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distribution of sage grouse in the Plilliams Fork Mountains • does not include the study sit=_ (Colorado Division of Wi1d- ~. life, 1976). One sage grouse was observed on the site, indicating a small population may exist in the Hayden Oulch -~' area. However, lack of optimal habitat precludes the study site from being good sage grouse country (see Figure 2. 1). - The study site's dense mountain shrub vegetation provides excellent blue grouse habitat. A covey of eleven blue grouse was flushed several times during the faunal _ survey in October. Blue grouse exhibit an altitudinal ' migration, moving to higher elevations in the winter where ~ they feed almost exclusively on coniferous needles and buds (Rogers, 1968). Blue grouse in the region of the study site probably move south of the F}illiams Fork River into the coniferous fore_ts on the Flat Tops heavy srcwfall winters. Colorado Division of f~ildlife estimate3 that the • overall density of blue grouse in the area of the study site was 2.5 grouse per square mile in 1975, a relati*rely poor year for grouse. Since grouse populations can fiuc*_uate from year to year by a factor as high as 105, a density of 25 blue grouse per square mile could be expected in the. study ~. area during good blue grouse years (Hector, 1976). The rolling hills within the Yampa River drainage, especially the area north of Hayden, support the largest population of sharp-tailed grouse in the state (see Rogers, • 1969, Baily and Neidenach, 1965). Although some shrub i~;= cover is needed by sharptails for nesting, roosting and escape, dense shrub cover limits their distribution. Optimal _, habitat requires either a numi:er of small openings (1 to 10 acres each) or a single large opening (50 to 100 acres) in ~~ the shrub cover (Rogers, 1969), especially for use during the breeding season. Dense shrub vegetation in the ;Pilliams , Fork Mountains restricts sharptails in the area of the study ~ site to openings resulting from fires (see Figure 2.3). -- During spring, sharptails congregate on "dance grounds" where the males perform elaborate courtship displays in connection with breeding. The same dance ground is utilized by the local population each year. A sharptail dance ground }mown as the Hayden Divide dance ground, is located less than ~~ one mile northwest of the study across County Road 53. Rogers (1969) reports that the clearings, which occur along grassy swales and in dense shrub cover, were created by fire. Because ~• the range of an individual sharptail is between one and two ~ miles (Hart et. a1., f.950; Marshall and Jenson, 1937), irdi- • viduals using the Havden~Divide dance ground may nest and forage on the study s}te. }Iowever, dense shrub cover over mast of the study site may limit sharptail use' to the more open area 1 ~~~ • -49-