Data Zone
Justification of Red List category
This species qualifies as Endangered because it has a very small population, which is feared to undergo local declines in the near future.
Population justification
Population size estimates vary for this species, ranging from roughly 3,300 mature individuals (Young et al. 2020) to 8,400 mature individuals (Partners in Flight 2019). High counts (3-year average; USFWS 2019) give numbers of 885 males on leks. Assuming an equal sex ratio, this would equate to 1,770 mature individuals. No information on detectability is given, but it is likely that the true population size is larger than this number. Studies have detected low levels of gene flow between sites; therefore the species is tentatively assessed as forming only one subpopulation (USFWS 2019, Zimmerman et al. 2019 and references therein).
Trend justification
The species has been undergoing a large, significant decline over the last five decades; the rate of decline amounts to more than 50% between 1970 and 2017, equating to ≥ 22.6% over three generations (17.4 years; Partners in Flight 2019, see also Panjabi et al. 2019). There have been long-term declines in lek sites, males at leks, offspring and juvenile recruitment (BLM 1999, J. R. Young in litt. 1999, Storch 2000, Young et al. 2000, Davis et al. 2016). It seems however, that these declines are historical, and the largest population in the Gunnison Basin is assessed as stable since the late 1990s (Davis et al. 2015, USFWS 2019). The seven satellite populations around Gunnison Basin are in more fragile states though: declines are still ongoing, and under a worst case scenario, up to five of the satellite populations may be in critical condition or even extirpated by 2050 (USFWS 2019). The species is therefore projected to undergo a decline as satellite populations are declining, but the impact on the overall population is likely low, given that up to 90% of the population in the Gunnison Basin is presumably safe. The species is therefore estimated to decline at a rate of < 20% over three generations, which is projected to continue in the future.
Centrocercus minimus is confined to the Gunnison basin in Gunnison and Saguache counties, south-west Colorado, with small, fragmented populations in Colorado and one in south-east Utah, U.S.A. (Storch 2000, Young et al. 2000, USFWS 2019). Historically, it presumably also occurred in Arizona, Oklahoma and New Mexico, but following intense habitat loss due to land-use change as well as hunting it is now confined to only 8% of its original range (BLM 1999, Schroeder et al. 2004, Braun et al. 2014, Young et al. 2020). 85-90% of the population occur in one site in the Gunnison Basin, with a further seven small populations in the vicinity (USFWS 2019, Zimmerman et al. 2019).
The species occupies sagebrush habitats which are naturally highly fragmented by forested mountains and river systems (Braun et al. 2014). Various adjacent habitats are required in the 2,300 m intermontane basin (J. R. Young in litt. 1999, Storch 2000). These differ seasonally and for age and sex classes (J. R. Young in litt. 1999). The species is totally reliant on sagebrush Artemisia spp. for seasonal cover and winter foraging (Young et al. 2000), but it also uses areas where sagebrush occurs together with more deciduous shrubs, e.g. Quercus spp., Amelanchier spp., Prunus spp. (Braun et al. 2014). Lek sites have low vegetation with sparse shrubs, and are often surrounded by the big sagebrush-dominated plant communities required for nesting (BLM 1999). Broods are reared (May to autumn) in adjacent riparian plant communities and in mesic upland sites (BLM 1999, J. R. Young in litt. 2005). Nesting success is relatively high and apparently unrelated or only weakly related to local-scale and landscape-scale features (Stanley et al. 2015). Similarly, adult survival was found to be constant across years and between populations (Davis et al. 2015). In winter, the species associates with watercourses on southerly or westerly slopes and ridge tops where deep snow is less likely (BLM 1999).
Habitat loss, degradation and fragmentation is resulting from conversion to roads, reservoirs, livestock-grazing, hay and other crops, real estate developments, powerlines, land treatments and increased deer populations (BLM 1999, J. R. Young in litt. 1999). Many winter sites are directly threatened and being enclosed by urbanisation (Storch 2000). Inbreeding depression appears to be occurring due to the skewed mating system at leks: six of the seven extant populations now appear to be low enough to be suffering from this (Stiver et al. 2008). Severe winters and potentially droughts may represent survival bottlenecks (e.g. in 1984, less than 10% of sagebrush emerged above the snow [Storch 2000]), as may other habitat factors influencing chick survival (J. R. Young in litt. 2005). Calls to increase gas prospecting in areas of sagebrush habitat represent a potential future threat. Overhunting and poaching have contributed to the severe population declines in the past, but hunting of the species has been entirely banned since 2000 (Young et al. 2020).
Conservation Actions Underway
The species is listed as threatened under the Endangered Species Act. In 1995 a working group was formed and, in 1998, a conservation plan identified over 200 actions (BLM 1999, J. R. Young in litt. 1999). By 2004, over 95% of the population was covered by local working groups' conservation plans (J. R. Young in litt. 2005). While the success of such local efforts may be controversial, hunting has ceased and significant gains have been made in land protection through conservation easements and land acquisitions (J. R. Young in litt. 2005). Current actions include lek enhancement, riparian area restoration, nest habitat treatments, improved livestock management, nest predator research, and education (J. R. Young in litt. 1999, Young et al. 2020). Education measures include sponsored grouse viewing, information brochures and talks given in local schools and fairs (W. Martinson in litt. 2003). Radio-telemetry and graduate research is helping to determine winter habitat use, and lek sites have been protected (W. Martinson in litt. 2003). Hunting of the species has been stopped (C. Braun in litt. 2005, J. R. Young in litt. 2005). In 2005 state and federal employees drafted a 'Rangewide Plan' and have begun contact with local landowners to present voluntary conservation agreements (J. R. Young in litt. 2005).
Male 44-51 cm, female 32-38 cm. Small, variegated greyish-brown grouse. Black belly and long, stiff, pointed tail feathers. Male has black throat and upper neck, separated by V-shaped white line. Large white ruff on breast and some white bars on tail. Large, yellowish cervical sacs and inconspicuous yellow eyecombs. Similar spp. The allopatric Sage Grouse C. urophasianus is 30% larger. Voice Male display involves brushing wings against pouch feathers to produce loud swishing noises.
Text account compilers
Hermes, C.
Contributors
Benstead, P., Bird, J., Braun, C., Harding, M., Keane, A., Martinson, W., Sharpe, C.J., Wege, D. & Young, J.
Recommended citation
BirdLife International (2024) Species factsheet: Gunnison Grouse Centrocercus minimus. Downloaded from
https://datazone.birdlife.org/species/factsheet/gunnison-grouse-centrocercus-minimus on 23/12/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 23/12/2024.