Conservation

The Common Raven Boom in the Rugged West Isn't Necessarily a Good Thing

The raven population has ballooned over past decades, upsetting ecosystems and endangering wildlife. To check the ravenous birds, conservationists are cleaning up trash and shooting lasers.

This past fall, the U.S. Fish and Wildlife Service convened dozens of conservation organizations in Palm Springs, California, for what might seem like an unlikely event given the ritzy locale: the first-ever Raven Management Workshop. Decades ago, ravens (and raven conservationists) might have seemed out of place among the spas and golf courses, but not anymore. Southern California is at the center of a Common Raven population boom plaguing the American West, and the groups at the workshop—including the U.S. Geological Survey, U.S. Department of Agriculture, and a variety of other parties and agencies—were there to discuss what exactly they were going to do about the growing flocks and their impacts on imperiled species.

Common Ravens are indeed common over much of the northern hemisphere, and are omnipresent in the northern wilderness of North America. South of the Canadian border, they're most prevalent in the west. They were practically wiped out in the eastern states long ago by the advance of civilization, and have been making a slow comeback there since the middle of the 20th century. But that population growth pales in comparison to what has happened in the west—the hawk-size corvids are everywhere. According to the Breeding Bird Survey, raven populations in the parched Mojave Desert have increased more than 700 percent over the past 40 years. This surge is spreading through the Great Basin region, from eastern California and Oregon across Nevada, Utah, and southern Idaho to the edge of Wyoming.

Often considered the raccoons of the bird world, ravens are opportunistic feeders willing to feast on everything from trash to other animals. This wide-ranging diet has allowed the birds to thrive in human-inhabited areas, but it’s also made them an ecological disaster as their population swells. Because they will feast on the eggs and young of other desert animals, ravens are upending ecosystems and pushing at-risk species even closer to the brink.

“This population crisis is taking a huge toll on many desert ecosystem species, and it’s all due to human subsidies,” says Kristen Berry, a U.S. Geological Survey research scientist and board member of the Desert Tortoise Preserve Committee. The “human subsidies” responsible for the raven influx include increased access to standing water from cattle farms, artificial watering holes called 'guzzlers,' and sewage facilities; an excess of perches from buildings, vehicles, and other man-made structures; and an abundance of food from human garbage and road kill.

With the raven population already booming and so many of these subsidies widely available, finding effective solutions to the raven problem has proven challenging. The situation is so dire, in fact, that one of the options briefly discussed at the raven workshop was to remove the birds from the Migratory Bird Treaty Act, which would allow them to be killed as a form of population control. But this extreme strategy garnered little support; the majority of researchers and conservationists believe they should stem the boom in non-lethal ways. After all, the birds are still vital to Western ecosystems—just in moderation.

Doing anything that puts ravens at risk is senseless, says Brian Rutledge, conservation strategy and policy advisor for Audubon's Central Flyway. “If we are going to handle this population crisis, then we must think about the long term,” he says.  A major step toward moderating the populations, Rutledge says, is to limit the birds' access to human waste and keep communities clean. "Then the raven population will slowly shrink to a healthy level," he says. 

Federal agencies such as the Bureau of Land Management promote proper waste disposal and cleaning landfills on federal land, but it hasn’t been enough, says Berry of the U.S. Geological Survey. “Our problem is now with the private sector—businesses and commercial-waste disposal companies—not taking enough initiative to clean their dumps and cover their dumpsters," she says.

The Coalition for a Better Environment (CBE), a partnership of California industry leaders and environmental groups including the Kerncrest Audubon Society, took a different approach to the problem last year by surveying small towns around the Mojave Desert and teaching communities about raven population issues. During the survey, the group found flocks of ravens scavenging from commercial dumpsters at all three locations they monitored; the group also discovered that 42 percent of private-waste disposal companies didn’t abide by city ordinances requiring that waste container lids stay closed.

After just a little educational outreach to residents and businesses, compliance jumped across all three communities and raven dumpster visits decreased by an average of 50 percent, according to a CBE report. Now the CBE aims to create a template in the next two years for any western city to follow. “If we can duplicate these kinds of results in other towns, we may have a good chance to help local endangered wildlife,” says Lawrence Alioto, CBE’s executive director.

While increased raven predation has been detrimental to many desert species, the Greater Sage-Grouse and the threatened desert tortoise have been hit especially hard. In the sagebrush steppe, ravens take advantage of easy food and water near grazing cattle and, while they're there, steal eggs and chicks from sage-grouse nests. They plunder tortoise nests, too, in southwestern deserts. “For the desert tortoises, there’s no greater threat than the abundance of ravens,” says Ron Berger, president of the non-profit Desert Tortoise Preserve Committee and founder of the CBE. “Many researchers have witnessed the aftermath from ravens hunting tortoise hatchlings: hundreds of soft shells picked clean and carcasses found at raven nests in the western Mojave.”

This scene is all too familiar for Tim Shields, who spent 35 years monitoring desert tortoise populations and founded the startup Hardshell Labs to save them. His company focuses on emerging technologies such as raven-repelling lasers that keep the birds away from tortoises and their nests without harming the birds. If these lasers become a viable solution, dozens of other species that suffer from raven predation, including the Greater Sage-Grouse, Least Terns, and Marbled Murrelets, could benefit, too.

While the CBE and Hardshell Labs both have taken very different approaches to dealing with the raven epidemic, CBE will partner with Hardshell Labs later this year to expand their efforts on both the activism and research fronts. Both groups also sent their founders to the raven workshop last fall to share their success stories and help educate others. But even with this work and the greater efforts of the U.S. Fish and Wildlife Service and the Bureau of Land Management, conservationists fear the problem will only worsen if individuals don't take greater responsibility for their consumption and waste. 

“This is a people problem,” Rutledge says, “regardless of how cunning and opportunistic these birds are."

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