Greater sage-grouse (Centrocercus urophasianus) COSEWIC assessment and status report: chapter 4

• Previous page
• Table of contents
• Next page

Distribution

United States

Greater Sage-Grouse distribution is associated with habitat dominated by sagebrush (Artemisia spp.) in western North America (Schroeder et al. 1999). The amount of potential pre-settlement habitat available encompassed 1,200,483 km² (Schroeder et al. 2004). The species’ current range extends 668,412 km² (Schroeder et al. 2004) and includes populations in southeastern Oregon; northeastern California; southern Idaho; northern two-thirds of Nevada; portions of northeast, north and south Utah; portions of western Colorado; Wyoming (except northwest and southeast corners); east and southwest Montana; northwest and southwest South Dakota; North Dakota; and small populations in central Washington (Schroeder et al. 1999).

Canada

In Canada, Greater Sage-Grouse is at the northern-most extent of the species’ range and represents < 1% of the global population (Lungle 2006). Their distribution is related to silver sagebrush (A. cana), the dominant sagebrush species in the mixed grassland ecoregion in Canada (Holcroft Weerstra 2001; Thorpe 2002). The current range (2002), based on occupied lek sites and telemetry locations, covers approximately 6,000 km²within southeast Alberta and southwest Saskatchewan (Aldridge and Brigham 2003) (Figure 3). The range prior to 1950 extended approximately 100,000 km² within Alberta and Saskatchewan (Figure 3). Historic range estimation is based on published information, museum specimens and anecdotal sightings (Aldridge and Brigham 2003).

Using landscape-level occurrence models and radio-telemetry locations (111 nests, 669 brood locations), researchers in southeast Alberta were able to predict the probability of occurrence of Greater Sage-Grouse nests and broods (Aldridge 2005; Aldridge and Boyce 2007). Variables included to predict grouse occurrence were sagebrush cover, soil-moisture index (related to herbaceous cover), and anthropogenic landscape features. About 30% and 20% of the 1,110 km² study area would likely be used for nesting and brood-rearing, respectively (Aldridge and Boyce 2007). Extrapolating this proportion over the range in Canada (6,000 km²) yields an area of occupancy for brood rearing and nesting of 1,800 km² and 1,200 km², respectively.

Monitoring by lek counts has occurred since 1968 in Alberta and 1987 in Saskatchewan. Survey effort and protocol has varied within and between provinces and between years (Aldridge and Brigham 2003; McAdam pers. comm. 2006; Connelly et al. 2004). Trends are further confounded when leks move or when satellite leks are discovered (Connelly et al. 2004). There have been no systematic searches for new leks in Saskatchewan (Sissons pers. comm. 2006) or Alberta (Eslinger pers. comm. 2006). Ahelicopter was used to successfully locate a previously unrecorded lek in Alberta in 2001 and aerial searches were conducted in Saskatchewan in 1983, 1984, 1988 and 2003 (McAdam 2003, McAdam, pers.. comm. 2006).From 1995-2005 only 5 new leks were discovered (Table 1).