Centrocercus minimus

Gunnison sage-grouse (Centrocercus minimus) formerly was regarded as conspecific with the greater sage-grouse (C. urophasianus). It was recognized as a distinct species by AOU (2000) on the basis of genetic differences (Kahn et al. 1999, Oyler-McCance et al. 1999) and differences in size (Hupp and Braun 1991), courtship behavior (Young et al. 1994), and plumage (Young et al. 2000).

Range extent and and area of occupancy have contracted greatly (90 percent or more) over the long term; now restricted to several small areas in southwestern Colorado and southeastern Utah; population size now approximately 4,700 individuals; overall population relatively stable; threatened primarily by ongoing loss, fragmentation, and degradation of sagebrush habitat.

This species occurs locally in the Gunnison Basin and southwestern Colorado, and in adjacent southeastern (San Juan County) Utah south and east of the Colorado River (AOU 2000, Beck et al. 2003, Schroeder et al. 2004, Gunnison Sage-grouse Rangewide Steering Committee 2005, USFWS 2014). The historical range is thought to have included southwestern Colorado, northwestern New Mexico, northeastern Arizona, and southeastern Utah (Schroeder et al. 2004). See Gunnison Sage-grouse Rangewide Steering Committee (2005) and USFWS (2014) for fairly detailed range maps. Coded range extent is based on a minimum convex polygon encompassing the seven extent populations.

Gunnison Sage-grouse Rangewide Steering Committee (2005) identified eight extant populations (these are metapopulations, each of which includes gaps in occupied habitat). USFWS (2014) stated that the species currently occurs in seven distinct populations (again, these are metapopulations).

This species is expected to be affected by a large number of threats over the next 10 years or 3 generations. Alone, each threat likely will be of relatively low impact, but cumulative/synergistic effects increase the overall impact level. USFWS (2014) summarized these threats as follows (minimally edited). See USFWS (2014) for extensive further discussion of each threat.

Habitat loss due to residential and infrastructural development (including roads and powerlines) is a current and future threat to Gunnison sage-grouse range-wide. Due to habitat decline, the seven individual populations are now mostly isolated, with limited migration and gene flow among populations, extirpations. Functional habitat loss also contributes to habitat decline as sage-grouse avoid areas due to human activities and noise, even when sagebrush remains intact. The collective disturbance from human activities around residences and infrastructure results in habitat decline that negatively impacts Gunnison sage-grouse survival. Human populations are increasing across the species’ range, a trend expected to continue into the future. Resulting habitat decline is diminishing the probability of Gunnison sage-grouse survival and persistence, particularly in the satellite populations. Other habitat-related threats that are impacting Gunnison sage-grouse include grazing practices inconsistent with local ecological conditions, fences, invasive plants, fire, mineral development, piñon-juniper encroachment, and large-scale water development and irrigation. The cumulative presence of all these features and activities constitutes a threat to Gunnison sage-grouse as they collectively contribute to habitat decline. In particular, the satellite populations are less resilient and more vulnerable to extirpation and environmental pressures including habitat loss and fragmentation. Several issues discussed above, such as fire, invasive species, and piñon-juniper encroachment, may not currently have a substantial impact on Gunnison sage-grouse. For example, while it may be impacting individual birds or populations, piñon-juniper encroachment does not currently pose a threat to the species because of its limited distribution throughout the range of Gunnison sage-grouse. However, the documented synergy among these three issues (piñon-juniper encroachment, fire, and invasive species), results in a high likelihood that they will pose a threat to the species in the future. Nonnative invasive plants, including cheatgrass and other noxious weeds, continue to expand their range, facilitated by ground disturbances such as fire, grazing incompatible with local ecological conditions, and human infrastructure. Invasive plants negatively impact Gunnison sage-grouse primarily by reducing or eliminating native vegetation that sage-grouse require for food and cover, resulting in habitat decline (both direct and functional). Cheatgrass is present at varying levels in nearly all Gunnison sage-grouse population areas, but there has not yet been a demonstrated change in fire cycle in the range of Gunnison sage-grouse. However, climate change will likely alter the range of invasive plants, intensifying the proliferation of invasive plants to the point that they become a threat to the species. Even with aggressive treatments, invasive plants will likely persist and continue to spread throughout the range of Gunnison sage-grouse. Livestock management inconsistent with local ecological conditions has the potential to degrade sage-grouse habitat at local scales by causing the loss of nesting cover and decreases in native vegetation, and by increasing the probability of incursion of invasive plants. Given the widespread nature of grazing within the range of Gunnison sage-grouse, the potential for population-level impacts is probable. Effects of domestic livestock grazing inconsistent with local ecological conditions are likely being exacerbated by intense browsing of woody species by wild ungulates in parts of the Gunnison Basin. We conclude that habitat degradation that can result from grazing practices inconsistent with local ecological conditions is a threat to Gunnison sage-grouse. We do not consider nonrenewable energy development to be impacting Gunnison sage-grouse habitat to the extent that it is a threat to the long-term persistence of the species at this time, because its current and anticipated extent is limited throughout the range of Gunnison sage-grouse. We do not consider renewable energy development to be a threat to the persistence of Gunnison sage-grouse rangewide at this time. However, geothermal and wind energy development could increase in the Gunnison Basin and Monticello areas, respectively, in the future. We recognize ongoing and proposed conservation efforts by all entities across the range of the Gunnison sage-grouse, and commend all parties for their vision and participation. Local communities, landowners, agencies, and organizations in Colorado and Utah have dedicated resources to Gunnison sage-grouse conservation and have implemented numerous conservation efforts. We encourage continued implementation of these efforts into the future to promote the conservation of Gunnison sage-grouse. Our review of conservation efforts indicates that the measures identified are not fully addressing the most substantial threats to Gunnison sage-grouse including habitat decline, small population size and structure, drought, climate change, and disease. All of the conservation efforts are limited in size and the measures provided to us were not implemented at the scale (even when considered cumulatively) that would be required to effectively reduce the threats to the species and its habitat across its range. The Gunnison Basin CCA, for example, provides some protection for Gunnison sage-grouse on Federal lands in the Gunnison Basin, but does not cover the remaining, more vulnerable satellite populations. Similarly, the existing CCAA benefits Gunnison sage-grouse on participating lands, but does not provide sufficient coverage of the species’ range to ensure the species’ long-term conservation. Thus, although the ongoing conservation efforts are a positive step toward the conservation of the Gunnison sage-grouse, and some have likely reduced the severity of some threats to the species, on the whole we find that current conservation efforts are not sufficient to offset the full scope of threats to Gunnison sage-grouse. We have evaluated the best scientific information available on the present or threatened destruction, modification, or curtailment of the Gunnison sage-grouse’s habitat or range. Based on the current and anticipated habitat threats identified above and their cumulative effects as they contribute to the overall decline of Gunnison sage-grouse habitat, we have determined that the present or threatened destruction, modification, or curtailment of Gunnison sage-grouse habitat poses a threat to the species throughout its range. This threat is substantial and current, and is projected to continue and increase into the future with additional anthropogenic pressures.

Overutilization for commercial, recreational, scientific, or educational purposes is not a threat to Gunnison sage-grouse.

The only disease that is known to be a threat to the survival of the Gunnison sage-grouse is West Nile virus. This virus is distributed throughout most of the species’ range. However, despite its near 100 percent lethality, disease occurrence is sporadic in other taxa across the species’ range and has not yet been detected in Gunnison sage-grouse. While we have no evidence of West Nile virus acting on Gunnison sage-grouse individuals or populations, because of its presence within the species’ range, its lethality to sage-grouse, and the continued development of anthropogenic water sources in the area that support mosquito vector populations, the virus is a future threat to the species. We anticipate that West Nile virus will persist within the range of Gunnison sage-grouse indefinitely and that the threat it presents will be exacerbated by any factor (e.g., drought, climate change) that increases ambient temperatures and the presence of the vector on the landscape. The best available information shows that existing and future habitat decline, and fragmentation in particular, will increase the effects of predation on this species, particularly in the six smaller populations, resulting in a reduction in sage-grouse productivity and abundance in the future. We evaluated the best available scientific information regarding disease and predation and their effects on the Gunnison sage-grouse. Based on the information available, we have determined that predation and disease are threats to the species throughout its range at the present time and are likely to increase in the future. In particular, West Nile virus poses a substantial threat to Gunnison sage-grouse rangewide in the foreseeable future.

Some regulatory mechanisms are in place to conserve Gunnison sage-grouse, but individually or collectively they do not fully address the substantial threats faced by Gunnison sage-grouse across their range. Further, while these existing regulatory mechanisms may help reduce current threats to the species, they are insufficient to fully reduce or eliminate the increase in threats that may act on the species in the future.

Resiliency, redundancy, and representation in Gunnison sage-grouse are inadequate, or will be inadequate in the near term, to ensure the species’ long-term viability. The best available information indicates population redundancy, in particular, will be limited or compromised in the near term, due to the probable extirpation of one or more satellite populations, thereby decreasing the species’ chances of survival in the face of limiting factors. The rangewide cumulative effects of ongoing and future threats will further compromise resiliency, redundancy, and representation of the species. Current and future threats to the Gunnison Basin population (in particular, drought, climate change, and disease), combined with the probable loss of satellite populations and overall reduction of range indicate the long-term persistence of Gunnison sage-grouse is at risk.
Drought has contributed to substantial declines in all Gunnison sage-grouse populations. Drought is a substantial threat to Gunnison sage-grouse populations rangewide, both now and into the future.

Recreational activities generally do not singularly pose a threat to Gunnison sage-grouse. However, there may be certain situations where recreational activities are impacting local concentrations of Gunnison sage-grouse, especially in areas where habitat is already fragmented such as in the six satellite populations and in certain areas within the Gunnison Basin.

At present, there is no information available to indicate that either herbicide or insecticide applications, or contaminants, pose a threat to the species.
Small population size and structure is a threat to the six satellite populations of Gunnison sage-grouse, both now and into the future. Genetics risks related to the small population size of Gunnison sage-grouse are a threat to the species.

Many of the threats to Gunnison sage-grouse may cumulatively or synergistically impact the species beyond the scope of each individual threat. For example, grazing practices inconsistent with local ecological conditions alone may only affect portions of Gunnison sage-grouse habitat. However, grazing practices inconsistent with local ecological conditions, combined with invasive plants, drought, and recreational activities may collectively result in substantial habitat decline across large portions of the species’ range. In turn, climate change may exacerbate those effects, further diminishing habitat and increasing the isolation of already declining populations, making them more susceptible to genetic deterioration, disease, or catastrophic events such as drought and fire. Drought, a substantial threat to Gunnison sage-grouse rangewide, likely intensifies other threats such as predation, invasive plants, habitat loss, and fire. The impact of residential development is increased by the additional disturbance footprint and area of species’ avoidance of other infrastructure such as roads, powerlines, and fences. Further, predation on Gunnison sage-grouse may increase as a result of the increase in human disturbance and development. The impact of residential development can be increased by other anthropogenic stressors resulting in habitat loss and decline, such as powerlines, roads, and other infrastructure. Numerous threats are likely acting cumulatively to further increase the likelihood that the species will become extinct in the future. The cumulative effects of ongoing and future threats and small and declining population size and structure, in particular, are likely to further reduce resiliency, redundancy, and representation of the species.