Ecology, Productivity and Management of Sage Grouse in Idaho

Dalke, Paul; Pyrah, Duane; Stanton, Don; Crawford, John; Schlatterer, Edward

A study of the seasonal movements, productivity, and management of sage grouse (Centrocercus urophasianus) was undertaken by the Idaho Cooperative Wildlife Research Unit from August, 1952, to May, 1960, on an area in Fremont and Clark counties in Idaho, directly west of Yellowstone National Park. Nineteen individual strutting grounds 1/10-10 acres in size were located along 12 miles of the Red Road. Summer brood range was found to be 13-27 miles north and northeast of the Red Road strutting grounds. Flocks of sage grouse began migrating west and southwest in October and November and traveled 30-50 miles, depending upon the depth of the snow. Winter concentrations were usually found where snow was less than 6 inches deep. Dispersal and return east and northeast to the breeding grounds began in late winter for a yearly round trip of 50-100 miles. The number of adult males increased quickly on strutting grounds, and the peak of breeding occurred April 7-21. Strutting grounds were abandoned early in May if there was a high ratio of adults to subadults. A late season peak of subadult males was often seen on strutting grounds after all other grouse had departed. Interstrutting movements of adult males varied from 22 to 53 percent and up to 4.3 miles from original banding sites. Sexing criteria included plumage differences on chin, throat, breast, undertail coverts, and minor marginal tectrices; size of feet; wing length and length of primaries; weights of adults. Identification of gonads provided the only ready internal diagnostic characteristics of sex. Aging criteria included measurement of bursa, and characteristics of outer two primaries, second primary covert, undertail coverts, and sternum. The mandible test is not reliable for adult sage grouse. The high counts of males on strutting grounds has provided a reasonably accurate method of determining breeding population trends. The method may be as much as 20 percent conservative because of cocks which are not on strutting grounds. The reproductive potential cannot be fully assessed without knowledge of the relative proportion of adult to subadult females. Ovulated-follicle counts as a measure of the number of eggs laid are unreliable, but are useful in determining the relative laying effort between yearlings and adult females. Adverse weather during hatching appreciably lowered number of grouse available for fall hunting. Brood census on summer range is useful in determining reproductive success and is reliable until the third week in July, when brood structure begins to deteriorate.

Ecology, Productivity and Management of Sage Grouse in Idaho

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