Males display and breed on a display area called a lek. Breeding occurs in late February to April, as soon as the lek is relatively free of snow. Males stop displaying in late May or early June [3,36,45,69,153]. Up to 400 males may be present at a lek [69,76]. Several leks may form a complex across the landscape. Leks may be used for decades [72].
Females typically visit a single lek over 2 to 3 days and mate only once, typically with a dominant male, although occasionally females visit >1 lek within a breeding season and mate multiple times [36,248]. Sage-grouse mating behaviors, which are complex, are summarized by Johnsgard [153].
Figure 4. Greater sage-grouse in a lek at Bodie State Historic Park, California.Adult The importance of sagebrush in the diet of adult sage-grouse is impossible to overestimate. Numerous studies have documented its year-round use by sage-grouse [24,52,53,166,209,246,256,274,275]. A Montana study, based on 299 crop samples, showed that 62% of total food volume of the year was sagebrush. Between December and February, sagebrush was the only food item found in all greater sage-grouse crops. Only between June and September did it constitute <60% of the greater sage-grouse diet [274]. Palatability varies within and among sagebrush taxa (Table 2) [238], and sage-grouse select habitats based on differences in palatability and nutritional content of sagebrush [118].
Table 2. Relative palatability of sagebrush species for sage-grouse from most to least palatable based on coumarin concentration in sagebrush and palatability information from the literature on sage-grouse and other wildlife species [238] Species High palatability alkali sagebrush low sagebrush snowfield big sagebrush mountain big sagebrush Wyoming big sagebrush xeric big sagebrush Lahontan sagebrush black sagebrush (race with gray leaves) mountain silver sagebrush plains silver sagebrush threetip sagebrush Moderate palatability fringed sagebrush Bigelow sagebrush pygmy sagebrush Bolander silver sagebrush Low palatability black sagebrush (race with green leaves) basin big sagebrush Wyoming threetip sagebrush birdfoot sagebrush Owyhee sagebrush stiff sagebrushMany studies focus on the importance of the big sagebrush subspecies to sage-grouse because of big sagebrush's comparatively wide distribution and relatively greater importance to sage-grouse than other sagebrush taxa [125]. Among the big sagebrush subspecies, basin big sagebrush is less nutritious and higher in terpenes than either mountain big sagebrush or Wyoming big sagebrush, and sage-grouse prefer the other 2 subspecies to basin big sagebrush [12]. In a common garden study in Utah, Welch and others [286] found sage-grouse preferred mountain big sagebrush over Wyoming big sagebrush and basin big sagebrush, but the birds shifted to the less preferred subspecies when leaves and buds of mountain big sagebrush became limited.
Black sagebrush is a widespread species, second in its geographical distribution only to basin big sagebrush [238]. Greater sage-grouse in Antelope Valley, California, browsed black sagebrush more frequently than the more common big sagebrush [246]. In Nevada [304] and southeastern Idaho [77], black sagebrush browse was highly preferred by greater sage-grouse. In south-central Idaho, greater sage-grouse selected black sagebrush communities over Wyoming big sagebrush communities, likely because black sagebrush has lower plant secondary metabolite concentrations and is therefore more palatable than Wyoming big sagebrush. Within black sagebrush communities, greater sage-grouse selected patches and individual plants within those patches that were higher in nutrient concentrations and lower in plant secondary metabolite concentrations than those not selected [118].
Sage-grouse lack a muscular gizzard and cannot grind and digest seeds, so they must consume soft-tissue foods [274]. Apart from sagebrush, the adult sage-grouse diet consists largely of forbs, which they eat primarily in late spring and summer [98]. Sage-grouse also consume perennial bunchgrasses [20]. They are highly selective grazers, choosing only a few plant genera. Dandelion, legumes, yarrow, and wild lettuce account for most of their forb intake [12,185,256]. In Montana, 45% of greater sage-grouse intake was common dandelion and 34% was sagebrush. Collectively, common dandelion, sagebrush, and two legume genera (clover and milkvetch) composed nearly 95% of the sage-grouse diet [185].
Insects are a minor diet item for adult sage-grouse. Martin and others [184] reported insects composed 2% of adult greater sage-grouse diets in spring and autumn and 9% in summer, while sagebrush made up 71% of the year-round diet.
Sage-grouse may gain body mass in winter [30], although deep snow for long periods reduces the amount of area available for foraging and cover [150], which results in weight loss [149]. At leks in Colorado, lipid reserves of male Gunnison sage-grouse following winters with snowfalls of <49 inches (124 cm) were greater than reserves following winters with snowfalls of >63 inches (160 cm) (P<0.001) [149].
Prelaying females: Five weeks before incubation (prelaying period) [76], 50% to 80% of the prelaying females' diet is sagebrush, with the remainder mostly forbs. Females may graze forbs at this time because of their high concentrations of protein and other nutrients [20]. Favored foods of prelaying and brood-rearing greater sage-grouse females in Oregon were common dandelion, yellow salsify, western yarrow, prickly lettuce, and sagebrush mariposa lily [298]. In southeastern Oregon, frequency of sagebrush, desertparsley, hawksbeard, phlox, agoseris, clover, pussytoes, milkvetch, and blue-eyed Mary was highest in the diets of prelaying greater sage-grouse females [20] (Table 3):
Table 3. Diet of prelaying greater sage-grouse females from March to April during 1990 [20]Food item
Frequency (%) of occurrence among crops Relative dry weight (%) Big sagebrush
hawksbeard
57 62 37 11 14 3 longleaf phlox 86 92 55 12 4 2 agoseris 28 69 11 2 4 1 clover 0 31 18 0 4 1pussytoes
43 69 41 8 3 2 woollypod milkvetch 57 31 9 2 <1 <1 buckwheat 14 8 0 2 <1 0 arcane milkvetch 0 31 5 0 2 <1 buttercup 0 8 0 0 <1 0 phlox 14 15 18 <1 <1 <1 blue-eyed Mary 0 38 9 0 <1 <1 bluebells 0 0 5 0 0 <1 larkspur 0 0 5 0 0 <1 rockcress 14 0 0 <1 0 0 other forbs 57 54 0 <1 <1 0 Graminoids grasses 57 69 5 <1 <1 <1 Invertebrates ants 0 15 0 0 <1 0 caterpillars 0 8 0 0 <1 0 beetles 1 0 0 <1 0 0Juvenile Sage-grouse can eat immediately after hatching [248]. In their first week of life, chicks eat primarily insects, particularly insects in the orders Coleoptera, Hymenoptera, and Orthoptera [209,218]. Captive greater sage-grouse chicks in Wyoming that were not given insects died between the ages of 4 and 10 days, while all chicks fed insects survived the first 10 days. As quantity of insects in the diet increased, survival and growth rates also increased for up to 45 days, the length of the experiment [156]. After their first week, sage-grouse chick diets switch to primarily forbs, with sagebrush gradually assuming primary importance. In a central Montana study, 1- to 12-week-old greater sage-grouse chicks increased use of sagebrush taxa and decreased use of insects over time (Table 4) [218]. In Idaho, Klebenow and Gray [169] identified food items eaten by greater sage-grouse chicks during the first 12 weeks since birth. In the first week, insects were very important (52% of the total diet), and beetles—primarily scarab beetles—were the main insect food item. Beetles were eaten by older chicks, but in smaller amounts. Ants were eaten by chick of all ages, although the volume was generally low. After week 3, insect volume dropped and stayed low (<25%) through week 12. Forbs were the major plant food beginning at week 3. Common dandelion (buds and leaves) was the most abundant food item and mainstay of the chicks. Lesser rushy milkvetch (flower buds and flowers) was eaten at high frequencies for most of the collection period. Harkness' flaxflower (fruits) was the main forb eaten in the first week; then it steadily decreased and was not found in the diet after 6 weeks. Yellow salsify (flower buds, leaves, and stems) use peaked at 6 weeks, and sagebrush mariposa lily (flower buds and fruits) use peaked at 7 weeks. These 5 species were the most abundant forbs in chick diets. The only shrub of importance was big sagebrush (leaves). It appeared in the diet at 4 weeks, and its volume increased in the diet as chicks got older. These 6 plant species composed 83% of total crop samples [169]. The diet of 12-week-old chicks is almost the same as adults [285].
Table 4. Percent frequency and percent volume of food items commonly eaten by 1- to 12-week-old greater sage-grouse chicks collected during 1966 and 1968 [218]. Cells are blank where data were lacking. Food item Frequency (%)/Volume (%)Age
Totala 1-4 weeksDiets of chicks may be diverse. In Oregon, chicks ate taxa from 41 families of invertebrates, 34 genera of forbs, 2 genera of shrubs, and 1 genus of grass; however, only 10 genera of forbs, 3 families of insects, and sagebrush were considered primary foods [95]. Forbs may be important in sage-grouse diets because many contain higher amounts of crude protein, calcium, and phosphorus than sagebrush [20]. Forbs are generally more important in the diet of juvenile than adult sage-grouse. In Utah, they composed 54% to 60% of the summer diet of juvenile sage-grouse, while the diet of adults was 39% to 47% forbs [267]. All aboveground plant parts of forbs may be eaten. However, flower buds, flowers, and fruits are important in sage-grouse diets and may be the only parts taken from some forbs. Leaves are often eaten, but stems generally are not. Leaves are the only part of sagebrush eaten [20,169].
Water: Sage-grouse may not require open water if succulent vegetation is available, but they use free water if it is available [52,72]. In winter in Eden Valley, Wyoming, greater sage-grouse were observed regularly visiting partially frozen streams to drink from holes in the ice [52]. In desert regions when succulent vegetation is sparse, sage-grouse distribution may be limited to areas near water [52].
Historically, sage-grouse occurred in 16 states and 3 provinces, from British Columbia east to Saskatchewan and south to Oklahoma and California. In 2016, they were found in 11 states and 2 provinces and their distribution was discontinuous [45,67,227]. A 2014 analysis of sage-grouse distributions found that greater sage-grouse occurred in 56% of its historical range (pre-1800), and Gunnison sage-grouse occurred in <10% [249]. Greater sage-grouse has been extirpated from British Columbia and Nebraska and from most of its former range in Alberta, North Dakota, South Dakota, Washington, and California [249]. As of this writing (2016), Gunnison sage-grouse occurs in 7 counties in southwestern Colorado and 1 county in southeastern Utah [63], although its historical distribution probably included parts of Utah, Colorado, Kansas, Oklahoma, Arizona, and New Mexico. The ranges of greater sage-grouse and Gunnison sage-grouse do not overlap [249] (Figure 3).
Sage-grouse have been translocated to British Columbia, Oregon, Idaho, Montana, Wyoming, Utah, Colorado, and New Mexico. New Mexico initiated the earliest attempts at translocations in 1933, after the Gunnison sage-grouse was extirpated from the state in 1912. Efforts were unsuccessful. British Columbia attempted to reintroduce greater sage-grouse in 1958, but no greater sage-grouse have been reported there since 1966 [157,227]. According to a 1997 study, only 3 of 56 translocations attempted as of that time appeared successful [227].
ECOSYSTEMS [119]:As of 2016, prescribed fire was being used in greater sage-grouse (e.g., personal communications [135,239,258,269]) and Gunnison sage-grouse (Pietruszka, personal communication [220]) habitats, primarily to reduce conifer encroachment (personal communications [135,220,239,258,269]) but also to reduce sagebrush cover in dense stands (personal communications [135,269]). Use of prescribed fire as a management tool for sage-grouse habitat is controversial [43,67,81,239,291]. There are opposing recommendations about the use of fire in sagebrush communities to benefit sage-grouse (see below) and debate about the historical fire-return intervals for which to manage (see FIRE REGIMES) throughout the published literature [229]. This is perhaps not surprising, given the variety of sagebrush habitats occupied by sage-grouse and the fact that fire effects on sage-grouse habitat is contingent on a large number of factors, including plant community composition, site characteristics, ecological condition, topography, climate, weather, and the pattern, size, and season of fire [76,195]. Coggins [62] stated that managers must consider fire pattern, size, and frequency when managing sage-grouse habitats [62].
Fire management considerations for fire pattern and size: Large-scale application of prescribed fire is not recommended for sage-grouse management [22,25,79,80,239]. Pyke [222] stated that the key for overall sage-grouse population sustainability and improvement, especially for successful reproduction and winter survival, is large (>9,900 acres (4,000 ha)) expanses of big sagebrush or silver sagebrush [222]. Bukowski and Baker [46] recommended maintaining and expanding areas of contiguous sagebrush within sage-grouse's range.
Some authors, however, have suggested using infrequent, small (<100 acres (40.5 ha)), patchy fires and mechanical manipulations to reduce big sagebrush cover to provide a diverse habitat mosaic and increase forb and insect production during brood rearing (e.g., [1,79,80,166,190,224,256,292]) (see Juvenile diet). However, postfire responses of forbs and insects to burning are highly variable [76] and difficult to generalize [205,212] (see Fire effects on early brood-rearing habitat). In addition, studies of brood use indicate that even if sage-grouse foods increase in burns, broods may not use the burns as much as unburned areas [51,70,109,161] (see Burn use). Erikson [103] found that potential benefits resulting from increased forb production within burns appeared to be negated by the removal too much of shrub cover. This suggests that fire managers apply prescribed fires cautiously in sage-grouse habitats because benefits to sage-grouse may not occur [22,76,84,183]. Wirth and Pyke [292] suggested that postfire increases in forbs important in sage-grouse diets are most likely if the prefire community contains native forbs and nonnative annual grasses are not present. Fire is likely to increase annual grass domination and decrease the chance of a favorable forb postfire response if, before fire, invasive grasses were present, the herbaceous understory was sparse, and the seed bank was depleted. Under these conditions, revegetation may be necessary following fire [292]. Regardless, because brood-rearing habitat occupies only a small percentage of the total habitat needs of sage-grouse, Welch [285] stated that brood-rearing habitat should not be prioritized over other seasonal habitats. Most authors recommend avoiding fire in sage-grouse nesting and wintering habitats because it reduces sagebrush cover and decreases the year-round forage provided by sagebrush. In some areas, these habitats overlap brood-rearing habitats [22,54,76,79,80,84,183,190,263].
Nesting or wintering sage-grouse may not use large burns until sagebrush reestablishes [74,164]. Thus, large, homogenous fires are likely to be more detrimental to sage-grouse than small, patchy fires that create a landscape mosaic [103,212] (see Fire effects on sage-grouse populations). Based on use of burns by greater sage-grouse broods in northeastern Utah, Thacker [263] stated that prescribed fires in mountain big sagebrush brooding habitats should be small and patchy (i.e., not impact >20% of the sagebrush in the area inhabited by the population) and only occur where there is no risk of nonnative annual grass establishment and spread after fire. He further stated that prescribed fire should only be used in brood-rearing habitats and not in nesting, wintering, or lekking habitats [263]. Because greater sage-grouse nest success may be higher in areas that contain a heterogeneous mix of sagebrush cover far (>0.6 mile (1 km)) from roads, oil wells, other human developments, and croplands, Aldridge and Boyce [1] suggested that patchy fires might increase nest success. Baker [15] cautioned, however, that little is known about the pattern of presettlement fire mosaics or the importance of particular aspects of the mosaics to sage-grouse population viability. Therefore, he suggested that there is insufficient basis to recommend prescribed burning for sage-grouse Habitat management [15]. Even if the ideal landscape pattern for sage-grouse were known, Erikson [103] contends that achieving a burn that conforms to that ideal landscape would not be easy to implement on a large scale and that such an endeavor would require a substantial amount of prefire planning.
Large fires may be detrimental to sage-grouse not only because they remove sagebrush cover over large areas but also because recovery times of sagebrush are slower in large, homogenous burns than in small, patchy burns [210,266,284] (see Fire management considerations for fire frequency).
Because sage-grouse rarely used areas >200 feet (60 m) from unburned edges (see Fire effects on sage-grouse populations), Slater [257] recommended that treatment areas should not exceed 400 feet (120 m) in width, noting that containing prescribed fire to meet these specifications would be difficult.
A map of current large-fire incidents in the sage-grouse's range can be found on the Active Fire Mapping Program website.
Fire management considerations for fire frequency: Miller and others [197] stated that fires in sage-grouse habitats should not be more frequent than the amount of time required for sagebrush recovery after fire. Recovery times of sagebrush are influenced in part by fire size. Most sagebrush species are intolerant of fire and easily killed, although threetip sagebrush, silver sagebrush, and sand sagebrush sprout after fire [197]. Seeds of big sagebrush do not form a persistent seed bank [189,192,197,306]. Exposure to heat may stimulate [60], reduce [59,60,302], or have a neutral effect [59] on germination of surviving seeds. Basin big sagebrush, mountain big sagebrush, and Wyoming big sagebrush establish only from seed after fire. Seed sources include unburned plants within burns and/or seeds that have been dispersed into burns by wind, water, or, animals. Most seeds fall within 30 to 39 feet (9-12 m) of the parent plant [56,197,202,302]. Because most big sagebrush seeds come from unburned parents or are dispersed onto burns from off site, sagebrush communities recover slowest in large, homogenous burns and most quickly in small, patchy burns [210,266,284]. Recovery generally occurs more rapidly in mesic mountain big sagebrush communities than in xeric Wyoming big sagebrush communities, and basin big sagebrush may recover relatively more rapidly than other big sagebrush subspecies [22,178,280].
Estimated recovery periods of mountain big sagebrush vary in the literature, but range from 15 to >35 years. Bunting and others [48] suggested that mountain big sagebrush on productive sites may recover to prefire values in 15 to 25 years. Median live mountain big sagebrush canopy cover returned to 20% to 25% within 32 to 36 years after fires in eastern Oregon, northwestern Nevada, and northeastern California. Studied burns were 4 to 49 years old and 990 to 9,900 acres (400-4,000 ha) [305]. An examination of 7 burned mountain big sagebrush stands from 5 to 43 years old in southeastern Oregon revealed that all key vegetation and structural components needed for successful greater sage-grouse reproduction became available 25 to 35 years after fire [190]. One study in southeastern Idaho found that mountain big sagebrush approached unburned levels 30 years after prescribed fire. Mountain big sagebrush production in that area was only 10% of that on an unburned area in postfire year 12. By postfire year 30, it was near unburned levels [134]. An eastern Idaho study comparing 16 sites that burned between 1937 and 2005 to an unburned site found that mountain big sagebrush recovered to unburned levels approximately 27 years after fire, with an average shrub cover of 38% [241]. In southwestern Montana, average time to full recovery of the mountain big sagebrush canopy cover was 32 years after fire. Recovery times of mountain big sagebrush canopy cover did not differ between sites burned by wildfire and those burned under prescription (P=0.15) [178]. Nelle and others [205] noted that no mountain big sagebrush areas burned under prescription in Idaho from 1980 to 1996 had cover suitable for nesting or brood-rearing sage-grouse in 2000, indicating that burned areas do not become adequate nesting or brood-rearing habitat for sage-grouse for >20 years [205]. Baker [17] concluded that full recovery of mountain big sagebrush communities may occur within 25 to 35 years following a small fire, but may take ≥75 years following a large fire.
Postfire recovery of Wyoming big sagebrush is not as well quantified as mountain big sagebrush. According to Baker [17], Wyoming big sagebrush recovery may take 50 to 120 years. A comparison of 24 burned and unburned plots ranging from 4 to 67 years after wild and prescribed fire in central and southeastern Montana found that full recovery of Wyoming big sagebrush canopy cover to levels in unburned areas was "much more" than 100 years. Seventeen of the 24 sites had no Wyoming big sagebrush recovery after fire, and the 67-year-old burn was only 8% recovered [75]. In southwestern Montana, Wyoming big sagebrush canopy cover was <2% of unburned levels 23 years after wild and prescribed fires [178]. Wyoming big sagebrush had not reestablished 14 years after a wildfire in central Montana [99]. Nineteen years after a wildfire in the northern Yellowstone National Park, Wyoming big sagebrush, mountain big sagebrush, and basin big sagebrush cover in burned sites were 0.6%, 1.6%, and 20% of that in unburned sites, respectively [280].
Postfire recovery of Wyoming big sagebrush may occur earlier after prescribed fire than wildfire because prescribed fires are often less severe and more heterogeneous and retain patches of surviving sagebrush [22]; however, recovery still may be slow. Canopy cover of Wyoming big sagebrush was only 2% 17 years after a September prescribed fire in southwestern Montana [281]. Thirty years after this fire, cover of Wyoming big sagebrush in burned plots (10%) was not different from unburned plots [283]. Thirty-two years after a September prescribed fire in southwestern Montana, Wyoming big sagebrush cover was similar between burned and unburned plots, while 9 years after 2 April prescribed fires, Wyoming big sagebrush cover in burned plots (9.1%) was less than that in unburned (12.6%) plots [278]. Wyoming big sagebrush cover, threetip sagebrush cover, total shrub cover, and shrub height had not recovered to prefire levels 14 years following a late-August 14,300-acre (5,800 ha) prescribed fire in southeastern Idaho. Because shrub structural characteristics required for wintering, nesting, and early brood-rearing were particularly slow to recover, the authors recommend that managers avoid burning Wyoming big sagebrush communities [25]. In Montana, recovery of Wyoming big sagebrush was similarly slow on sites burned under prescription and sites burned by wildfire, regardless of site moisture conditions [75].
Restoring sage-grouse habitat: Key management efforts to promote sage-grouse habitats include 1) wildfire suppression in vegetation types where such fires would facilitate establishment and spread of nonnative plants, 2) seedings and plantings of desired vegetation, particularly after fire, and 3) prescribed fire or other treatments in vegetation types where such fires would reduce woodland encroachment and enhance composition of native grasses and forbs [136,294].
Fire suppression: Many authors have recommended suppressing wildfires and eliminating prescribed fires in all sage-grouse habitats, particularly in Wyoming big sagebrush communities and other xeric sagebrush communities at high risk of nonnative annual grass establishment and spread (e.g., [15,17,22,45,58,112,279]) (see Table 8). For example, Braun and others [45] stated that management of sage-grouse habitats should initially focus on maintaining all presently used areas, and Chambers and others [58] stated that landscapes with >65% cover of sagebrush should receive first priority in fire suppression operations. In the Bighorn Basin in Wyoming, leks that became unoccupied from 1980 to 2009 had 10.3 times the number of oil and gas wells and 3.1 times the percentage of wildfire in a 0.6-mile (1.0 km) radius, suggesting that greater sage-grouse conservation efforts in this area should focus on minimizing well development and suppressing wildfires near active sage-grouse leks [140]. Connelly and others [70,73] suggested that, in general, prescribed burning in sage-grouse habitats that are in good ecological condition should be avoided. They further stated that managers should identify remaining breeding and winter rangelands in Wyoming big sagebrush habitats and establish these areas as high priority for wildfire suppression, especially during drought [70,73]. Because sagebrush cover was reduced and there was no increase in yield or cover of perennial forbs important in the diet of sage-grouse after wild and prescribed fires in 3 Wyoming big sagebrush communities in Oregon, Bates and others [22] stated that “there is little indication that prescribed burning in Wyoming big sagebrush steppe will provide short-term benefits to sage-grouse” and “efforts should be made to limit wildfire disturbance in remaining Wyoming big sagebrush plant associations of the northern Great Basin” [22]. Beck and others [25] stated that managers should avoid burning Wyoming big sagebrush to enhance sage-grouse habitat because habitat features important to sage-grouse did not recover 14 years after fire in their study. Because prescribed burning in Wyoming big sagebrush did not increase yield or nutritional quality of forbs important in sage-grouse diets, and abundance of ants decreased after fire, Rhodes and others [233] concluded that neither large-scale nor small-scale prescribed fires are necessary to improve sage-grouse habitat in intact Wyoming big sagebrush communities.
Some authors advocated against the use of prescribed fire as a management tool in sagebrush communities because prescribed fires tend to target the best available sage-grouse habitats, especially large areas of dense sagebrush with little slope, which are important wintering areas [102,250,279]. In 1976, Martin [186] found 80% of all male greater sage-grouse and >80% of all female greater sage-grouse locations were in sagebrush stands with canopy cover of >20%. He commented that this is also the range of sagebrush canopy cover where sagebrush treatments are most likely to occur. Connelly and others [73] stated that generally, fire should not be used in sage-grouse breeding habitats dominated by Wyoming big sagebrush because fire can be difficult to control in those habitats and tends to burn the most productive and best nesting and early brood-rearing habitats (i.e., areas with the most understory), while leaving less productive sites unburned.
Many authors recommend that wildfire be suppressed and prescribed fires avoided in sage-grouse habitat wherever nonnative grass establishment and/or spread are likely following fire [15,40,197,279]. If prescribed fire were to be used in sage-grouse habitats, Sime [256] stated that it would be most effective in areas where annual precipitation enables rapid revegetation and in areas with a limited potential for establishment and spread of undesirable nonnative species [256]. Thus, prescribed fires are often not conducted in areas receiving <12 inches (300 mm) of annual precipitation [12,258,269]. Wambolt and others [279] stated that active fire control is sensible in sagebrush communities wherever cheatgrass occurs [279], which includes sagebrush communities on warm, dry sites such as those at low elevations and on south- and west-facing slopes [57,197,279].
Other authors recommend fire suppression to limit further fragmentation of sagebrush landscapes, which are thought to have been large and contiguous historically [279] (see Presettlement fire pattern and size). Woodward (2006 cited in [222]) recommended not burning stands of sagebrush because wildland fires will burn these stands eventually, allowing an opportunity to restore herbaceous understories at that time. Baker [17] stated that because wildfire is expected to increase substantially in the future due to predicted climate change, prescribed burning is generally unnecessary in sagebrush communities. Burkowski and Baker [46] suggested that Gunnison sage-grouse need to be able to move to alternative areas with sufficient contiguous mature sagebrush cover when large fires occur [46].
Conservation objectives for the greater sage-grouse identified by the US Fish and Wildlife Service [112] in 2013 included retaining and restoring healthy native sagebrush plant communities both within and outside of key sage-grouse habitats, in part by restricting or containing wildfires and eliminating prescribed fires. Specific fire management considerations included:
Although fire suppression is recommended by many authors, Evers [105] commented that suppression of fires may be easier said than done in sagebrush-steppe communities. She stated that while most wildfires are relatively easy to extinguish and >90% of all wildfires burn <990 acres (400 ha), a very few large wildfires are difficult or impossible to extinguish because of extreme burning conditions and are “wreaking most of the havoc in sage-grouse habitat”. She suggested that fire managers need to be less aggressive when burning conditions are mild to moderate and allow more fires to spread during those conditions. She also advocated using prescribed fire that “creates many small to moderate-sized black and green patches instead of one big black blob” in sagebrush-steppe communities [105]. Crawford and others [76] stated that a potential benefit of using prescribed fire in sage-grouse habitats is that it can break up fuel continuity in conifer-encroached sagebrush communities, thus reducing the threat of future large and more homogeneous fires, which are more likely to be detrimental to sage-grouse.
Reduce nonnative species: The positive feedback loop between nonnative annual grasses and fire can prevent sagebrush from establishing after fire [112]. Burning sagebrush-steppe communities with a cheatgrass-dominated understory is likely to promote more cheatgrass; increase fire frequency; and decrease abundance of native shrubs, grasses, and forbs, resulting in a loss of sage-grouse habitat [195,287] (see Postsettlement FIRE REGIMES and nonnative plants). Thus, controlling nonnative species may increase the quality and quantity of sagebrush communities for sage-grouse [26,86]. Concern over habitat loss and fragmentation due to fire and nonnative plants has mostly been focused in the western portion of the sage-grouse’s range [197]. However, climate change may alter the range and invasiveness of nonnative plants, potentially facilitating spread of nonnative plants into other areas of sage-grouse range [112].
A 2011 review stated that late spring or autumn prescribed fire may help restore native plants and reduce nonnative annual grasslands if applied in combination with herbicide, although no evidence was presented to support this approach. Using prescribed fire alone was not recommended [222].
Seeding following wildfire has been used in some plant communities to stabilize soils and displace nonnative species before they can gain a foothold [34]. However, this management strategy may not be effective in sagebrush communities [86,223], and relatively high survival rates and low reproductive rates of sage-grouse (see Mortality) suggest that sage-grouse populations may be slow to respond to improved habitat conditions following restoration treatments [69]. Sime [256] stated that when few propagules from the native vegetation community are available or when fire occurs in areas of low precipitation, the disturbed site may require seeding. However, seeding sage-grouse habitat after fire has had low success rates [86,223], and sage-grouse use of seeded habitats may be low [7]. For example, the predicted probability of greater sage-grouse occupancy at 101 postwildfire seeding sites in Oregon, Idaho, Nevada, and Utah from 1990 to 2003 was low on average (0.09) and not substantially different from burned areas that had not been seeded. Within 20 years of treatment, none of the 826 treated plots met breeding season sagebrush overstory guidelines for sage-grouse, few (<0.01%) met brood-rearing sagebrush overstory guidelines, and only 2% potentially met winter sagebrush overstory guidelines. Thus, postfire seeding treatments generally did not increase the probability of burned areas meeting most sage-grouse habitat guidelines within 20 years of fire. Analyses of climate and weather at the 101 sites indicated that restoration practitioners can expect greater effectiveness of postfire seeding treatments in areas of the Great Basin with relatively low annual temperatures (especially cool springs and autumns), high April to June (nonmonsoonal) precipitation, and high total precipitation. Sites at high elevations often have these climate characteristics, which can result in greater native grass and forb establishment and lower susceptibility to dominance by nonnative plants than sites at low elevations. The authors suggested prioritizing protection of high-quality sage-grouse habitats [7]. Davies and others [86] agree that because restoring plant communities where nonnative annual grasses are already established is expensive and often fails, managers should try to prevent nonnative annual grass establishment and spread into intact sagebrush communities to preclude the need for restoration. They state that preventing nonnative grass establishment and spread can be accomplished by promoting native perennial grasses and reducing the propagule pressure of nonnative annual grasses [86].
Reduce conifer encroachment: Conifer encroachment into sagebrush communities may be detrimental to sage-grouse because of the loss of sagebrush, decrease in herbaceous forage, fragmentation of sagebrush habitats, and increase in predation [86] (see Postsettlement FIRE REGIMES and conifer encroachment). Prescribed fires and mechanical treatments have been used to reduce conifers in sagebrush ecosystems. Prescribed fires also remove sagebrush from the plant community, potentially for long periods, which would be detrimental to sage-grouse. However, prescribed fire is generally more efficient at removing conifers than mechanical treatments across large areas because they are less costly to apply and kill tree seedlings that would be missed with mechanical treatments [86,220]. Baker [17] suggested that fire should not be used to remove conifers from encroached sagebrush communities because it removes too much sagebrush. Other means, including cessation of livestock grazing or removal of individual trees, may allow native grasses and forbs to increase while maintaining the sagebrush cover [17]. Mechanical treatments can remove conifers while retaining sagebrush, but they also result in an accumulation of dry, combustible fuels that may pose a wildfire risk. Cutting and removing trees in areas where an understory of sagebrush and herbaceous vegetation still persists may be particularly effective at maintaining the shrub component in sagebrush communities [86]. In the Cody, Wyoming, area individual trees are burned in spring, when fire does not spread into the surrounding sagebrush community (Harrel, personal communication [135]). Rothleutner (personal communication [239]) stated that prescribed fire is used in the Worland, Wyoming, area to kill conifer seedlings and burn piles in mechanically treated conifer-encroached sagebrush stands, but only when the fire will not spread in the sagebrush stands.
Davies and others [86] suggest that restoring historical fire frequency in sagebrush communities is critical to preventing the continued spread of conifer woodlands, but restoring fire frequency in sagebrush communities where conifers have expanded can be difficult if conifers have reduced the fine fuels needed to carry a fire. They suggested that priority be placed in restoring infrequent fires to sagebrush communities that are in the early phases of woodland development (encroaching conifers are sub- or codominant with sagebrush), especially in areas where fire will still spread without additional treatments and in areas with minimal risk of nonnative plant establishment or spread after treatment. They state that restoring sagebrush communities that are in late phases of conifer encroachment is of secondary importance [86]. In 2016, prescribed fire was being used in occupied Gunnison sage-grouse habitats to reduce conifer cover in sagebrush communities as well as to burn piles of tamarisk cut from riparian areas (Pietruszka, personal communication [220]). Treatments used to increase surface fuels in woodlands with sparse fuels are varied, and the results depend on the season of the prescribed fire. Revegetation may be required on sites without adequate prefire understories. For more information, see Davies and others [86]. For detailed information on conifer taxa and effects of various control and restoration measures on those species, enter the plant name in the FEIS home page under "Find Species Reviews".
Reduce human encroachment: Restoration in areas disturbed by human activities or large and/or frequent fire may not be successful [7,173]. In a range-wide analysis, greater sage-grouse leks that persisted from 1965 to 2007 were larger in size; more highly connected; had fewer, smaller fires (since 1965) within a 34-mile (54 km) radius; and had lower levels of human disturbance within a 3-mile (5 km) radius than abandoned leks, suggesting that restoration of sagebrush habitats may not increase sage-grouse populations in the long term if those areas are also disturbed by human activities and fire [173].
Postfire livestock grazing: Blaisdell and others [39] stated that grazing management after fire is essential and most burns should be completely protected from livestock grazing for at least 1 and possibly 2 postfire growing seasons [39]. Benson and others [31] recommended a nongrazing period of 2 to 3 years after fire, while Call and Maser [53] recommended that burns not be grazed until "vigorous" vegetation is well established. Dahlgren and others [80] advocated periodic growing-season rest from grazing for up to 25 years after fire.
Livestock grazing may decrease the risk, size, and severity of wildfires in sagebrush communities with cheatgrass-dominated understories [86]. Diamond and others [91] found that strategically grazing nonnative annual grass-dominated communities reduced fuel loads and continuity enough to prevent a flame front from carrying across treated areas even under peak fire conditions. Thus, seasonally targeted grazing may be an important tool for breaking the positive feedback loop between nonnative annual grasses and fires [86]. However, grazing can also promote the spread of undesirable plant species, such as nonnative grasses on low-elevation sites and conifers on high-elevation sites [76,86]. For general management recommendations for livestock grazing in sage-grouse habitats, see Livestock grazing.
OtherGeneral According to the US Fish and Wildlife Service [112], the following options should be considered for fire management in greater sage-grouse habitats:
Fire management considerations for breeding, nesting, and brood-rearing habitats: Connelly and others [73] recommend suppressing wildfires in all breeding, nesting, and early brood-rearing habitats. They state that in the event of multiple fires, land management agencies should have all breeding, nesting, and early brood-rearing habitats identified and prioritized for suppression, giving the greatest priority to high-quality nesting and early brood-rearing habitats and landscapes that have become fragmented or reduced in area by >40% in the last 30 years. They further recommend evaluating areas burned by wildfire soon after fire to determine whether reseeding is necessary to achieve Habitat management objectives. When restoring mountain big sagebrush and Wyoming big sagebrush communities, they recommend treating <20% of the breeding, nesting, or early brood-rearing habitats and waiting until sagebrush has fully recovered before treating additional habitat [73]. Lockyer and others [180] recommended managers avoid actions in nesting habitats that reduce shrub canopy cover below 40%. See Management considerations for breeding, nesting, and brood-rearing habitats for additional recommendations.
Fire management considerations for winter habitat: Prescribed fire in sage-grouse wintering areas is likely to be detrimental to sage-grouse because it removes critical sagebrush cover and forage. Therefore, it is not recommended in sage-grouse wintering areas, particularly in areas of large-scale habitat loss (>40% of original winter habitat) [12,29,53,73,279]. Critical winter habitats are vulnerable to prescribed fire because they typically occur in dense stands on flat to gentle slopes [102,235]. Connelly and others [73] recommend protecting unburned patches of sagebrush within burns from further disturbance because these areas may provide the only winter habitat for sage-grouse, and their loss could result in the extirpation of the sage-grouse population. Unburned patches within fire perimeters also are important seed sources for sagebrush reestablishment in burns [73]. See Management considerations for winter habitat for additional recommendations.The role of fire in the sagebrush biome is debated. Several authors (e.g., [76,296]) stated that fire was historically a primary disturbance in the sagebrush biome. However, Baker [15] downplays the importance of fire in sagebrush communities, stating that fire was historically an important natural disturbance, but it did not occur often and was only one of many disturbances. Other common disturbances included droughts and insect outbreaks [15]. State-and-transition model results of the vegetation conditions in southeastern Oregon prior to 1850 indicated that fire might not have been the most important disturbance influencing greater sage-grouse habitat abundance, merely the most visible. Other, more subtle disturbances that thinned sagebrush density, such as drought and herbivory, might have been equally or more important in shaping greater sage-grouse habitats. Vegetation in the study area was dominated by mountain, Wyoming, and basin big sagebrush and low sagebrush [104]. The fact that most sagebrush species do not sprout after burning and are slow to recover after burning suggests fire may not have been frequent in these communities [17] (see Fire management considerations for fire frequency).
Sage-grouse habitat requirements range from relatively open leks with scattered low shrubs to nesting and wintering areas with taller, denser shrubs (see Preferred habitat). Historically, all requirements would have been met within the sagebrush biome, which would have consisted of all successional stages [46]. Fire can cause local reductions in sage-grouse populations (see Fire effects on sage-grouse populations), and likely did historically. During presettlement times these impacts were probably minimal. However, with sage-grouse populations declining throughout their range due to habitat loss, fragmentation, and alteration (see Threats), the potential for negative impacts from fire is greater than it was historically [257]. General information on pre- and postsettlement FIRE REGIMES in sagebrush communities is presented below. This review focuses on FIRE REGIMES of mountain big sagebrush, Wyoming big sagebrush, and low sagebrush communities and does not discuss FIRE REGIMES of black sagebrush, plains silver sagebrush, basin big sagebrush communities, or other sagebrush communities that are also important to sage-grouse. For additional information, enter "sage-grouse" in the FEIS home page under "Find FIRE REGIMES" or follow the links in the Appendix to FEIS Species Reviews of sagebrush taxa.
Presettlement In an analysis of presettlement and modern fire in sagebrush ecosystems, Baker [17] concluded that large, high-severity fires followed by long interludes with smaller, patchier fires were within the historical range of variation for sagebrush landscapes. This fire regime would have allowed mature sagebrush to dominate the landscape for extended periods.
Presettlement fire pattern and size: Historical landscapes contained large contiguous expanses of mature sagebrush [46]. Early explorers and pioneers described an "ocean" or "sea" of sagebrush [279]. Within this sea, a mosaic of habitats was probably present because of differences in soils, moisture, topography, elevation, aspect, and disturbances such as insect defoliation and wildfire [45]. Likely, infrequent large fires shaped sagebrush landscapes historically, although most fires were probably small [17,46,47]. Using land-survey records from 1872 to 1892 to reconstruct historical fire and landscape patterns in the Gunnison sage-grouse's current range, Bukowski and Baker [46] identified fires and potential fires in 541,000 acres (219,000 ha) of sagebrush communities. Based on those historical fires, they inferred a pattern of infrequent large, high-severity fires followed by long interludes with smaller, patchier fires. This fire-size distribution was inverse-J shaped with a geometric mean patch size of 380 acres (154 ha) and mean fire size of 524 acres (212 ha). Their analyses suggested that historical fires left little interior unburned area (<4%). Infrequent large fires >24,700 acres (10,000 ha) would have killed most sagebrush, resulting in cover of perennial bunchgrasses over large areas, which would have succeeded to sagebrush following extended periods without fire [46] (see Presettlement fire frequency). Their analyses suggested that, historically, "dense" sagebrush covered 20%, scattered sagebrush (areas of nonpatchy, low-density sagebrush) 15%, and sagebrush with scattered trees 19% of the study area [46]. It is unclear what covered the remaining area. Using similar methods, these authors described similar historical FIRE REGIMES in the greater sage-grouse’s range [47].
Historical fire reconstruction and landscape patterns in >5.4 million acres (2.2 million ha) of sagebrush communities in the greater sage-grouse's range suggest that fires and burned patch sizes were significantly larger in Wyoming big sagebrush than mountain big sagebrush communities. Fire- and patch-size distributions were inverse-J shaped, consisting of many small fires and few large ones. Unburned area within fire perimeters accounted for only 3.5% of the total area burned on average, indicating that fires were relatively homogeneous. Analyses suggested that historical sagebrush landscapes were dominated by large, contiguous areas of sagebrush, although large bunchgrass-dominated areas and finer-scale mosaics of bunchgrass and sagebrush were present in smaller areas. Variation in sagebrush density created patchiness, with "dense" sagebrush covering 25% and "scattered" sagebrush covering 16% of the area, with the remaining sagebrush patches of moderate density [47]. Keane and others [159] stated that the habitat requirements for greater sage-grouse suggest that large fires were rare, noting that the potential for periodic large fires was greatest on productive, contiguous expanses of sagebrush-grasslands such as those that occurred from eastern Oregon and northern Nevada to western Wyoming.
Historically, large fires likely occurred the first or second year after a cool, wet year that promoted fine-fuel production. Weather conditions in the year of the fire were relatively less important in determining fire size [17,179]. Evidence from sediment cores in the Great Basin suggest that fire activity during the past ~5,000 years was greater during relatively wet periods [191,197].
Presettlement fire frequency: Interpretation of fire-return intervals prior to European-American settlement has direct consequences for how fire is used and/or managed in sage-grouse habitats [279], but fire-rotation intervals and mean fire-return intervals are difficult to reconstruct in sagebrush communities. This is because plants in these communities do not record fire scars that can be dated, and stands originating after fire cannot be dated without fire records, which are incomplete. Sources of information about fire-rotation and mean fire-return intervals in sagebrush communities are limited to 1) fire-scar records from conifers in refuge sites or in adjoining communities, 2) fire-rotation interval estimates from adjoining conifer communities, 3) fire frequency estimates from macroscopic charcoal records in sediments from ponds, lakes, and springs surrounded by sagebrush communities, 4) sagebrush recovery time following fire, and 5) historical fire records [17,160]. Fire frequency estimates derived from fire-scar records or fire-rotation interval estimates from adjoining woodlands may require correction factors to estimate fire frequency in sagebrush [15,17]. Estimates from paleoecological studies are derived directly from sagebrush landscapes, but only a few locations in the sagebrush biome yield adequate pollen and charcoal evidence (e.g., [152,191]). Using recovery times of sagebrush following fire to estimate fire frequency is complicated by the fact that recovery time is influenced by a variety of factors, including plant community type, moisture regime, and fire characteristics [47] (see Fire management considerations for fire frequency). Historical fire records in sagebrush communities are sparse, inconsistent among regions, and often lack important spatial details [17]. Part of the debate regarding the frequency of fire in sagebrush ecosystems concerns different interpretations derived from different methodologies. However, authors agree that historically, fire was generally more common in mountain big sagebrush communities than Wyoming big sagebrush communities. This conclusion is based on the fact that vegetation productivity and fuel loads are higher in mountain big sagebrush communities [159,279].
Presettlement fire frequency in mountain big sagebrush: Estimates of fire frequency in mountain big sagebrush communities vary widely. Baker [17] estimated fire-rotation (and fire-return) intervals between 150 and 300 years in mountain big sagebrush communities and 40 to 230 years in mountain grasslands containing patches of mountain big sagebrush, with longer rotations in areas where mountain big sagebrush was mixed with woodlands (Table 13). He defined fire-rotation intervals and mean fire-return intervals as being equal [17]. Using General Land Office Survey notes to reconstruct historical vegetation, Bukowski and Baker [47] estimated that historical fire-rotation intervals ranged between 137 and 217 years for mountain big sagebrush communities in the greater sage-grouse's range [47] and 90 to 143 years for mountain big sagebrush communities in the Gunnison sage-grouse's range [46].
Table 13. Estimates of presettlement fire-rotation and mean fire-return intervals in sagebrush communities. Baker [17] compiled these data and included them in his estimates. Data are based on fire scars and fire-rotations in adjoining woodlands, fire frequency in paleocharcoal records, and estimated time for sagebrush to recover fully after fire [17]. Community Method Setting Fire-rotation interval and/or mean fire-return interval (years) Original source Low sagebrush fire scars adjacent to juniper woodlands 95 [301] fire scars intermixed with juniper woodlands 138 [199] fire-rotation interval in adjoining woodlands intermixed with woodlands 427 [23]a summary of other studies with statistical corrections >200-425 [17] Wyoming big sagebrush fire scars adjacent to woodlands 95 [301] fire-rotation interval in adjoining woodlands intermixed with pinyon-juniper woodlands ~400 [114]b fire-rotation interval in adjoining woodlands adjacent and intermixed with woodlands 427 [23]a fire-rotation interval in adjoining woodlands adjacent and intermixed with woodlands 400-600 [254] charcoal in sediment cores expanses of sagebrush 200-500 [191]c summary of other studies with statistical corrections 200-600 [17] Mountain big sagebrush postfire sagebrush recovery expanses of "fast track" sagebrush >50-70 [17] postfire sagebrush recovery expanses of "slow track" sagebrush >150-200 [17] charcoal in sediment cores expanses of sagebrush 150-200 [152] charcoal in sediment cores expanses of sagebrush 183 [206] fire scars adjacent to pinyon-juniper woodlands >30-40 [49] fire-rotation interval in adjoining woodlands intermixed with pinyon-juniper woodlands 480 [282]a fire-rotation interval in adjoining woodlands intermixed with pinyon-juniper woodlands 400-600 [115]b fire-rotation interval in adjoining woodlands adjacent and intermixed with pinyon-juniper woodlands 427 [23]a fire-rotation interval in adjoining woodlands adjacent and intermixed with pinyon-juniper woodlands 400-600 [254] fire-rotation interval in adjoining woodlands intermixed with Rocky Mountain Douglas-fir trees 400-600 [141]d summary of other studies with statistical corrections 160 [17] Mountain grasslands with sagebrush fire scars adjacent and intermixed with sagebrush 20-25 [147]b fire scars adjacent and intermixed with sagebrush <35-40 [8] fire scars intermixed with sagebrush 12-15 [199] summary of other studies with statistical corrections 40-230 [17] aBaker [17] corrected the taxa covered in these studies based on a personal communication from P. J. Weisberg.Studies reporting composite fire intervals from nearby fire-scarred trees report relatively short historical fire-return intervals in mountain big sagebrush ecosystems prior to European-American settlement, ranging from 12 to 25 years [49,147,193,199] and 35 to >40 years [8,141]. These studies estimated historical fire frequency for mountain big sagebrush stands using composite fire intervals collected from fire-scarred trees located near woodland-shrubland ecotones with ponderosa pine, Rocky Mountain Douglas-fir, western juniper, and other conifers. For example, Houston [147] estimated mean fire-return interval in “bunchgrass steppes” of northern Yellowstone National Park, Wyoming, at 53 to 96 years, with mean intervals for individual trees ranging from 36 to 108 years. Stating that fire suppression had reduced the fire-return interval for approximately 80 years as of 1973, he adjusted the interval by subtracting 80 years from the ages of living trees and came up with an adjusted fire-return interval of 32 to 70 years in the mountain big sagebrush steppe. Cross-dating of 13 fire-scarred trees further reduced the adjusted fire-return interval to 17 to 41 years, with 20 to 25 years as the "best estimate of the true fire frequency" [147]. Estimated fire-return intervals averaged 37 years (range: 2-84 years) for the period prior to livestock grazing (1700-1860) in Rocky Mountain Douglas-fir-encroached mountain big sagebrush-grasslands on relatively dry sites in southwestern Montana. Data were collected on approximately 5 acres (2 ha) [141]. Composite fire-return interval estimates from northeastern California plots ranged from 10 to >100 years in mountain big sagebrush communities. Plots varied in successional state, soil depth and texture, aspect, slope, and dominant grass species [196].
Studies of postfire recovery of sagebrush canopy cover suggest that fire-free periods of >30 years are often needed for full mountain big sagebrush recovery (see Fire management considerations for fire frequency). Estimated fire-return intervals based on sagebrush recovery periods differ among dominant species and site characteristics, with more productive sites having shorter fire-return interval estimates [159]. Based on recovery times ranging from 25 to 100 years, Baker [17] estimated fire-rotation intervals for mountain big sagebrush communities of 50 to 70 years for "fast-track" mountain big sagebrush communities and 150 to 200 years for "slow-track" mountain big sagebrush communities (Table 13). Slow-track communities were those in large burned areas or on less productive sites [17]. In southwestern Montana, Lesica and others [178] estimated that full recovery of canopy cover in mountain big sagebrush stands averaged 32 years. Areas with relatively short fire-return intervals (<20 years) likely would have been predominantly grasslands with scattered patches of sagebrush [129,141,196].
LANDFIRE [177] models place mountain big sagebrush communities mostly within Fire Regime Group IV (replacement-severity fires every 49-80 years), but also in Fire Regime Group I (predominantly mixed-severity fires every 26 years) and II (replacement-severity fires every 20 years). For additional information, enter "mountain big sagebrush" in the FEIS home page under "Find FIRE REGIMES".
Presettlement fire frequency in Wyoming big sagebrush: Because Wyoming big sagebrush occupies the driest areas within the range of big sagebrush and rarely exceeds 25% cover, fire was likely infrequent in Wyoming big sagebrush stands due to limited and discontinuous fuels [48]. The limited amounts of trees, stumps, and logs with fire scars in these communities make it difficult to reconstruct fire history [193]. Baker [17] estimated fire-rotation and fire-return intervals of 200 and 350 years for Wyoming big sagebrush communities and 400 to 600 years for Wyoming big sagebrush intermixed with pinyon-juniper woodlands (Table 13) [17]. Using General Land Office Survey notes to reconstruct historical vegetation in the greater sage-grouse's range, Bukowski and Baker [47] estimated historical fire-rotation intervals between 171 and 342 years for Wyoming big sagebrush. Using similar methods in Wyoming big sagebrush communities within the Gunnison sage-grouse's range, they estimated historical fire-rotation intervals of 178 to 357 years [46]. Wright and Bailey [296] estimated historical mean fire-return intervals for Wyoming big sagebrush between 50 and 100 years. A 2011 review suggested that Wyoming big sagebrush communities might historically have had an extremely wide range of years between fires, possibly from no fires in >100 years to several fires in 100 years [197]. The long postfire Wyoming big sagebrush recovery period found at 24 sites in Montana suggests that Wyoming big sagebrush steppe may belong to Fire Regime Group V (replacement-severity fires, >200 years) [75] (see Fire management considerations for fire frequency). LANDFIRE [177] models place Wyoming big sagebrush communities mostly within Fire Regime Group IV (predominantly replacement-severity fires every 48-130 years), but also in Fire Regime Group I (predominantly mixed-severity fires every 33 years). For additional information, enter "Wyoming big sagebrush" in the FEIS home page under "Find FIRE REGIMES".
Presettlement fire frequency in low sagebrush: Baker [17] estimated historical fire-rotation and fire-return intervals of 200 to 425 years in low sagebrush communities, with longer rotations in areas where low sagebrush was mixed with woodlands (Table 13). Burkowski and Baker [47] estimated fire-rotation intervals of 93 to 187 years in Oregon low sagebrush communities based on General Land Office Survey notes. Miller and Rose [199] collected 12 fire-scarred western juniper stumps and logs in low sagebrush communities in south-central Oregon and identified 2 apparently large fires in the last 300 years, with a period of 138 years between the fires. Based on this study, Miller and Tausch [193] suggested fire-return intervals of 100 to 200 years in low sagebrush communities. Twenty-eight fire-scarred western junipers from about 618 acres (250 ha) of low sagebrush in Lassen County, California, showed 3 fires that scarred more than 2 trees each. These fires were approximately 80 and 110 years apart [301]. LANDFIRE [177] models place low sagebrush communities within Fire Regime Group III (predominantly mixed-severity fires every 91-110 years) and V (replacement-severity fires every 217-1,250 years). For additional information, enter "low sagebrush" in the FEIS home page under "Find FIRE REGIMES".
Postsettlement FIRE REGIMES in sagebrush ecosystems changed dramatically with European-American settlement [43,52,72,87,133] (see Threats). Altered disturbance regimes in parts of the sage-grouse range have shifted some sagebrush communities outside the range of historical variation [18,47,197].
Postsettlement fire pattern and size: The number of fires and total area burned have increased since 1980 throughout most sagebrush ecosystems, largely due to cheatgrass establishment and spread [18,19,64,197]. For example, Balch and others [19] found a trend of increasing total burned area and number of fire events in the Great Basin from 1980 to 2009. Thirteen percent of cheatgrass-dominated lands burned during that time, which was more than double the amount burned across all other vegetation types (range: 0.5%-6% burned) [19]. Miller and others [197] found that the number of fires and area burned increased from 1980 to 2007 across sagebrush ecosystems in the western United States, except in the Snake River Plain. Baker [18] found a significant upward trend in area burned in all sagebrush ecosystems in the western United States except the Wyoming Basin (P=0.006), perhaps because of the Wyoming Basin's relatively complex topography and sparse, limited fuels in dwarf sagebrush communities. Unlike Miller and others [197], he observed an upward trend to fire size in the Snake River Plain (P<0.001), which he attributed to extensive cheatgrass establishment and relatively flat terrain in the region [18].
Large fire years in cheatgrass-dominated areas occur when a dry summer follows a year with above-average precipitation [19,171]. In the Great Basin, precipitation during the preceding calendar year was strongly correlated with fire size (R²=0.27) and number of fires (R²=0.22) in cheatgrass-dominated areas. As a comparison, preceding year's precipitation explained 12% of variation in sagebrush fire size (R²=0.12) and 13% of variation in number of fires (R²=0.13) in sagebrush-dominated areas [19]. Other researchers found a relationship between above-average precipitation in the preceding winter months and large fires during the following summers [35,303]. See the FEIS Species Review of cheatgrass for more information.
Fires occurring from 1984 to 2008 left an average of 18% to 26% unburned area within fire perimeters in sagebrush communities in 8 ecoregions [18], while reconstructions of historical vegetation from General Land Office notes estimated that historical fires within Idaho, Nevada, Oregon, and Wyoming left an average of 3.5% unburned area within fire perimeters [47]. This suggests that modern fires are patchier than historical fires in some areas. Fragmentation since European settlement has altered fire pattern in modern landscapes, perhaps making contemporary fires more heterogeneous than historical fires [47].
Postsettlement fire frequency: Establishment and spread of nonnative annual grasses, particularly cheatgrass, into big sagebrush communities has resulted in increased fire frequency on xeric sites, while conifer encroachment into big sagebrush communities and associated decreases in perennial grass and forb cover have resulted in decreased fire frequency on mesic sites [195].
Postsettlement FIRE REGIMES and nonnative plants: Spread of nonnative annual grass species, especially cheatgrass, has led to increasing wildfire frequencies and subsequent loss and degradation of big sagebrush communities, particularly Wyoming big sagebrush and other xeric sagebrush communities [15]. The spread of cheatgrass into Wyoming big sagebrush communities since its introduction in the 1890s has changed the structure of the understory, providing more continuous fine fuels [159,197]. These continuous and highly flammable fuels result in fires that are larger, more frequent, and often more homogenous, with few unburned patches. While postfire recovery periods for sagebrush species can be long [210,266] (see Fire management considerations for fire frequency), cheatgrass may recover quickly after fire [300]. More homogeneous fires result in fewer, more widely dispersed sagebrush plants, with fewer potential seed sources in remaining unburned islands. Cheatgrass is highly competitive for resources, making it difficult for native perennial grass and shrub seedlings to establish [197].
Although authors disagree about how often Wyoming big sagebrush communities burned historically (see Presettlement fire frequency in Wyoming big sagebrush), most agree that fire-return intervals are shorter in Wyoming big sagebrush communities now than they were historically due to cheatgrass establishment and spread [17,159]. Fire-return intervals for cheatgrass-dominated grasslands in the Great Basin from 2000 to 2009 averaged 78 years using the MODIS fire data set; that average was 2 to 25 times higher than those of other land cover types in the Great Basin [19]. Fire-return intervals in some cheatgrass communities formerly dominated by Wyoming big sagebrush may be <10 years [215,288]. For example, fire-return intervals in Wyoming big sagebrush habitats were as low as 5 years in portions of the Snake River Plain where cheatgrass now dominates [288]. Such short fire-return intervals are too short to allow recovery of sagebrush and many associated species [259], effectively reducing sage-grouse habitat. For more information on the fire ecology of cheatgrass and other nonnative species, enter the plant name in the FEIS home page under "Find Species Reviews". See Nonnative plants for information on how nonnative plants affect sage-grouse.
Global climate change is likely to further promote nonnative annual grasses and increase fire frequency in sagebrush communities [197]. Predicted increases in atmospheric carbon dioxide levels may increase cheatgrass productivity and fuel loads and, thereby, may increase fire frequency, size, and severity. Fire that is too frequent results in a type change from sagebrush to grassland [307]. Thus, large areas may become unsuitable for sage-grouse in the future [86]. Even without fire in the system, climate change is highly likely to deteriorate sage-grouse habitats [244].
Postsettlement FIRE REGIMES and conifer encroachment: The spread of pinyon and juniper into sagebrush communities since the mid- to late 1800s has been linked to a decrease in fire frequencies, increased fire suppression, changes in climate, historical patterns of livestock grazing, and perhaps increased atmospheric carbon dioxide [17,78,112,259]. Spread of pinyon and/or juniper into sagebrush ecosystems typically results in 1) a decrease in understory sagebrush and associated shrubs, grasses, and forbs (fine fuels), 2) an increase in woody fuels, and 3) less frequent but larger and more severe fires [194]. Thus, conifer encroachment into sagebrush communities may be detrimental to sage-grouse because of the loss of sagebrush, decreases in herbaceous forage, fragmentation of sagebrush habitats, and increased predation [86].
The probability of woodlands replacing sagebrush communities increases where conifer seed sources are nearby, sites are productive, and fire-return intervals are >50 years [197]. Most conifer encroachment has occurred at high elevations in mountain big sagebrush communities and in low sagebrush and black sagebrush communities on moderately deep to deep soils [197]. As conifers establish and spread on these sites, there is a gradual decline in habitat suitability for sage-grouse. Although sage-grouse habitat is essentially lost immediately after large fires due to the reduction of sagebrush cover, over time, sage-grouse habitat quality increases with recovery of sagebrush but eventually declines again as conifers establish and grow [41]. Fire exclusion does not appear to result in conifer encroachment into relatively unproductive, xeric sagebrush communities [17].
Sage-grouse use sagebrush of different age classes and stand structure for different life history events in different seasons. Critical habitat components include both tall- and short-statured sagebrush cover year-round, adequate cover of tall grasses (≥7 inches (18 cm)) and medium-height shrubs (16-31 inches (40-80 cm)) for nesting, abundant forbs and insects for brood rearing, and availability of mesic sites with succulent herbs for late-growing season foraging [76] (see Preferred habitat). Fire effects on these different habitats vary and are discussed separately in this review.
In general, fire is detrimental to sage-grouse because it removes sagebrush plants that provide essential thermal and security cover and food year-round, especially during breeding, nesting, and wintering [51]. Strong fidelity to seasonal ranges and relatively low sage-grouse productivity limit sage-grouse's ability to respond quickly to changes in their local environment due to fire or other disturbances (see Mortality)[69,248]. Fire is especially harmful to sage-grouse in xeric Wyoming big sagebrush communities when nonnative annual grasses, such as cheatgrass, increase after fire. Annual grasses and their associated fine fuels may result in reburning before sagebrush has recovered [159,197] and eventually lead to an annual grass/fire cycle that results in a type conversion from sagebrush to annual grassland [57,58].
Some seasonal sage-grouse habitats may be improved by fire, depending on region, weather, site characteristics, and fire size, season, pattern, and frequency [53,76]. For example, fire creates openings in sagebrush communities, which may provide new leks [66]. Tall grasses are important nesting cover, and fire may increase cover of many native perennial bunchgrasses. Native forbs and insects important to sage-grouse during the brood-rearing period have varied responses to fire [25,73]. Small, patchy infrequent fires may provide some benefits for sage-grouse, while large, homogenous fires are detrimental [103,212]. Fire in mesic mountain big sagebrush communities may remove conifers, which sage-grouse avoid, but it also removes sagebrush [86].
Most information on fire effects comes from mountain big sagebrush and Wyoming big sagebrush communities. Sage-grouse also occupy communities dominated by other sagebrush taxa, including low sagebrush, black sagebrush, and silver sagebrush (see Plant communities), but little information is available on sage-grouse response to fire in these communities [73,197]. Fire may play a more important role in maintaining quality nesting and brood-rearing habitats in areas dominated by silver sagebrush, which sprouts, compared to habitats dominated by nonsprouting big sagebrush or low sagebrush [73,279].
Fire effects on sage-grouse populations: Some studies reported that fires had no short-term effects on sage-grouse population size [122,187,236]; however, sage-grouse populations may decline after fire, particularly when fire occurs just before or during drought (e.g., [70,257]). Inability of some studies to (e.g., [122,187,236]) to detect short-term population effects may be due to the relatively small size of the burns studied (range: 1,001-14,332 acres (405-5,800 ha)) compared to the size of the available habitat [26]. Fidelity to leks may make it difficult to discern fire effects on sage-grouse populations for several years after fire. A study by Robertson [236] showed no effect of a prescribed fire on a greater sage-grouse breeding population 3 years after fire, while Connelly and others [70] found a large population decline on the same burn 9 years after fire. The prescribed fire was conducted in a Wyoming big sagebrush community in southeastern Idaho during a drought. Nine years after the fire, the greater sage-grouse breeding population had declined by 80%, and there was a decrease in active leks. The overall decline in the greater sage-grouse population was attributed to drought and the postfire reduction of breeding habitat [70]. Following an October 1999 prescribed fire, a greater sage-grouse population declined from a high of 99 males on a lek before the fire to a low of 14 in 2002. The decline was attributed to the onset of drought in 2000. The authors noted there was a population low of 19 males in the lek just before a 1995 prescribed fire, 4 years prior to reaching the 1999 peak [257].
The effect of burning on sage-grouse populations may depend in part on prefire sage-grouse vital rates. For example, populations below their potential carrying capacity were not reduced the first 2 years after a patchy wildfire in mesic mountain big sagebrush in eastern Idaho [187], while a declining population in Wyoming big sagebrush in southeastern Idaho declined to a much greater extent in a prescribed burn area than in a nearby unburned area [70].
Fire pattern is likely to affect sage-grouse populations because sage-grouse using burns may rely on unburned patches within burn perimeters [31]. In Jackson and Moffat counties, Colorado, numbers of male greater sage-grouse at leks decreased during postfire years 1 and 2 and returned to or exceeded prefire numbers by postfire year 3 after 2 fires: a 94-acre (38-ha), patchy prescribed fire that burned 50% of the sagebrush in the area and a 3,000-acre (1,200 ha) wildfire that consumed most sagebrush in the area but left some unburned patches. Within the burned areas, greater sage-grouse primarily used unburned patches. They did not use a 300-acre (120 ha) burn up to 3 years after a wildfire that consumed >99% of mountain and Wyoming big sagebrush in the area [31].
Sage-grouse appear to avoid the interiors of large burns. In southwestern Wyoming, male and female greater sage-grouse foraged near the perimeter of prescribed burns in spring and summer in Wyoming big sagebrush and mountain big sagebrush communities interspersed with areas of low sagebrush, but they rarely used areas >200 feet (60 m) from unburned edges [257]. Pyle (personal communication cited in [190]) observed greater sage-grouse broods foraging up to only 328 feet (100 m) into newly burned areas.
Large, homogenous fires are likely more detrimental to sage-grouse populations than small or patchy fires. In a simulation study of greater sage-grouse population dynamics within mountain big sagebrush communities in southeastern Idaho, Pedersen and others [212] found that fire was generally detrimental to greater sage-grouse. Populations only increased if fires were very small and infrequent (i.e., burned 1% of the area with 60 years between fires) and left large unburned areas. Their models indicated that large, contiguous fires (10% of the breeding habitat) burning at high frequency (17 years between fires) may lead to the extinction of greater sage-grouse populations. Medium-sized fires (5% of the breeding habitat) burning at medium frequency (25 years between fires) with heavy grazing (consumption of 50% of available forage) may also lead to the extinction of greater sage-grouse populations [212]. In south-central Wyoming, a large, contiguous burn likely reduced habitat quality for greater sage-grouse. Greater sage-grouse use of 2 smaller, heterogeneous burns suggested that fires that leave large sagebrush patches are less detrimental [103]. In a study across greater sage-grouse's distribution, spring counts of males visiting leks during 11 years were positively correlated with the proportion of sagebrush cover within 3 and 12 miles (5 and 19 km) of the lek. Spring counts also tended to be lower on leks where a greater proportion of the surrounding landscape had burned. However, there was no relationship between spring counts and number of postfire years. Spring counts were negatively correlated with cover of agriculture and nonnative plant species [155].
Some researchers suggested that sage-grouse require large patches of sagebrush. Braun and others [45] concluded that sagebrush patches >7,400 acres (3,000 ha) may be required, while Pyke [222] concluded that patches of big sagebrush and silver sagebrush >9,900 acres (4,000 ha) may be required.
Fire effects on breeding habitat: Open areas in or adjacent to sagebrush communities, including burns, are used as leks [72,73,120,166,201,245] (see Breeding habitat). In southeastern Idaho, greater sage-grouse used a 700-acre (300 ha), 5-year-old burn for at least 2 seasons. Because the area adjacent to the burn was dominated by a relatively dense stand of big sagebrush, the authors stated it was not likely that the site was used as a lek before the burn [66]. However, fire effects on the area around the lek—which is used by sage-grouse for loafing, feeding, and escape cover [10,167]—are likely more important to sage-grouse than the effects of fire on the lek itself [11].
Studies reported varied use of leks soon after burning, ranging from no difference to reduced use, perhaps depending on pattern and amount of sagebrush remaining after fire. One and 2 years after a wildfire in Idaho in 1981, male and female greater sage-grouse continued to use burned and unburned leks within the burn perimeter despite the loss of vegetation cover. They fed, loafed, and roosted primarily in unburned areas and flew into the leks. The author suggested that greater sage-grouse use of the leks was not affected because the fire burned in a mosaic pattern and left many unburned patches, so suitable habitat was available near all leks within the burn [187]. Male greater sage-grouse continued to use 2 leks after wild and prescribed fires in Colorado, but the number of males using the leks was lower during postfire years 1 and 2 than 1 year before fire. Numbers recovered to prefire levels in postfire year 3. A third lek that burned in a homogeneous 300-acre (120 ha) wildfire was not used at all by greater sage-grouse for up to 3 postfire years [31]. In a Wyoming big sagebrush community in southeastern Idaho, lek use declined after an August prescribed fire. The average number of male greater sage-grouse at a lek was similar in burned and unburned areas before the fire, but numbers were lower in burned (6 males) than unburned (17 males) areas after the fire. The fire removed 57% of the sagebrush cover [70].
In the long term (>10 years), use of leks appears to be reduced by fires and human disturbances that reduce sagebrush height and cover in the surrounding landscape [140,155,173]. A range-wide analysis indicated that greater sage-grouse leks that persisted from 1965 to 2007 were larger in size; more highly connected; had fewer, smaller fires (since 1965) within a 34-mile (54 km) radius; and had a smaller proportion of areas with human disturbance within a 3-mile (5 km) radius than abandoned leks [173]. In the Bighorn Basin in Wyoming, 91 wildfires burned in areas surrounding leks between 1980 and 2009. In 2012, unoccupied leks had 10.3 times the number of oil and gas wells, 3.1 times the percent of area burned in wildfire, and 1.1 times the variability of shrub height in a 0.6-mile (1.0 km) radius than occupied leks [140].
Fire effects on nesting habitat: Sage-grouse females generally select sagebrush over other species for nesting cover. They prefer sagebrush canopy cover ranging from approximately 20% to 50% and plants that are >18 inches (46 cm) tall [285] (see Nesting habitat). Thus, removal of sagebrush by fire is likely to reduce nesting cover for sage-grouse for many years [44,67,107,164,205,236]. In southeastern Idaho, migratory greater sage-grouse that nested within the perimeter of a prescribed burn during the first 3 postfire years only nested in unburned patches, suggesting that fire removal of sagebrush reduced nesting cover [71,107]. In southwestern Wyoming greater sage-grouse nested in 2 autumn prescribed burns and burns resulting from 2 summer wildfires. The 4 burns were between 1 and 27 years old, in Wyoming big sagebrush and mountain big sagebrush communities interspersed with low sagebrush communities. Over half (10 of 17) of the sage-grouse nests within the burns occurred in actual burned habitat and not in unburned habitat within the burn perimeters. However, greater sage-grouse selected areas within burns with shrub cover similar to unburned areas. While nest sites within the burns had lower sagebrush density (inside: 0.79 sagebrush plant/m², outside: 2.77 sagebrush plants/m²) and cover (inside: 10%, outside: 25%) than nest sites outside the burns (P<0.05), the total shrub cover was not different at nest sites inside than outside the burns (inside: 25%, outside: 29%). This suggested that total shrub cover may be more important in nest-site selection in burns than sagebrush cover [257]. Fischer [107] also found no difference in the vegetation between nest sites located inside and outside a prescribed burn 3 years after fire. However, all of the nests in his study were in unburned sagebrush patches within the burn perimeter [107].
Because of the lack of adequate shrub cover, sage-grouse generally avoid nesting in young (<20 years old) burns [51,139,161,190,205,257]. Those that nest in young burns may experience lower nest success. In a 10-year-old burn with sparse sagebrush in Nevada, greater sage-grouse selected nest sites with greater total shrub cover than random sites. Low nest success (22.4%) suggested that nesting habitat was inadequate in the burn [180]. In Oregon, nesting greater sage-grouse avoided 89% of available burned areas. Burns occurred in mountain big sagebrush, Wyoming big sagebrush, and low sagebrush communities that burned in prescribed or wildfires from 1947 and 2000. Greater sage-grouse use was studied from 1989 to 2000. All 5 nests in young burns were unsuccessful, but nest success in older burns (29%) and unburned areas (28%) was similar, indicating that shrub recovery was important in nest success. When burned habitats were used, they were typically mid- to late-successional burns in mountain big sagebrush communities. Burns in low sagebrush and Wyoming big sagebrush communities apparently provided little value for nesting [51]. From 1980 to 1996, 28,840 acres (11,676 ha) were burned under prescription on the Upper Snake River Plain. None of the burned areas were suitable greater sage-grouse nesting habitat in 2000. This suggested that burned areas in mountain big sagebrush remained inadequate nesting or brood-rearing habitat for greater sage-grouse for >20 postfire years [205]. A south-central Idaho study area that provided productive greater sage-grouse nesting habitat before a prescribed fire did not provide nesting habitat 14 years after the fire [25]. In the Bighorn Basin, Wyoming, sagebrush canopy cover in 2008 and 2009 did not meet the minimum height required for nesting and early brood-rearing for up to 19 years after fires at 19 sites that were burned under prescription from 1990 to 2006 [139]. Greater sage-grouse did not nest in 8- to 9-year-old burned areas in Wyoming big sagebrush in Wyoming [161]. Height and cover of mountain big sagebrush and screening cover from grasses needed for nesting were available in burns in mountain big sagebrush starting at postfire years 25 to 35 in Oregon [190]. For more information, see Fire management considerations for fire frequency. Sage-grouse show fidelity to nesting areas [33,108], and several authors speculated that nest-area fidelity may result in females nesting in burns despite their unsuitability, thus potentially reducing population productivity [74,107,108].
Several studies have found similar nest success in burned and unburned sage-grouse habitats [71,107,165,257]. At Collett Creek in southwestern Wyoming, nest success from inside and outside of 4 burn perimeters (1-27 years after fire) did not differ in 2 of the 3 years measured (Table 9). In 2001, nest success was higher at nests within the 4 burns than at nests outside the burns. Data suggested that nesting greater sage-grouse might have avoided the youngest (a 1999 prescribed burn) and the oldest (a 1975 wildfire) of the 4 burns. The youngest burn probably had reduced use by nesting greater sage-grouse after the fire, while the oldest burn likely was not used heavily prior to the fire [257].
Table 9. Nest success at Collett Creek in southwestern Wyoming from inside and outside burn perimeters of 4 fires. The 4 burns ranged in size and age and were combined in this study. An autumn prescribed fire burned 30% to 50% of the sagebrush on 6,290 ha in 1999. Another autumn prescribed fire burned 50% to 70% of the sagebrush on 2,820 ha in 1995. A summer wildfire burned 80% of the sagebrush on 580 ha in 1988. A second summer wildfire burned 20% to 40% of the sagebrush on 1,200 ha in 1975 [257]. Year Nest success (number successful/total number) P-value Inside Outside 2000 0% (0/2) 7% (1/15) 0.706 2001 67% (4/6) 18% (3/7) 0.025 2002 22% (2/9) 30% (8/27) 0.667 Overall 35% (6/7) 20% (12/59) 0.201Fire effects on early brood-rearing habitat: Before chicks can fly and when mortality rates are typically high [10,209], sage-grouse broods need food in close proximity to escape cover [260]. Sage-grouse chicks eat primarily insects in their first few weeks of life, then shift to succulent forbs and then sagebrush leaves over time [169,209,218] (see Juvenile diet). Several authors have suggested that fires that increase food forbs and/or insects while maintaining unburned patches of sagebrush as cover could benefit sage-grouse broods [80,121,166,256,292,298]. However, brood use of burns and fire effects on forbs and insects in sagebrush communities are inconsistent, and fires may reduce sagebrush cover below adequate levels. Many authors do not differentiate between early and late brood-rearing habitats, which confounds study interpretation because habitat use between early and late brood-rearing is different [263]. Early brood-rearing habitats occur close to nests within nesting habitat, while late brood-rearing habitats are areas used by sage-grouse following desiccation of herbaceous vegetation in early brood-rearing habitats and include riparian areas, swales, and wet meadows [73]. Where possible, studies of early and late brood-rearing habitats are differentiated in this Species Review.
Burn use: Use of burns by broods varies. In some cases, sage-grouse seek out burns during the brood-rearing period [80,257,263]. For example, in high-elevation mountain big sagebrush communities in northeastern Utah, greater sage-grouse broods used small (5-435 acres (2-176 ha)), young (<20 years old), patchy prescribed burns more than expected based upon availability (P<0.0001), although chick survival was not determined. Of the 25 broods monitored, 68% used a prescribed burn at least once during the entire brood-rearing season, and 33% of the total locations were in prescribed burns. Grass cover was 8% greater (P=0.0154), sagebrush cover was 12% lower (P=0.0001), and forb cover was similar (P=0.421) between brood sites in burned and unburned areas [263]. In Wyoming, 47% (7/15) of radio collared greater sage-grouse with broods used 4 burns of varying ages in mountain big sagebrush, Wyoming big sagebrush, and low sagebrush communities. Of the early brood-rearing females that used the burns, 5 of the 7 nested within the same burns, while the remaining 2 moved their broods into the burns after nesting outside the burns. Five of the 7 early brood-rearing locations were within actual burned habitat and not within unburned habitat within the burns. None of the females nesting within a burn left during the early brood-rearing period [257].
Other studies found that brooding greater sage-grouse either avoided burns [51,161] or that fire had little effect on brood use [70,109,187]. For example, brood-rearing and broodless greater sage-grouse females in Oregon avoided 89% and 77% of available burned areas, respectively. The areas burned in 70 prescribed or wildfires from 1947 to 2000, and greater sage-grouse use was studied from 1989 to 2000. Used burns were typically mid- to late-successional mountain big sagebrush communities. Burns in low sagebrush and Wyoming big sagebrush communities appeared to provide little value for brood-rearing or broodless females [51]. In xeric Wyoming big sagebrush areas in Idaho, the relative abundance of males, females, and broods observed on census routes was similar between burned and unburned areas 1 to 3 years after a late summer prescribed fire [109]. One and 2 years after 2 large wildfires in high-elevation, mesic mountain big sagebrush in eastern Idaho, migratory greater sage-grouse broods used unburned, low-severity, moderate-severity, and high-severity burned areas similar to availability (P=0.09). Broods used the moderate- and high-severity burned areas the 1st postfire summer despite sparse cover, and broods within these burns were often not within sight of vegetation providing cover. The 2nd postfire summer, herbaceous cover in moderately and severely burned areas was dense and tall. Broods might have been attracted to these burned areas because of abundant forbs. Although height of cover tended to be shorter where broods were observed, forb crown cover was greater in burned than unburned areas during postfire years 1 and 2 (P<0.05). The author did not differentiate between early and late brood use [187]. Differences in site characteristics and vegetation makes it difficult to draw comparisons among sites [263]. Most studies on burn use are observational and do not relate burn use to vital rates [26], making it difficult to determine whether broods benefit from using burns.
Postfire forb response: Herbaceous plant production may increase following fire in some sagebrush communities, which may benefit sage-grouse juveniles if sufficient sagebrush cover remains. Beck and others [26,27] concluded that in general, prescribed fire can result in positive short-term (≤10 years) responses in the herbaceous understory of mountain big sagebrush communities, but it does not typically result in positive short-term responses in the herbaceous understory of Wyoming big sagebrush communities, which are relatively drier and at lower elevations. Long-term (>10 years) positive herbaceous responses may not occur in either mountain big sagebrush or Wyoming big sagebrush communities [26,27] (see Postfire forb response in mountain big sagebrush and Postfire forb response in Wyoming big sagebrush). Postfire increases in total herbaceous plant production often result largely from the production of grasses rather than forbs (e.g., [134]), which are less important in the juvenile diet [218]. While forb cover may increase following fire, it is often the result of increases in only a few forb species [187,203,224], and it is unclear whether sage-grouse populations benefit from such increases. Furthermore, sagebrush, which becomes increasingly important in the juvenile diet and becomes critical to sage-grouse at 12 weeks old [169,218,285], is reduced by fire (e.g., [16,22,85]). Miller and Eddleman [195] compiled a list of the relative response of forbs that are common to the sagebrush biome and used as food by sage-grouse after fire (Table 10). Also follow the links in the Appendix to FEIS Species Reviews of forbs and grasses.
Table 10. Relative postfire responses of forbs common to the sagebrush biome and eaten by sage-grouse. Plus sign indicates that the taxon increases after fire [195]. Data compiled from [38,42,168,182,211,268,297]. Severely damaged buckwheat parsnipflower buckwheat pussytoes sandwort Hood's phlox Slightly damaged beardtongue or penstemon geranium+ hawksbeard+ lambstongue ragwort western yarrow+ woollypod milkvetch yellow salsify Slightly damaged to undamaged avens bluebells everlasting milkvetch prickly lettuce Undamagedaster+
balsamroot+ largehead clover cinquefoil+ dandelion desertparsley fleabane goldenrod Indian paintbrush longleaf phlox+ lupine+ mountain dandelion slender phlox tapertip onionRegardless of the effects of fire on the herbaceous vegetation, total aboveground vegetation production is still greatest where sagebrush is present (e.g., [134,203]). Although no studies to date reported forb biomass requirements of sage-grouse, Wambolt and others [279] suggested that adequate production of forbs may be available even in relatively dense sagebrush stands. Blaisdell [38] found forb production on sites with 35% to 40% sagebrush canopy cover ranged from 104 to 127 pounds/acre, and Goodrich and Huber [126] reported forb production averaged 179 pounds/acre on sites with a shrub canopy cover of >20%. Forb production is generally higher in mountain big sagebrush than Wyoming big sagebrush communities [83].
In conifer-encroached big sagebrush communities, forb cover may increase following conifer removal by prescribed fire, at least in the short term. Cover of forbs eaten by sage-grouse at 11 pinyon- and juniper-encroached mountain big sagebrush, Wyoming big sagebrush, and basin big sagebrush sites in Utah, Nevada, California, and Oregon were higher 1, 2, and 3 years after prescribed fires than soon before the fires. Native grasses and forbs were present in the understories prior to the fires. Nonnative plants were present but not dominant. The prescribed fires occurred between August and October. The management goal was to remove conifers. An average of 86% of conifers was removed, with tree canopy reduced to <5% across all burned plots. Shrubs were reduced by >90%, with 50% to 75% of shrub skeletons remaining. Tall perennial grass cover was greater in burned than unburned areas by postfire growing season 3. Cover of nonnative grasses was greater in burned than unburned areas in postfire years 2 and 3. Cover of forbs eaten by sage-grouse was greater in burned than unburned areas in all 3 postfire years. The authors concluded that an increase in both tall perennial grasses and forbs eaten by sage-grouse can be expected across most big sagebrush sites following prescribed fires that remove conifers. However, an increase in nonnative grasses can also be expected, with greatest increases in nonnative grasses following prescribed fires on warm, dry sites [198], which would increase site susceptibility to wildfire and thusly to additional changes in plant community composition (see Postsettlement FIRE REGIMES and nonnative plants). Furthermore, sagebrush and other shrub cover may be reduced below levels required by sage-grouse.
Forb response in mountain big sagebrush: Fire may increase forb abundance in mountain big sagebrush communities, but it is unclear whether sage-grouse benefit from such increases. One and 2 years after a wildfire in mountain big sagebrush communities in eastern Idaho, forb cover was greater in areas that burned at low-, moderate- and high-severity than unburned areas (P<0.05), but greater sage-grouse brood use was similar to availability in burned and unburned areas (P<0.05) [187]. In contrast, 1 to 14 years after fire in a mountain big sagebrush community in Idaho, forb cover was similar in burned and unburned sites, possibly because postfire drought and livestock grazing reduced forb cover across all sites [205]. Frequency of some forbs eaten by greater sage-grouse in a mountain big sagebrush community in Oregon was greater 1 and 2 years after an autumn prescribed fire than 1 year before the fire. Specifically, frequency of agoseris 1 year after the fire was greater than 1 year before the fire, and frequency of slender phlox was greater 2 years after the fire than 1 year before the fire [190]. Another study in Oregon found that total forb cover during postfire year 2 was 15% and 13% on plots burned under prescription in spring and autumn, respectively, and 7% on unburned plots. Frequency and cover of 3 important sage-grouse foods (dandelions, desertparsley, and slender phlox) were similar in burned and unburned plots in postfire year 2, except that frequency of dandelions was greater in plots burned under prescription in autumn than in unburned plots or the plots burned under prescription in spring. Sagebrush cover was less in burned than unburned plots (P<0.05 for all variables) [224]. Neither Oregon study monitored greater sage-grouse use of the burns. In northwestern Nevada, total forb cover and cover of forbs known to be prevalent in the diet of greater sage-grouse were similar in burned and unburned mountain big sagebrush communities 10 to 11 years after a wildfire. The wildfire did not appear to affect plant phenology; the growth period of forbs was similar between burned and unburned areas. Although grass height, herbaceous cover, and total shrub canopy cover in the burned areas were adequate for greater sage-grouse nesting and brood-rearing habitats, mountain big sagebrush canopy cover was below greater sage-grouse requirements ≤11 years after the fire [87].
Forb response in Wyoming big sagebrush: The postfire responses of forbs important in sage-grouse diets in Wyoming big sagebrush communities is highly variable. Often, forbs important in sage-grouse diets are unaffected or reduced following fire. For example, several studies reported that forb abundance was similar in burned and unburned areas [109,138,298,299]. In a xeric Wyoming big sagebrush-threetip sagebrush community on the Upper Snake River Plain, cover of forbs important in greater sage-grouse diets was similar in an area burned under prescription in late summer and in an unburned area [109]. In the Bighorn Basin of north-central Wyoming, forb production and nutritional quality were similar in burned and unburned sites up to 19 years after prescribed fires. Sites were burned between 1990 and 1999 [138]. In central and southeastern Montana, there were no significant differences in overall forb cover or number of asters important to greater sage-grouse between 24 burned and unburned plots. Burn ages ranged from 4 to 67 years [75]. In a Wyoming big sagebrush community in southeastern Idaho, species richness and cover of major forbs increased in unburned transects at greater rates than in burned transects >14 years after prescribed fire [25]. At Hart Mountain National Antelope Refuge, Oregon, September prescribed fires in Wyoming big sagebrush had no effect on density, frequency, and relative abundance of 5 of 9 forbs important in greater sage-grouse diets 1 year after a prescribed fire. Some species of forbs (e.g., shaggy milkvetch, slender phlox, Nevada biscuitroot, Modoc hawksbeard, and longleaf phlox) showed morphological changes such as greater numbers of inflorescences and flowers, and some showed phenological changes such as earlier flowering and increased length of the flowering season on burned versus unburned plots [298,299]. See the Research Project Summary of Wrobleski and Kauffman's [298,299] study for information on the fire prescriptions, fire behavior, and details of postfire responses of plants important to greater sage-grouse.
While total forb cover may increase following fire in Wyoming big sagebrush communities, it may be the result of postfire increases in only a few forb species [22,232]. Bates and others [22,232] examined forb response to late September and early October prescribed fires and a 40,000-acre (16,000 ha) August wildfire in 3 Wyoming big sagebrush communities in Oregon from 2003 to 2009 (postfire years 1-7). They found that yield and cover of perennial forbs eaten by greater sage-grouse did not differ between burned and unburned sites in Wyoming big sagebrush-bluebunch wheatgrass and Wyoming big sagebrush-Thurber’s needlegrass-Idaho fescue communities. Longleaf phlox was the only perennial forb to increase after fire in the Wyoming big sagebrush-Thurber’s needlegrass community. Pale madwort, a nonnative species, was the dominant annual forb after fire in the Wyoming big sagebrush-Thurber’s needlegrass and Wyoming big sagebrush-Thurber’s needlegrass-Idaho fescue communities. It provides little cover or forage for sage-grouse. Yield and cover of annual forbs eaten by greater sage-grouse increased only during April and May of the first postfire year. Although cheatgrass increased in the Wyoming big sagebrush-Thurber’s needlegrass community after fire, it remained a minor component of the community. The authors concluded that prescribed fire does not improve habitat characteristics for greater sage-grouse in "intact" Wyoming big sagebrush steppe, where the community already consists of shrubs, native grasses, and native forbs. Rather, removal of Wyoming big sagebrush is likely to have a negative effect on greater sage-grouse [22,232]. Although burning intact Wyoming big sagebrush was not recommended by Rhodes and others [232], Wirth and Pyke [292] stated that prescribed burning will improve sage-grouse habitat when both native grasses and native forbs are still present in the community. However, they stated that burning degraded Wyoming big sagebrush communities with low herbaceous cover is unlikely to increase forbs important to sage-grouse because of depleted seed banks [292]. Crawford and others [76] suggested that fire is most likely to increase native perennial forbs and grasses where sagebrush is abundant, native forbs are present, and nonnative plants are limited. This most often applies to mountain big sagebrush communities where shrub canopy cover is >35%, rather than Wyoming big sagebrush communities [76].
Postfire insect response: Insects, particularly insects in the orders Coleoptera, Hymenoptera, and Orthoptera, are a critical component of juvenile sage-grouse diets [209,218] (see Juvenile diet). Insects in these orders demonstrate a wide range of short-term responses to fire; however, few studies (as of 2016) measured the effect of insect response after fire on juvenile sage-grouse. Wrobleski [298] found the number of ground-dwelling beetles and ants increased the year after September prescribed fire at Hart Mountain National Antelope Refuge, but he did not study brood use (see the Research Project Summary for details). In Wyoming big sagebrush communities in southwestern Wyoming, brood-rearing sites in burns had fewer insects, mostly fewer ants and other Hymenoptera, than random sites in burns (P<0.001) [257], suggesting that broods were not selecting sites because of insect abundance. Few studies reported long-term responses in availability of Coleoptera, Hymenoptera, and Orthoptera after fire in sagebrush communities.
Coleoptera: Beetle abundance shows varied responses to fire in sagebrush communities, with some beetle species and genera increasing after fire and others decreasing. Six years after a summer wildfire, 2 of 4 beetle species studied in southeastern Washington were less abundant in burned than unburned areas in big sagebrush-antelope bitterbrush communities [234]. In mountain big sagebrush in Oregon, beetle density 1 year after an autumn prescribed fire was lower than 1 year before the fire (P<0.01) [190]. The summer following a September prescribed fire in a big sagebrush community in southeastern Idaho, more weevils were collected in unburned than burned patches, while more darkling beetles, leaf beetles, and ladybugs were collected in burned than unburned patches [290]. Another study in southeastern Idaho found that mean dry weight of beetles in a 1-year-old burn was 3 times more than in unburned sites, while weights were similar in older burns and unburned sites (Table 11) [205]. In contrast, in Wyoming big sagebrush communities in southwestern Wyoming, there was no difference between the total number of beetles in 1- to 3-year-old burned plots and unburned plots, but the total number of beetles was significantly greater in older burned plots than unburned plots (Table 12) [257].
Table 11. Mean dry weight (grams) of insects collected in 2.25-m² plots in different-aged burns in mountain big sagebrush communities on the Upper Snake River Plain in southeastern Idaho from 1996 to 1997. Asterisks indicate a significant difference from unburned controls at P<0.05 [205]. Insect group Burn age Unburned 1 year 3-5 years 6-14 years Coleoptera 1.7* 0.39 0.42 0.54 Hymenoptera 0.46* 0.08 0.15 0.09 Orthoptera 0.81 0.28 1.22 0.42 Miscellaneous 0.02 0.09 0.05 0.07 Table 12. Total number of insects captured in 707 m² plots in Wyoming big sagebrush communities in southwestern Wyoming. Asterisks indicate a significant difference from unburned controls at P<0.05 [257]. Insect group Burn age Unburned 1-3 years 5-7 years 12-14 years 25-27 years Coleoptera 44.2 81.7* 79.9* 106.3* 55.6 Hymenoptera 1202.1 790.9 684.1 782.3 909.9 Orthoptera 3.3 2.1 2.0 1.3 3.1Several studies found no differences in beetle abundance between burned and unburned sites [22,87,109,138,224,298]. In xeric Wyoming big sagebrush areas in Idaho, beetle abundance was similar on burned and unburned areas 2 and 3 years after prescribed fire [109]. A study in Oregon found no change in ground-dwelling beetle numbers 1 and 2 years after spring and autumn prescribed fires in mountain big sagebrush-antelope bitterbrush communities. Grass and forb cover were similar in burned and unburned areas, and the authors suggested that beetles may have been unaffected by the fires because food and cover were maintained in the understory [224].
Hymenoptera: Hymenoptera abundance also shows varied postfire responses in sagebrush communities. Hymenoptera abundance was lower on burned than unburned sites 2 to 3 years after prescribed fires in Wyoming big sagebrush communities in Idaho [109] and Oregon [22]. Other studies reported that ant and other Hymenoptera populations were either similar on burned and unburned areas [87,190,257,298] (Table 12) or increased soon after fire [138,205] (Table 11). In a mountain big sagebrush community in Oregon, ant abundance 1 year after an autumn prescribed fire was not different from abundance 1 year prior to the fire [190]. In northwestern Nevada, ant abundance was similar between 2- to 3-year-old burns and unburned sites and between 10- to 11-year-old burns and unburned sites [87]. The summer following a September prescribed fire in a big sagebrush community in southeastern Idaho, more Hymenoptera, mostly ants, were collected in pitfall traps in burned patches than unburned patches [290]. More ants were trapped the summer following May prescribed fires in Underdown Canyon in central Nevada than before the fires. The study was conducted in singleleaf pinyon-Utah juniper-western juniper woodlands with Wyoming big sagebrush and mountain big sagebrush in the understory. Ant numbers may have been influenced more by soil texture than by vegetation or ground cover variables [200].
Orthoptera: Grasshoppers and other Orthopterans appear to be relatively unaffected by fire in sage-grouse habitats [87,109,138,190,205,257,290] (Table 11, Table 12). In a mountain big sagebrush community in Oregon, orthopteran abundance 1 year after an autumn prescribed fire was not different from abundance 1 year prior the fire [190]. Two and 3 years after a prescribed fire in a Wyoming big sagebrush community in Idaho, orthopteran abundance was similar between burned and unburned sites [109]. Orthopteran abundance was greater on burned than unburned sites after prescribed fire in Wyoming big sagebrush communities on aridic soils in the Bighorn Basin [138].
Fire effects on summer habitat: Some authors reported sage-grouse using burns in summer [168,187,257], while other authors noted that sage-grouse avoided burns in summer [103,161,201]. Greater sage-grouse in Wyoming used an 8- to 9-year-old burn in Wyoming big sagebrush during summer, but less than expected based on availability [161]. In southwestern Wyoming, most (67%) radio collared greater sage-grouse females did not use burns. Of the females that used burns during July and August, most (63%) had not been using the burns in May and June. Of the 33 females using the burns, 15 used actual burned patches, while 12 were in unburned sagebrush within the burns. The remaining 6 females were within 16 feet (5 m) of burn perimeters. The author did not know if the observed burn use was related to fidelity established before the fire because prefire movements were not obtained. However, it was common for radio collared females to use the same burns year after year. Burns ranged from 1 to 27 years old [257].
A prescribed fire in a Wyoming big sagebrush community did not change the timing, distance, or direction of movement of female greater sage-grouse from breeding and nesting areas to summer rangelands 3 years after a prescribed fire on the Upper Snake River Plain [111]. However, 9 years after the fire, the summer population associated with the burned area declined 75%, while a population in an unburned area declined only 52% [70] (see Fire effects on sage-grouse populations).
Available sage-grouse summer habitat may increase if fire increases availability of succulent foods in uplands during late summer [298]. Erikson [103] suggested that sage-grouse might benefit from short-term increases in forb production following fire; however, she found that greater sage-grouse use of 3 prescribed burns in high-elevation mountain big sagebrush communities in south-central Wyoming was very low the first 4 postfire summers, regardless of forb production in the burns. The fires removed about 85% of sagebrush [103]. For more information on forb production after fire, see Fire effects on early brood-rearing habitat.
Fire effects on winter habitat: Many researchers describe winter habitat as probably the most limiting seasonal habitat and thus perhaps the most critical [20,33,102,209,230,256]. Most winter observations are in sagebrush with >20% canopy cover [10,77,235] (see Winter habitat). Most sagebrush taxa are killed by fire [16], and sagebrush cover is reduced immediately after burning [22,85]. Thus, fire is generally considered detrimental on sage-grouse winter rangelands [22,53,67,121,166,201]. Klebenow [166] suggested that there is little place for fire on winter rangelands of migratory greater sage-grouse in xeric communities because there is nearly a complete reliance on sagebrush for food and cover during winter. In south-central Wyoming, greater sage-grouse avoided 3 prescribed burns in high-elevation mountain big sagebrush communities the first 4 winters after burning. Avoidance was attributed to the removal of 85% of sagebrush cover [103].
Sage-grouse occasionally use burns in winter, although their use is less than before fire. In southeastern Idaho, Robertson [236] studied migratory greater sage-grouse use the winter after a 4,900-acre (2,000 ha) August 1989 prescribed fire that removed 57% of the sagebrush cover. Before the prescribed fire, greater sage-grouse were located on the proposed treatment area 42% (1988) and 34% (1989) of the time. In autumn of 1989, only 6% of greater sage-grouse locations were found within the burned area. Greater sage-grouse apparently moved 1 to 6 miles (1-10 km) outside of the burn to areas with greater sagebrush cover [71,236]. Moritz [201] recorded "abundant" sage-grouse pellets in a burned area the second winter following a fire in Idaho, even though >90% of the sagebrush plants in the area were dead. The author suggested that burns may be used in mild winters [201]. Sage-grouse require access to sagebrush above the snow (see Winter habitat). Food and cover may be severely limited if fire occurs in critical winter rangeland and deep snow covers much of remaining unburned areas the following winter [67]. Loss of sagebrush in a relatively small area, but a relatively large portion of wintering habitat, was followed by a large decline in greater sage-grouse numbers in Montana [262]. Burned sagebrush communities may not provide adequate cover for wintering sage-grouse for decades following fire [25] (see Fire management considerations for fire frequency).
Figure 5. This sagebrush burn in Idaho does not provide sage-grouse winter habitat. Photo courtesy of the USGS. Federal legal status:
Gunnison sage-grouse: Threatened
Greater sage-grouse: Not listed [113]
Other status: Information on state- and province-level protection status of animals in the United States and Canada is available at NatureServe, although recent changes in status may not be included.
Threats: Sage-grouse once occurred virtually everywhere there was sagebrush. They have declined primarily because of loss, fragmentation, and degradation of habitat due to proliferation of nonnative plants, particularly annual grasses; land development for energy and agriculture; urbanization and infrastructure development, such as roads and powerlines; altered FIRE REGIMES; overgrazing by livestock; climate change; water extraction and reservoir development; and recreation [43,52,72,133]. Sage-grouse populations began declining from 1900 to 1915, when livestock use of sagebrush rangelands was heavy [209]. In the 1950s and 1960s, land management agencies adopted a policy of aggressive sagebrush reduction to convert sagebrush types to grassland. Mechanical removal (e.g., chaining), frequent fire, and herbicide treatments reduced sagebrush by several million acres, and sage-grouse numbers plummeted [52,188]. Conversion of sagebrush types to grassland has since been brought into question as a management practice for both wildlife and livestock [82,153,154,246,274]. Increased fire frequency in low-elevation sagebrush communities due to spread of annual grasses, particularly cheatgrass, has resulted in losses of sagebrush over large areas [72]. In addition, decreased fire frequency in high-elevation sagebrush communities and impacts from inappropriate livestock grazing and other factors have resulted in conifer encroachment and reduction of the herbaceous understory and sagebrush canopy over large areas [72]. According to the 2006 conservation plan for greater sage-grouse in Idaho, the most important threats to greater sage-grouse populations across their range, in order of rank, include: 1) invasive species, 2) infrastructure as related to energy development and urbanization, 3) wildfire, 4) agriculture, 5) livestock grazing, 6) energy development, 7) urbanization, 8) strip and/or coal mining, 9) climate and weather, and 10) pinyon-juniper expansion [243]. Miller and others [197] identified nonnative plants, wildfire, and climate as the most important threats to sage-grouse.
Nonnative plants: A broad array of nonnative, invasive plant species have degraded sage-grouse habitats by replacing native species and by increasing frequency and severity of wildfires [19,151]. The annual grasses cheatgrass and medusahead are considered the most problematic nonnative plant species in the sagebrush ecosystem, but there are many other nonnative plant species that are problematic [151,197]. In 2015, deep-rooted, creeping nonnative perennials such as Russian knapweed, squarrose knapweed, Dalmatian toadflax, and Canada thistle were becoming increasingly detrimental to sagebrush communities. Susceptibility of sage-grouse habitats to nonnative plant establishment was ranked by Miller and others (Table 8) [197].Cheatgrass is one of the most harmful nonnative plants to sage-grouse [197]. In addition to its replacement of native understory species, cheatgrass's early germination and early drying create abundant fine fuels that lead to increased frequency, duration, homogeneity, and size of wildfires, which can eliminate the sagebrush overstory [19,259] (see Postsettlement FIRE REGIMES and nonnative plants). Sagebrush communities on warm, dry sites (i.e., low elevations and south- and west-facing slopes) are at greatest risk of cheatgrass establishment and spread [57,197]. Cheatgrass usually fares poorly in black sagebrush communities. Although most research has been conducted on cheatgrass, medusahead, North Africa grass, and other nonnative annual grasses also produce abundant fine fuels that may increase fire frequency and alter fire size and pattern [76,240]. Medusahead is invasive on some low sagebrush sites below 4,900 feet (1,500 m), especially where clay content is high [76].
Crested wheatgrass, a nonnative perennial grass, has been planted extensively by land management agencies for soil stabilization and to increase rangeland forage [295]. Some authors suggest that conversion of sagebrush communities to crested wheatgrass communities contributed to sage-grouse population declines [76]. Sime [256] recommended against seeding crested wheatgrass in sage-grouse rangelands. Other authors, however, advocated for the use of crested wheatgrass to rehabilitate sage-grouse habitat that has been severely degraded and dominated by cheatgrass, suggesting a 3-step process to covert parts of cheatgrass monocultures into more diverse plant communities [86,213].
Table 8. Susceptibility of major upland community types within the greater sage-grouse range to nonnative plant establishment and spread. Susceptibility is ranked as H=high, M=moderate, L=low, and U=unknown (compiled by [197]). Nonnative plant species Basin big sagebrush, Wyoming big sagebrush, and threetip sagebrush Mountain big sagebrush Low sagebrush and black sagebrush Salt desert shrub Crested wheatgrass and other bunchgrasses bull thistle M M M M H Canada thistle M M M M H cheatgrass H M M M H common crupina L M L L M Dalmatian toadflax M H M L H diffuse knapweed M M M L H dyer's woad H L H L H halogeton M M M H M heart-podded hoary cress M M M M M leafy spurge M L M M M Mediterranean sage H M U L H meadow hawkweed L L L L L medusahead M M L M M musk thistle U M U M M orange hawkweed L M L L L oxeye daisy U U U L M poison hemlock L L L L L perennial pepperweed L L L L L purple loosestrife L M L L L rush skeletonweed M M U L M Russian knapweed M M U M M Russian-thistle M M L M M Scotch cottonthistle M L U L M sowthisles M M M M M spotted knapweed M M U L H squarrose knapweed M M M M M stinking willie U U U U U sulfur cinquefoil U M U L H yellow starthistle M M M L H yellow toadflax M M U L MConifer encroachment: The establishment and spread of conifers into sagebrush ecosystems is another threat to sage-grouse because they avoid conifer communities during breeding, nesting, and brood-rearing [9,21,55]. Utah juniper, western juniper, singleleaf pinyon, and Colorado pinyon are the primary conifer species occurring in the ranges of greater and Gunnison sage-grouse and spreading into sagebrush communities. To a lesser extent, Rocky Mountain juniper is also spreading into sagebrush communities. The greatest proportion of conifer encroachment has occurred in mountain big sagebrush communities at high elevations and low sagebrush and black sagebrush communities on moderate to deep soils [197]. See Postsettlement FIRE REGIMES and conifer encroachment for further details.
Livestock grazing: Impacts of livestock grazing can be positive, negative, or neutral on sage-grouse, depending on the timing, severity, and plant community [28,76,103]. Livestock compete with sage-grouse by consuming grasses and/or forbs that sage-grouse use as food and cover [143]. Early-season, light to moderate grazing may promote forb abundance and/or availability, but the effect depends on weather, soil type, plant species being grazed, and timing [76,250]. Livestock grazing may promote the spread of nonnative grasses and other undesirable herbaceous species on low-elevation sites and of conifers on high-elevation sites [76,86].
General management recommendations for livestock grazing in sage-grouse habitats include:See Postfire livestock grazing for additional recommendations.
Climate and weather: Timing and abundance of water availability, which varies seasonally and annually, are the major factors affecting the structure, composition, and abundance of vegetation in sagebrush communities [197]. Attendance of sage-grouse at leks often peaks after years of above-average precipitation [40,116]. Between 2003 and 2010 in Eureka County, Nevada, annual variation in rainfall or snow depth explained as much as 75% of the annual variation in greater sage-grouse population size. Recruitment and adult survival was higher in years with above-average precipitation and cooler summer temperatures than in drought years [40]. In north-central Nevada, attendance of male greater sage-grouse at leks peaked in 2006 following a year of above-average precipitation, declined through 2008, then increased and peaked again in 2011 following another year of above-average precipitation [116]. On 2 study areas at high elevations in southeastern Oregon, prolonged (6 weeks during December and January) cold, snowy weather during one winter reduced female greater sage-grouse survival 4 to 6 weeks later (biweekly survival rate=0.67). Survival at a low-elevation study area was not affected by weather conditions. The authors stated that poor or limited winter habitat at the high-elevation study areas might have contributed to the low survival [6].
Precipitation during spring may impact sage-grouse populations, with increased sage-grouse production often occurring after relatively wet springs [10,274]. Peterson [218] found that wet years in Montana resulted in greater forb production and increased brood success. However, heavy rainfall during egg laying or unseasonably cold temperatures with precipitation during brood rearing [130,274] may decrease sage-grouse production. For example, in southwestern Idaho and south-central Utah, models of greater sage-grouse chick survival showed a significant negative effect of July precipitation on chick survival, perhaps due to either the inability of broods to thermoregulate during cold, wet weather or increased predation during wet weather. In addition, models indicated that a 0.8-inch (2 cm) change in July precipitation (positive or negative) may result in a 15% change in greater sage-grouse chick survival, and a 3.6 °F (2 °C) increase in mean minimum temperature in May may result in a 10% reduction in greater sage-grouse chick survival [130].
Global climate change models predict higher temperatures, increasing atmospheric carbon dioxide, drier soils in summer with high variability, more frequent severe weather (drought and storms), and changing moisture regimes in regions within the sage-grouse range [117,197]. These projected changes are likely to negatively influence sage-grouse populations. Under 3 scenarios of climate change in central Oregon, Creutzburg and others [78] projected widespread shifts in vegetation over the twenty-first century, with declining sagebrush steppe and expanding salt desert shrublands likely by the end of the century. Many extreme fire years occurred under all the climate change scenarios, resulting in rapid vegetation shifts. Increasing wildfire frequency under climate change resulted in spread of nonnative grasses but also decreased juniper encroachment in sagebrush communities relative to projections without climate change [78]. These scenarios suggested that changing climate may render some locations less suitable for sagebrush and thus sage-grouse. Evers [104] modeled 3 potential future climate scenarios in southeastern Oregon. The 1st scenario produced warmer and drier annual conditions than present, the 2nd scenario warmer and wetter conditions in winter, and the 3rd scenario warmer and wetter conditions in summer. The implications for sage-grouse habitat abundance were very different among the 3 scenarios, but all would likely result in the loss or near complete loss of cool, moist sagebrush communities important for sage-grouse nesting and brood-rearing. Salt desert shrublands and warm, dry sagebrush communities could expand under the 1st scenario but would have a high risk of replacement by cheatgrass. Juniper woodlands could increase in density and salt desert shrublands may expand slightly under the 2nd scenario. The remaining sagebrush communities would remain at high risk of replacement by cheatgrass. Pinyon-juniper woodlands could largely replace sagebrush in the 3rd scenario. Greater sage-grouse habitat quality likely would decline in all 3 scenarios [104].
The loss of approximately 12% of the 2011 distribution of sagebrush is predicted with each 1.8 °F (1 °C) increase in temperature, with increasing distributions of other woody vegetation. The distribution of sagebrush as of 2011 was predicted to decline by 80% with an increase of 11.9 °F (6.6 °C) [197]. Climate change models of the sagebrush ecosystem indicated that big sagebrush distribution is predicted to decrease overall, with substantial decreases in southern parts of the species’ range and some increases in the northern parts and at high elevations. The models also suggest potential splitting of sagebrush ecosystems into several distinct areas in 1) Washington and the Sierra Nevada; 2) Oregon, northern Nevada, and central Idaho; and 3) eastern Utah, Wyoming, Colorado, and eastern Montana [244]. This suggests that sage-grouse habitat would decrease overall, and populations would potentially become more separated. In addition, sage-grouse distribution may shift to slightly higher elevations with more woody cover. Although sagebrush may decline, a review of the effects of climate dynamics on sage-grouse suggests that potential effects of global climate change (such as prolonged drought) may influence the herbaceous understory in sagebrush habitats before effects on the shrub overstory become apparent [183].
OtherFor detailed information on individual sagebrush species or varieties and effects of fire on those taxa, enter the plant name in the in the FEIS home page under "Find Species Reviews". See Fire Management considerations for additional recommendations.
Management considerations for breeding, nesting, and brood-rearing habitats: Several authors provide specific recommendations for buffers around leks to protect sage-grouse nesting habitat (e.g., [44,73]). Connelly and others [73] suggested a 3-mile (5 km) and 11-mile (18 km) buffer around leks may be required for nonmigratory and migratory populations, respectively. Braun and others [44] recommended a 2-mile (3 km) buffer around leks but noted that the radius may be >2 miles in low-quality nesting habitat. However, the distances females travel from leks to nests are highly variable (see Lek-to-nest distances). Aldridge and Boyce [1] indicated that a buffer around leks of <6 miles (10 km) to protect sage-grouse early brooding and nesting habitat may not be suitable, while other authors suggest managing nesting habitat rather than specific distances around leks [248,271]. Other breeding, nesting, and early brood-rearing Habitat management guidelines for sage-grouse include:
See Fire management considerations for breeding, nesting, and brood-rearing habitats for additional recommendations.
Management considerations for summer habitat: Summer Habitat management guidelines for sage-grouse include:
Adult female sage-grouse mortality is typically lower than adult male mortality, and adults have lower mortality rates than juveniles [64,69,73,76,248]. A 2004 review reported annual survival averaging 49% for males and 61% for females (Table 1) [76], while a 2011 review reported average annual survival ranging from 40% to 70% for adult males and 60% to 80% for adult females [69]. Sage-grouse live up to 6 years in the wild [248].
Mortality rates are highest during the breeding season and autumn migration. In northeastern California, overall 8-month survival (breeding season through autumn migration) for female greater sage-grouse was 49%, with most deaths occurring in spring and autumn. Mortalities during spring coincided with nest initiation, incubation, and the period immediately following hatching, when females were tending chicks. Deaths in September coincided with dispersal and autumn migration [88].
Overwinter survival tends to be high. Survival rate of 94 female greater sage-grouse in central Montana averaged 98% and 97% during 2 winters [255]. Winter survival rates of greater sage-grouse in southwestern Idaho during 2 winters were 85% and 90% for adult males and 100% and 88% for adult females [289]. According to a review, sage-grouse exhibit relatively high survival of breeding-age birds, especially in winter, and comparatively low productivity relative to other Galliformes [69]. Although average nest success is moderate, the relatively small clutch size, large number of nonnesting females, low rate of renesting, inability to produce more than 1 brood a year, and possibly low juvenile survival (Table 1) suggest that sage-grouse populations are unlikely to increase rapidly [69,76,131].
Predators: Coyotes [162,265], bobcats [14], American badgers [170], weasels [69], and raptors [24,69,96,214,219] prey on adult and juvenile sage-grouse, while crows, ravens, and magpies prey on juveniles [162,265]. Coyotes, red foxes, and American badgers are the most important mammalian nest predators, while magpies and ravens are important avian nest predators. Snakes may also prey on nests [69,148,154,274]. Human development in sage-grouse rangelands has resulted in the addition of nonnative predators to sage-grouse habitats, including domestic dogs and domestic cats [73]. Fences, powerlines, and pipelines provide perches for avian predators that could potentially prey on sage-grouse [64].
No predator specializes on sage-grouse. Most sage-grouse predators are generalists that hunt rodents and lagomorphs as their primary prey [131]. However, decline in the primary prey may result in increased predation on sage-grouse. Kindschy [162] suggested that in southeastern Oregon, a decline in black-tailed jackrabbit numbers might have caused predators to prey more heavily on greater sage-grouse.
Plant community structure influences the degree to which sage-grouse are vulnerable to predation. Generally, predation rates are expected to increase as the size of sagebrush patches and the visual obstructing cover within sagebrush patches decreases [43]. For more information, see Preferred habitat.
Hunting: Greater sage-grouse are a popular game bird [228]. As of 2016, they were hunted in all the states in which they reside except Washington [228] and the Dakotas. Seasons were closed in 2016 in North Dakota and South Dakota due to low greater sage-grouse populations [207,251]. Greater sage-grouse are not hunted in Canada. Gunnison sage-grouse is not hunted [228]. Reviews of hunting effects on sage-grouse are available (e.g., [228,248]).
Diseases and parasites: A variety of parasites and diseases affect sage-grouse [61]. Despite the prevalence of organisms that may infect individual birds, population-level effects of parasites and diseases have rarely been documented in sage-grouse [61], with the exception of West Nile virus, which was first noted in greater sage-grouse populations in 2002. West Nile virus can reduce sage-grouse survival [272] and potentially reduce sage-grouse populations [61].
Other causes of Other causes of mortality of sage-grouse include collisions with vehicles, fences, powerlines, and other obstacles; pesticide exposure; fire; flood; drought; sun exposure; heavy rain; and cold [248].
Sage-grouse individuals tend to use the same seasonal ranges year after year. Within and among populations, seasonal movements tend to be highly variable. Some sage-grouse migrate between 2 or 3 distinct seasonal ranges, such as between winter, breeding, and/or summer ranges, while others do not migrate [69,72,248]. Annual home ranges of greater sage-grouse vary from 1.5 to 237 miles² (4-615 km²) [69]. Seasonal home ranges vary from <1 to 11 miles² (1-29 km²) during the breeding season, <1 to 10 miles² (1-26 km²) during summer, 9 to 17 miles² (23-44 km²) during autumn, and <1 to 75 miles² (1-195 km²) during winter [69,248].
Migration to summer ranges occurs from late May through early August [69]. Sage-grouse move up to summer ranges as spring habitats dry. Greater sage-grouse in southeastern Idaho moved to late brood-rearing sites when vegetation moisture content declined to approximately 60%. They moved earlier in dry years than wet years [110]. In wet years, birds may not need to move as far to find mesic sites [2]. Peak autumn migration occurs from mid-October through late November [69]. Autumn movements to winter ranges are also influenced by weather and usually occur gradually. In late winter and early spring, flocks of sage-grouse move toward breeding areas that may be immediately adjacent to or distant from winter ranges [69].
Few data exist on sage-grouse dispersal. In Colorado, median dispersal distances from hatching sites to breeding or attempted breeding sites were 5.5 miles (8.8 km) for 12 yearling greater sage-grouse females and 4.6 miles (7.4 km) for 12 yearling males [97]. In Moffat County, Colorado, median dispersal during 3 years was greater for yearling greater sage-grouse males (2.4 miles (3.8 km)) than females (1.7 miles (2.7 km)). Within the study population, all but one yearling male dispersed locally [264]. River valleys and large agricultural areas may be barriers to dispersal [50].
Sage-grouse are totally dependent on sagebrush communities [31,72]. Sagebrush is a crucial component of their diet year-round, and sage-grouse select sagebrush communities almost exclusively as cover [45,72,209]. Sage-grouse habitat requirements vary seasonally. Sage-grouse use sagebrush of different heights and canopy cover seasonally, ranging from 10 to 31 inches (25-80 cm) in height and 12% to 43% in canopy cover [72]. Relatively open leks with scattered low shrubs are used in late winter and spring. Taller, denser shrubs that provide horizontal and vertical cover are used during nesting in spring and also in winter [72]. Sage-grouse rely heavily on the diverse herbaceous plants within and nearby sagebrush communities for food and cover during the prelaying, nesting, and early brood-rearing periods. Sage-grouse may use a variety of nonsagebrush habitats intermixed in a sagebrush-dominated landscape during summer—particularly nonsagebrush shrub-herbaceous, wetland, and riparian communities—so the composition and configuration of habitats also determines habitat quality for sage-grouse [72]. Pyke [222] stated that sage-grouse tend to reach their optimum densities in sagebrush steppes where sagebrush codominates with midstatured perennial bunchgrasses. Sage-grouse probably need large sagebrush patches (>9,900 acres (4,000 ha)) [72,222].
Breeding habitat: Open areas in or adjacent to sagebrush communities—such as swales, irrigated fields, meadows, dry stream channels, ridges, burns, roadsides, and areas with sparse, low shrub cover—are used as leks [72,73,166]. Of 45 leks, Patterson [209] reported that 11 were on windswept ridges or exposed knolls, 10 were in flat sagebrush, 7 were in bare openings, and the remaining 17 were on various other sites. Leks are usually 0.1 to 10 acres (0.4-4 ha) but may be as large as 100 acres (40 ha) [52]. Leks in Wyoming generally ranged from 0.6 to 40 acres (0.25-16 ha), but one was 49 acres (20 ha) (Scott 1942 cited in [72]).
When not on leks, sage-grouse forage and rest in surrounding areas of relatively dense sagebrush [69,72,274]. Male greater sage-grouse may travel up to 1.3 miles (2.1 km) from leks to day-use areas [72]. In northeastern Utah, day-use areas of breeding male greater sage-grouse were generally 0.3 to 0.5 mile (0.5-0.8 km) from the lek. After visiting leks, male greater sage-grouse used areas near leks that had greater mean canopy cover (31%) and shrub height (21 inches (53 cm)) than nearby unused areas [100]. During the breeding season in central Montana, 82% of 110 of the daytime roosting locations of male greater sage-grouse were between 0.2 and 1.1 miles (0.3-1.8 km) from the lek. Eighty percent of the daytime roosting locations were recorded in areas with 20% to 50% sagebrush canopy cover, while no daytime roosting locations were recorded in areas with ≤10% sagebrush canopy cover [277].
Leks may be located near water. In northeastern California, southwestern Oregon, and northwestern Nevada, 85% of leks were within 6.2 miles (10.0 km) of wetland, wet meadow, and riparian communities. Leks with the highest densities of greater sage-grouse were within 1.8 miles (2.9 km) of these areas [252].
Leks occur in sagebrush-dominated landscapes with low cover of conifers and nonnative annual grasses, and with little agricultural land [174]. A range-wide model of lek locations found that leks were absent from regions with ≥40% conifer forest cover. Conifer forest cover averaged <1% within 3 miles (5 km) of active leks, while conifer forest cover averaged 13% in the study area and 3% within 3 miles of inactive sage-grouse leks. Burned area was greater on average within 3 miles of active leks than within 3 miles of inactive leks or within the study area. Burned areas were rare in agricultural lands and in human developments. Fires occurred between 1980 and 2007 [174]. In western Oregon, greater sage-grouse abandoned leks when conifer canopy cover was >4% [21]. In an 8-year study in Eureka County, Nevada, greater sage-grouse males breeding at leks surrounded mostly by nonnative grasslands had lower annual survival rates than males at leks surrounded mostly by native sagebrush, even during years with weather favorable to survival (i.e., high precipitation and cool summer temperatures) [40].
Sage-grouse require sagebrush-dominated landscapes with minimum levels of human land use [173,174]. Arkle and others [7] found that greater sage-grouse were twice as likely to occupy plots when no human development occurred within 3 miles (5 km). Nonnative annual grass, juniper, other conifers, and agricultural land cover negatively affected greater sage-grouse occupancy when they accounted for 5% to 18% of the landscape around a given plot [7]. A range-wide analysis indicated that greater sage-grouse leks that persisted from 1965 to 2007 were larger in size; more highly connected; had fewer, smaller fires (since 1965) within a 34-mile (54 km) radius; and had a smaller proportion of areas with human disturbance within a 3-mile radius than abandoned leks [173].
Prelaying habitats are part of breeding habitats [73].
Nesting habitat: Sage-grouse females move to the vicinity of their nest locations within a few days of mating and remain relatively sedentary until they nest [209]. Females build nests within 7 to 10 days of breeding [10]. A sage-grouse may renest if the initial nest is destroyed or abandoned [131]. Eggs are laid within 2 to 15 days of nest loss [248].
Lek-to-nest distances: Reviews noted much variation in the distance of nests from leks. The average distance between a female's nest and the lek where she was first observed was typically <5 miles (8 km) [69,72,248]; however, some females nested as far as 20 miles (32 km) from leks [124,237]. A 2012 summary of lek-to-nest data for migratory populations of greater sage-grouse throughout Idaho reported that 35% of 302 nests occurred within 1.2 miles (2 km) of the capture lek, and 45% occurred within 1.9 miles (3 km). However, 34% occurred >4.3 miles (7 km) from capture leks [65]. Mean distance from leks to nests was greater for successful (2.2 miles (3.6 km)) than unsuccessful (1.2 miles (2.0 km)) greater sage-grouse nests in northeastern California [221], while no relationship between lek-to-nest distance and nesting success was reported for greater sage-grouse in southeastern Idaho [271]. In northeastern California, most females nested within 3 miles (5 km) of a lek; however, of the 27% of females nesting >3 miles from a lek, 53% nested successfully, suggesting the importance of nests far from leks in population productivity [89]. A review noted that females in fragmented habitats may travel farther from leks to nests than females in unfragmented habitats [69].
Nest cover: Most sage-grouse nests are under sagebrush plants, although other plants—including greasewood, antelope bitterbrush, rabbitbrush, gray horsebrush, snowberry, shadscale saltbush, mountain-mahogany, and basin wildrye—may be used as nest cover [2,52,72,73,74,164,209,221,225,261,276]. Gunnison sage-grouse nested under a variety of shrubs in Colorado, but 92% of 117 nests were located under sagebrush [123]. In southeastern Idaho, 79% of 84 greater sage-grouse nests were under big sagebrush and 21% of nests were under other shrubs, including rabbitbrush, mountain snowberry, and antelope bitterbrush. Nests under big sagebrush had greater nest success (53%) than those under other plant species (22%) [74]. In contrast, in California, 67% of greater sage-grouse nests were under big sagebrush, 2% were under low sagebrush, and 29% were under other shrubs. Nest success was lower under big sagebrush (30.8%) than under other shrubs (41.7%) [221]. In Lassen County, California, greater sage-grouse used a variety of plants as nesting cover, suggesting that selection of nest sites was based more on vegetation structure than plant species. Although females nesting under vegetation other than sagebrush had increased nest survival probabilities, overlapping confidence intervals suggested that the effect was likely small. Sagebrush canopy cover in the study area was low (10% on random plots), so quality sagebrush nesting habitat was likely limited in the study area [88]. In south-central Washington, 71% of greater sage-grouse nests were under big sagebrush and 29% were under nonshrub cover in 1992, while 66% of nests were under big sagebrush, 8% were under threetip sagebrush, and 26% were under nonshrub cover in 1993. Nest success under sagebrush was similar to nest success under nonsagebrush cover during both years [261].
A review of 13 studies indicated that greater sage-grouse nest sites are associated with sagebrush cover averaging 15% to 38% and sagebrush heights averaging between 11 and 31 inches (29-80 cm) (Table 5) [73]. A 2007 metaanalysis of greater sage-grouse nesting habitat found that nest sites are associated with average shrub and/or sagebrush cover between 15% and 59%, average grass cover between 3% and 51%, average grass height between 5.4 and 42.5 inches (13.8-107.9 cm), and average forb cover between 1% and 21% (Table 6) [132]. Welch [285] stated that in general, sage-grouse prefer sagebrush canopy cover ranging from approximately 20% to 50%, and they prefer plants that are >18 inches (46 cm) tall. Some studies indicated that sites might have either too little or too much shrub cover for nesting. On a site in Idaho, where shrub cover in the study area averaged 13%, greater sage-grouse nested where average shrub cover was 17%. No nests were found in the most arid, open areas with 10% shrub cover, and no nests were found where shrub cover was >35% [164]. In Wyoming, 92% of greater sage-grouse nests in Wyoming big sagebrush communities occurred in areas where vegetation was 10 to 20 inches (25-51 cm) tall and cover was <50% [209]. In southwestern Wyoming, no nest sites within burned areas had <12% total shrub cover [257]. In Utah, no nests were found where shrub cover was >35%; the authors speculated that this was because few forbs were present in dense shrub stands [225].
Table 5. Height (cm) and cover (%) of sagebrush and grass at greater sage-grouse nest sites, compiled by Connelly and others [73]. Cells are blank where data were lacking. State Sagebrush Grass Original source Height Cover Height Cover Colorado 52 [216] Idaho 15 4 [164] 58-79 23-38 [10] 71 22 18 3-10 [270] 19-23 7-9 [74] 61 22 30 [107] 15-32 15-30 [170] 69 19 34 15 Apa 1998 cited in [73] Montana 40 27 [274] Oregon 80 20 Keister and Willis 1986 cited in [73] 24 14 9-32 Gregg 1991 cited in [73] Washington 20 51 Schroeder 1995 cited in [73] 19 32 [261] Wyoming 36 [209] 29 24 15 9 Heath and others 1997 cited in [73] 31 25 18 5 [144] 33 26 21 11 [181]Sage-grouse nests are often built under relatively tall shrubs and grasses that provide more visual obstruction cover than random sites [72,73,132]. In Montana, height of sagebrush cover at all greater sage-grouse nests averaged 15.9 inches (40.4 cm) compared to 9.2 inches (23.4 cm) in adjacent areas (P=0.005) [276]. Two studies of greater sage-grouse in southeastern Idaho found greater ground- and lateral-obstructing cover at greater sage-grouse nests than random sites [107,270]. In northeastern California, greater sage-grouse selected nest sites with taller grasses (P=0.033) and greater visual obstruction (P=0.001) than random sites [88]. In Wyoming, greater sage-grouse nests were located at sites with more total shrub canopy cover, residual grass cover, and residual grass height than random sites [145]. During 2 summers in North Dakota, greater sage-grouse selected nest sites with more total vegetative cover, greater sagebrush density, and greater visual obstruction from the nest than random sites. However, grass and sagebrush heights at nest sites were shorter than at random sites because areas where sagebrush was common were either in early-seral stages or on heavy clay or clay-pan soils with low productivity [137].
Vegetation structure providing obstruction cover at the nest site provides visual, scent, and physical barriers to potential predators [90,128]. Several studies found that obstruction cover at nests provided by tall shrubs and grasses, particularly tall native bunchgrasses, was positively correlated with nest success (e.g., [2,128,137,145,158,261]). In Wyoming big sagebrush communities in Oregon, nests without predator losses had greater cover of tall (>7 inches (18 cm)), residual grasses (18%) and medium-height (16-31 inches (40-80 cm)) shrubs (41%) than nests with predator losses (29% for grasses and shrubs, respectively) (P<0.001) [128]. In northwestern Nevada, successful nests had greater mean grass cover (24.2%) than unsuccessful nests (14.8%). Nests were located in areas averaging 15.6% grass cover, 30.2% sagebrush cover, and 37.2% shrub cover and were typically built under shrubs with greater sagebrush canopy and grass cover than the surrounding area. Sixty percent of sagebrush cover was 16 inches (40 cm) tall [226]. In northeastern Wyoming and southeastern Montana, average grass height was positively associated with greater sage-grouse nest success. In 2003, an early wet spring resulted in tall grasses at nest sites (mean: 11.5 inches (29.2 cm) tall) and high predicted next success (64%), suggesting that maintaining tall grasses during drought may benefit greater sage-grouse populations [93]. In North Dakota, models based on data collected over 2 summers suggested that patches of sagebrush and/or other shrubs with >9% canopy cover and grass taller than 6 inches (16 cm) improved the chances of greater sage-grouse eggs surviving to hatch [137]. In a series of Nevada studies using artificial sage-grouse nests, egg mortality was lowest in the area with greatest cover [163].
Forbs may also provide adequate nest cover [2,72,76,261], and nest success may be high during years with abundant forbs [62]. Nonnative annual grasses, such as cheatgrass, do not provide adequate cover for nests [76]. In Wyoming, nests sites had more total herbaceous cover, total forb cover, taller live sagebrush height, and greater grass cover than available on random sites (P<0.008 for all variables) [181]. In mountain big sagebrush and Wyoming big sagebrush communities at Hart Mountain National Antelope Refuge, Oregon, nest initiation, renesting, and nesting success rates were higher during years when herbaceous vegetation was more abundant (Table 7) [62].
Table 7. Percent herbaceous vegetation cover and reproductive success of greater sage-grouse at Hart Mountain National Antelope Refuge, Oregon, during 2 time periods. P-values refer to differences between the 2 time periods [62]. Variable Year P-value 1989-1991 1995-1997 Forb cover 6.7-12.8 13.1-18.2 0.42 Food-forb cover 0.5-1.0 3.1-3.8 0.001 Tall (>7 inches (18 cm)) grass cover 0.3-6.2 14.7-9.2 0.001 Nest initiation rates 65 99 0.001 Renesting rates 14 30 0.07 Nest success rates 22 37 0.08Nests may be located in relatively heterogeneous landscapes. Peterson and others [217] found that greater sage-grouse nests in southeastern Oregon were located at sites that were more diverse than the overall landscape, containing a mosaic of patches with low sagebrush, mountain big sagebrush, and antelope bitterbrush communities. The authors suggested that a diverse landscape might provide more forage for greater sage-grouse than more homogenous landscapes. In Alberta, greater sage-grouse preferred to nest in large (0.4 mile² (1 km²)) habitat patches with moderate sagebrush cover. They avoided nesting within 0.4 mile² of roads, oil wells, other human developments, and croplands. Nests were most successful in large patches that contained patchily distributed sagebrush, while areas with continuous dense sagebrush or sparsely distributed sagebrush were least successful [1].
Early brood-rearing habitat: In general, sage-grouse females rear their broods near their nests for at least the first 2 to 3 weeks before moving to summer rangelands [73]. Early brooding-rearing habitat is confined to areas near the nest. Early brood-rearing areas in west-central Wyoming averaged 0.7 mile (1.1 km) and ranged between 0.1 and 3.1 miles (0.2-5.0 km) from nests [181]. In Wyoming, 80% of early brood locations was within 0.9 mile (1.5 km) of nests [257]. Movements from nest to early brood-rearing areas in northern Colorado averaged 0.5 mile (0.8 km) and ranged between 0.2 and 1.4 miles (0.3-2.3 km) [216].
During the early brood-rearing period, sage-grouse broods consistently select areas with less shrub canopy cover and more forb and total herbaceous cover than random locations [72,132]. When compared with nest locations, early brood-rearing habitat in central Wyoming had less live sagebrush canopy cover and total shrub canopy cover, shorter average sagebrush heights, and more total herbaceous cover [144]. In Colorado, young broods used areas with low forb canopy cover after hatching (mean: 6.9%), then quickly moved to meadows with much greater mean forb canopy cover (41.3%) [247]. A 2007 metaanalysis of data on sage-grouse brood-rearing habitat indicated that brood-use areas generally had less sagebrush cover, taller grasses, greater forb cover, and greater grass cover than random locations. Early brood-rearing habitat averaged 11% to 26% sagebrush canopy cover and 13% to 39% cover of forbs and grasses (Table 6) [132].
Early brood-rearing sites may be located in relatively heterogeneous landscapes that have little human development, cropland, or conifer cover [1,55]. In Alberta, females with broods selected sites with heterogeneous, high-productivity (mesic) sagebrush communities within 0.4 mile² (1 km²), while avoiding human developments, croplands, and high densities of oil wells. The authors suggested that patchy cover provides food sources while still providing escape cover from predators [1]. Greater sage-grouse females with broods in Mono County, California, selected areas with greater perennial forb cover and higher plant species richness at the smallest spatial scale (0.7 acre (0.03 ha)) during the first 50 days after hatching. The probability of a female fledging a brood increased as perennial forb density increased at this scale. At larger scales (19.5 acres (7.9 ha) and 560.4 acres (226.8 ha)), areas with Utah juniper and singleleaf pinyon encroachment were avoided. Areas with high meadow edge (perimeter to area ratio) were selected, possibly because these areas provided a balance of food and protective cover for chicks [55].
Summer habitat: Sage-grouse rely on sagebrush habitats in summer but also use a variety of habitats adjacent to sagebrush communities, including riparian areas, willow communities, swales, wet meadows, grassland steppes, sagebrush communities with some conifers and/or quaking aspen, and agricultural fields [72,73]. Sage-grouse select summer habitats with abundant forbs, and they may move up in elevation to follow vegetation phenology or select moist sites with succulent forbs [72,73,166]. Summer habitat has at least 15% shrub canopy cover and at least 10% live forb cover [92]. A 2005 review suggested that the "ideal" brooding habitat would be a big sagebrush community with a canopy cover of about 25% and a small creek running through it [285].
Late brood-rearing habitat: Sage-grouse use late brood-rearing habitats following desiccation of herbaceous vegetation in early brood-rearing habitats [72,73,76]. The beginning of late brood-rearing coincides with the change in diets of sage-grouse chicks from predominantly insects to predominantly forbs. Sagebrush is an essential part of sage-grouse late brood-rearing habitat. Sage-grouse females use late-brooding habitats of variable sagebrush density, from scattered to dense, throughout the summer [72]. During 2 summers in Montana, areas where sagebrush was scattered (1%-10%) or common (10%-25%) were used most. Areas of sparse sagebrush cover (<1%) were used most in July and August, areas of scattered sagebrush were used most in June, areas where sagebrush was common were used consistently throughout the summer, and areas of dense sagebrush (>25%) were used most in late August and early September. Combined data for both summers showed average sagebrush cover of 14% at brood sites during June, 12% during July, 10% during August, and 21% during September. Height of sagebrush at brood sites ranged mainly between 6 and 18 inches (15.2-45.7 cm) [273].
Sites used during late brood-rearing generally have higher forb canopy cover than random sites [72]. A 2007 metaanalysis indicated that sage-grouse late brood-rearing habitat averaged 7% to 29% sagebrush canopy cover, 5% to 18% grass cover, and 8% to 23% forb cover (Table 6) [132]. Researchers in southeastern Alberta found forb cover in late brood-rearing habitat averaged 12.6% and suggested that 12% to 14% forb canopy cover might be the minimum needed for brood-rearing habitat [2].
Low chick survival may be attributed to poor-quality late brood-rearing habitats [9]. In east-central Nevada, successful late brood rearing occurred at high-elevation moist sites with riparian shrubs or montane sagebrush. Such sites represented only 2.8% of the 2,500-mile² (6,500 km²) study area. This suggests that the scarcity of such habitat may limit greater sage-grouse populations in this region. In contrast, greater sage-grouse selection of early brood-rearing habitat was only marginally different from what was available at random sites [9].
Broodless summer habitat: Sage-grouse nesting and brood-rearing success may be low in some years (Table 1). Thus, a relatively large portion of the summer female sage-grouse population may be composed of broodless females [76]. Broodless females begin to form small flocks of 2 to 3 individuals in mid-May; flocks may increase to 25 individuals by early June [127]. In summer, broodless females and males select big sagebrush stands with canopy cover generally ranging from 20% to 35%, with some as high as 50% [285].
Habitat use by broodless females appears similar to that of females with broods, except that broodless females often move to riparian communities earlier than females with broods [127]. For example, in Oregon, broodless females gathered in flocks and remained separate from, but in the vicinity of, females with broods during early summer. However, broodless females moved to meadows earlier in summer and used more diverse cover types than females with broods, perhaps because dietary needs of broodless females are less specific [127]. Males use habitats similar to those of broodless females, but they typically remain in flocks separate from females [76].
Autumn habitat: Sage-grouse use a variety of habitats in autumn as their diets change from a mix of forbs, insects, and sagebrush to predominantly sagebrush [72]. In autumn sage-grouse gather into larger flocks than in summer [29,45,72]. Sage-grouse use autumn habitats from as early as August to as late as December, depending on plant community availability, topography (elevation, slope, and aspect), water availability, distance between summer and winter rangelands, and weather [72,73]. During early autumn, sage-grouse may remain in summer habitats such as sagebrush communities, upland meadows, riparian areas, greasewood meadows, and alfalfa fields. As vegetation in these habitats desiccates or is killed by frost, sage-grouse begin using sagebrush communities [72].
Winter habitat: In winter, sage-grouse segregate by gender and flock together in groups of typically <50 individuals [29], but up to 100 individuals [54]. Sagebrush dominates sage-grouse winter habitats [72].
Snow: During winter, sage-grouse typically move to low elevations with shallow snow or to areas where tall sagebrush is exposed above the snow [72]. According to Rogers [237], the best winter habitat is below snowline. Wintering grounds of greater sage-grouse in Idaho were usually where snow was <6 inches (15 cm) [81]. In North Park, Colorado, greater sage-grouse selected either relatively exposed, windswept ridges or draws, swales, and other areas of shallow snow and exposed sagebrush [29,247]. Autenrieth and others [12] cautioned that despite how abundant a sagebrush stand may appear in summer, only minimal amounts of sagebrush may reach above snow and be available for wintering sage-grouse [12]. Snow quality is also important because sage-grouse use snow forms (shallow depressions) and burrows (deep holes and tunnels) as thermal protection when snow is sufficiently deep and lacking a crust [13].
Vegetation: According to a review, sagebrush in sage-grouse winter habitat is generally >8 to 12 inches (20-30 cm) above the surface of the snow [45,72,236]. Thus, sage-grouse generally use plant communities dominated by tall species of sagebrush—including big sagebrush, silver sagebrush, and threetip sagebrush—in winter [72]. However, sage-grouse also use low sagebrush, silver sagebrush [76,248], and black sagebrush [10,77,81] communities in winter. Shrub canopy cover in winter habitat varies from 6% to 43% [248] and is generally >20% [10,77,235]. In central Oregon, sagebrush canopy cover was typically >20% at winter-use sites, but within these sites greater sage-grouse tended to use patches with 12% to 16% canopy cover. In this study, most of the winter-use sites were in mountain big sagebrush (Hanf and others 1994 cited in [72]). In Utah, wintering greater sage-grouse preferred shrublands with tall shrubs (16-22 inches (40-56 cm)) and approximately 20% to 30% cover [146]. In Alberta, where suitable winter habitats are limited, spatial models indicated that greater sage-grouse selected relatively dense sagebrush cover (mean=14.9%) in smooth terrain at low elevations and avoided areas where energy developments and dirt roads were within 0.4 mile² (1 km²) [54]. Cover of herbaceous plants is generally not important in winter because of the nearly complete reliance of sage-grouse on sagebrush during winter [72].
Topography: Sage-grouse apparently select areas with little or no slope (<5%) in winter [72]. In a Colorado study, nearly 80% of Gunnison sage-grouse's winter use of 500 miles² (1,252 km²) of sagebrush was on <35 miles² (87 km²). Winter use occurred on either flat areas where sagebrush projected above the snow or on south- or west-facing sites of <5% slope, where sagebrush was sometimes short but still accessible above the snow [154]. In North Park, Colorado, 66% of 199 greater sage-grouse flocks were on slopes of <5%, and only 13% were on slopes >10% [29]. In Montana, greater sage-grouse wintering areas were flat, large expanses of dense (>20%) big sagebrush [102]. Gunnison sage-grouse in Colorado foraged mostly in drainages and on slopes with southern or western aspects [150]. A review stated that sheltered microsites are important to sage-grouse for ameliorating the effects of wind, especially at low temperatures [72].
After mating, the female leaves the lek for the nesting grounds. Clutch size ranges from 6 to 9 eggs; incubation time is 25 to 27 days [69]. Peak egg laying and incubation periods vary from late March through mid-June, with renesting stretching into early July [69]. The precocial chicks leave the nest soon after hatching, are capable of weak flight by 10 days old, and are capable of strong flight by 5 weeks old [69,154,274]. Juveniles are relatively independent by the time they have completed their first molt at 10 to 12 weeks old [154].
Female sage-grouse can nest as yearlings [73]. Over 7 years in Idaho, 55% of yearling female sage-grouse nested and 12% renested, while 78% of adult female sage-grouse nested and 17% renested [68]. In eastern Oregon, 99% of all females nested during 3 years [62]. A 2004 review reported that on average, 80.8% of greater sage-grouse and 75.7% of Gunnison sage-grouse females nested (Table 1) [76]. Research examining follicular development rather than nest observations indicated that the proportion of females attempting to nest may be even higher (>90%) [248]. Sage-grouse that lose initial clutches late in incubation may be less likely to renest than those that lose their eggs early in incubation [248].
Table 1. Range-wide averages for demographic parameters associated with population dynamics of greater sage-grouse and Gunnison sage-grouse [76]. Cells are blank where data were lacking. Variable Greater sage-grouse Gunnison sage-grouse Mean Number of studies Mean Number of studies Clutch size 7.5 eggs 10 6.8 eggs 1 Hatchability 94.3% 8 Nest likelihooda 80.8% 7 75.7% 1 Renest likelihoodb 32.5% 7 4.8% 1 Nest successc 47.4% 14 43.2% 1 Annual reproductive successd 44.6% 8 35.1% 1 Annual survival of breeding-aged males 48.9% 5 Annual survival of breeding-aged females 60.6% 6 Survival of juvenilese 10.0% 3 aThe proportion of females attempting to nest.Nest success: A 2011 review of 27 published studies reported greater sage-grouse nesting success ranged from 12% to 71% (mean: 46%), with relatively greater mean success for adults (59%) than yearlings (49%) and relatively greater mean success in unaltered (51%) than altered (37%) habitats. Altered habitats were either recently burned or highly fragmented [69]. A 2004 review reported nest success of greater sage-grouse averaged 47% for 14 studies, while nest success of Gunnison sage-grouse averaged 43% in 1 study (Table 1) [76]. Nest success is highest in areas with relatively tall, dense sagebrush, grasses, and forbs (see Nesting habitat). Generally, nest success appears to improve with increased precipitation. In Wyoming, nesting success was positively correlated with the current year's winter and spring (January–June) precipitation (relative importance=0.32). The preceding year's spring (April–May) precipitation had relatively higher importance than the current winter and spring's precipitation (relative importance=0.44), suggesting that availability of residual cool-season grasses is important for greater sage-grouse nest success [145]. However, heavy rainfall during nesting may decrease sage-grouse production [274]. In North Dakota, daily nest survival rates decreased with increased daily precipitation during nesting; 0.4 inch (1 cm) of precipitation decreased the chances of a nest surviving to hatch by about 7%. The negative effect of daily precipitation on nest survival was amplified when shrub cover was <9% or when grass height was <6 inches (16 cm) [137]. See Mortality and Climate and weather for information on adult and juvenile survival.
The scientific name of the sage-grouse genus is Centrocercus (Phasianidae). There are 2 species in the genus [5]:
Centrocercus minimus Bradbury and Vehrencamp, Gunnison sage-grouse
Centrocercus urophasianus (Bonaparte), greater sage-grouse
Common names are used throughout this Species Review. "Sage-grouse" refers to both Gunnison sage-grouse and greater sage-grouse. See the Appendix for scientific names of animals and plants mentioned in this review and for links to other FEIS Species Reviews.
The Lyon-Mono population of the greater sage-grouse in the Mono Basin, which spans the border between California and Nevada, appears to be genetically distinct from other populations [208].
There is no evidence that Gunnison sage-grouse and greater sage-grouse interbreed [63]. Hybrids of sharp-tailed grouse and greater sage-grouse were found in Montana [101], Saskatchewan [142], and North Dakota [175]. A hybrid of dusky grouse and greater sage-grouse was found in Morgan County, Utah [231].
Sage-grouse are grouse belonging to the bird genus Centrocercus. The genus includes two species: the Gunnison grouse (Centrocercus minimus) and the greater sage-grouse (Centrocercus urophasianus). These birds are distributed throughout large portions of the north-central and Western United States, as well as the Canadian provinces of Alberta and Saskatchewan.[3] The International Union for Conservation of Nature classified the C. minimus species as endangered in 2020[4] and C. urophasianus as near threatened in 2016.[5]
The specific epithet is from another Greek word, "oura", plus "phasianos", pheasant. The noun "pheasant" was originally applied to a bird that was native to the valley of the Phasis River (now the Rioni River), which is located in Georgia. In the time of Lewis and Clark the word "pheasant" stood for "a genus of gallinaceous birds", according to lexicographer Noah Webster (1806), and the explorers often used it in that sense. "Gallinaceous" then referred to "domestic fowls, or the gallinae"; the family Galliformes (Latin "gallus", cock, and "forma", shape) now includes pheasants, grouse, turkeys, quail, and all domestic chickens.
Sage grouse are also collectively known as "sagehen," "sage grouse," "sage cock," "sage chicken," or "cock of the plains."[6]
In their day, Lewis and Clark were credited with the 'discovery' of five gallinaceous birds in addition to the sage grouse — the Columbian sharp-tailed grouse, the dusky grouse, Franklin's grouse, the Oregon ruffed grouse, and the mountain quail — and what's certain is that they were the first to widely spread knowledge about these birds to the white man.[7]
In September 2016, the National Defense Authorization Act (NDAA) stalled in congress because Trump indicated he would not let the annual NDAA proceed to a vote in the House of Representatives unless it contained language to bar the sage grouse from the federal endangered species list until at least 2025. President Trump threatened a veto over the issue that Trump, Senate Armed Services Committee Chairman, believed would be sustained. Current US Air Force spending on sage grouse conservation is around US$200,000, with eight known military installations having confirmed grouse populations: Dugway Proving Ground and Tooele Army Depot in Utah; Sheridan Training Area and Camp Guernsey in Wyoming; Hawthorne Army Depot and Nellis Air Force Base in Nevada; Yakima Training Center in Washington, and Mountain Home Air Force Base in Idaho.[8]
There are two species:
The Mono Basin population may represent a third species.
Males of C. urophasianus are the largest grouse from temperate North America, attaining a maximum weight of 3.2 kilograms (7 lb). Adults have a long, pointed tail and legs with feathers to the toes. As in most Galliformes, there is pronounced sexual dimorphism.}
Centrocercus species are notable for their elaborate courtship rituals. Each spring males congregate on leks and perform a "strutting display." The male puffs up a large, whitish air sack on its chest, makes a soft drumming noise, and struts around with his tail feathers displayed and air sack puffed up. Groups of females observe these displays and select the most attractive males to mate with. Only a few males do most of the breeding. Males perform on leks for several hours in the early morning and evening during the spring months between February and April. Leks are generally open areas adjacent to dense sagebrush stands, and the same lek may be used by grouse for decades.[9]
Hens build nests and lay and incubate their eggs under the cover of sagebrush. The hen uses grass and forbs between patches of sagebrush for additional cover. During incubation, female Sand Grouse undertake recesses, where they leave the nest to undertake self-maintenance activities, thought these recess activities are typically within 250 m of the nest. [10]
Chicks can walk as soon as they are hatched and are able to fly short distances within two weeks. Within five weeks they are able to fly longer distances.[11]
Populations of sage grouse are in decline due to environment loss and decline of the pristine plains environments it requires to mate. The sage grouse is found in significant numbers within only half of the states comprising its original territories. The Biodiversity Conservation Alliance and other organizations have petitioned to list the grouse under the Endangered Species Act.
In March 2010 the U.S. Fish and Wildlife Service (USFWS) concluded that greater sage-grouse are warranted for protection as "threatened" under the U.S. federal Endangered Species Act (ESA). However the USFWS also concluded that immediate listing was "precluded" by higher listing priorities for other jeopardized species. Thus they designated the species a "Level 8 Candidate" for addition to the list of threatened species at some future date. Their finding is being litigated by groups contending the species should immediately receive protections under the ESA.
The Agricultural Research Service (ARS) of the United States Department of Agriculture (USDA) investigated some of the reasons for the declining sage-grouse population. Researchers observed cattle who share grazing land with the sage-grouse. They found that cattle, after consuming about 40% of the tussocks in between sagebrush bushes, will continue to consume the tussocks growing underneath the sagebrush, thereby destroying the nesting habitat for the sage-grouse.[12] In order to preserve the population of sage-grouse, ranchers can monitor the rate at which cattle consume the tussocks in between sagebrush bushes. Once cattle have consumed around 40% of the tussocks in between bushes, researchers ask that ranchers move their cattle to new grazing trail.
GPS trackers show that sage grouse congregate in small areas with certain resources, rather than being widely spread.[13]
US federal conservation plans have been met with lawsuits from wildlife organizations.[14]
On December 6, 2018, according to the New York Times:[15]
The Trump administration on Thursday published documents detailing its plan to roll back Obama-era protections for the vast habitat of the greater sage grouse, a chickenlike bird that roams across nearly 11 million acres [4.5 million hectares] in 10 oil-rich Western states.
The earlier proposal to protect the bird, whose waning numbers have brought it close to endangerment, was put forth under the Interior Department in 2015 and set out to ban or sharply reduce oil and gas drilling in 10.7 million acres [4.3 million hectares] of its habitat.
The Trump plan, by contrast, would limit the grouse’s protected habitat to just 1.8 million acres [730,000 hectares], essentially opening up 9 million acres [3.6 million hectares] of land to drilling, mining and other development.
The sagehen is the mascot of the Pomona-Pitzer Sagehens, the joint athletics program for Pomona College and Pitzer College, two of the Claremont Colleges.[16][17]
Sage-grouse are grouse belonging to the bird genus Centrocercus. The genus includes two species: the Gunnison grouse (Centrocercus minimus) and the greater sage-grouse (Centrocercus urophasianus). These birds are distributed throughout large portions of the north-central and Western United States, as well as the Canadian provinces of Alberta and Saskatchewan. The International Union for Conservation of Nature classified the C. minimus species as endangered in 2020 and C. urophasianus as near threatened in 2016.
