BUFFALO — Annual counts of male Greater Sage-grouse dancing at their springtime mating grounds are up in the Powder River Basin and appear to have leveled out across Wyoming after 5% declines in each of the past three years.
Overall, counts dropped just 0.3% in 2020, leading Wyoming Game and Fish Department officials to speculate that this could be the bottom of another trough in the birds' oscillating
population cycle. The counts are conducted in April and May each year by Game and Fish and the Bureau of Land Management representatives, as well as other trained consultants and volunteers.
Locally, lek observations in indicate that there may have even been an increase in strutting birds in the region.
If the trend continues, it could be a good sign for sage-grouse, which were considered for listing under the Endangered Species Act in 2015. Statewide, the average 19.7 males observed per lek in 2020 is higher than the 16.8 observed in 2013 at the pit of the last trough.
Yet average male counts aren't the only important measure of species health, say the
state's avian experts. The number of birds per lek may be stabilizing, but over the past year, the number of active leks statewide dropped by 4%. For a lek to be considered active, observers must see either strutting birds, fresh scat, tracks or feathers.
Lek activity is an important marker, because Game and Fish does not include the “zero” of a newly inactive lek in its average attendance statistics, said BLM supervisory natural resource specialist Bill Ostheimer at a recent Northeast Sage-Grouse Technical Team meeting.
"If at one lek, there's two birds, and another lek there's 50, your average is going to be 52, divided by two,” Ostheimer said. "If you go out the next year and there's 50 birds (at one lek), and that second lek is at zero when you're averaging, it shows an increase, where on the ground, you lost birds, maybe permanently.”
In northeast Wyoming, where the terrain is rugged and the sagebrush sparse, populations are smaller and lek attendance lower than in other regions of the state. Yet here, 2020 counts jumped substantially, charting a 33% annual increase in the average number of lekking males. At the same time, however, the region's active leks dropped more than the state average, falling 10% from 2019 figures.
If a lek remains “inactive” for four non-consecutive years in a 10-year period, its management status changes to “unoccupied” with Game and Fish. Even though biologists continue to discover more leks in the northeast, the total number of known occupied leks has decreased steadily for more than a decade, indicating that the drop in active leks this year may be part of a larger trend in which birds show up at fewer and fewer locations each spring.
Leslie Schreiber, Game and Fish's sage-grouse and sagebrush biologist, cautioned against drawing too many conclusions about northeast Wyoming's population health based on the 2020 counts. Due to COVID-19 restrictions, she said, counts were not as robust as usual.
Although the department aims to survey at least 80% of the leks in a region each year, in 2020, observers were only able to visit 65% of the 352 occupied leks in northeast Wyoming. The department was also unable to conduct its annual aerial lek surveys.
"I'm not willing to make a huge inference about (the population trend), because these other things are throwing question marks at me,” Schreiber said. "I'd like to see if it continues next year, and then we might have some more confidence.”
Next spring's count will also show the impact of wildfires that damaged significant swaths of sagebrush in the Powder River Basin this summer. At least three separate fires torched thousands of acres of sage-grouse core areas, protected for their strong habitat characteristics and high grouse mating activity. Local biologists are working to map the extent of the damage before releasing recommendations for any necessary restoration work.
According to Brad Fedy, a professor at the University of Waterloo who pioneered research on the cyclical behavior of sage-grouse populations, observing cycles closely can reveal deeper information about regional species health.
“When populations become unstable and disturbed, you see the prominence of cycles start to decline,” Fedy said. “So, if we have a natural cycling amplitude, one of the patterns we see is, in more disturbed areas, those cycles start to disappear. We're seeing that in this region now.”
Oil and gas development and wildfire are some of the largest local challenges to maintaining adequate sage-grouse habitat. Research by Fedy and his collaborators showed that the birds in the northeast are genetically linked to sage-grouse in Montana, rather than the rest of Wyoming, which has the strongest cycles across the birds’ 11-state range, Fedy said. As a relatively isolated population, the northeast's birds are therefore more at risk.
“Unfortunately, in the management world, much of that research gets ignored because nonlinear models can be challenging to interpret,” Fedy said. "But they're incredibly important.”