Sage grouse winter range discussed
Casper – Natural resource experts and stakeholders from around the state gathered in Casper on Sept. 8-9 for research updates, panel discussions and other presentations on the current status of habitat restoration during the Wyoming Habitat Restoration Workshop.
The workshop was presented by the Wyoming Reclamation and Restoration Center and the University of Wyoming (UW) School of Energy Resources.
During the conference, UW PhD Candidate Kurt Smith presented his research comparing the current core area stipulations for Greater sage grouse to their use of winter habitat.
“We’re interested in evaluating how well the core area concept that was designed for breeding habitat does at protecting winter habitat for these birds,” said Smith.
Greater sage grouse are defined as a landscape species, meaning that they migrate over a large range of habitat throughout the year.
“They exhibit long distance movements between seasonal habitats. Even within those seasonal habitats, they can have a lot of movement,” explained Smith.
Typically, birds will show a high fidelity to seasonal areas, returning to the same locations year-after-year.
Not all birds will move over large distances to access seasonal habitat, however.
“The species is a partial migrant, so some individuals within the same species will move to distinct seasonal ranges, whereas others will stay in a single location,” said Smith.
In Wyoming studies, it was found that birds will travel an average of 14.5 kilometers from their nest to winter range.
Smith explained that the core areas were developed based on leks and buffers around the leks to protect breeding habitat.
“I would say it works pretty darn well in terms of how it was designed for breeding habitat,” said Smith.
There are winter use stipulations that are put into place through the Natural Resource Conservation Service, depending on location and the concentration of birds at the site. The stipulations are largely based on what is defined as a winter concentration area.
“Winter concentration areas are areas where a large concentration of core area birds – so birds that are breeding in core areas – congregate and occupy from Dec. 1 to March 14,” continued Smith.
The definition typically includes groups that are consistently 50 birds or greater.
If a non-core area is identified as a concentration area, a seasonal use restriction is put into place from Dec. 1 to March 14. Core areas identified as concentration areas receive the most protection.
“There’s the seasonal use restriction, but then there’s also the five percent disturbance cap,” said Smith.
Core versus non-core
As part of their study, Smith and his team gathered 44,000 tracked locations from 77 individual birds.
“In our Big Horn Basin site, we had about 56 percent of individuals nested in core. Of those, about 63 percent of their winter use was in core,” said Smith.
Alternatively, approximately 30 percent of use was outside of core areas.
“Nearly 18 percent wintered entirely outside of core, so there’s a pretty substantial amount of use that is outside of core areas,” he continued.
In that study area, birds moved an average of 8.5 kilometers to winter range. Their winter range movement was from Oct. 26 to March 21.
“As we can see, they’re moving earlier and staying a little bit later than current timing stipulations,” said Smith.
Less movement was found in the Jeffery City study area, but similar winter range movement times were found.
“Our current seasonal use stipulations of Dec. 1 to March 14 are not quite matching the time of use that we’re seeing at a fine scale,” he concluded.
“Basically, we assessed seasonal home ranges and looked at the overlap with ranges in relation to core areas,” explained Smith.
He noted that more overlap occurred in larger core areas, which could be seen in comparing two of the study areas used.
In the Greater South Pass site, “The ratio of summer to winter use was a little less than one. That’s indicating that summer use is pretty well related to winter use,” said Smith.
Alternatively, the much smaller Rawlins site had a ratio of proportional use of 0.44 in the summer and 0.12 in the winter.
“Individuals are using these core areas much more in the summer than in the winter,” he continued.
According to the study, Smith determined that core areas do not proportionally protect winter habitat as well as they protect breeding habitat.
“If populations are using core mostly during the summer, it does not necessarily mean that they’ll use the core during winter. It’s really a habitat specific context,” concluded Smith.
Emilee Gibb is editor of Wyoming Livestock Roundup and can be reached an firstname.lastname@example.org.