Sage grouse have been a candidate for federal protection under the Endangered Species Act for more than two decades.

The U.S. Fish and Wildlife Service has so far declined to list the species as threatened or endangered.

The sage grouse population in Baker County declined by an estimated 73% between 2006 and 2016, according to ODFW.

More recently, in a September 2023 report, ODFW stated that sage grouse populations in the BLM’s Baker Resource Area, which includes Baker County, appear to be “stable” over the past five to eight years.

Baker County accounts for less than 10% of Oregon’s sage grouse habitat, and 3.5% of the state’s population, according to ODFW. The bird’s primary habitat, and populations, in Oregon are in the southeast corner, including Malheur, Harney and Lake counties.

Following the 2016-19 raven density surveys, ODFW applied for a federal permit to kill ravens during a four-year experiment in the Baker Priority Area of Conservation — PAC — for sage grouse. It covers about 336,000 acres, all east of Interstate 84. The PAC extends north to near Thief Valley Reservoir, east to the Love Reservoir area about 20 miles east of Baker City, and southeast to near Durkee.

The state agency needed a permit because ravens are protected by the 1918 Migratory Bird Act.

The Fish and Wildlife Service granted ODFW the permit in 2021, despite objections from some conservation groups.

Joe Liebezeit, assistant director of statewide conservation for the Bird Alliance of Oregon, said in April 2024 that the organization opposes the ODFW policy of killing one native species — ravens — with the putative goal of helping another — sage grouse.

“We just don’t feel like the science was there to back up killing ravens to protect sage grouse,” Liebezeit said.

He said the organization also objects to killing ravens on “ethical grounds.”

Liebezeit said multiple factors likely have contributed to the significant decline in sage grouse populations in Baker County over the past two decades or so, including livestock grazing and invasive weeds.

He said the organization sometimes endorses nonlethal methods, such as removing raven nests.

Escalating efforts to reduce raven numbers

ODFW enlisted a federal agency, Wildlife Services, to target ravens during the four-year project.

For the first two years, 2021 and 2022, Wildlife Services destroyed raven nests but didn’t poison or shoot any birds, Ratliff said.

The tactic was largely fruitless, he said, because ravens “are really good at renesting.”

In some cases ravens rebuilt nests twice, Ratliff said.

“Ravens are very smart birds,” he said.

The federal permit allowed ODFW in the final two years, 2023 and 2024, to distribute poisoned chicken eggs or meat near raven nests with a goal of killing ravens.

The poison, known as DRC-1339, is especially toxic to ravens and other corvids, which include crows, jays and magpies, but has little to no effect on other birds, such as hawks and eagles, or on mammals, Ratliff said.

According to the Fish and Wildlife Service’s March 2021 decision allowing ODFW to kill ravens, “the risk of exposure to non-target birds is low because bait sites will be monitored. Any incidental take of corvids (or other scavengers) are likely to be very few or non-existent and there not have any significant effect on local populations.”

In 2023, Wildlife Services workers targeted 18 nests where there was documented evidence, in the form of sage grouse egg remnants, that ravens from that nest had eaten sage grouse eggs, Ratliff said.

Poisoned eggs were also set near raven nests within two miles of a sage grouse “lek” — the areas where birds gather each spring during the breeding season.

Before setting out poisoned eggs, workers placed untainted chicken eggs near the nests along with remote cameras, Ratliff said. If ravens took the eggs, Wildlife Service employees returned to place poisoned eggs.

If birds other than ravens took the eggs, then workers didn’t put out poisoned eggs to avoid killing species other than ravens, Ratliff said.

Wildlife Services workers distributed 490 poisoned eggs in 2023.

Ratliff said studies of the poisoned egg technique showed that, on average, one raven was killed for every 10 eggs. Based on that ratio, ODFW estimated that 49 ravens were killed in 2023.

(The permit allowed the agency to kill up to 400 ravens.)

Ratliff said employees did find three raven carcasses near nests. The dead birds were destroyed to prevent scavengers from eating them and potentially being poisoned.

Last year’s project also showed that ravens in some cases cache eggs rather than eating them immediately, Ratliff said.

Because the poison dissipates within a few days to nonlethal levels, those cached eggs won’t kill ravens, he said.

2024 campaign

The permit allows ODFW in the final year to continue distributing poisoned eggs, but it also authorizes workers to shoot ravens.

Wildlife Services employees set out more than three times as many eggs — 1,379.

Based on the 1 to 10 ratio, Ratliff estimates that the poisoned eggs killed 137 ravens.

Workers also shot 22 ravens, bringing the estimated total to 159 ravens killed.

Ratliff said workers used multiple tactics to try to avoid poisoning birds other than ravens, particularly other corvids such as magpies.

For instance, employees set out untainted eggs near raven nests and sage grouse leks and then returned to see if the eggs had been pecked by birds.

Ratliff said ravens are capable of picking up eggs and flying away with them, but magpies are not. If workers found peck marks on eggs, that suggested that magpies or other birds had been there, and no poisoned eggs were distributed in that area, Ratliff said.

Workers also avoided placing poisoned eggs in draws, where magpies tend to congregate, he said.

Results waiting on research

Ratliff said it’s not clear how effective the four-year campaign has been.

Biologists from ODFW and Oregon State University are studying results from the project but they have not published any conclusions about whether killing ravens and destroying their nests is helping sage grouse populations rebound in Baker County.

There is anecdotal evidence that the effort has benefited sage grouse, Ratliff said.

Workers counted five fewer raven nests than in 2023, he said.

“We are seeing fewer ravens than a few years ago, which makes sense,” he said.

However, Ratliff said the only long-term solution is to keep raven densities from exceeding the threshold that research shows is especially dangerous for sage grouse.

He said ravens, left to their own devices, almost certainly would start to grow in numbers.

“Ravens can rebound quickly,” he said. “They’re prolific, and they can live just about anywhere.”

Ratliff said ODFW officials haven’t decided which measures they might take to try to limit raven densities in the future.

Officials are considering another method to try to bolster Baker County’s sage grouse population, he said — capturing birds in the southeast corner of the state and releasing them in Baker County over several years.

ODFW has never tried that tactic, but “we’re willing to give it a shot,” he said.

Sage grouse have done well this year in much of the state, although that trend didn’t include Baker County, Ratliff said.