Greater sage-grouse (Centrocercus urophasianus) COSEWIC assessment and status report: chapter 3

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Species Information

Name and classification

The Greater Sage-Grouse was first described as Tetrao urophasianus (Bonaparte 1828) and renamed Centrocercus urophasianus in 1831 (Aldrich 1963). The Latin name is derived from the Greek word “kentron” meaning spiny, “kerkos” meaning tail, and “oura phasianos” meaning tail of a pheasant (Gill 1966). Centrocercus is one of 10 genera in the sub-family Tetraoninae, family Phasianidae, of the order Galliformes.

Two species fall under the genera Centrocercus (Young et al. 2000): Greater Sage-Grouse, C. urophasianus, and Gunnison Sage-Grouse, C. minimus. Current research suggests the Greater Sage-Grouse population in California (Lyon/Mono) has been isolated from all other populations and may be sufficiently genetically distinct to warrant protection and management as a separate unit (Oyler-McCance et al. 2005). Vernacular names include Sage Chicken and Sage Hen (Patterson 1952).

Greater Sage-Grouse are separated into eastern (C. u. urophasianus) and western (C. u. phaios) subspecies (Hupp and Braun 1991, Schroeder et al. 1999). C. u. urophasianus is found in Alberta and Saskatchewan, while C. u. phaios was formerly present in the Okanagan Valley of British Columbia. C. u. phaios was extirpated from Canada in the early 1900s (Cannings et al. 1987). This report will deal almost entirely with the Canadian C. u. urophasianus populations. Recent genetic and ecological analysis of 16 populations (n = 332) throughout the North American range produced no evidence to support delineation of these subspecies (Benedict et al. 2003).

Morphological description

Greater Sage-Grouse are the largest grouse in North America (Beck and Braun 1978). Males can be distinguished from females by their conspicuous plumage and larger size (Figure 1). During courtship display, the males fan their tails and inflate air sacs, thus exposing two patches of bare, yellowish skin on the breast (Schroeder et al. 1999). Other features the males exhibit are yellow fleshy combs above the eyes and long filoplumes that arise from the nape (Figure 1, figure2). The undertail coverts of the male have white-tipped black feathers while the front of the neck and upper breast are white. Both genders have diagnostic black feathers on the belly. The female has more cryptic plumage, an inconspicuous comb above the eye, and is smaller (1.0-1.8 kg, length 50-60 cm) than the male (1.7-2.9 kg, length: 65-75 cm) (Schroeder et al. 1999) (Figure 1).

Genetic description

A range-wide genetic survey was conducted for 46 populations and 1000 individuals using mitochondrial DNA and sequence data from 7 nuclear microsatellites (Oyler-McCance et al. 2005). Results indicated that Greater Sage-Grouse movements are mostly among neighbouring populations and not across the species’ range (Oyler-McCance et al. 2005). In this study, grouse from Alberta scored the second highest level of genetic variation across the species’ range (Oyler-McCance et al. 2005). The significance of these results may be compromised by variable sample sizes (Bush pers. comm. 2006).

Preliminary analysis of 19 microsatellite loci in Canada indicates Greater Sage-Grouse north of the Missouri River form a single population which is likely further divided into 3 sub-populations: Sage Creek (western Saskatchewan, Alberta, and northern Blaine County, Montana), Grasslands (Grasslands National Park, Saskatchewan and northern Phillips and Valley Counties, Montana), and South of the Milk River (southern Blaine, Phillips, and Valley Counties) (Bush pers. comm. 2006).

Designatable units

This report will use the two subspecies known from Canada as the most logical designatable units for this taxon. Although recent genetic and ecological analysis of 16 populations (n = 332) throughout the North American range produced no evidence to support delineation of these subspecies (Benedict et al. 2003), they are still recognized on morphological characters (Schroeder et al. 1999). The two subspecies occupy two different COSEWIC National Ecological Areas (Southern Mountains and Prairie) with substantial ecological differences (e.g. different sagebrush and grass species).