The greater sage-grouse (Centrocercus urophasianus), also known as the sagehen, is the largest grouse in North America. Its range is sagebrush country in the western United States and southern Alberta and Saskatchewan, Canada. It was known as simply the sage grouse until the Gunnison sage-grouse was recognized as a separate species in 2000. The Mono Basin population of sage grouse may also be distinct.
The greater sage-grouse is a permanent resident in its breeding grounds but may move short distances to lower elevations during winter. It makes use of a complex lek system in mating and nests on the ground under sagebrush or grass patches. It forages on the ground, mainly eating sagebrush but also other plants and insects. Greater sage-grouse do not have a muscular crop and are not able to digest hard seeds like other grouse.
The species is in decline across its range due to habitat loss, and has been recognized as threatened or near threatened by several national and international organizations.
Description Adult greater sage-grouse have a long, pointed tail and legs with feathers to the toes. The adult male has a yellow patch over each eye, is grayish on top with a white breast, and has a dark brown throat and a black belly; two yellowish sacs on the neck are inflated during courtship display. The adult female is mottled gray-brown with a light brown throat and dark belly. Adult males range in length from and weigh between . Adult females are smaller, ranging in length from and weighing between .
Distribution and habitat Greater sage-grouse are obligate residents of the sagebrush (Artemisia spp.) ecosystem, usually inhabiting sagebrush-grassland or juniper (Juniperus spp.) sagebrush-grassland communities. Meadows surrounded by sagebrush may be used as feeding grounds. Use of meadows with a crown cover of silver sagebrush (A. cana) is especially important in Nevada during the summer.Savage, David E. 1969. Relation of sage grouse to upland meadows in Nevada. Job Completion Report: Federal Aid in Wildlife Project No. W-39-R-9. Reno, NV: University of Nevada, Nevada Cooperative Wildlife Research Unit
Greater sage-grouse occur throughout the range of big sagebrush (A. tridentata), except on the periphery of big sagebrush distribution. Greater sage-grouse prefer mountain big sagebrush (A. t. subsp. vaseyana) and Wyoming big sagebrush (A. t. subsp. wyomingensis) communities to basin big sagebrush (A. t. subsp. tridentata) communities.
Sagebrush cover types other than big sagebrush can fulfill greater sage-grouse habitat requirements; in fact, the grouse may prefer other sagebrush cover types to big sagebrush. Greater sage-grouse in Antelope Valley, California, for example, use black sagebrush (A. nova) cover types more often than the more common big sagebrush cover types. Hens with broods on the National Antelope Refuge in Oregon were most frequently found (54–67% of observations) in low sagebrush (A. arbuscula) cover. Desert shrub habitat may also be used by greater sage-grouse.
Sagebrush communities supporting greater sage-grouse include silver sagebrush and fringed sagebrush (A. frigida).
Their historic range spanned 16 American states and Alberta, British Columbia, and Saskatchewan in Canada. Between 1988 and 2012, the Canadian population declined by 98%. By 2012, they were extinct in British Columbia and left with only remnant populations in Alberta with 40 to 60 adult birds, and in Saskatchewan with only 55 to 80 adult birds. By 2013, sage grouse were also lost from five U.S. states. In 2013, the Canadian Governor in Council on behalf of the Minister of the Environment, under the Species at Risk Act, annexed an emergency order for the protection of the greater sage-grouse.
Sage-grouse are largely resident, but in Idaho have been known to move up to in winter to avoid deep snow.
Ecology
Lek mating system
Greater sage-grouse are notable for their elaborate courtship rituals. Each spring, males congregate in leks and perform a "strutting display". Groups of females observe these displays and select the most attractive males with which to mate. The dominant male located in the center of the lek typically copulates with around 80% of the females on the lek. Males perform in leks for several hours in the early morning and evening during the spring. Males gather in leks to court, usually in late February to April. Only a few dominant males, usually two, breed. Sage grouse mating behaviors are complex. After mating, the hen leaves the lek for the nesting grounds.
Open areas such as swales, irrigated fields, meadows, burns, roadsides, and areas with low, sparse sagebrush cover are used as leks. Of 45 leks, 11 were on windswept ridges or exposed knolls, 10 were in flat sagebrush, seven were in bare openings, and the remaining 17 were on various other site types. Leks are usually surrounded by areas with 20 to 50% sagebrush cover, with sagebrush no more than tall. Daily morning lek attendance by male Sage grouse can vary considerably between years, with lower attendance on days with precipitation.
Nest selection Greater sage-grouse disperse to areas surrounding the leks for nesting. In a study of habitat selection by male greater sage grouse in central Montana during breeding season, sagebrush height and canopy cover at 110 daytime feeding and loafing sites of cocks were recorded. About 80% of the locations occurred in sagebrush with a canopy cover of 20–50%. In another Montana study, sagebrush cover averaged 30% on a cock-use area, and no cocks were observed in areas of less than 10% canopy cover.
Some females probably travel between leks. In Mono County, California, the home range of marked females during one month of the breeding season was , enough area to include several active leks. DNA from feathers dropped at leks showed that about 1% of grouse may travel long distances to explore breeding areas up to away, a type of long-distance dispersal that can potentially boost populations and temper inbreeding.
Within a week to ten days following breeding, the hen builds a nest in the vicinity of the lek. Hens usually nest near the lekking grounds, but some hens have been noted to fly as far as to favorable nesting sites.Gill, R. Bruce. 1966. A literature review on the sage grouse. Special Report No. 6. Denver, CO: Colorado Department of Game, Fish, and Parks, Game Research Division, Cooperative Wildlife Research UnitRogers, Glenn E. 1964. Sage grouse investigations in Colorado. Tech. Publ. No. 16. Denver, CO: Colorado Game, Fish and Parks Department, Game Research Division
Quality of nesting habitat surrounding the lek is the most important factor in population success. Adequacy of cover is critical for nesting. Too little can exist: where 13% was the average total crown cover on Idaho range, nests were located where average cover was 17%. No hens nested in the most arid, open areas with less than 10% total shrub cover. Too much also can occur: average shrub cover at 87 nest sites was 18.4%, and in more dense cover, greater sage-grouse did not nest where total shrub cover was greater than 25%. In Utah, no nests occurred where threetip sagebrush cover exceeded 35%.
Sagebrush forms the nesting cover for most greater sage-grouse nests throughout the West, with concealment being the basic requirement. Rabbitbrush (Chrysothamnus spp.) is occasionally used for nesting cover with greasewood (Sarcobatus vermiculatus) and shadscale (Atriplex canescens) being rarely used.
Greater sage-grouse prefer relatively tall sagebrush with an open canopy for nesting. In Utah, 33% of 161 nests were under silver sagebrush that was tall, while big sagebrush of the same height accounted for 24% of nests.Rasmussen, D. I.; Griner, Lynn A. 1938. Life history and management studies of the sage grouse in Utah, with special reference to nesting and feeding habits. In: Transactions, 3rd North American Wildlife Conference: 852–864 In a threetip sagebrush (A. tripartata) habitat averaging in height, hens selected the tallest plants for nesting cover. Similarly in Wyoming, 92% of nests in Wyoming big sagebrush were in areas where vegetation was tall and cover did not exceed 50%.
In Montana, when sagebrush characteristics around 31 successful and 10 unsuccessful nests were compared, successful nests had greater than average sagebrush cover surrounding the nest and were located in stands with a higher average canopy cover (27%) than unsuccessful nests (20%). The average height of sagebrush cover over all nests was as compared to an average height of in adjacent areas.
During the nesting season, cocks and hens without nests use "relatively open" areas for feeding, and roost in "dense" patches of sagebrush.
Brood rearing Clutch size ranges from six to eight eggs; incubation time is 25 to 27 days. The eggs measure in length and in width. Greater sage-grouse apparently have high rates of nest desertion and nest predation. Data from several sage grouse studies indicate a range of nesting success from 23.7 to 60.3%, with predation accounting for 26 to 76% of lost nests.
Chicks are precocial and can feed themselves. They fly by two weeks of age, although their movements are limited until they are two to three weeks old. They can do sustained flight by five to six weeks old. Juveniles are relatively independent by the time they have completed their first molt at 10 to 12 weeks old.
Diet Adults The importance of sagebrush in the diet of adult greater sage-grouse is great; numerous studies have documented its year-round use.Call, Mayo W.; Maser, Chris. 1985. Wildlife habitats in managed rangelands—the Great Basin of southeastern Oregon: sage grouse. Gen. Tech. Rep. PNW-187. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Forest and Range Experiment StationSchneegas, Edward R. 1967. Sage grouse and sagebrush control. Transactions, North American Wildlife Conference. 32: 270–274.Klebenow, Donald A. 1973. The habitat requirements of sage grouse and the role of fire in management. In: Proceedings, annual Tall Timbers fire ecology conference; 1972 June 8–9; Lubbock, TX. No. 12. Tallahassee, FL: Tall Timbers Research Station: 305–315Patterson, Robert L. 1952. The sage grouse in Wyoming. Federal Aid to Wildlife Restoration Project 28-R. Denver, CO: Sage Books, Inc.Wallestad, Richard. 1975. Life history and habitat requirements of sage grouse in central Montana. Helena, MT: Montana Department of Fish and GameCall, Mayo W. 1979. Habitat requirements and management recommendations for sage grouse. Denver, CO: U.S. Department of the Interior, Bureau of Land Management, Denver Service Center A Montana study, based on 299 crop samples, showed that 62% of total food volume of the year was sagebrush. Between December and February, it was the only food item found in all crops. Only between June and September did sagebrush constitute less than 60% of their diet. Sage grouse select sagebrush species differentially. Greater sage-grouse in Antelope Valley, California, browsed black sagebrush more frequently than the more common big sagebrush. The browse of black sagebrush is highly preferred by greater sage-grouse in Nevada. In southeastern Idaho, black sagebrush was preferred as forage.
Among the big sagebrush subspecies, basin big sagebrush is less nutritious and higher in terpenes than either mountain or Wyoming big sagebrush. Sage grouse prefer the other two subspecies to basin big sagebrush. In a common garden study done in Utah, greater sage-grouse preferred mountain big sagebrush over Wyoming and basin big sagebrush.
Sage grouse lack a muscular gizzard and cannot grind and digest seeds; they must consume soft-tissue foods. Apart from sagebrush, the adult diet consists largely of herbaceous leaves, which are used primarily in late spring and summer. Additionally, greater sage-grouse use perennial bunchgrasses for food.