Sage grouse are a group of chicken-sized birds with a unique breeding behavior and dependence on sagebrush shrubs (genus Artemisia) for food and shelter throughout their life cycle. In the last century, human population expansion throughout western North America has reduced the amount of sagebrush and degraded and fragmented the remaining areas. Vanishing sagebrush has resulted in sage grouse (genus Centrocercus) population declines and elevated conservation concern. Western Colorado is home to both species of sage grouse: greater sage grouse (Centrocercus urophasianus) and Gunnison sage grouse (Centrocercus minimus). Populations in the state, and throughout their range, have declined sufficiently to warrant consideration for federal protection for both species under the Endangered Species Act.
The scientific name (genus) of sage grouse is Centrocercus. Both members of the genus have dark brown wings and bodies. Females of both species have dark gray, brown, and white feathers covering the body and head. In addition to being larger in body size, male sage grouse are “showier” with plumage (feather) markings females do not possess. Males have long, brown tail feathers with coarse black bars and scale like white feathers covering the breast and greenish-yellow air sacs on their chests used in mating displays. Male Gunnison sage grouse weigh approximately just under five pounds (females weigh approximately two and a half pounds), while male greater sage grouse weigh between five and seven pounds (females weigh between three and four pounds).
For many years, all sage grouse were thought to be of one species. Beginning in the 1970s scientists noticed differences in morphology, behavior, and genetics between sage grouse in southwestern Colorado and southeastern Utah compared to the rest of the range. This led sage grouse in southern Colorado and southeastern Utah to be formally recognized as a separate species: Gunnison sage grouse. The larger-bodied sage grouse in the rest of the range were subsequently renamed greater sage grouse.
Historically, sage grouse occupied sagebrush rangelands in Washington, Oregon, California, Nevada, Idaho, Montana, Wyoming, Utah, Colorado, North Dakota, South Dakota, Nebraska, Arizona, and New Mexico in the United States and British Columbia, Saskatchewan, and Alberta in Canada. In Colorado sage grouse occur only in the western portion of the state. The Colorado–Eagle River Valley seems to be the dividing line between the two species’ ranges, with greater sage grouse occupying sagebrush rangelands north of the river valley and Gunnison sage grouse to the south. Larger populations of greater sage grouse occur in Grand, Jackson, and Moffat Counties. The largest population of Gunnison sage grouse occurs in Gunnison County, with smaller populations in Saguache, Delta, Montrose, Mesa, Dolores, and San Miguel Counties.
Sage grouse have a lek mating system. A lek is typically formed in an area of short vegetation, surrounded by sagebrush, where males congregate during the spring to compete for breeding access to females by strutting. During the display, males fan their tail feathers while they inflate their air sacs, emitting a popping sound. The vocalizations produced by Gunnison sage grouse are structurally different and slower than that of greater sage grouse. Vocalizations are different enough that females from each species do not respond to the male vocalizations from the other. Sage grouse are typically elusive and difficult to observe, but lekking provides bird enthusiasts a seasonal opportunity to see both species in the wild. Colorado has designated viewing areas for greater sage grouse near the town of Walden, and for Gunnison sage grouse near the town of Gunnison.
Although both species depend on sagebrush, their habitat needs vary throughout the year. In spring, sage grouse require areas of short vegetation for leks, but these areas must be surrounded by intact sagebrush rangelands. Sagebrush surrounding leks serves as cover for females to hide their nests from predators and as escape cover for displaying males when predators approach. For nesting, females generally select taller-than-average sagebrush shrubs with greater shrub canopies and grass cover for concealment. Females are the only parent to care for the brood of chicks. Sage grouse chicks rely on the surrounding area for food and are not directly fed by their parents. Early in the brooding period, hens and chicks are found in open shrub canopy areas that contain many different types of plants, including soft flowering plants or forbs, as well as abundant insects, which are eaten by chicks.
As the chicks grow and summer progresses, the hen moves the brood farther from the nest in search of food, usually into wetter, low-lying areas. In the fall, sage grouse seek lush forage upslope and on ridges. During the winter, sage grouse rely solely on sagebrush shrubs for food, eating the leaves. Sagebrush also provides shelter during harsh weather conditions; the birds may seek shelter by making snow burrows and caves. In the spring, sage grouse become more active and make their way back to lek sites. Over the course of a year, a sage grouse may move as far as sixty-two miles between seasonal areas, but not all sage grouse migrate. Regardless of movements, sage grouse usually return to the same general area each year to breed and nest.
Threats to Populations
Currently, greater sage grouse occupy approximately 56 percent of their former extent prior to European settlement, and Gunnison sage grouse occupy only 8 percent. There have been many contributing factors to observed population declines. The first was most likely the US westward expansion and settlement beginning in the 1800s. Conversion of land for agriculture, overgrazing by domestic livestock, an increase in nonnative plant species, and the development of towns all effectively reduced sage grouse habitat. Excessive hunting also had a significant role in decreasing some populations. While many of the threats are historical, current threats include oil and gas development, exurban sprawl, recreational activities, continued agricultural practices, and an increase in fire frequency. All of these threats reduce available sagebrush habitat either directly or by fragmenting and degrading habitats. For instance, sage grouse tend to avoid oil or gas wells and associated roads, which can make otherwise suitable habitat unsuitable. Invasive species, such as cheatgrass—in conjunction with climate change and drought—have led to an increase in fire frequency and intensity, which have reduced sagebrush habitat.
Populations of both species have declined enough to be considered for federal listing under the Endangered Species Act on multiple occasions. Federal protection for the greater sage grouse has been requested numerous times throughout its range, and in 2010 the US Fish and Wildlife Service (FWS) found that classifying the greater sage grouse as endangered was “warranted but delayed” on account of higher conservation priorities. But in September 2015 the FWS deemed that federal protection was not warranted for greater sage grouse, due to extensive, collaborative efforts to protect sage grouse habitat. The effectiveness of these efforts will need to be evaluated in the future.
The Gunnison sage grouse was removed from any federal protection in 2006, despite being recognized by the Audubon Society as one of the ten most-endangered bird species in North America. Protection of the Gunnison sage grouse was found warranted but delayed in 2010. The species was deemed endangered in 2013 but downgraded to threatened in 2014. As of fall 2015, the 2014 decision is being litigated. Greater sage grouse do not have a special status in Colorado, but Gunnison sage grouse is a species of special concern within the state.
Conservation and Management
There is a limited hunting season for greater sage grouse in Colorado, but Gunnison sage grouse cannot be legally harvested. Range-wide hunting is still allowed in eight of eleven states but banned in both Canadian provinces where the birds remain. Management agencies, such as Colorado Parks and Wildlife, support maintaining and improving habitat through the alteration of grazing practices, restoration projects, and closing areas to hunting. Because much of the remaining sagebrush habitat is on private land, cooperation with private landowners is critical. In addition, federal funding aids habitat management and restoration projects on private lands through the enrollment of agricultural land for wildlife habitat or the establishment of conservation agreements to maintain or improve habitat for species under consideration for federal protection. Local working groups also help the Sage-grouse through voluntary changes in land-use regulations, area and road closures during sensitive seasons, public education, and other cooperation with federal and state agencies.
In addition to conserving and improving habitat, local agencies and working groups monitor greater and Gunnison sage grouse during the breeding season. Lekking behavior in the spring provides a convenient opportunity to count males in order to track population size and yearly trends.
Without conservation, sage grouse may not be part of our future. Historically, sage grouse were an abundant resource for hunting and sustenance and may be able to return to the level of a stable resource with appropriate safeguards and actions. However, this could likely only occur in a few locations that feature vast expanses of undisturbed sagebrush habitat, which are increasingly difficult to find. From a recreational standpoint, viewing the early-morning breeding displays draws many bird watchers and nature enthusiasts. From a management and conservation standpoint, sage grouse are excellent indicators of sagebrush ecosystem health. If sage grouse populations are declining, other sagebrush-associated species are also likely to be declining.