Sage grouse researchers endure summer heat to gauge nest survival

Kayla Ruth, a biologist working on her doctorate at Oregon State University, and field technician Devin Hendricks examine sage grouse nests to determine what kind of predator ravaged the eggs. Ruth is doing a study on nest survival and predators to grouse in the Big Horn Basin. Photo by Mark Davis, Powell Tribune.

POWELL — Insensitive to those laboring below, the sun bore down on the shadeless Chapman Bench. 

But biologist Kayla Ruth, carrying an armful of electronic tracking equipment and a backpack of essentials, was more concerned with a strong finish to her coronavirus-shortened research project than the agonizing heat. 

Ruth is studying for her doctorate at Oregon State University. She guided project technicians Devin Hendricks and Julianne Herrick through the desert by truck and on foot. The three had been pummeled in the rudely cast rays for three weeks while continuing a study of the Big Horn Basin’s greater sage grouse habitat and factors that affect their numbers — like predators, agricultural practices and, in a much smaller sense, energy exploration and extraction. 

Due to the university’s COVID-19 restrictions, they were forced to camp at Hogan Reservoir through the first three weeks of August — coinciding with one of the longest hot spells in the Big Horn Basin in years. 

They pushed through the 90-plus-degree days, crunching across the mostly bone-dry high desert while chasing radio signals of greater sage grouse hens previously captured and fitted with transmitters in the multiyear project. At night there was little relief other than the air conditioner in their vehicles in desperate attempts to end the discomfort. 

Arriving at the first nest on one of the most brutal days, they found broken egg shells, obvious predation by a mammal during nesting season, Ruth said.

They’ve seen their fair share of raided nests and the condition of the eggs often tell the story. First she looks to the shells for attached membranes; telling the story of whether the eggs had hatched or if they were part of a meal. At this nest, the chicks never had claws on the ground. When chicks get a chance to hatch, the shells are broken uniformly at one end. When avian or mammalian predators get to the nest, the shells are scattered and in pieces, and the thick membrane is still present. 

“Snakes swallow them whole,” she said. Coyotes, badgers, skunks and a short list of other toothy critters are the top suspects to raid grouse nests. Ravens are the number one avian predator of the nests, but Ruth also has hawks, eagles and even northern shrikes on her watch list. 

She paused, looking for clues — typically tracks or feces. 

“It’s amazing how much of our time is spent looking at feces,” she quipped. “It’s real fun when we’re doing our predator surveys to get right up on it and, OK, it’s this length across …” her voice trailing off while closely inspecting the fecal “evidence.” 

Ruth carries a guide with her to help determine who might have raided the nest based on the size and shape of the feces left behind. Of course, it could have been more than one predator. One of several predators may have had a feast on the hen prior to yet another predator(s) eating the eggs or recently hatched chicks. There are many possibilities, she explains, noting there were no feathers at the scene of the crime. 

The team doesn’t just rely on tracks and scat. They’ve deployed several scout cameras in three locations near Powell, including the Polecat, Yu and Chapman benches. They also use transmitters on hens to follow their nesting and brood success through the years of her study. 

Earlier in the week the duo had taken a day off from the slow march to meet with the Big Horn Basin Greater Sage Grouse Working Group in the Grizzly Room at the Park County Library. 

COVID-19 has slowed collaboration, especially in the way the working groups are meeting, with some participants joining by Zoom. 

The Wyoming Game and Fish Department spends about $550,000 a year to fund local grouse working groups, which then look for projects to fund. The Big Horn Basin working group, upon hearing Ruth’s presentation, awarded $55,000 to fund the study along with co-principal investigators John Dinkins and Jimmy Taylor. 

The team is also funded by the Bureau of Land Management, which has contributed more than $335,000 to date. 

“We don’t have much information on the movements or habitat use of sage grouse in the [Big Horn Basin], said BLM wildlife biologist Destin Harrell. “Part of the objectives of the study the BLM is really interested in is mapping the seasonal ranges of sage grouse nesting and winter habitats so we can better manage their habitat.” 

Knowing the ranges will help the agencies biologists better understand how to best conserve populations — especially important as BLM properties in sage grouse habitat are increasingly offered in lease sales for mineral extraction. 

“In this multiple use landscape, if you understand what habitats are being used and what’s most important, then you can better manage the species,” Harrell said. 

While there are currently about 15 sage grouse studies being undertaken in the state, it’s important to remember sage grouse aren’t all the same across the species’ 11-state range. Each region, if not down to each individual lek, is different and all have a unique story to tell those who aim to protect the key species in the sagebrush steppe. 

From 2011 to 2014, Taylor studied hen and chick survival. It’s the most important type of data for population growth, Ruth said. Her own transmitters help her to track hens and their broods, watching closely to estimate chick survival. Taylor used GPS and high frequency transmitters on female sage grouse to identify 204 nests and monitor incubation on five sites in the Big Horn Basin. 

“We determined nest fate and identified predators with camera traps,” he said.

The study found coyotes were the greatest contributor to nest failure, followed by common ravens. The direct effect of nest depredation by coyotes was greater than other reported sage grouse studies, yet nest survival rates in the Basin were consistent with others reported throughout the species’ range. 

“Nest survival was least on a site where coyotes and ravens depredated nests at nearly the same rate, and where ravens were observed nesting on infrastructure close to nesting sage grouse,” Taylor said. 

The Polecat Bench is such a site. Ravens and coyotes seem to have a stronghold in the area. Despite multiple attempts, coyotes are always a problem. And raven populations are continuing to grow in the region. Their numbers have grown more than 400% in the past 40 years across the west, according to a Western Association of Fish and Wildlife Agencies (WAFWA) white paper. Human subsidies, like landfills, are linked to increased populations. 

Some consider predators the biggest problem facing the imperiled ground-nesting species. This past spring, a group working to locate nests for Diamond Wings captive breeding experiment failed to locate a single viable nest in three weeks of searching. At the same time, they discovered 11 nests consumed by predators. 

Others consider fragmentation of habitat to be at the core of the issue as populations of sage grouse have plummeted from more than 16 million to an estimated 400,000, possibly less. Studies have demonstrated that fragmentation of habitat goes hand in hand with predation. 

“Sage grouse have co-evolved with the normal complement of predators in sagebrush habitats. However, populations that are isolated due to habitat fragmentation or those in degraded habitats may be more vulnerable to predation,” according to research cited by the white paper titled, “Predator control as a conservation measure for sage grouse.” 

In other words, predators are more efficient in fragmented or degraded landscapes, like that on the Polecat Bench, which has recreational, agricultural and mineral extraction. 

Some of Taylor’s project data will also be used in Ruth’s project down the line. 

But results and recommendations are still years away. One of the immediate impacts to funding studies is collaboration between biologists from different entities across the species’ habitat. 

Ruth is working closely with the BLM Cody Field Office, especially with Harrell and Patricia Hatle, range management specialist for the bureau. 

“Collaboration and partnerships for surveys, studies, and monitoring of sage grouse and their habitat provide the necessary basis for the BLM to make informed decisions about how to manage public lands,” said Sarah Beckwith, a regional spokesperson for the BLM. “Every year, the BLM evaluates potential projects that help us achieve our land management goals and determines the amount of project funding based on annual budget allocations.” 

Sage grouse populations are holding fairly steady over the entire state, down 1.5% from 2019 numbers, said Leslie Schreiber, sage grouse program manager for the Wyoming Game and Fish Department. “They are holding steady from 2019 to 2020, and we’ll see what happens next year,” she said. 

Sage grouse have been in the trough of what is believed to be a eight- to nine-year cycle.

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