New Studies Look At How Ravens Affect Sage Grouse Nest Success

Feb 6, 2015

Ravens flock at Cody landfill.
Credit Melodie Edwards

When people think of ravens, they often think Edgar Allen Poe:

But talk to a sage grouse ecologist and it’s a different story. In the last 50 years, as energy development has moved in, raven numbers have skyrocketed, by some estimates 20 percent. Several new studies across the West show that these “ominous birds of yore” are feasting on sage grouse eggs and chicks, a species that’s already on the brink of extinction. And so, to protect them, the U.S. Fish and Wildlife Service is considering upping the number of ravens they’re controlling lethally.

Visit any landfill in Wyoming and you’d think you’d stepped into a Hitchcock film. Hundreds of black birds flapping overhead, fighting over scraps, and making strange, almost human-like sounds. It might seem like a weird place to go bird watching. But wildlife ecologist Dr. Charles Preston in Cody says a landfill is a great place to see how ravens take advantage of disturbed landscapes such as this one: a dump in the middle of the otherwise wild sagebrush.

“Ravens are one of the few species that we know will communicate with one another about a distant activity,” Preston says. “That’s called displacement.”

Displacement is when ravens gather at night and pass along information about where to find the best food--a fresh roadkill carcass, say--and then show up the next day by the dozens. And he says that’s also what makes ravens formidable predators to sage grouse.

“It’s a challenge because they are so smart,” Preston says, laughing. “So it’s not easy to trick them, it’s not easy to put a scarecrow up or something.”

University of Wyoming researcher Jonathan Dinkins concurs. “There are raven hot spots,” he says. Dinkins is working on a 4-year study of ravens and their effects on sage grouse nests. He says other studies in Nevada and Idaho agree—ravens populations aren’t out of control everywhere, just in isolated zones.

“Our raven data suggests that a good portion of Wyoming doesn’t have a raven problem. So how do you identify where those areas are?”

Dinkins says it’s important to know exactly where these so-called hot spots are if you want to control their numbers. He says one way is to find swaths of sagebrush disturbed by human structures. For instance, “…Communication towers, oil structures, power lines. Those produce nesting structure for ravens,” Dinkins says.

And he says you can’t necessarily assume raven hot spots are going to spring up around energy development.

“Interestingly, during our study, over half of our study sites that we had that had high raven abundance, they were not in oilfields.”

But the kind of sprawl and traffic and roadkill that come as part of the oilfield package does mean more ravens. Dinkins’ study and others all seem to show: more ravens appears to mean fewer sage grouse are hatching.

Armed with this data, Wyoming recently decided to change its rules about killing ravens, which are protected as migratory birds. In the past, ravens could only be killed to protect livestock or human health. But for the first time, it’ll be legal to use poison control on ravens to benefit a wildlife species--sage grouse.

Credit Photo by Omar Runolfsson, Flickr Creative Commons

Wyoming Sage Grouse Coordinator Tom Christiansen says ravens are fed dog food with a poison that only effects corvid species like ravens, crows and magpies. “They use a very specific corvicide that targets only those ravens on those dump sites.

Researcher Dinkins says, ideally, only in those areas where raven hot spots overlap with the best sage grouse habitat.

But even Christiansen concedes that killing ravens is a temporary fix since they’re territorial. An empty roost is like an empty hotel room at Cheyenne Frontier Days…it fills up instantly.

“The other thing that’s an unknown here is if actually controlling ravens results in a benefit to sage grouse,” Christiansen says. “We surmise that, but we don’t have hard data to say that the control of ravens results in more sage grouse.

And that’s why ecologist Charles Preston says a campaign to kill ravens could be a job with no end in sight. The best way to control ravens, he says, is to bring sagebrush country back into balance. Cluster energy structures in limited areas, close down dumps in sage grouse habitat, and help raven predators thrive.

Who likes to eat ravens? Golden eagles do, and so do weasels, coyotes, owls.

“So encouraging some of the predators of ravens is often one of the best ways. That’s the natural biological control,” says Preston.

He says ravens aren’t Poe’s evil bird—they’re just opportunists. To control them, he says we need healthier sage lands.

Otherwise, the greater sage grouse could be… nevermore.