Gunnison sage grouse activity may be impacted by climate change

Other animals also having to adapt after harsh winter

By Katherine Nettles

Humans on Colorado’s Western Slope are not the only ones dealing with snow and spring fever. Local wildlife are also having to manage their breeding and migration behavior given the snowier, colder than average conditions across the Gunnison Valley that lingered longer than usual. Wildlife officials say the heavy snow and late cold snaps even into this spring have likely had an impact, particularly on Gunnison sage grouse, but also for big game animals who are ready for fresh foliage. 

Gunnison sage grouse were listed as “threatened” under the federal Endangered Species Act in 2014 and have been identified by the National Audubon Society as one of the most endangered birds in North America. Their largest habitat is within Gunnison County, primarily within Bureau of Land Management (BLM) land. The U.S. Fish and Wildlife Service identified the most substantial threats to sage grouse habitat as human disturbance, small population size and structure, drought, invasive plants, improper grazing practices, climate change and disease.

The Gunnison sage grouse may be experiencing a double threat from climate issues, both from a harder than usual winter and a less accessible lekking area this spring. Nathan Seward, a wildlife conservation biologist with Colorado Parks and Wildlife (CPW), explains that a lek is the breeding area and strutting grounds of Gunnison sage grouse where they show off to attract a mate. These are often sites the sage grouse return to each year, which is how CPW and other wildlife experts are able to study and keep track of them.

Patrick Magee, associate professor of Wildlife and Conservation Biology at Western Colorado University and a Gunnison sage grouse specialist, says that in general, winter is a time when Gunnison sage grouse do well. “They survive well and even gain body mass during winter on a diet of sagebrush leaves,” he says. 

The issue is our changing snowpack. 

“They normally take advantage of the snowpack and burrow within it or go ‘subnivean’ during winter – this reduces their thermoregulatory costs and protects them from predation. 

“One thing we have been noticing in recent years is that some of the storms we get are wetter than historically, even rain in January. This ends up freezing hard and changes the snowpack dramatically from powder to an ice crust. Ranchers have driven their tractors on top of this ice without breaking the snow crust. If the sage grouse can’t enter the snow, they are left on top in the cold winds and deep dark winter nights where they lose a lot of body heat and expend a lot of calories to try to stay warm. They are much more vulnerable to predators as well,” says Magee. 

“This spring it has been interesting to see how snow may be influencing distribution of sage grouse across the landscape, especially at a time when the birds are being endogenously driven to move to their leks (dance floors) to mate,” reports Magee. “They do arrive on leks covered with snow and dance away, but there could be some impacts where they try to find snow-free areas and use some fairly non-traditional sites. Usually, the birds are amazingly faithful to their dance floors and return annually for generations to this one spot. But we are seeing some unusual behavior this spring with large concentrations of grouse at certain leks and few birds at some of the more snow-covered leks. We are seeing some great numbers at a few sites with over 200 grouse counted on two different leks.” 

Seward says the current snowpack is also limiting access for CPW’s annual spring lek counts for Gunnison sage grouse. CPW conducts these counts early in the morning to monitor the bird’s population trend from late March through mid-May. It started later this year and may need to run later as well.

“Gunnison sage grouse have high site fidelity to leks because these areas have unique characteristics that allow the grouse to survey for predators and allow their calls to carry a greater distance and attract females,” says Seward. “Most leks are open areas within the sagebrush vegetation community, but some leks are hay meadows associated with agricultural properties/ranches with adjacent sagebrush cover nearby.”

Seward says lek counting is very challenging under current conditions. “And we won’t likely be able to conduct the same number of counts this year, so our population estimate could be conservative. A similar situation happened in 2017 where the snowpack persisted and hindered our ability to conduct counts,” he said. 

CPW monitors a subset of leks during the last week of March to gauge breeding activity. “The past two years sage grouse have started a bit early because of the dry drought conditions, lack of snowpack, and have been widely distributed. This year breeding activity has started, but only at lower elevation leks or where the snowpack has opened up. It currently appears that sage grouse are still in large winter flocks and have not dispersed from their winter range (taller sagebrush at lower elevation) because of the abundant, hard crust snowpack.  I suspect after these couple of warm days, grouse will disperse more and we’ll start to see better numbers of grouse across the elevational range of leks,” says Seward.

This year’s official count period started April 1 and will continue through May 10.  Lek counters try to access and conduct a count (the highest number of males and females observed) once every 10 days, says Seward. “Lek counters try to get to their vantage point where they can observe the lek an hour before sunrise. We have specific areas to view the leks so our presence doesn’t impact breeding behavior and attendance.”

Seward says some leks that have been impacted by past human development are considered “historic” and biologists only visit them once or twice to look for grouse. “If we observe grouse then we continue counts through the breeding season, but if we don’t see grouse then we’ll revisit next spring.”

The goal is for most of the leks to be counted at least four times, says Seward, but during years with abundant snowpack like this spring, it is very challenging. “We are currently considering whether we should conduct a count between May 11–20 to see if breeding activity this spring was slightly delayed,” he says.

Seward describes how lek count data allows CPW to determine peak breeding activity, peak attendance for males and females, the high male and female count which determines annual population estimates, types of disturbance (predators, cars, humans, etc.), annual lek status (active, inactive, unknown, historic), and when peak hatching will occur. 

“This is important in case we get a late snowstorm or cold freezing rain when chicks first hatch. These events could increase chick mortality and prevent a whole generation from being recruited. Gunnison sage grouse do not commonly renest because of the amount of energetic cost it requires to lay a clutch of eggs, so it’s important to reduce any type of disturbance that may flush hens during incubation or cause them to abandon their nest. Our current seasonal restrictions on roads and some trails, typically March 15 – May 15 depending on the specific area, help alleviate disturbance during the breeding season and early nesting season. Several State Wildlife Areas stay closed through June to provide greater protection to nesting and early brood-rearing,” Seward explains.

Seward advises that folks need to know the regulations before venturing out. Current seasonal restrictions can be found at gunnisontrails.org/ and Gunnison County’s wildlife conservation page, www.gunnisoncounty.org/162/Wildlife-Conservation.

“We do not disclose the locations of leks on public lands as we do not want to attract interested parties to these areas when grouse are sensitive to disturbance,” says Seward. The Waunita Watchable Wildlife area for public viewing is co-managed by Siskadee and Western Colorado University students and there is a formal application process for wildlife photographers that need original photos for their conservation-oriented projects. The Gunnison Basin sage grouse Strategic Committee reviews and approves these applications for photography opportunities.

Kevin Blecha, a big game biologist with CPW, spoke to the current distribution of deer and elk, and potential impacts of a snowy winter for them as well.  

“For the major big game animals (deer, elk and pronghorn) most susceptible to hard winters, their winter range looks very similar to the winter of 2018/2019. Except, in that previous winter, snow conditions were slightly deeper leading up to the deepest and crustiest March snows than what we are experiencing this current 2022/2023 winter,” says Blecha.

“During winters with deep snow events, deer and elk often spend more time near steeper slopes that hold less snow and burn off quicker. Often these steep slopes occur near roadways. Thus, ultimately, the deep and crusty snows explain the surge in vehicle collisions in March. However, it can be difficult to compare the two winters in terms of roadkill levels given the differences in big game population sizes (we have more deer/elk now than winter 2018/2019) and possible differences in traffic volume patterns between the years,” he continued. 

“We have been monitoring the survival rates of deer and elk with radio collars for over a decade. So far, this particular winter is just slightly harder than average in terms of deer and elk survival rates. The individual deer and elk that went into this winter in poor body condition (low body weight) are the ones most likely to show up at the roadsides to feed and are thus the ones most likely to get hit by vehicles.”

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