High Country News: Are we smart enough to solve our raven problem?
August 24, 2014
For millennia, the sagebrush steppe that sprawls from Wyoming to California was a treeless scrubland, unbroken by anything taller than the occasional piñon or juniper. Common ravens, which prefer to nest in trees and on cliffs, were scarce. That changed during the 20th century, when transmission towers and telephone poles sprouted in the high desert. With the advancing infrastructure — not only power lines, but also roads, dumps and towns — came the ravens. Today, Corvus corax is ubiquitous in the West.
The birds' success testifies to an intelligence nearly unmatched in the animal kingdom. Ravens are resourceful, talkative, capable of using tools. They can hunt in packs. They solve puzzles. They're one of only two vertebrates known to be capable of displacement, the ability to communicate about objects and events distant in time and space. Humans are the other.
The brilliance and adaptability of ravens have helped them triumph in an era that has been disastrous for most wildlife. Ravens feast on refuse and roadkill, drink from livestock troughs and nest on and hunt from human power structures. They are what biologists call a subsidized predator, thriving on the food and habitat humans provide. In the last 40 years, raven numbers have grown fourfold in the West at large, fivefold in Idaho, sixfold in Nevada.
We humans, however, have not greeted them warmly. Ravens devour crops, attack livestock, and, perhaps most notoriously, clash with sage grouse. In response, Westerners have shot and poisoned thousands of them. Ravens have become victims of their own success. The question is, what do we do about them?
In the early 2000s, Peter Coates was a graduate student at Idaho State University, completing a dissertation on the greater sage grouse, a balloon-chested, ground-dwelling bird whose population has declined by 90 percent over the past century. While the grouse faced many threats — including invasive cheatgrass, wildfire and habitat fragmentation — Coates and his adviser, biologist David Delehanty, wanted to investigate a less-studied peril: nest predation.
What was eating grouse eggs? Other scientists suspected coyotes, badgers, even ground squirrels, but Coates and Delehanty had a different hunch. Over the course of two years, they set up cameras at 55 grouse nests, disguising them behind vegetation and stealthily changing the batteries when the grouse left to forage. When they watched the footage at study's end, they didn't see any coyotes or ground squirrels. Instead, most of the preyed-on nests had been plundered by ravens, who absconded with the eggs in their hooked beaks. "We'd always suspected they were a nest predator," says Coates, now a wildlife biologist at the U.S. Geological Survey. "What we learned was just how frequent predation actually was."
This wasn't the first time ravens have been accused of devouring an imperiled species. In the Mojave Desert, researchers found the shells of threatened desert tortoises, holes pecked through their scutes, in middens beneath raven nests. Preying on sage grouse, though, was more egregious. In 2010, the same year that Coates published his camera research, the U.S. Fish and Wildlife Service listed the grouse as "warranted but precluded" under the Endangered Species Act — meaning the bird deserved protection, but that other species demanded more urgent attention — and promised to revisit its ruling in 2015.
Starting in 2010, the West had five years to convince the feds that grouse populations were healthy; otherwise, industries like ranching and energy could face painful land-use restrictions. Landowners and agencies in a half-dozen states responded by undertaking a range of sage grouse conservation projects, from removing invasive plants to modifying grazing rotations. But the region has also been gripped by a scientifically dubious passion for killing off ravens.
Jared Brackett, the burly president of the Idaho Cattle Association, is among the ranchers trying to save grouse. Brackett, whose livestock graze a 50,000-acre allotment southwest of Twin Falls, has tweaked his operation — for instance, shutting down water troughs near leks, where sage grouse perform their mating displays — to help the birds survive. "We've got a pretty progressive rotation system in place,"
he says. "And we have a thriving population of grouse."
Around 10 years ago, Brackett realized he also had a thriving population of ravens. The occasional calf turned up with a pecked-out eye; one afternoon, a trio of birds ate an entire flock of turkey chicks that Brackett had raised in his yard. Fearing the ravens would hinder his grouse conservation work, he began discussing raven control with other ranchers — including his uncle, state Sen. Bert Brackett, who owns around a thousand head of cattle.
Next door, in Nevada, raven-killing fever had already taken hold. In 2007, the Nevada Department of Wildlife launched an initiative called Project 21, a plan to boost sage grouse survival by killing their predators. From 2007 to 2013, the state poisoned 9,423 ravens with DRC-1339, a poison that induces kidney failure in corvids, the family that includes ravens, crows and magpies — and spent around $200,000 doing it. Meanwhile, commissioners in ranching-dominated Elko County, in the state's northeastern corner, recently petitioned the Fish and Wildlife Service to remove ravens from the Migratory Bird Treaty Act, a law that restricts how many can be killed.
This spring, raven mania spread to Idaho. Under the state's plan, announced in March, the U.S. Department of Agriculture's Wildlife Services would scatter thousands of chicken eggs filled with DRC-1339 in three grouse-nesting areas. Idaho's permit allowed it to kill as many as 4,000 ravens over two years; rancher-cum-senator Bert Brackett was among the lawmakers who advocated for the program.
The Idaho Department of Fish and Game calls the plan an experiment. But to Clait Braun, a research biologist who's been studying sage grouse since 1973, the program isn't sound science — it's slaughter. "They don't have any control group" — i.e., places where the state won't cull ravens for the sake of comparison, Braun says. "There's no way on God's green earth that they can attribute any effects (on grouse) to ravens."
If Idaho truly cared about saving grouse, he argues, it would prohibit ranchers from grazing livestock on public lands. "I've seen ravens predating sage grouse nests in Idaho," says Braun. "Why? Because the understory is so thin that ravens fly over and see the eggs and say, 'Aha, food!' And why are the forbs and grasses so thin? Cows ate them."
As Idaho embraces lethal raven control, Nevada, ironically, has begun to back off. In its most recent predator-management plan, the state Department of Wildlife acknowledged that raven-killing's "long-term benefits have yet to be documented." And although Project 21 is funded through next year, it may not continue beyond 2015.
Why doesn't lethal control have lasting effects? The problem, suggests Delehanty, is that poisoning often kills nesting pairs of ravens, territorial individuals that command areas as large as five square miles.
When those nesters vanish, new ravens fill the vacuum — and because the arrivistes are often non-territorial birds, poisoning might even produce greater densities.
"Does raven poisoning reduce numbers?" concludes Delehanty. "You bet it does. But it's temporary. You're bailing out a little spot in an ocean of ravens, and that spot fills in very quickly."
That dynamic has led scientists to seek more lasting ways of managing C. corax — namely, ending the accidental stimulus packages that have allowed the birds to thrive. Peter Coates is researching how to raven-proof transmission towers — lattice structures provide inviting nesting platforms, while tubular structures are less tempting — and Nevada has begun removing roadkill and separating food waste at landfills. "We're not blindly killing everything we can," insists Chris Healy, public information officer at the state's Department of Wildlife. "We're trying to reduce the subsidies."
For its part, Idaho won't poison any ravens in 2014, though not out of newfound love for the birds; federal Wildlife Services didn't complete its environmental assessment in time. Intense public scrutiny may have had an effect. One online anti-poisoning petition received over 65,000 signatures, despite being circulated by a California food writer who's never even been to Idaho. Still, the reprieve is only temporary. By next year, the permits should be in order, and the killing will commence apace.
With Wildlife Services' poisoned eggs sidelined this spring, the Idaho Department of Fish and Game initiated raven control measures by itself, without much luck: The agency destroyed just 18 nests, and shot only 11 adults. "We placed some roadkill near leks to draw ravens in," says Jeff Gould, the agency's wildlife bureau chief, "but shooting them proved to be difficult. "They're very wary, very intelligent birds."