Tracking predators: Sage grouse study keeps close watchWritten by Christy Martinez
Big Horn Basin – Beginning as a simple suggestion from area conservation districts, a Wildlife Services-led study in the Big Horn Basin looking at predators and sage grouse has now become a multi-agency effort with the potential to be a five-year project.
Although the study just began last April, USDA APHIS Wildlife Services (WS) Northwest District Manager Jim Pehringer says they’ve already collected a lot of information.
“The purpose of this project is to identify the major predators of sage grouse in every phase of the year,” says Pehringer, adding that the study also assesses the affects of human impacts on sage grouse, as well as what habitats the birds prefer. “One question is how far they’re moving from a lek to nest, what it takes to disturb a lek, and the affect of oil and gas activities,” he explains.
After getting out and looking for the birds and nests, Pehringer says he found that many leks have never been counted, and his theory is that there are two populations of sage grouse – those that adapt to human activities, and those that are never around humans.
Although he wanted to choose six areas to study across the Big Horn Basin, because of a late start this year the study only looks at a control and treatment area this summer. The treatment area’s predator work consists of strategies to deal with livestock and coyote problems, while the control area has historically not had much predator control. Pehringer says next year the study will expand to other areas.
To begin the study, WS personnel and a contractor visited leks with a rocket net that was shot over the birds, which were then caught and collared.
“It was neat to handle the grouse, and we had zero mortality due to captures,” says Pehringer.
The collars are used to follow the grouse daily, with receivers used to find the grouse. During nesting, if a hen stayed for three days under the same sagebrush, someone would sneak in close to the nest with a camouflaged trail camera, placing it down in the vegetation so it wasn’t visible and wouldn’t affect the bird.
“So far we’ve had 23 confirmed nests and five successful hatches,” says Pehringer, noting that eight nests were lost to bird predation, six were abandoned due to hen predation and three were partially predated and abandoned.
“Many of the birds we caught had already lost a previous nest this spring, and sage grouse will re-nest up to three times in a season,” says Pehringer.
Pehringer says he and his team have seen a lot of eagle predation.
“We’ve had five sage grouse hens predated by eagles. When we were trying to capture the birds, they’d all the sudden move next to a sagebrush and quit lekking, and that was because there was an eagle coming,” he states. “Eagles are a big deal, from what we can see.”
The collars on the birds emit a mortality signal when the collar lies dormant for four to eight hours, so the researchers are able to get to the birds quickly to identify the source of predation.
Pehringer says he didn’t think ravens were a problem when the study first started, but he’s found they’re the worst predators on nests.
Coyote activity has been found at 90 percent of the control area’s nests, while the predators have only visited 20 percent of the treatment area’s nests.
“The coyotes eat eggs and birds, and they hunt in a pairs – an activity that’s learned,” comments Pehringer, who can monitor their activity through the cameras, which are set to take three- to five-shot bursts so photos can be seen in progression. “When the grouse nest in sagebrush they nestle out a hole so there’s an in and an out, and the coyotes walk in pairs and one will flush and the other will get the grouse.”
He says the infrared flash will drive some coyotes away, and that he’s convinced that flash saved one nest, as there was a coyote that would come back every day to stare at the camera.
Behavior observed on the part of the sage grouse through the trail cameras is that they’ll leave the nests during the major hunting hours each day, when coyotes are most active, which are from about 8 to 11 p.m. and in the early morning hours before sunrise.
“They leave the nest to avoid attracting predators, especially when it’s wet and the ‘stinky bird’ scent can draw more predators,” says Pehringer.
He says a rare predator is the badger, but they did have one take a nest and kill the hen.
The project is in cooperation with counties, county commissioners, predator management boards, the Animal Damage Management Board and at least six oil and gas companies.
“We’ve put together a steering committee to oversee the whole project and make it very transparent,” says Pehringer. “In fact, we’ll document every little thing we can think of. We’re over-collecting information, because there’s a wealth of it out there.”
Pehringer says the BLM is also involved. One area in which the agency is helping is with the nest preference areas, where the researchers are trying to figure out why a nest’s location was a preferred area.
“I have a feeling the habitat in the Big Horn Basin is good, and I have seen every nest site on the birds we’ve collared,” he states. “We’ve had sage grouse nest where there was one piece of sagebrush in a flat of nothing.”
“We have found some birds that, once their nest is predated, will move to within three meters of a road, or they’ll move into the oilfield with all kinds of activity. I think that keeps the predators at bay,” says Pehringer. “From the lek they’ll move into areas of high human activity to nest.”
In addition to the trail cameras, the project also has aerial photos of each nesting site.
When a nest is predated, the eggs are sent to the WS research center in Fort Collins, Colo. for DNA testing to confirm the predator.
“That’s another fact of proof,” says Pehringer, adding that they’re also working on the correct protocol for collecting DNA off carcasses and feathers from predated adult birds. “We look at every site where we find a predated bird and treat it like a crime scene.”
Of livestock’s affect on nesting sites, Pehringer says that one theory is that cattle will eat eggs.
“One nest site constantly had cows around it, and when it was predated I sent the eggs I found all around the nest for testing, and they found a 98 percent match on the DNA for coyotes,” he says. “The cows had knocked the camera down, so we missed the act of predation, and we sent the eggs in because we really wanted to know the cause.”
Pehringer says they also haven’t seen antelope hunting sage grouse nests, as some say they will.
“They’re constantly finding the nests – they’re curious, and it’s a different smell,” he says. “But they don’t even flush the bird – we have yet to seen a bird flush from a cow, antelope or deer.”
As the study moves through the summer, Pehringer says that in mid-July they were looking at birds 35 days post-hatch.
“They’re feathered up, about the size of a partridge, and they can flush,” he says.
The researchers are also documenting every human impact they could think of.
“Right now I see the grouse being very adapted,” observes Pehringer. “In the latest survey, we found that, after the chicks hatch, the grouse slowly move a half mile a day toward farm fields.”
To date, the Wildlife Services team has four months of data, and hopes to keep up the study for five years, if possible.