The latest data on greater sage grouse in Wyoming indicate an “alarming” likelihood of populations regressing to a 1996 nadir, the state’s top grouse biologist said Thursday.
The preliminary data from hunter submitted sage grouse wings during the 2021 shooting season show a ratio of 0.8 chicks per hen. That’s below what’s needed to stabilize the shrinking population, Wyoming Game and Fish sagebrush and sage grouse biologist Leslie Schreiber said Thursday.
“Zero point eight chicks per hen is associated with a declining population because 1.5 chicks per hen is needed for population stability,” Schreiber said.
The wing data suggests that another key population metric anticipated in 2022 — a count of strutting males on breeding-ground leks — also will be lower, she said.
A lower count on leks in 2022 would extend the trend of declining numbers in Wyoming from five to six-years. Grouse have declined dramatically West-wide over recent decades. Game and Fish’s alarm, however, evidences a new worry.
“This is outside cyclical trends, or oscillations, as the most recent [U.S. Geological Survey] report calls them,” Schreiber said. “Ups and downs in sage grouse populations are natural and typically not cause of concern — unless they deviate significantly from the norm.”
That deviation is upon us, Schreiber said.
“Based on the data in hand, Wyoming sage grouse populations are heading back to mid 1990s levels, which is alarming,” she said. “This is particularly concerning because it does not follow the historic patterns of population cycles in the state.”
Confidence in survey
Hunters submitted 621 wings from chicks, 750 from hens and 210 from male grouse, depositing them in barrels near hunting areas, mainly in central and southwest Wyoming. “It adds up to an overall sample size of 1,581, which gives me confidence in the ratio,” Schreiber said.
The 0.8 ratio, “it’s a decrease from two previous years where reproduction ratios held at 1.1 chicks/hen,” Game and Fish said in a statement. The 2021 chick-to-hen ratio portends a lower count of males on leks in the coming spring, a count that serves as a barometer of the species’ overall population.
“In 2021, an average of 16.8 males per active lek, were counted in Wyoming.” Schreiber said. “Based on these numbers,” she said of the wing counts, “in 2022, Wyoming’s [average] sage grouse lek count will be lower than 16 — the lowest since 1996.”
Surveys at the 1996 nadir found an average of 13 males per occupied lek, according to Game and Fish data. The most recent high in the last 50 years came in 2006 when observers counted an average of 35.6 males per lek.
Lek counts have oscillated over the last five decades. But the count has declined without pause since 2016 when biologists counted an average of 35.6 strutting males per active lek.
Wyoming has more than 1,700 known, occupied leks, Game and Fish says. Biologists and other trained observers count grouse on some 1,000 leks a year depending on weather and other factors.
There’s no official estimate of overall sage grouse numbers in Wyoming, or established method of pinpointing that figure; lek-count trends are the principal metric determining the status of greater sage grouse populations.
Schreiber said the species should come back.
“I believe the population will rebound because that’s what it’s done in the past,” she said. “How much or why, I can’t answer.”
Gov. Mark Gordon’s executive order on sage grouse, which seeks to limit development in core grouse areas and provide other safeguards, will continue to guide management, she said.
Chicks dig bugs
Chicks depend on favorable climate and weather, among other things, to survive. “I would say drought had a hand in 2021’s low chick ratio,” Schreiber said.
“Drought alone cannot be blamed for the overall decline,” she said. “Other factors I could see contributing to the cause would be habitat loss and degradation.”
Game and Fish can’t control drought, but it does encourage and emphasize the development of water projects — such as stock tanks — and weighs in on development proposals that impact habitat, she said.
During the first month of life, chicks eat insects and need “adequate habitat cover,” Game and Fish wrote in an outline of the bird’s development. “As the bird grows, grass and forbs — like wildflowers — become another important food source. Older birds rely almost exclusively on sagebrush….”
Debate continues regarding whether grouse populations are naturally cyclical, as the USGS stated last year. There’s also debate in the scientific literature regarding what percentage of a fall population hunters can kill before affecting it, Schreiber said.
Wyoming, which allows hunting but has restricted it considerably in recent decades, does not officially calculate the fall numbers.
Nevertheless, “we believe hunters take between 5% and 10% of the fall population,” Schreiber said.
Schreiber would not comment on whether biologists are considering any recommendations for new hunting restrictions, including a suggested permit system that would direct hunters away from some stressed areas.
“We are just in the beginning stages of that process,” she said of season-setting recommendations.
The Game and Fish Commission will set grouse seasons this spring, based on biologists’ recommendations. Game and Fish calls the newly released wing ratio information preliminary. A full analysis of the 2021 sage grouse population also is expected this spring.
Wyoming holds 38% of the world’s population of greater sage grouse which live only in the western U.S. and parts of Canada.
The U.S. Fish and Wildlife Service in 2015 considered protecting the species under the Endangered Species Act but found that unnecessary. It is widely believed that an ESA listing for sage grouse would be devastating to Wyoming’s economy.