Endangered and Threatened Wildlife and Plants; Determination for the Gunnison Sage-grouse as a Threatened or Endangered Species

DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[DOCKET NO. FWS-R6-ES-2009-0080]

MO 92210-0-0008

Endangered and Threatened Wildlife and Plants; Determination for the Gunnison Sage-grouse as a Threatened or Endangered Species

AGENCY:

Fish and Wildlife Service, Interior.

ACTION:

Notice of the results of a status review.

SUMMARY:

We, the U.S. Fish and Wildlife Service (Service), announce our 12-month finding on whether to list the Gunnison sage-grouse (

Centrocercus minimus

) as threatened or endangered under the Endangered Species Act of 1973, as amended (Act). After reviewing the best available scientific and commercial information, we find that the species is warranted for listing. Currently, however, listing the Gunnison sage-grouse is precluded by higher priority actions to amend the Lists of Endangered and Threatened Wildlife and Plants. Upon publication of this 12-month finding, we will add the Gunnison sage-grouse to our candidate species list. We will develop a proposed rule to list this species as our priorities allow. We will make any determination on critical habitat during development of the proposed listing rule.

DATES:

The determination announced in this document was made on September 28, 2010.

ADDRESSES:

This finding is available on the Internet at

http://www.regulations.gov

at Docket Number FWS-R6-ES-2009-0080. Supporting documentation we used in preparing this finding is available for public inspection, by appointment, during normal business hours at the U.S. Fish and Wildlife Service, Western Colorado Ecological Services Field Office, U.S. Fish and Wildlife Service, 764 Horizon Drive, Building B, Grand Junction, Colorado 81506-3946. Please submit any new information, materials, comments, or questions concerning this finding to the above address.

FOR FURTHER INFORMATION CONTACT:

Allan Pfister, Western Colorado Supervisor (see

ADDRESSES

section); by telephone at (970) 243-2778 ext. 29; or by facsimile at (970) 245-6933. If you use a telecommunications device for the deaf (TDD), please call the Federal Information Relay Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION:

Background

Section 4(b)(3)(A) of the Act (16 U.S.C. 1531

et seq.

) requires that, for any petition to revise the Federal Lists of Threatened and Endangered Wildlife and Plants that contains substantial scientific or commercial information that listing a species may be warranted, we make a finding within 12 months of the date of receipt of the petition. In this finding, we determine whether the petitioned action is: (a) Not warranted, (b) warranted, or (c) warranted, but immediate proposal of a regulation implementing the petitioned action is precluded by other pending proposals to determine whether species are threatened or endangered, and expeditious progress is being made to add or remove qualified species from the Federal Lists of Endangered and Threatened Wildlife and Plants. Section 4(b)(3)(C) of the Act requires that we treat a petition for which the requested action is found to be warranted but precluded as though resubmitted on the date of such finding, that is, requiring a subsequent finding to be made within 12 months. We must publish these 12-month findings in the

Federal Register

.

Previous Federal Actions

On January 18, 2000, we designated the Gunnison sage-grouse as a candidate species under the Act, with a listing priority number of 5. However, Candidate Notices of Review (CNOR) are only published annually; therefore, the

Federal Register

notice regarding this decision was not published until December 28, 2000 (65 FR 82310). Candidate species are plants and animals for which the Service has sufficient information on their biological status and threats to propose them as endangered or threatened under the Act, but for which the development of a proposed listing regulation is precluded by other higher priority listing activities. A listing priority of 5 is assigned to species with high magnitude threats that are non-imminent.

On January 26, 2000, American Lands Alliance, Biodiversity Legal Foundation, and others petitioned the Service to list the Gunnison sage-grouse (Webb 2000, pp. 94-95). In 2003, the U.S. District Court ruled that the species was designated as a candidate by the Service prior to receipt of the petition, and that the determination that a species should be on the candidate list is equivalent to a 12-month finding (

American Lands Alliance

v.

Gale A. Norton

, C.A. No. 00-2339, D. D.C.). Therefore, we did not need to respond to the petition.

In the 2003 CNOR, we elevated the listing priority number for Gunnison sage-grouse from 5 to 2 (69 FR 24876; May 4, 2004), as the imminence of the threats had increased. In the subsequent CNOR (70 FR 24870; May 11, 2005), we maintained the listing priority number for Gunnison sage-grouse as a 2. A listing priority number of 2 is assigned to species with high magnitude threats that are imminent.

Plaintiffs amended their complaint in May 2004, to allege that the Service's warranted but precluded finding and decision not to emergency list the Gunnison sage-grouse were in violation of the Act. The parties filed a stipulated settlement agreement with the court on November 14, 2005, which included a provision that the Service would make a proposed listing determination by March 31, 2006. On March 28, 2006, the plaintiffs agreed to a one-week extension (April 7, 2006) for this determination.

In April 2005, the Colorado Division of Wildlife (CDOW) applied to the Service for an Enhancement of Survival Permit for the Gunnison sage-grouse pursuant to section 10(a)(1)(A) of the Act. The permit application included a proposed Candidate Conservation Agreement with Assurances (CCAA) between CDOW and the Service. The standard that a CCAA must meet is that the “benefits of the conservation measures implemented under a CCAA, when combined with those benefits that would be achieved if it is assumed that conservation measures were also to be implemented on other necessary properties, would preclude or remove any need to list the species.” The CCAA, the permit application, and the Environmental Assessment were made available for public comment on July 6, 2005 (70 FR 38977). The CCAA and Environmental Assessment were finalized in October 2006, and the associated permit was issued on October 23, 2006. Landowners with eligible property in southwestern Colorado who wish to participate can voluntarily sign up under the CCAA and associated permit through a Certificate of Inclusion by providing habitat protection or enhancement measures on their lands. If the Gunnison sage-grouse is listed under the Act, the permit authorizes incidental take of Gunnison sage-grouse due to otherwise lawful activities in accordance with the terms of the CCAA (e.g., crop cultivation, crop harvesting, livestock grazing, farm equipment operation, commercial/residential development, etc.), as long as the participating landowner is performing

activities identified in the Certificate of Inclusion. Four Certificates of Inclusion have been issued by the CDOW and Service to private landowners to date.

On April 11, 2006, the Service determined that listing the Gunnison sage-grouse as a threatened or endangered species was not warranted and published the final listing determination in the

Federal Register

on April 18, 2006 (71 FR 19954). Consequently, we removed Gunnison sage-grouse from the candidate species list at the time of the final listing determination. On November 14, 2006, Plaintiffs (the County of San Miguel, Colorado; Center for Biological Diversity; WildEarth Guardians; Public Employees for Environmental Responsibility; National Audubon Society; The Larch Company; Center for Native Ecosystems; Sinapu; Sagebrush Sea Campaign; Black Canyon Audubon Society; and Sheep Mountain Alliance) filed a Complaint for Declaratory and Injunctive relief, pursuant to the Act, and on October 24, 2007, filed an amended Complaint for Declaratory and Injunctive relief, alleging that the 12-month finding on the Gunnison sage-grouse violated the Act. On August 18, 2009, a stipulated settlement agreement and Order was filed with the court, with a June 30, 2010, date by which the Service shall submit to the

Federal Register

a 12-month finding, pursuant to 16 U.S.C. § 1533(b)(3)(B), that listing the Gunnison sage-grouse under the Act is (a) warranted; (b) not warranted; or (c) warranted but precluded by higher priority listing actions. We published a notice of intent to conduct a status review of Gunnison sage-grouse on November 23, 2009 (74 Fr 61100). The Court approved an extension of the June 30, 2010, deadline for the 12-month finding to September 15, 2010.

Additional Special Status Considerations

The Gunnison sage-grouse has an International Union for Conservation of Nature (IUCN) Red List Category of “endangered” (Birdlife International 2009). NatureServe currently ranks the Gunnison sage-grouse as G1—Critically Imperiled (Nature Serve 2010, entire). The Gunnison sage-grouse is on the National Audubon Society's WatchList 2007 Red Category which is “for species that are declining rapidly or have very small populations or limited ranges, and face major conservation threats.”

Biology and Ecology of Gunnison Sage-grouse

Gunnison Sage-grouse Species Description

Sage-grouse are the largest grouse in North America. Sage-grouse (both greater and Gunnison) are most easily identified by their large size, dark brown color, distinctive black bellies, long pointed tails, and association with sagebrush habitats. They are dimorphic in size, with females being smaller. Both sexes have yellow-green eye combs, which are less prominent in females. Sage-grouse are known for their elaborate mating ritual where males congregate on strutting grounds called leks and “dance” to attract a mate. During the breeding season, males have conspicuous filoplumes (specialized erectile feathers on the neck), and exhibit yellow-green apteria (fleshy bare patches of skin) on their breasts (Schroeder

et al.

1999, p. 2, 18). Gunnison sage-grouse are smaller in size, have more white barring in their tail feathers, and have more filoplumes than greater sage-grouse.

Since Gunnison and greater sage-grouse were only recognized as separate species in 2000, the vast majority of the research relative to the biology and management of the two species has been conducted on greater sage-grouse. Gunnison sage-grouse and greater sage-grouse have similar life histories and habitat requirements (Young 1994, p. 44). In this finding, we use information specific to the Gunnison sage-grouse where available but still apply scientific management principles found relevant for greater sage-grouse to Gunnison sage-grouse management needs and strategies, a practice followed by the wildlife agencies that have responsibility for management of both species and their habitat.

Taxonomy

Gunnison sage-grouse and greater sage-grouse are members of the Phasianidae family. For many years, sage-grouse were considered a single species. Gunnison sage-grouse (

Centrocercus minimus

) were identified as a distinct species based on morphological (Hupp and Braun 1991, pp. 257-259; Young

et al

. 2000, pp. 447-448), genetic (Kahn

et al

. 1999, pp. 820-821; Oyler-McCance

et al

. 1999, pp. 1460-1462), and behavioral (Barber 1991, pp. 6-9; Young 1994; Young

et al

. 2000, p. 449-451) differences and geographical isolation (Young

et al

. 2000, pp. 447-451). Based on these differences, the American Ornithologist's Union (2000, pp. 849-850) accepted the Gunnison sage-grouse as a distinct species. The current ranges of the two species do not overlap (Schroeder

et al.

2004, p. 369). Due to the several lines of evidence separating the two species cited above, we determined that the best available information indicates that the Gunnison sage-grouse is a valid taxonomic species and a listable entity under the Act.

Life History Characteristics

Gunnison and greater sage-grouse depend on a variety of shrub-steppe habitats throughout their life cycle and are considered obligate users of several species of sagebrush (Patterson 1952, p. 42; Braun

et al.

1976, p. 168; Schroeder

et al.

1999, pp. 4-5; Connelly

et al.

2000a, pp. 970-972; Connelly

et al.

2004, p. 4-1, Miller

et al.

in press, p. 10). Dietary requirements of the two species are also similar, being composed of nearly 100 percent sagebrush in the winter, and forbs and insects as well as sagebrush in the remainder of the year (Wallestad

et al.

1975, p. 21; Schroeder

et al.

1999, p. 5; Young

et al.

2000, p. 452). Gunnison and greater sage-grouse do not possess muscular gizzards and, therefore, lack the ability to grind and digest seeds (Leach and Hensley 1954, p. 389).

In addition to serving as a primary year-round food source, sagebrush also provides cover for nests (Connelly

et al.

2000a, pp. 970-971). Thus, sage-grouse distribution is strongly correlated with the distribution of sagebrush habitats (Schroeder

et al.

2004, p. 364). Connelly

et al.

(2000a, p. 970-972) segregated habitat requirements into four seasons: (1) breeding (2) summer - late brood-rearing (3) fall and (4) winter. Depending on habitat availability and proximity, some seasonal habitats may be indistinguishable. The Gunnison Sage-grouse Rangewide Steering Committee (GSRSC) (2005, p. 27-31) segregated habitat requirements into three seasons: (1) breeding (2) summer-late fall and (3) winter. For purposes of this finding, the seasons referenced in GSRSC (2005) are used because that publication deals specifically with Gunnison sage-grouse.

Sage-grouse exhibit strong site fidelity (loyalty to a particular area) to seasonal habitats, which includes breeding, nesting, brood rearing, and wintering areas, even when the area is no longer of value (Connelly

et al.

2004, p. 3-1). Adult sage-grouse rarely switch among these habitats once they have been selected, limiting their adaptability to changes. Sage-grouse distribution is associated with sagebrush (Schroeder

et al

. 2004 p. 364), although sagebrush is more widely distributed than sage-grouse because sagebrush does not

always provide suitable habitat due to fragmentation and degradation (Schroeder

et al.

2004, pp. 369, 372). Very little of the extant sagebrush in North America is undisturbed, with up to 50 to 60 percent having altered understories (forb and grass vegetative composition under the sagebrush) or having been lost to direct conversion (Knick

et al.

2003, p. 612 and references therein). Mapping altered and depleted understories is challenging, particularly in semi-arid regions, so maps depicting only sagebrush as a dominant cover type are deceptive in their reflection of habitat quality and, therefore, use by sage-grouse (Knick

et al.

2003, p. 616 and references therein). As such, variations in the quality of sagebrush habitats for sage-grouse (from either abiotic or anthropogenic events) are better reflected by sage-grouse distribution and densities, rather than by broad geographic scale maps of the distribution of sagebrush.

Sage-grouse exhibit a polygamous mating system where a male mates with several females. Males perform courtship displays and defend their leks (Patterson 1952, p. 83). Lek displaying occurs from mid-March through late May, depending on elevation (Rogers 1964, p. 21; Young

et al.

2000, p. 448). Numerous researchers have observed that a relatively small number of dominant males account for the majority of copulations on each lek (Schroeder

et al.

1999, p. 8). However, an average of 45.9 percent (range 14.3 to 54.5 percent) of genetically identified males in a population fathered offspring in a given year (Bush 2009, p. 106). This more recent work suggests that males and females likely engage in off-lek copulations. Males do not incubate eggs or assist in chick rearing.

Lek sites can be located on areas of bare soil, wind-swept ridges, exposed knolls, low sagebrush, meadows, and other relatively open sites with good visibility and low vegetation structure (Connelly

et al.

1981, pp. 153-154; Gates 1985, pp. 219-221; Klott and Lindzey 1989, pp. 276-277; Connelly

et al.

2004, pp. 3-7 and references therein). In addition, leks are usually located on flat to gently sloping areas of less than 15 percent grade (Patterson 1952, p. 83; Giezentanner and Clark 1974, p. 218; Wallestad 1975, p. 17; Autenrieth 1981, p. 13). Leks are often surrounded by denser shrub-steppe cover, which is used for escape, and thermal and feeding cover. Leks can be formed opportunistically at any appropriate site within or adjacent to nesting habitat (Connelly

et al.

2000a, p. 970). Lek habitat availability is not considered to be a limiting factor for sage-grouse (Schroeder 1997, p. 939). However, adult male sage-grouse demonstrate strong yearly fidelity to lek sites (Patterson 1952, p. 91; Dalke 1963

et al.

, pp. 817-818), and some Gunnison sage-grouse leks have been used since the 1950s (Rogers 1964, pp. 35-40).

The pre-laying period is from late-March to April. Pre-laying habitats for sage-grouse need to provide a diversity of vegetation including forbs that are rich in calcium, phosphorous, and protein to meet the nutritional needs of females during the egg development period (Barnett and Crawford 1994, p. 117; Connelly

et al.

2000a, p. 970). During the pre-egg laying period, female sage-grouse select forbs that generally have higher amounts of calcium and crude protein than sagebrush (Barnett and Crawford 1994, p. 117).

Nesting occurs from mid-April to June. Average earliest nest initiation was April 30, and the average latest nest initiation was May 19, in the western portion of the Gunnison Basin (Childers 2009, p. 3). Radio-tracked Gunnison sage-grouse nest an average of 4.3 kilometers (km ) (2.7 miles (mi)) from the lek nearest to their capture site, with almost half nesting within 3 km (2 mi) of their capture site (Young 1994, p. 37). Nest sites are selected independent of lek locations, but the reverse is not true (Bradbury

et al

. 1989, p. 22; Wakkinen

et al

. 1992, p. 382). Thus, leks are indicative of nesting habitat. Eighty-seven percent of all Gunnison sage-grouse nests were located less than 6 km (4 mi) from the lek of capture (Apa 2004, p. 21). While earlier studies indicated that most greater sage-grouse hens nest within 3 km (2 mi) of a lek, more recent research indicated that many hens actually move much further from leks to nest based on nesting habitat quality (Connelly

et al.

2004, p. 4-4). Female greater sage-grouse have been documented to travel more than 20 km (13 mi) to their nest site after mating (Connelly

et al.

2000a, p. 970). Female Gunnison sage-grouse exhibit strong fidelity to nesting locations (Young 1994, p. 42; Lyon 2000, p. 20, Connelly

et al.

2004, p. 4-5; Holloran and Anderson 2005, p. 747). The degree of fidelity to a specific nesting area appears to diminish if the female's first nest attempt in that area was unsuccessful (Young 1994, p. 42). However, there is no statistical indication that movement to new nesting areas results in increased nesting success (Connelly

et al.

2004, p. 3-6; Holloran and Anderson 2005, p. 748).

Gunnison sage-grouse typically select nest sites under sagebrush cover with some forb and grass cover (Young 1994, p. 38), and successful nests were found in higher shrub density and greater forb and grass cover than unsuccessful nests (Young 1994, p. 39). The understory of productive sage-grouse nesting areas contains native grasses and forbs, with horizontal and vertical structural diversity that provides an insect prey base, herbaceous forage for pre-laying and nesting hens, and cover for the hen while she is incubating (Schroeder

et al.

1999, p. 11; Connelly

et al.

2000a, p. 971; Connelly

et al.

2004, pp. 4-5-4-8). Shrub canopy and grass cover provide concealment for sage-grouse nests and young, and are critical for reproductive success (Barnett and Crawford 1994, pp. 116-117; Gregg

et al.

1994, pp. 164-165; DeLong

et al.

1995, pp. 90-91; Connelly

et al.

2004, p. 4-4). Few herbaceous plants are growing in April when nesting begins, so residual herbaceous cover from the previous growing season is critical for nest concealment in most areas (Connelly

et al.

2000a, p. 977).

Nesting success for Gunnison sage-grouse is highest in areas where forb and grass covers are found below a sagebrush canopy cover of 15 to 30 percent (Young

et al.

2000, p. 451). These numbers are comparable to those reported for the greater sage-grouse (Connelly

et al.

2000a, p. 971). Nest success for greater sage-grouse is greatest where grass cover is present (Connelly

et al.

2000a, p. 971). Because of the similarities between these two species, we believe that increased nest success in areas of forb and grass cover below the appropriate sagebrush canopy cover is likely the case for Gunnison sage-grouse as well.

Mean clutch size for Gunnison sage-grouse is 6.8 ± 0.7 eggs (Young 1994, p. 37). The mean clutch size for Gunnison sage-grouse in the Gunnison Basin was 6.3, with 94 percent of eggs in successful nests hatching (Childers 2009, p. 3). Despite average clutch sizes of 7 eggs (Connelly

et al.

in press, p. 15), little evidence exists that populations of sage-grouse produce large annual surpluses (Connelly

et al.

in press, p. 15, 24). The inability of sage-grouse to produce large annual surpluses limits their ability to respond under favorable environmental conditions to make up for population declines. Re-nesting rates following the loss of the original nest appear very low in Gunnison sage-grouse, with one study reporting re-nesting rates of 4.8 percent (Young 1994, p. 37). Only one instance of re-nesting was observed over a 5-year period during which a total of 91 nesting Gunnison sage-grouse hens were monitored (Childers 2009, p. 3).

Most sage-grouse eggs hatch in June, with a peak between June 10 and June

20 (GSRSC, 2005, p. 24). Chicks are precocial (mobile upon hatching) and leave the nest with the hen shortly after hatching. Forbs and insects are essential nutritional components for sage-grouse chicks (Klebenow and Gray 1968, pp. 81-83; Peterson 1970, pp. 149-151; Johnson and Boyce 1991, p. 90; Connelly

et al.

2004, p. 3-3). Therefore, early brood-rearing habitat for females with chicks must provide adequate cover adjacent to areas rich in forbs and insects to assure chick survival during this period (Connelly

et al.

2000, p. 971; Connelly

et al.

2004, p. 4-11). Gunnison sage-grouse chick dietary requirements of insects and forbs also are expected to be similar to greater sage-grouse and other grouse species (Apa 2005, pers. comm.).

The availability of food and cover are key factors that affect chick and juvenile survival. During the first 3 weeks after hatching, insects are the primary food of chicks (Patterson 1952, p. 201; Klebenow and Gray 1968, p. 81; Peterson 1970, pp. 150-151; Johnson and Boyce 1990, pp. 90-91; Johnson and Boyce 1991, p. 92; Drut

et al.

1994b, p. 93; Pyle and Crawford 1996, p. 320; Fischer

et al.

1996a, p. 194). Diets of 4- to 8-week-old greater sage-grouse chicks were found to have more plant material as the chicks matured (Peterson 1970, p. 151). Succulent forbs are predominant in the diet until chicks exceed 3 months of age, at which time sagebrush becomes a major dietary component (Klebenow 1969, pp. 665-656; Connelly and Markham 1983, pp. 171-173; Fischer

et al.

1996b, p. 871; Schroeder

et al.

1999, p. 5).

Early brood-rearing habitat is found close to nest sites (Connelly

et al.

2000a, p. 971), although individual females with broods may move large distances (Connelly 1982, as cited in Connelly

et al.

2000a, p. 971). Young (1994, pp. 41-42) found that Gunnison sage-grouse with broods used areas with lower slopes than nesting areas, high grass and forb cover, and relatively low sagebrush cover and density. Broods frequently used the edges of hay meadows, but were often flushed from areas found in interfaces of wet meadows and habitats providing more cover, such as sagebrush or willow-alder (

Salix-Alnus

).

By late summer and into the early fall, individuals become more social, and flocks are more concentrated (Patterson 1952, p. 187). Intermixing of broods and flocks of adult birds is common, and the birds move from riparian areas to sagebrush-dominated landscapes that continue to provide green forbs. During this period, Gunnison sage-grouse can be observed in atypical habitat such as agricultural fields (Commons 1997, pp. 79-81). However, broods in the Gunnison Basin typically do not use hay meadows further away than 50 meters (m) (165 feet (ft)) of the edge of sagebrush stands (Colorado Sage Grouse Working Group (CSGWG) 1997, p. 13).

As fall approaches, sage-grouse move from riparian to upland areas and start to shift to a winter diet (GSRSC 2005, p. 25). Movements to winter ranges are slow and meandering (Connelly

et al.

1988, p. 119). The extent of movement varies with severity of winter weather, topography, and vegetation cover. Sage-grouse may travel short distances or many miles between seasonal ranges. In response to severe winters, Gunnison sage-grouse move as far as 27 km (17 mi) (Root 2002, p. 14). Flock size in winter is variable (15 to 100+), and flocks frequently consist of a single sex (Beck 1977, p. 21).

From late autumn through early spring, greater and Gunnison sage-grouse diet is almost exclusively sagebrush (Rasmussen and Griner 1938, p. 855; Batterson and Morse 1948, p. 20; Patterson 1952, pp. 197-198; Wallestad

et al.

1975, pp. 628-629; Young

et al.

2000, p. 452). Many species of sagebrush can be consumed (Remington and Braun 1985, pp. 1056-1057; Welch

et al.

1988, p. 276, 1991; Myers 1992, p. 55). Characteristics of sage-grouse winter habitats are also similar through the range of both species (Connelly

et al.

2000a, p. 972). In winter, Gunnison sage-grouse are restricted to areas of 15 to 30 percent sagebrush cover, similar to the greater sage-grouse (Connelly

et al.

2000a, p. 972; Young

et al.

2000, p. 451). However, they may also use areas with more deciduous shrubs during the winter (Young

et al.

2000, p. 451).

Sagebrush stand selection in winter is influenced by snow depth (Patterson 1952, pp. 188-189; Connelly 1982 as cited in Connelly

et al.

2000a, p. 980) and in some areas, topography (Beck 1977, p. 22; Crawford

et al.

2004, p. 5). Winter areas are typically characterized by canopy cover greater than 25 percent and sagebrush greater than 30 to 41 cm (12 to 16 in) tall (Shoenberg 1982, p. 40) associated with drainages, ridges, or southwest aspects with slopes less than 15 percent (Beck 1977, p. 22). Lower flat areas and shorter sagebrush along ridge tops provide roosting areas. In extreme winter conditions, greater sage-grouse will spend nights and portions of the day burrowed into “snow burrows” (Back

et al.

1987, p. 488).

Hupp and Braun (1989, p. 825) found that most Gunnison sage-grouse feeding activity in the winter occurred in drainages and on slopes with south or west aspects in the Gunnison Basin. During a severe winter in the Gunnison Basin in 1984, less than 10 percent of the sagebrush was exposed above the snow and available to sage-grouse (Hupp, 1987, pp. 45-46). In these conditions, the tall and vigorous sagebrush typical in drainages was an especially important food source.

Sage-grouse typically live between 3 and 6 years, but individuals up to 9 years of age have been recorded in the wild (Connelly

et al.

2004, p. 3-12). Adult female Gunnison sage-grouse apparent survival rates from April through September averaged 57 percent, and adult male survival averaged 45 percent (Childers 2009, p. 2). From October through March, adult female Gunnison sage-grouse apparent survival rates averaged 79 percent, and adult male survival averaged 96 percent (Childers 2009, p.2). In one study, Gunnison sage-grouse survival from April 2002 through March 2003 was 48 (± 7) percent for males and 57 (± 7) percent for females (Apa 2004, p. 22). Preliminary results from the Gunnison and San Miguel populations indicate potential important temporal and spatial variation in demographic parameters, with apparent annual adult survival rates ranging from approximately 65 to 80 percent (CDOW 2009a, p. 8). Gunnison sage-grouse female survival in small isolated populations was 52 (± 8) percent, compared to 71 (± 11) percent survival in the Gunnison Basin, the only population with greater than 500 individuals (Apa 2004, p. 22). Higher adult survival has been observed in a lower elevation and warmer area (Dry Creek Basin of the San Miguel population - 90 percent) than in a higher elevation and colder, snowier, area (Miramonte portion of the San Miguel population - 65 percent) (CDOW 2009a, p.8). Other factors affecting survival rates include climatic differences between years and age (Zablan 1993, pp. 5-6).

Apparent chick survival from hatch to the beginning of fall (30 September) averaged 7 percent over a 5-year period in the western portion of the Gunnison Basin (Childers 2009, pp. 4-6). Apparent chick survival to 90 days of age has ranged from approximately 15 to 30 percent in the Gunnison Basin, with no juvenile recruitment observed over several years in the San Miguel population (CDOW 2009a, p. 8). Based on a review of many field studies, juvenile survival rates range from 7 to 60 percent (Connelly

et al.

2004, p. 3-12). The variation in juvenile survival rates may be associated with sex, weather, harvest rates (no harvesting of Gunnison sage-grouse is currently permitted), age of brood female (broods with adult females have higher

survival), and with habitat quality (rates decrease in poor habitats) (Schroeder

et al.

1999, p. 14; Connelly

et al

., in press, p. 20).

Greater sage-grouse require large, interconnected expanses of sagebrush with healthy, native understories (Patterson 1952, p. 9; Knick

et al

. 2003, p. 623; Connelly

et al.

2004, pp. 4-15; Connelly

et al.

in press, p. 10; Pyke in press, p. 7; Wisdom

et al.

in press, p. 4). However, little information is available regarding minimum sagebrush patch sizes required to support populations of greater or Gunnison sage-grouse. Gunnison sage-grouse have not been observed to undertake the large seasonal and annual movements observed in greater sage-grouse. However, movements of up to 24 km (15 mi) have been observed in individual Gunnison sage-grouse in the Gunnison Basin population only (Phillips 2010, pers. comm.).

Sage-grouse typically occupy large expanses of sagebrush-dominated habitats composed of a diversity of sagebrush species and subspecies. Use of other habitats intermixed with sagebrush, such as riparian meadows, agricultural lands, steppe dominated by native grasses and forbs, scrub willow (

Salix spp.

), and sagebrush habitats with some conifer or quaking aspen (

Populus tremuloides

), is not uncommon (Connelly

et al

2004, p. 4-18 and references therein). Sage-grouse have been observed using human-altered habitats throughout their range.

However, the use of non-sagebrush habitats by sage-grouse is dependent on the presence of sagebrush habitats in close proximity (Connelly

et a.lal

2004, p. 4-18 and references therein).

Historic Range and Distribution of Gunnison Sage-grouse

Based on historical records, museum specimens, and potential habitat distribution, Gunnison sage-grouse historically occurred in southwestern Colorado, northwestern New Mexico, northeastern Arizona, and southeastern Utah (Schroeder

et al.

2004, pp. 370-371). Accounts of Gunnison sage-grouse in Kansas and Oklahoma, as suggested by Young

et al.

(2000, pp. 446-447), are not supported with museum specimens, and Schroeder

et al.

(2004, p. 371) found inconsistencies with the historical records and the sagebrush habitat currently available in those areas. Applegate (2001, p. 241) found that none of the sagebrush species closely associated with sage-grouse occurred in Kansas. He attributed historical, anecdotal reports as mistaken locations or misidentification of lesser prairie chickens. For these reasons, southwestern Kansas and western Oklahoma are not considered within the historic range of Gunnison sage-grouse (Schroeder

et al.

2004, p. 371).

The GSRSC (2005) modified the historic range from Schroeder

et al.

(2004), based on more complete information on historic and current habitat and the distribution of the species (GSRSC 2005, pp. 34-35). Based on this information, the maximum Gunnison sage-grouse historical (presettlement) range is estimated to have been 55,350 square kilometers (km

2

) (21,370 square miles (mi

2

)) (GSRSC 2005, p. 32). To be clear, only a portion of the historical range would have been occupied at any one time, while all of the current range is considered occupied. Also, we do not know what portion of the historical range was simultaneously occupied, or what the total population was.

Much of what was once Gunnison sage-grouse sagebrush habitat was already lost prior to 1958. A qualitative decrease in sagebrush was attributed to overgrazing from the 1870s until about 1934 (Rogers 1964, p. 13). Additional adverse effects occurred as a result of newer range management techniques implemented to support livestock by the Bureau of Land Management (BLM), Soil Conservation Service, and U.S. Forest Service (USFS) (Rogers 1964, p. 13). In the 1950s, large areas of sagebrush within the range of Gunnison sage-grouse were eradicated by herbicide spraying or burning (Rogers 1964, pp. 12-13, 22-23, 26).

About 155,673 hectares (ha) (384,676 ac) of sagebrush habitat was lost from 1958 to 1993 within southwestern Colorado (Oyler-McCance

et al.

2001, p. 327). Sagebrush loss was lower in the Gunnison Basin (11 percent) compared to all other areas in southwestern Colorado (28 percent) (Oyler-McCance

et al.

2001, p. 328). Considerable fragmentation of sagebrush vegetation was also quantitatively documented during that same time period (Oyler-McCance

et al.

2001, p. 329). Sage-grouse habitat in southwestern Colorado (the majority of the range of Gunnison sage-grouse) has been more severely impacted than sagebrush habitat elsewhere in Colorado.

The Colorado River Storage Project (CRSP) resulted in construction of three reservoirs within the Gunnison Basin in the mid-late 1960s (Blue Mesa and Morrow) and mid-1970s (Crystal). Several projects associated with CRSP were constructed in this same general timeframe to provide additional water storage and resulted in the loss of an unquantified, but likely small, amount of sagebrush habitat. These projects provide water storage and, to a certain extent, facilitate agricultural activities that maintain the fragmentation and habitat lost historically throughout the range of Gunnison sage-grouse.

In summary, a substantial amount of sagebrush habitat within the range of the Gunnison sage-grouse had been lost prior to 1960. The majority of the remaining habitat is highly fragmented, although to a lesser extent in the Gunnison Basin than in the remainder of the species habitat.

Current Distribution and Population Estimates

The historic and current geographic ranges of Gunnison's and greater sage-grouse were quantitatively analyzed to determine the species' response to habitat loss and detrimental land uses (Wisdom

et al.

, in press, 2009, entire). A broad spectrum of biotic, abiotic, and anthropogenic conditions were found to be significantly different between extirpated and occupied ranges (Wisdom

et al

., in press, 2009, p. 1.). Sagebrush area is one of the best landscape predictors of sage-grouse persistence (Wisdom

et al

., in press, 2009, p. 17 and references therein). Because of the loss and fragmentation of habitat within its range, no expansive, contiguous areas that could be considered strongholds (areas of occupied range where the risk of extirpation appears low) are evident for Gunnison sage-grouse (Wisdom

et al

., in press, 2009, p. 24). We do not know the minimum amount of sagebrush habitat needed by Gunnison sage-grouse to ensure long-term persistence. However, based on Wisdom

et al

., in press, we do know that landscapes containing large and contiguous sagebrush patches and sagebrush patches in close proximity increase the likelihood of sage-grouse persistence.

Gunnison sage-grouse currently occur in seven widely scattered and isolated populations in Colorado and Utah, occu2pying 3,795 km

2

(1,511mi

2

) (GSRSC 2005, pp. 36-37; CDOW 2009b, p. 1). The seven populations are Gunnison Basin, San Miguel Basin, Monticello-Dove Creek, Pi

non Mesa, Crawford, Cerro Summit-Cimarron-Sims Mesa, and Poncha Pass (Figure 1). A comparative summary of the land ownership and recent population estimates among these seven populations is presented in Table 1 and Table 2, respectively. Population trends over the last nine years indicate that six of the populations are in decline. The Gunnison Basin population, while showing variation over the years, has been relatively stable through the period (CDOW 2009a p. 2). Six of the

populations are very small and fragmented (all with less than 40,500 ha (100,000 acres) of habitat likely used by grouse and less than 50 males counted on leks) (CDOW 2009a, p. 5). The San Miguel population, the second largest, comprises six fragmented subpopulations.

Figure 1. Locations of Current Gunnison Sage-grouse Populations.

EP28se10.000

Table 1. Percent surface ownership of total Gunnison sage-grouse occupied

a

habitat (from GSRSC

b

2005, pp. D-3-D-6; CDOW

c

2009b, p. 1)

Population

hectares

acres

Gunnison Sage-grouse Occupied Habitat Management and Ownership

BLM

d

%

NPS

e

%

USFS

f

%

CDOW

%

CO State Land Board

%

State of UT

%

Private

%

Gunnison Basin

239,953

592,936

51

2

14

3

<1

0

29

San Miguel Basin

41,022

101,368

36

g

0

1

11

3

g

0

49

g

Monticello-Dove Creek (Combined)

45,275

111,877

7

0

0

3

0

<1

90

Dove Creek

16,706

41,282

11

0

0

8

0

0

81

Monticello

28,569

70,595

4

0

0

0

0

1

95

Piñon Mesa

15,744

38,904

28

0

2

19

0

0

51

Cerro Summit-Cimarron-Sims Mesa

15,039

37,161

13

<1

0

11

0

0

76

Crawford

14,170

35,015

63

12

0

2

0

0

23

Poncha Pass

8,262

20,415

48

0

26

0

2

0

23

Rangewide

379,464

937,676

42

2

10

5

<1

<1

41

a

Occupied Gunnison sage-grouse habitat is defined as areas of suitable habitat known to be used by Gunnison sage-grouse within the last 10 years from the date of mapping, and areas of suitable habitat contiguous with areas of known use, which have no barriers to grouse movement from known use areas (GSRSC 2005, p. 54).

b

Gunnison Sage-grouse Rangewide Steering Committee

c

Colorado Division of Wildlife

d

Bureau of Land Management

e

National Park Service

f

United States Forest Service

g

Estimates reported in San Miguel Basin Gunnison Sage-grouse Conservation Plan (2009 p. 28) vary by up to 2 percent in these categories from those reported here. We consider these differences insignificant.

Table 2. Gunnison Sage-grouse population estimates by year derived from the formula presented in the Gunnison sage-grouse Rangewide Conservation Plan (GSRSC

a

2005, pp. 44-45) applied to high male counts on leks (CDOW

b

2009a, p. 2).

Population

Estimated Population

Year

2001

2002

2003

2004

2005

2006

2007

2008

2009

2010

Gunnison Basin

3,493

3,027

2,453

2,443

4,700

5,205

4,616

3,669

3,817

3,655

San Miguel Basin

392

383

250

255

334

378

324

216

162

123

Monticello-Dove Creek (Combined)

363

270

186

162

196

191

245

245

191

n/a

c

Monticello

231

172

147

152

162

118

216

216

182

n/a

c

Dove Creek

132

98

39

10

34

74

29

29

10

44

Piñon Mesa

152

132

123

142

167

152

123

108

78

74

Cerro Summit-Cimarron-Sims Mesa

59

39

29

39

25

49

34

10

39

5

Crawford

137

206

118

128

191

201

113

103

78

20

Poncha Pass

25

44

34

39

44

44

25

25

20

15

Totals

4,621

4,101

3,194

3,208

5,656

6,220

5,480

4,376

4,386

n/a

c

a

Gunnison Sage-grouse Rangewide Steering Committee

b

Colorado Division of Wildlife

c

2010 lek count data for the Monticello group was not available at the time of publication

Gunnison Basin Population

- The Gunnison Basin is an intermontane basin that includes parts of Gunnison and Saguache Counties, Colorado. The current Gunnison Basin population is distributed across approximately 240,000 ha (593,000 ac), roughly centered on the town of Gunnison. Elevations in the area range from 2,300 to 2,900 m (7,500 to 9,500 ft). Approximately 70 percent of the land area is managed by Federal agencies (67 percent) and CDOW (3 percent), and the remaining 30 percent comprises primarily private lands. Big sagebrush (

Artemesia tridentata

) dominates the upland vegetation and has a highly variable growth form depending on local site conditions. In 2009, 83 leks were surveyed for breeding activity in the Gunnison Basin, and 42 of these leks were active (at least two males in attendance during at least two of four 10-day count periods), 6 inactive

(inactive for at least 5 consecutive years), 9 historic (inactive for at least 10 consecutive years), and 26 were of unknown status (variability in counts resulted in lek not meeting requirements for active, inactive, or historic) (CDOW 2009d, pp. 28-30). Approximately 45 percent of leks in the Gunnison Basin occur on private land and 55 percent on public land, primarily BLM (GSRSC 2005, p. 75). The 2010 population estimate for the Gunnison Basin was 3,655 (CDOW 2010a, p. 2). Rogers (1964, p. 20) stated that Gunnison County was one of five counties containing the majority of sage-grouse in Colorado in 1961. The vast majority (87 percent) of Gunnison sage-grouse are now found only in the Gunnison Basin population.

San Miguel Basin Population

- The San Miguel Basin population is in Montrose and San Miguel Counties in Colorado, and is composed of six small subpopulations using different areas—(Dry Creek Basin, Hamilton Mesa, Miramonte Reservoir, Gurley Reservoir, Beaver Mesa, and Iron Springs) occupying a total of approximately 41,000 ha (101,000 ac). Some of these six areas are used year-round by sage-grouse, and others are used seasonally. The overall acreage figure for this population is heavily skewed by the large percentage (approximately 62 percent) of land in the Dry Creek Basin (San Miguel Basin Gunnison Sage-grouse Working Group 2009, p. 28). The Dry Creek Basin area contains some of the poorest habitat and smallest grouse populations in the San Miguel population (San Miguel Basin Gunnison sage-grouse Conservation Plan 2009, pp. 28, 36). Gunnison sage-grouse in the San Miguel Basin move widely between these areas (Apa 2004, p. 29; Stiver and Gibson 2005, p. 12). The area encompassed by this population is believed to have once served as critical migration corridors between populations to the north (Cerro Summit-Cimarron-Sims Mesa) and to the south (Monticello-Dove Creek) (San Miguel Basin Gunnison Sage-grouse Working Group 2009, p. 9).

Sagebrush habitat in the Dry Creek Basin area is patchily distributed, and the understory is either lacking in grass and forb diversity or nonexistent. Where irrigation is possible, private lands in the southeast portion of Dry Creek Basin are cultivated. Sagebrush habitat on private land has been heavily thinned or removed entirely (GSRSC 2005, p. 96). Gunnison sage-grouse use the Hamilton Mesa area (1,940 ha (4,800 ac)) in the summer, but use of Hamilton Mesa during other seasons is unknown. Gunnison sage-grouse occupy approximately 4,700 ha (11,600 ac) around Miramonte Reservoir (GSRSC 2005, p. 96). Sagebrush stands there are generally contiguous with a mixed grass and forb understory. Occupied habitat at the Gurley Reservoir area (3,305 ha (7,500 ac)) is heavily fragmented by urban development, and the understory is a mixed grass and forb community. Farming attempts in the early 20th century led to the removal of much of the sagebrush, although agricultural activities are now restricted primarily to the seasonally irrigated crops (hay meadows), and sagebrush has reestablished in most of the failed pastures. However, grazing pressure and competition from introduced grasses have kept the overall sagebrush representation low (GSRSC 2005, pp. 96-97). Sagebrush stands in the Iron Springs and Beaver Mesa areas (2,590 ha and 3,560 ha (6,400 ac and 8,800 ac respectively)) are contiguous with a mixed grass understory. The Beaver Mesa area has numerous scattered patches of oakbrush (

Quercus gambelii

). Rogers (1964, p. 9) reported that all big sagebrush-dominated habitats in San Miguel and Montrose Counties were historically used by Gunnison sage-grouse.

The 2010 population estimate for the entire San Miguel Basin was 123 individuals on nine leks (CDOW 20010, p. 3). With the exception of 2007, CDOW has been translocating Gunnison sage-grouse from the Gunnison Basin to Dry Creek Basin on a yearly basis since the spring of 2006 (CDOW 2009a, p. 133). In the spring of 2006, six individuals were released near the Desert Lek. An additional two individuals were released in the fall. Nine individuals were translocated in the spring of 2008. An additional 30 individuals were translocated in the fall of 2009. A 40 to 50 percent mortality rate has been observed within the first year after release, compared to an average annual mortality rate of approximately 20 percent for radiomarked adult sage-grouse (CDOWa 2009, p. 9).

Monticello-Dove Creek Population

- This population is divided into two disjunct subpopulations of Gunnison sage-grouse. Currently, the largest group is near the town of Monticello, in San Juan County, Utah. Gunnison sage-grouse in this subpopulation inhabit a broad plateau on the northeast side of the Abajo Mountains, with fragmented patches of sagebrush interspersed with large grass pastures and agricultural fields. The Utah Division of Wildlife Resources (UDWR) estimated population numbers between 583 and 1,050 individuals in 1972 and between 178 and 308 individuals in 2002 (UDWR 2009, 29.21 p. 1). The UDWR estimates that Gunnison sage-grouse currently occupy about 24,000 ha (60,000 ac) in the Monticello area. The 2009 population estimate for Monticello was 182 individuals with three active and one inactive leks (UDWR 2009, p. 5).

The Dove Creek subpoulation is located primarily in western Dolores County, Colorado, north and west of Dove Creek, although a small portion of occupied habitat extends north into San Miguel County. Habitat north of Dove Creek is characterized as mountain shrub habitat, dominated by oakbrush interspersed with sagebrush. The area west of Dove Creek is dominated by sagebrush, but the habitat is highly fragmented. Lek counts in the Dove Creek area were over 50 males in 1999, suggesting a population of about 245 birds, but declined to 2 males in 2009 (CDOW 2009a, p. 71), suggesting a population of 10 birds. A new lek was found in 2010, and the 2010 population estimate was 44 individuals on 2 leks (CDOW 2010, p. 1). Low sagebrush canopy cover, as well as low grass height, exacerbated by drought, may have led to nest failure and subsequent population declines (Connelly

et al.

2000a, p. 974; Apa 2004, p. 30). Rogers (1964, p. 9) reported that all sagebrush-dominated habitats in Dolores and Montezuma Counties within Gunnison sage-grouse range in Colorado were historically used by Gunnison sage-grouse.

Pi

non Mesa Population

- The Pi

non Mesa population occurs on the northwest end of the Uncompahgre Plateau in Mesa County, about 35 km (22 mi) southwest of Grand Junction, Colorado. The 2010 population estimate for Pi

non Mesa was 74 (CDOW 2010, p. 2). Of the ten known leks, only four were active in 2009 (CDOW, 2009a, p. 3). The Pi

non Mesa area may have additional leks, but the high percentage of private land, a lack of roads, and heavy snow cover during spring make locating additional leks difficult. Gunnison sage-grouse likely occurred historically in all suitable sagebrush habitat in the Pi

non Mesa area, including the Dominguez Canyon area of the Uncompaghre Plateau, southeast of Pi

non Mesa proper (Rogers 1964, p. 114). Their current distribution has been substantially reduced from historic levels to 15,744 ha (38,904 ac) (GSRSC 2005, p. 87).

Crawford Population

- The Crawford population of Gunnison sage-grouse is in Montrose County, Colorado, about 13 km (8 mi) southwest of the town of Crawford and north of the Gunnison River. Basin big sagebrush (

Artemisia tridentata tridentata

) and black

sagebrush (

A. nova

) dominate the mid-elevation uplands (GSRSC 2005, p. 62). The 2010 population estimate for Crawford was 20 individuals (CDOW 2010, p. 1) in 14,170 ha (35,015 ac) of occupied habitat. Four active leks are currently in the Crawford population on BLM lands in sagebrush habitat adjacent to an 11-km (7-mi) stretch of road. This area represents the largest contiguous sagebrush-dominated habitat within the Crawford boundary (GSRSC 2005, p. 64).

Cerro Summit-Cimarron-Sims Mesa Population

- This population is divided into two geographically separated subpopulations, both in Montrose County, Colorado. The Cerro Summit-Cimarron subpopulation is centered about 24 km (15 mi) east of Montrose. The habitat consists of 15,039 ha (37,161 ac) of patches of sagebrush habitat fragmented by oakbrush and irrigated pastures. Five leks are currently known in the Cerro Summit-Cimarron group, but only one individual was observed on one lek in 2010 resulting in a population estimate of 5 individuals for the population (CDOW 2010, p. 1). Rogers (1964, p. 115) noted a small population of sage-grouse in the Cimarron River drainage, but did not report population numbers. He noted that lek counts at Cerro Summit in 1959 listed four individuals.

The Sims Mesa area, about 11 km (7 mi) south of Montrose, consists of small patches of sagebrush that are heavily fragmented by pinyon-juniper, residential and recreational development, and agriculture. The one known lek in Sims Mesa has lacked Gunnison sage-grouse attendance for the last six years, which indicates this population is likely extirpated (CDOW 2009a, p. 43). In 2000, the CDOW translocated six Gunnison sage-grouse from the Gunnison Basin to Sims Mesa (Nehring and Apa 2000, p. 12). Rogers (1964, p. 95) recorded eight males in a lek count at Sims Mesa in 1960. We do not know if sage-grouse move between the Cerro Summit-Cimarron and Sims Mesa subpopulations.

Poncha Pass Population

- The Poncha Pass Gunnison sage-grouse population is located in Saguache County, approximately 16 km (10 mi) northwest of Villa Grove, Colorado. This population was established through the reintroduction of 30 birds from the Gunnison Basin in 1971 and 1972 during efforts to reintroduce the species to the San Luis Valley (GSRSC 2005, p. 94). The known population distribution is in 8,262 ha (20,415 ac) of sagebrush habitat from the summit of Poncha Pass extending south for about 13 km (8 mi) on either side of U.S. Highway 285. Sagebrush in this area is continuous with little fragmentation; sagebrush habitat quality throughout the area is adequate to support the species (Nehring and Apa 2000 p. 25). San Luis Creek runs through the area, providing a year-round water source and lush, wet meadow riparian habitat for brood-rearing.

A high male count of 3 males was made in 2010 (CDOW 2009a, p. 121), resulting in an estimated population size of 15 for the Poncha Pass population (CDOW 2010, p. 3). The only current lek is located on BLM-administered land. In 1992, a CDOW effort to simplify hunting restrictions inadvertently opened the Poncha Pass area to sage-grouse hunting, and at least 30 grouse were harvested from this population. Due to declining population numbers since the 1992 hunt, CDOW translocated 24 additional birds from the Gunnison Basin (Nehring and Apa 2000, p. 11). In 2001 and 2002, an additional 20 and 7 birds, respectively, were moved to Poncha Pass by the CDOW (GSRSC 2005, p. 94). Translocated females have bred successfully (Apa 2004, pers. comm.), and display activity resumed on the historic lek in spring 2001.

Summary of Information Pertaining to the Five Factors

Section 4 of the Act (16 U.S.C. 1533), and implementing regulations (50 CFR 424), set forth procedures for adding species to the Federal Lists of Endangered and Threatened Wildlife and Plants. Under section 4(a)(1) of the Act, a species may be determined to be endangered or threatened based on any of the following five factors: (1) The present or threatened destruction, modification, or curtailment of its habitat or range; (2) overutilization for commercial, recreational, scientific, or educational purposes; (3) disease or predation; (4) the inadequacy of existing regulatory mechanisms; or (5) other natural or manmade factors affecting its continued existence. In making this finding, information pertaining to the Gunnison sage-grouse, in relation to the five factors provided in section 4(a)(1) of the Act, is discussed below.

In considering what factors might constitute threats to a species, we must look beyond the exposure of the species to a factor to evaluate whether the species may respond to the factor in a way that causes actual impacts to the species. If there is exposure to a factor and the species responds negatively, the factor may be a threat and we attempt to determine how significant a threat it is. The threat is significant if it drives, or contributes to, the risk of extinction of the species such that the species warrants listing as endangered or threatened as those terms are defined in the Act.

The Gunnison Basin contains 87 percent of the current rangewide Gunnison sage-grouse population and 62 percent of the area occupied by the species. The remaining six populations cumulatively and individually have substantially smaller population sizes and occupy substantially less habitat than the Gunnison Basin population (see Table 2).

A. The Present or Threatened Destruction, Modification, or Curtailment of Its Habitat or Range

Sagebrush habitats within the range of Gunnison sage-grouse are becoming increasingly fragmented as a result of various changes in land uses and the expansion in the density and distribution of invasive plant species (Oyler-McCance

et al.

2001, pp. 329-330; Schroeder

et al.

2004, p. 372). Habitat fragmentation is the separation or splitting apart of previously contiguous, functional habitat components of a species. Fragmentation can result from direct habitat losses that leave the remaining habitat in non-contiguous patches, or from alteration of habitat areas that render the altered patches unusable to a species (i.e., functional habitat loss). Functional habitat losses include disturbances that change a habitat's successional state or remove one or more habitat functions; physical barriers that preclude use of otherwise suitable areas; or activities that prevent animals from using suitable habitat patches due to behavioral avoidance.

A variety of human developments including roads, energy development, and other factors that cause habitat fragmentation have contributed to or been associated with Gunnison and greater sage-grouse extirpation (Wisdom

et al.

in press, p. 18). Based on a quantitative analysis of environmental factors most closely associated with extirpation, no strongholds (areas where the risk of Gunnison sage-grouse extirpation is low) exist (Wisdom

et al.

in press, p. 26). Estimating the impact of habitat fragmentation on sage-grouse is complicated by time lags in response to habitat changes (Garton

et al.,

in press, p. 71), particularly since these relatively long-lived birds will continue to return to altered breeding areas (leks, nesting areas, and early brood-rearing areas) due to strong site fidelity despite nesting or productivity failures (Rogers 1964, pp. 35-40; Wiens and Rotenberry 1985, p. 666; Young 1994, p. 42; Lyon

2000, p. 20, Connelly

et al.

2004, p. 45; Holloran and Anderson 2005, p. 747).

Habitat fragmentation can have an adverse effect on Gunnison sage-grouse populations. Many of the factors that result in fragmentation may be exacerbated by the effects of climate change, which may influence long-term habitat and population trends. The following sections examine factors that can contribute to habitat fragmentation to determine whether they threaten Gunnison sage-grouse and their habitat.

Historic Modification of Gunnison Sage-grouse Habitat

The historic and current distribution of the Gunnison sage-grouse closely matches the distribution of sagebrush. Potential Gunnison sage-grouse range is estimated to have been 5,536,358 ha (13,680,640 ac) historically (GSRSC 2005, p. 32). Gunnison sage-grouse currently occupy approximately 379,464 ha (937,676 ac) in southwestern Colorado and southeastern Utah (CDOW 2009b, p. 1; GSRSC 2005, p. 81), an area that represents approximately 7 percent of the species' potential historic range. The following describes the factors affecting Gunnison sage-grouse and Gunnison sage-grouse habitat within the current range of the species.

The onset of EuroAmerican settlement in the late 1800s resulted in significant alterations to sagebrush ecosystems throughout North America (West and Young 2000, pp. 263-265; Miller

et al

. in press, p. 6), primarily as a result of urbanization, agricultural conversion, and irrigation projects. Areas that supported basin big sagebrush (

Artemisia tridentata

ssp.

tridentata

) were among the first sagebrush community types converted to agriculture because their typical soils and topography are well suited for agriculture (Rogers 1964, p. 13).

In southwestern Colorado, Oyler-McCance

et al.

(2001, p. 326) found that, between 1958 and 1993, 20 percent (155,673 ha (384,676 ac)) of sagebrush was lost in Colorado, and 37 percent of sagebrush plots examined were fragmented. In another analysis, it was estimated that approximately 342,000 ha (845,000 ac) of sagebrush, or 13 percent of the pre-EuroAmerican settlement sagebrush extent, were lost in Colorado, which includes both greater sage-grouse and Gunnison sage-grouse habitat (Boyle and Reeder 2005, p. 3-3). However, the authors noted that the estimate of historic sagebrush area used in their analyses was conservative, possibly resulting in a substantial underestimate of historic sagebrush losses (Boyle and Reeder 2005, p. 3-4). Within the range of Gunnison sage-grouse, the principal areas of sagebrush loss were in the Gunnison Basin, San Miguel Basin, and areas near Dove Creek, Colorado. The authors point out that the rate of loss in the Gunnison Basin was lower than other areas of sagebrush distribution in Colorado. The Gunnison Basin contains approximately 250,000 ha (617,000 ac) of sagebrush; this area partially comprises other habitat types such as riparian areas and patches of non-sagebrush vegetation types, including aspen forest, mixed-conifer forest, and oakbrush (Boyle and Reeder 2005, p. 3-3). Within the portion of the Gunnison Basin currently occupied by Gunnison sage-grouse, 170,000 ha (420,000 ac) comprises exclusively sagebrush vegetation types, as derived from Southwest Regional Gap Analsis Project (SWReGAP) landcover data (multi-season satellite imagery acquired between 1999 and 2001) (USGS 2004, entire).

Conversion to Agriculture

While sage-grouse may forage on agricultural croplands, they avoid landscapes dominated by agriculture (Aldridge

et al.

2008, p. 991). Influences resulting from agricultural activities extend into adjoining sagebrush, and include increased predation and reduced nest success due to predators associated with agriculture (Connelly

et al

. 2004, p. 7-23). Agricultural conversion can provide some limited benefits for sage-grouse. Some crops, such as alfalfa (

Medicago sativa

) and young bean sprouts (

Phaseolus

spp.), are eaten or used for cover by Gunnison sage-grouse (Braun 1998, pers. comm.). However, crop monocultures do not provide adequate year-round food or cover (GSRSC 2005, pp. 22-30).

Current Agriculture in All Gunnison Sage-grouse Population Areas

- The following estimates of land area dedicated to agriculture (including grass/forb pasture) were derived from SWReGAP landcover data (USGS 2004, entire). Habitat conversion to agriculture is most prevalent in the Monticello-Dove Creek population area where approximately 23,220 ha (57,377 ac) or 51 percent of Gunnison sage-grouse occupied range is currently in agricultural production. In the Gunnison Basin, approximately 20,754 ha (51,285 ac) or 9 percent of the occupied range is currently in agricultural production. Approximately 6,287 ha (15,535 ac) or 15 percent of the occupied range in the San Miguel Basin is currently in agricultural production. In the Cerro Summit-Cimarron-Sims Mesa population, approximately 14 percent (5,133 ha (2,077 ac)) of the occupied range is currently in agricultural production. Habitat conversion due to agricultural activities is limited in the Crawford, Pi

non Mesa, and Poncha Pass populations, with 3 percent or less of the occupied range currently in agricultural production in each of the population areas.

Other than in Gunnison County, total area of harvested cropland has declined over the past two decades in all counties within the occupied range of Gunnison sage-grouse (USDA NASS 2010, entire). Information on the amount of land area devoted to cropland was not available for Gunnison County, most likely because the majority of agricultural land use in the county is for hay production. However, total area in hay production has correspondingly declined in Gunnison County over the past two decades (USDA NASS 2009, p. 1). Because of this long-term trend in reduced land area devoted to agriculture, we do not expect a significant amount of Gunnison sage-grouse habitat to be converted to agricultural purposes in the future.

Conservation Reserve Program

- The loss of Gunnison sage-grouse habitat to conversion to agriculture has been mitigated somewhat by the Conservation Reserve Program (CRP). The CRP is administered by the United States Department of Agriculture (USDA) Farm Service Agency (FSA) and provides incentives to agricultural landowners to convert certain cropland to more natural vegetative conditions. Except in emergency situations, CRP-enrolled lands are not hayed or grazed.

Lands within the occupied range of Gunnison sage-grouse enrolled into the CRP are limited to Dolores and San Miguel counties in Colorado, and San Juan County in Utah (USDA FSA 2010, entire). From 2000 to 2008, CRP-enrollment averaged 10,622 ha (26,247 ac) in Dolores County, 1,350 ha (3,337 ac) in San Miguel County, and 14,698 ha (36,320 ac) in San Juan County (USDA FSA 2010, entire). These CRP enrolled areas potentially constitute approximately 56 percent of the Monticello-Dove Creek population and 3 percent of the San Miguel population; however, we are unsure of the proportion of these CRP lands that are within Gunnison sage-grouse habitat. Approximately 735 ha (1,816 ac) of leases on these CRP-enrolled lands expired on September 30, 2009, and 10,431 ha (25,778 ac) are due to expire on September 30, 2010 (UDWR 2009, p. 7).

In San Juan County, Gunnison sage-grouse use CRP lands in proportion to their availability (Lupis

et al.

2006, p. 959). The CRP areas are used by grouse primarily as brood-rearing habitat, but

these areas vary greatly in plant diversity and forb abundance, and generally lack any shrub cover (Lupis

et al.

2006, pp. 959-960). In response to a severe drought, four CRP parcels totaling 1,487 ha (3,674 ac) in San Juan County, UT, were emergency grazed for a duration of 1 to 2 months in the summer of 2002 (Lupis 2006, p. 959).

Largely as a result of agricultural conversion, sagebrush patches in the Monticello-Dove Creek subpopulation area have progressively become smaller and more fragmented, which has limited the amount of available nesting and winter habitat (GSRSC 2005, pp. 82, 276). Overall, the CRP has protected a portion of the Monticello-Dove Creek population from more intensive agricultural use and development. However, the overall value of CRP lands is limited because they largely lack sagebrush cover required by Gunnison sage-sage grouse throughout most of the year. The CRP was renewed under the Food, Conservation, and Energy Act of 2008. A new CRP sign-up for individual landowners is not anticipated until 2012 and the extent to which existing CRP lands will be re-enrolled is unknown (UDWR 2009, p. 4).

Summary of Conversion to Agriculture

Throughout the range of Gunnison sage-grouse there is a declining trend in the amount of land area devoted to agriculture. Therefore, although we expect a large proportion of land currently in agricultural production to remain so indefinitely, we do not expect significant additional, future habitat conversion to agriculture within the range of Gunnison sage-grouse. The loss of sagebrush habitat from 1958 to 1993 was estimated to be approximately 20 percent throughout the range of Gunnison sage-grouse (Oyler-McCance

et al.

2001, p. 326). The exception is the Monticello-Dove Creek population where more than half of the occupied range is currently in agriculture or other land uses incompatible with Gunnison sage-grouse conservation. This habitat loss is being somewhat mitigated by the current enrollment of lands in the CRP. Even so, this relative scarcity of sagebrush cover indicates a high risk of population extirpation (Wisdom

et al.

in press, p. 19) for this population. Because of its limited extent, we do not consider the conversion of sagebrush habitats to agriculture alone to be a current or future significant threat to Gunnison sage-grouse and its habitat. However, we recognize lands already converted to agriculture are located throughout all Gunnison sage-grouse populations and are, therefore, contributing to the fragmentation of remaining habitat.

Water Development

Water Development in All Population Areas

- Irrigation projects have resulted in loss of sage-grouse habitat (Braun 1998, p. 6). Reservoir development in the Gunnison Basin flooded 3,700 ha (9,200 ac), or 1.5 percent of likely sage-grouse habitat (McCall 2005, pers. comm.). Three other reservoirs inundated approximately 2 percent of habitat in the San Miguel Basin population area (Garner 2005, pers. comm.). We are unaware of any plans for additional reservoir construction. Because of the small amount of Gunnison sage-grouse habitat lost to water development projects and the unlikelihood of future projects, we do not consider water development alone to be a current or future significant threat to the Gunnison sage-grouse. However, we expect these existing reservoirs to be maintained indefinitely, thus acting as another source of fragmentation of Gunnison sage-grouse habitat.

Residential Development

Human population growth in the rural Rocky Mountains is driven by the availability of natural amenities, recreational opportunities, aesthetically desirable settings, grandiose viewscapes, and perceived remoteness (Riebsame 1996, p. 396, 402; Theobald 1996, p. 408; Gosnell and Travis 2005, pp. 192-197; Mitchell

et al.

2002, p. 6; Hansen

et al

. 2005, pp. 1899-1901). This human population growth is occurring throughout much of the range of Gunnison sage-grouse. The human population in all counties within the range of Gunnison sage-grouse averaged a 70 percent increase since 1980 (Colorado Department of Local Affairs (CDOLA) 2009a, pp. 2-3). The year 2050 projected human population for the Gunnison River basin (an area that encompasses the majority of the current range of Gunnison sage-grouse) is expected to be 2.3 times greater than the 2005 population (CWCB 2009, p. 15). The population of Gunnison County, an area that supports over 80 percent of all Gunnison sage-grouse, is predicted to more than double to approximately 31,100 residents by 2050 (CWCB 2009, p. 53).

The increase in residential and commercial development associated with the expanding human population is different from historic land use patterns (Theobald 2001, p. 548). The allocation of land for resource-based activities such as agriculture and livestock production is decreasing as the relative economic importance of these activities diminishes (Theobald 1996, p. 413; Sammons 1998, p. 32; Gosnell and Travis 2005, pp. 191-192). Currently, agribusiness occupations constitute approximately 3 percent of the total job base in Gunnison County (CDOLAb 2009, p. 4). Recent conversion of farm and ranch lands to housing development has been significant in Colorado (Odell and Knight 2001, p. 1144). Many large private ranches in the Rocky Mountains, including the Gunnison Basin, are being subdivided into both high-density subdivisions and larger, scattered ranchettes with lots typically greater than 14 ha (35 ac), which encompass a large, isolated house (Riebsame 1996, p. 399; Theobald 1996, p. 408).

The resulting pattern of residential development is less associated with existing town sites or existing subdivisions, and is increasingly exurban in nature (Theobald

et al

. 1996, pp. 408, 415; Theobald 2001, p. 546). Exurban development is described as low-density growth outside of urban and suburban areas (Clark

et al.

2009, p. 178; Theobald 2004, p.140) with less than one housing unit per 1 ha (2.5 ac) (Theobald 2003, p. 1627; Theobald 2004, p. 139). The resulting pattern is one of increased residential lot size and the diffuse scattering of residential lots in previously rural areas with a premium placed on adjacency to federal lands and isolated open spaces (Riebsame

et al.

1996, p. 396, 398; Theobald 1996, pp. 413, 417; Theobald 2001, p. 546; Brown

et al.

2005, p. 1858). The residential subdivision that results from exurban development causes landscape fragmentation (Gosnell and Travis 2005, p. 196) primarily through the accumulation of roads, buildings, (Theobald 1996, p. 410; Mitchell

et al

. 2002, p. 3) and other associated infrastructure such as power lines, and pipelines. In the East River Valley of Gunnison County, residential development in the early 1990s increased road density by 17 percent (Theobald

et al

. 1996, p. 410). The habitat fragmentation resulting from this development pattern is especially detrimental to Gunnison sage-grouse because of their dependence on large areas of contiguous sagebrush (Patterson 1952, p. 48; Connelly

et al

. 2004, p. 4- 1; Connelly

et al

. in press a, p. 10; Wisdom

et al

. in press, p. 4).

Residential Development in the Gunnison Basin Population Area

- Nearly three quarters (approximately 71 percent) of the Gunnison Basin population of Gunnison sage-grouse occurs within Gunnison County, with the remainder occurring in Saguache

County. Within Gunnison County, approximately 30 percent of the occupied range of this species occurs on private lands. We performed a GIS analysis of parcel ownership data that was focused on the spatial and temporal pattern of human development within occupied Gunnison sage-grouse habitat. Some of our analyses were limited to the portion of occupied habitat in Gunnison County because parcel data was only available for Gunnison County and not for Saguache County. The cumulative number of human developments has increased dramatically in Gunnison County, especially since the early 1970s (USFWS 2010a, p. 1). The number of new developments averaged approximately 70 per year from the late 1800s to 1969, increasing to approximately 450 per year from 1970 to 2008 (USFWS 2010a, pp. 2-5). Furthermore, there has been an increasing trend toward development away from major roadways (primary and secondary paved roads) into areas that had previously undergone very limited development in occupied Gunnison sage-grouse habitat (USFWS 2010b, p. 7). Between 1889 and 1968, there were approximately 51 human developments located more than 1.6 km (1 mi) from a major road in currently occupied Gunnison sage-grouse habitat. Between 1969 and 2008, this number increased to approximately 476 developments (USFWS 2010b, p. 7).

In order to assess the impacts of existing residential development, we relied on two evaluations of Gunnison sage-grouse response and habitat availability in relation to development. The first was a landscape-scale spatial model predicting Gunnison sage-grouse nesting probability in the Gunnison Basin (Aldridge

et al

. 2010, entire). The model indicated that Gunnison sage-grouse select nest sites in areas with moderate shrub cover, and avoid residential development within a radius of 1.5 km (0.9 mi) (Aldridge

et al.

2010, p. 18). The model was applied to the entire Gunnison Basin population area to predict the likelihood of Gunnison sage-grouse nesting based on data from the western portion (Aldridge

et al.

2010, p. 16). We used Aldridge

et al

. (2010)'s radius of 1.5 km (0.9 mi) avoidance distance to calculate the indirect effects likely from the current level of development within occupied Gunnison sage-grouse habitat in Gunnison County. We found that 49 percent of the land area within the range of Gunnison sage-grouse has at least one housing unit within a radius of 1.5 km (0.9 mi) (USFWS 2010b, p. 7). This residential development is currently compromising the likelihood of use by Gunnison sage-grouse for nesting habitat in these areas.

Furthermore, since early brood-rearing habitat is often in close proximity to nest sites (Connelly

et al.

2000a, p. 971), the functional loss of nesting habitat is closely linked with the loss of early brood-rearing habitat. Limitations in the quality and quantity of nesting and early brood-rearing habitat are particularly problematic because Gunnison sage-grouse population dynamics are most sensitive during these life-history stages (GSRSC 2005, p. G-15). We recognize that the potential percentages of habitat loss mentioned above, whether direct or functional, will not necessarily correspond to the same percentage loss in sage-grouse numbers. The recent efforts to conserve Gunnison sage-grouse and their habitat within the Basin provide protection for the foreseeable future for several areas of high-quality habitat (see discussion in Factor D). Nonetheless, given the large landscape-level needs of this species, we expect this current level of habitat loss, degradation, and fragmentation, from residential development, as described above, to substantially limit the probability of persistence of Gunnison sage-grouse in the Gunnison Basin.

We also calculated a “lower” development impact scenario using the smaller impact footprint hypothesized by the GSRSC (2005, pp. 160-161). This analysis assumed that residential density in excess of one housing unit per 1.3 km

2

(0.5 mi

2

) could cause declines in Gunnison sage-grouse populations. Within Gunnison County, 18 percent of the land area within the range of Gunnison sage-grouse currently has a residential density greater than one housing unit per 1.3 km

2

(0.5 mi

2

) (USFWS 2010b, p. 8). Therefore, according to the GSRSC estimate of potential residential impacts, human residential densities in the Gunnison Basin population area are such that we expect they are limiting the Gunnison sage-grouse population in at least 18 percent of the population area.

We expect the density and distribution of human residences to expand in the future. Based on our GIS analysis, we estimate that approximately 20,236 ha (50,004 ac) of private lands on approximately 1,190 parcels not subject to conservation easements currently lack human development in occupied Gunnison sage-grouse habitat in Gunnison County (USFWS 2010b, p. 11). These lands are scattered throughout occupied Gunnison sage-grouse habitat in the Gunnison Basin. We used the 20,236 ha (50,004 ac) as an initial basis to assess the potential impacts of future development. A lack of parcel data availability from surrounding counties precluded expanding this analysis beyond Gunnison County; however, the analysis area constitutes 71 percent of the Gunnison Basin population area. Approximately 93 percent of occupied Gunnison sage-grouse habitat in Gunnison County consists of parcels greater than 14.2 ha (35 ac), allowing exemptions from some county land development regulations. Applying a 1.7 percent average annual population increase under a “middle” growth scenario (CWCB 2009, p. 56) and an average 2.29 persons per household (CDOLA 2009b, p. 6) to the 2008 Gunnison County human population estimate results in the potential addition of nearly 7,000 housing units to the county by 2050.

Currently, approximately two-thirds of the human population in Gunnison County occurs within the currently mapped occupied range of Gunnison sage-grouse. Assuming this pattern will continue, two-thirds of the population increase will occur within occupied Gunnison sage-grouse habitat. The above projection could potentially result in the addition of approximately 4,630 housing units and the potential for 25,829 ha (63,824 ac) of new habitat loss, whether direct or functional, on parcels that currently have no development. Based on the estimated area of impact determined by Aldridge

et al

. (2010), this potential functional habitat loss constitutes an additional impact of 15 percent of the current extent of the Gunnison Basin population area (USFWS 2010b, p. 14). When combined with the existing loss, whether direct or functional, of 49 percent of Gunnison sage-grouse nesting habitat, the total amount of habitat subject to the indirect effects of residential development now and in the foreseeable future increases to 64 percent.

Using the same methodology as discussed above, but applying the estimated area of impact determined by GSRSC (2005, p. F-3), results in a future potential functional habitat loss of 9 percent. When combined with the existing loss, whether direct or functional, of 18 percent of Gunnison sage-grouse habitat, an estimated 27 percent of habitat will be functionally lost for Gunnison sage-grouse under this minimum impact scenario. We believe that impacts to Gunnison sage-grouse implicit in even the lower or more conservative estimates of direct and

functional habitat loss are limiting the persistence of the species.

We also anticipate increased housing density in many areas of occupied Gunnison sage-grouse habitat because the anticipated number of new housing units will exceed the number of undeveloped parcels by nearly four times (USFWS 2010b, p. 16). Some of this anticipated development and subsequent functional habitat loss will undoubtedly occur on parcels that currently have existing human development, which could lessen the effects to Gunnison sage-grouse. However, the above calculation of an increase in future housing units is likely an underestimate because it does not take into account the expected increase in second home development (CDOLA 2009b, p. 7), which could increase negative effects to Gunnison sage-grouse. The U.S. Census Bureau only tallies the inhabitants of primary residences in population totals. This methodology results in an underestimate of the population, particularly in amenity communities, because of the increased number of part-time residents inhabiting second homes and vacation homes in these areas (Riebsame 1996, p. 397; Theobald 2001, p. 550, Theobald 2004, p. 143). In Gunnison County, approximately 90 percent of vacant housing units were seasonal-use units (CDOLA 2009c, p. 1). The housing vacancy rate, which is computed by dividing the number of vacant housing units by the total housing units, was 42.5 percent in Gunnison County over the last two decades (CDOLA 2009d, p. 2).

We expect some development to be moderated by the establishment of additional voluntary landowner conservation easements such as those currently facilitated by the CDOW and land trust organizations. While conservation easements can minimize the overall impacts to Gunnison sage-grouse, because less than 5 percent of occupied Gunnison sage-grouse habitat in the Gunnison Basin has been placed in conservation easements to date, we do not expect the amount of land potentially placed in future easements will significantly offset the overall affects of human development.

Our analyses, based on the evaluations of impacts to Gunnison sage-grouse discussed above, result in estimates of existing functional habitat loss of 18 to 49 percent of the Gunnison Basin population area. Future estimates of functional habitat loss result in an increase of 9 to 15 percent, for a cumulative total of 27 and 64 percent loss of the Gunnison Basin population area. We believe that impacts within these ranges limit the persistence of Gunnison sage-grouse.

Residential Development in All Other Population Areas

- In 2004, within the Crawford Population area, approximately 951 ha (2,350 ac), or 7 percent of the occupied Gunnison sage-grouse habitat, was subdivided into 48 parcels ranging in size from 14.2 ha (35 ac) to 28.3 ha (70 ac) (CDOW 2009a, p. 59). Local landowners and the National Park Service (NPS) have ongoing efforts to protect portions of the subdivided area through conservation easements. Residential subdivision continues to occur in the northern part of the Poncha Pass population area, and the CDOW considers this to be the highest priority threat to this population (CDOW 2009a, p. 124). The rate of residential development in the San Miguel Basin population increased between 2005 and 2008 but slowed in 2009 (CDOW 2009a, p. 135). However, a 429 ha (1,057 ac) parcel north of Miramonte Reservoir is currently being developed as a retreat. The CDOW reports that potential impacts to Gunnison sage-grouse resulting from the development may be reduced by possibly placing a portion of the property into a conservation easement and the relocation of a proposed major road to avoid occupied habitat (CDOW 2009a, p. 136). No recent or planned residential developments are known for the Cerro Summit-Cimarron-Sims Mesa population area (CDOW 2009a, p. 45), Monticello-Dove Creek population area (CDOW 2009a, p. 73), or Pi

non Mesa population area (CDOW 2009a, p. 109). The remaining limited amounts of habitat, the fragmented nature of this remaining habitat, and the anticipated increases in exurban development within each of the six smaller populations pose a significant threat to these six populations.

Summary of Residential Development

Because Gunnison sage-grouse are dependent on expansive, contiguous areas of sagebrush habitat to meet their life-history needs, the development patterns described above have resulted in the direct and functional loss of sagebrush habitat and have negatively affected the species by limiting already scarce habitat, especially within the six smaller populations. The collective influences of fragmentation and disturbance from human activities around residences and associated roads reduce the effective habitat around these areas, making them inhospitable to Gunnison sage-grouse (Aldridge

et al.

2010, pp. 24-25; Knick,

et al

. 2009, in press, p. 25 and references therein; Aldridge and Boyce 2007, p.520). Human population growth that results in a dispersed exurban development pattern throughout sagebrush habitats will reduce the likelihood of sage-grouse persistence in these areas. Human populations are increasing throughout the range of Gunnison sage-grouse, and we expect this trend to continue. Given the current demographic trends described above, we believe the rate of residential development in Gunnison sage-grouse habitat will continue at least through 2050, and likely longer. The resulting habitat loss and fragmentation from residential development is a significant threat to Gunnison sage-grouse now and in the foreseeable future.

Fences

The effects of fencing on sage-grouse include direct mortality through collisions, creation of raptor and corvid (Family Corvidae: crows, ravens, magpies, etc.) perch sites, the potential creation of predator corridors along fences (particularly if a road is maintained next to the fence), incursion of exotic species along the fencing corridor, and habitat fragmentation (Call and Maser 1985, p. 22; Braun 1998, p. 145; Connelly

et al

. 2000a, p. 974; Beck

et al

. 2003, p. 211; Knick

et al

. 2003, p. 612; Connelly

et al

. 2004, p. 1-2). Corvids are significant sage-grouse nest predators and were responsible for more than 50 percent of nest predations in Nevada (Coates 2007, pp. 26-30). Sage-grouse frequently fly low and fast across sagebrush flats, and fences can create a collision hazard resulting in direct mortality (Call and Maser 1985, p. 22). Not all fences present the same mortality risk to sage-grouse. Mortality risk appears to be dependent on a combination of factors including design of fencing, landscape topography, and spatial relationship with seasonal habitats (Christiansen 2009). This variability in fence mortality rate and the lack of systematic fence monitoring make it difficult to determine the magnitude of impacts to sage-grouse populations; however, in some cases the level of mortality is likely significant to localized areas within populations. Fences directly kill greater sage grouse (Call and Maser 1985, p. 22; Christiansen 2009, pp. 1-2); we assume that Gunnison sage-grouse are also killed by fences but do not have species-specific data. Although the effects of direct strike mortality on populations are not fully analyzed, fences are ubiquitous across the landscape. Fence collisions continue to be identified as a source of mortality for Gunnison and greater sage-grouse and we expect this source of mortality to continue into the foreseeable future (Braun 1998, p. 145;

Connelly

et al.

2000a, p. 974; Oyler-McCance

et al.

2001, p. 330; Connelly

et al.

2004, p. 7-3).

Fence posts create perching places for raptors and corvids, which may increase their ability to prey on sage-grouse (Braun 1998, p. 145; Oyler-McCance

et al.

2001, p. 330; Connelly

et al.

2004, p. 13-12). We anticipate that the effect on sage-grouse populations through the creation of new raptor perches and predator corridors into sagebrush habitats is similar to that of powerlines discussed below (Braun 1998, p. 145; Connelly

et al.

2004, p. 7-3). Fences and their associated roads also facilitate the spread of invasive plant species that replace sagebrush plants upon which sage-grouse depend (Braun 1998, p. 145; Connelly

et al.

2000a, p. 973; Gelbard and Belnap 2003, p. 421; Connelly

et al.

2004, p. 7-3). Greater sage-grouse avoidance of habitat adjacent to fences, presumably to minimize the risk of predation, effectively results in habitat fragmentation even if the actual habitat is not removed (Braun 1998, p. 145). Because of similarities in behavior and habitat use, we believe the response of Gunnison sage-grouse is similar to that observed in greater sage-grouse.

At least 1,540 km (960 mi) of fence are on BLM lands within the Gunnison Basin (Borthwick 2005a, pers. comm.; BLM 2005a, 2005e) and an unquantified amount of fence on land owned or managed by other landowners. Fences are present within all other Gunnison sage-grouse population areas, but we have no quantitative information on the amount or types of fencing in these areas.

Summary of Fences

While fences contribute to habitat fragmentation and increase the potential for loss of individual grouse through collisions or enhanced predation, such effects have been ongoing since the first agricultural conversions occurred in sage-grouse habitat. We expect that the majority of existing fences will remain on the landscape indefinitely. However, because we do not expect a major increase in the number of fences, particularly 3-wire range fencing, we do not believe fencing, on its own, is a significant threat to Gunnison sage-grouse at the species level. In the smaller Gunnison sage-grouse populations, the impacts of fencing could become another source of mortality that cumulatively affects the species. We also recognize that fences are located throughout all Gunnison sage-grouse populations and are, therefore, contributing to the fragmentation of remaining habitat.

Roads

Impacts from roads may include direct habitat loss, direct mortality, barriers to migration corridors or seasonal habitats, facilitation of predation and spread of invasive vegetative species, and other indirect influences such as noise (Forman and Alexander 1998, pp. 207-231). Greater sage-grouse mortality resulting from collisions with vehicles does occur, but mortalities are typically not monitored or recorded (Patterson 1952, p. 81). Therefore, we are unable to determine the importance of this factor on sage-grouse populations. We have no information on the number of direct mortalities of Gunnison sage-grouse resulting from vehicles or roads; however, because of similarities in their habitat and habitat use, we expect similar effects as those observed in greater sage-grouse. Roads within Gunnison sage-grouse habitats have been shown to impede movement of local populations between the resultant patches, with road avoidance presumably being a behavioral means to limit exposure to predation (Oyler-McCance

et al.

2001, p. 330).

The presence of roads increases human access and resulting disturbance effects in remote areas (Forman and Alexander 1998, p. 221; Forman 2000, p. 35; Connelly

et al.

2004, pp. 7-6 to 7-25). In addition, roads can provide corridors for predators to move into previously unoccupied areas. For some mammalian species known to prey on sage-grouse, such as red fox (

Vulpes vulpes

), raccoons (

Procyon lotor

), and striped skunks (

Mephitis mephitis

), dispersal along roads has greatly increased their distribution (Forman and Alexander 1998, p. 212; Forman 2000, p. 33; Frey and Conover 2006, pp. 1114-1115). Corvids also use linear features such as primary and secondary roads as travel routes, expanding their movements into previously unused regions (Knight and Kawashima 1993, p. 268; Connelly

et al.

2004, p. 12-3). Corvids are significant sage-grouse nest predators and were responsible for more than 50 percent of nest predations in Nevada (Coates 2007, pp. 26-30). Ravens were documented following roads in oil and gas fields while foraging (Bui 2009, p. 31).

The expansion of road networks contributes to exotic plant invasions via introduced road fill, vehicle transport, and road maintenance activities (Forman and Alexander 1998, p. 210; Forman 2000, p. 32; Gelbard and Belnap 2003, p. 426; Knick

et al.

2003, p. 619; Connelly

et al.

2004, p. 7-25). Invasive species are not limited to roadsides, but also encroach into surrounding habitats (Forman and Alexander 1998, p. 210; Forman 2000, p. 33; Gelbard and Belnap 2003, p. 427). In their study of roads on the Colorado Plateau of southern Utah, Gelbard and Belnap (2003, p. 426) found that improving unpaved four-wheel drive roads to paved roads resulted in increased cover of exotic plant species within the interior of adjacent plant communities. This effect was associated with road construction and maintenance activities and vehicle traffic, and not with differences in site characteristics. The incursion of exotic plants into native sagebrush systems can negatively affect Gunnison sage-grouse through habitat losses and conversions (see further discussion below in Invasive Plants).

Additional indirect effects of roads may result from birds' behavioral avoidance of road areas because of noise, visual disturbance, pollutants, and predators moving along a road. The landscape-scale spatial model predicting Gunnison sage-grouse nest site selection showed strong avoidance of areas with high road densities of roads classed 1 through 4 (primary paved highways through primitive roads with 2-wheel drive sedan clearance) within 6.4 km (4 mi)) of nest sites (Aldridge

et al

. 2010 p. 18). The occurrence of Gunnison sage-grouse nest sites also decreased with increased proximity to primary and secondary paved highways (roads classes 1 and 2) (Aldridge

et al.

2010, p. 27). Male greater sage-grouse lek attendance was shown to decline within 3 km (1.9 mi) of a methane well or haul road with traffic volume exceeding one vehicle per day (Holloran 2005, p. 40). Male sage-grouse depend on acoustical signals to attract females to leks (Gibson and Bradbury 1985, p. 82; Gratson 1993, p. 692). If noise interferes with mating displays, and thereby female attendance, younger males will not be drawn to the lek and eventually leks will become inactive (Amstrup and Phillips 1977, p. 26; Braun 1986, pp. 229-230).

In a study on the Pinedale Anticline in Wyoming, greater sage-grouse hens that bred on leks within 3 km (1.9 mi) of roads associated with oil and gas development traveled twice as far to nest as did hens that bred on leks greater than 3 km (1.9 mi) from roads. Nest initiation rates for hens bred on leks close to roads also were lower (65 versus 89 percent), affecting population recruitment (33 versus 44 percent) (Lyon 2000, p. 33; Lyon and Anderson 2003, pp. 489-490). Lyon and Anderson (2003, p. 490) suggested that roads may be the primary impact of oil and gas

development to sage-grouse, due to their persistence and continued use even after drilling and production have ceased. Lek abandonment patterns suggested that daily vehicular traffic along road networks for oil wells can impact greater sage-grouse breeding activities (Braun

et al.

2002, p. 5). We believe the effects of vehicular traffic on Gunnison sage-grouse, regardless of its purpose (e.g., in support of energy production or local commuting and recreation), are similar to those observed in greater sage-grouse.

Aldridge

et al.

(2008, p. 992) did not find road density to be an important factor affecting greater sage-grouse persistence or rangewide patterns in sage-grouse extirpation. However, the authors did not consider the intensity of human use of roads in their modeling efforts. They also indicated that their analyses may have been influenced by inaccuracies in spatial road data sets, particularly for secondary roads (Aldridge

et al.

2008, p. 992). Historic range where greater and Gunnison sage grouse have been extirpated has a 25 percent higher density of roads than occupied range (Wisdom

et al.

in press, p. 18). Wisdom

et al.

's (in press) greater and Gunnison sage-grouse rangewide analysis supports the findings of numerous local studies showing that roads can have both direct and indirect impacts on sage-grouse distribution and individual fitness (reproduction and survival) (e.g., Lyon and Anderson 2003 p. 490 , Aldridge and Boyce 2007, p. 520).

Recreational activities including off highway vehicles (OHV), all-terrain vehicles (ATV), motorcycles, mountain biking and other mechanized methods of travel have been recognized as a potential direct and indirect threat to Gunnison sage-grouse and their habitat (BLM 2009, p. 36). In Colorado, the number of annual off highway vehicle (OHV) registrations has increased from 12,000 in 1991 to 131,000 in 2007 (BLM 2009, p. 37). Four wheel drive, OHV, motorcycle, specialty vehicle, and mountain bike use is expected to increase in the future based on increased population in general and increased population density in the area (as discussed above). Numerous off-road routes and access points to habitat used by Gunnison sage-grouse combined with increasing capabilities for mechanized travel and increased human population further contribute to habitat fragmentation.

Roads in the Gunnison Basin Population Area

- On BLM lands in the Gunnison Basin there are currently 2,050 km (1,274 mi) of roads within 6.4 km (4 mi) of Gunnison sage-grouse leks. Eighty-seven percent of all Gunnison sage-grouse nests were located less than 6.4 km (4 mi) from the lek of capture (Apa 2004, p. 21). However, the BLM proposes to reduce road length to 1,157 km (719 mi) (BLM 2010, p. 147). Currently, 1,349 km (838 mi) of roads accessible to 2-wheel drive passenger cars exist in occupied Gunnison sage-grouse habitat in the Gunnison Basin. Four-wheel-drive vehicle roads, as well as motorcycle, mountain bike, horse, and hiking trails are heavily distributed throughout the range of Gunnison sage-grouse (BLM 2009, pp. 27, 55, 86), which further increases the overall density of roads and their direct and indirect effects on Gunnison sage-grouse. User-created roads and trails have increased since 2004 (BLM 2009, p. 33), although we do not know the percentage increase.

Using a spatial dataset of roads in the Gunnison Basin we performed GIS analyses on the potential effects of roads to Gunnison sage-grouse and their habitat. To account for secondary effects from invasive weed spread from roads (see discussion below in Invasive Plants), we applied a 0.7 km (0.4 mi) buffer (Bradley and Mustard 2006, p. 1146) to all roads in the Gunnison Basin. Results of these analyses indicate that approximately 85 percent of occupied habitat in the Gunnison Basin has an increased likelihood of current or future road-related invasive weed invasion. When all roads in the Gunnison basin are buffered by 6.4 km (4 mi) or 9.6 km (6 mi) to account for nesting avoidance (Aldridge

et al.

2010, p. 27) and secondary effects from mammal and corvid foraging areas (Knick

et al

in press, p. 113), respectively, all occupied habitat in the Gunnison Basin is indirectly affected by roads.

Roads in All Other Population Areas

- Approximately 140 km (87 mi), 243 km (151 mi), and 217 km (135 mi) of roads (all road classes) occur on BLM lands within the Cerro Summit-Cimarron-Sims Mesa, Crawford, and San Miguel Basin population areas, respectively, all of which are managed by the BLM (BLM 2009, p. 71). We do not have information on the total length of roads within the Monticello-Dove Creek, Pi

non Mesa, or Poncha Pass Gunnison sage-grouse populations. However, several maps provided by the BLM show that roads are widespread and common throughout these population areas (BLM 2009, pp. 27, 55, 86).

Summary of Roads

As described above in the ‘Residential Development' section, the human population is increasing throughout the range of Gunnison sage-grouse (CDOLA 2009a, pp. 2-3; CWCB 2009, p. 15), and we have no data indicating this trend will be reversed. Gunnison sage-grouse are dependent on large contiguous and unfragmented landscapes to meet their life-history needs (GSRSC 2005, pp. 26-30), and the existing road density throughout much of the range of Gunnison sage-grouse has negatively affected the species. The collective influences of fragmentation and disturbance from roads reduce the effective habitat around these areas making them inhospitable to sage-grouse (Aldridge

et al.

2010, pp. 24-25; Aldridge and Boyce 2007, p. 520; Knick

et al

. 2009, in press, p. 25 and references therein). Given the current human demographic and economic trends described above in the Residential Development section, we believe that increased road use and increased road construction associated with residential development will continue at least through 2050, and likely longer. The resulting habitat loss, degradation, and fragmentation from roads is a significant threat to Gunnison sage-grouse now and in the foreseeable future.

Powerlines

Powerlines can directly affect greater sage-grouse by posing a collision and electrocution hazard (Braun 1998, pp. 145-146; Connelly

et al.

2000a, p. 974), and can have indirect effects by decreasing lek recruitment (Braun

et al.

2002, p. 10), increasing predation (Connelly

et al.

2004, p. 13-12), fragmenting habitat (Braun 1998, p. 146), and facilitating the invasion of exotic annual plants (Knick

et al.

2003, p. 612; Connelly

et al.

2004, p. 7-25). Proximity to powerlines is associated with Gunnison and greater sage-grouse extirpation (Wisdom

et al.

in press, p. 20). Due to the potential spread of invasive species and predators as a result of powerline construction and maintenance, the impact from a powerline is greater than its actual footprint. We believe the effects to Gunnison sage-grouse are similar to those observed in greater sage-grouse and that the impact from a powerline is greater than its footprint.

In areas where the vegetation is low and the terrain relatively flat, power poles provide an attractive hunting and roosting perch, as well as nesting stratum for many species of raptors and corvids (Steenhof

et al.

1993, p. 27; Connelly

et al.

2000a, p. 974; Manville 2002, p. 7; Vander Haegen

et al.

2002, p. 503). Power poles increase a raptor's range of vision, allow for greater speed during attacks on prey, and serve as

territorial markers (Steenhof

et al.

1993, p. 275; Manville 2002, p. 7). Raptors may actively seek out power poles where natural perches are limited. For example, within 1 year of construction of a 596-km (3-2 -mi) transmission line in southern Idaho and Oregon, raptors and common ravens began nesting on the supporting poles (Steenhof

et al.

1993, p. 275). Within 10 years of construction, 133 pairs of raptors and ravens were nesting along this stretch (Steenhof

et al.

1993, p. 275). Raven counts increased by approximately 200 percent along the Falcon-Gondor transmission line corridor in Nevada within 5 years of construction (Atamian

et al.

2007, p. 2). The increased abundance of raptors and corvids within occupied greater and Gunnison sage-grouse habitats can result in increased predation. Ellis (1985, p. 10) reported that golden eagle (

Aquila chryrsaetos

) predation on sage-grouse on leks increased from 26 to 73 percent of the total predation after completion of a transmission line within 200 meters (m) (220 yards (yd)) of an active sage-grouse lek in northeastern Utah. The lek was eventually abandoned, and Ellis (1985, p. 10) concluded that the presence of the powerline resulted in changes in sage-grouse dispersal patterns and caused fragmentation of the habitat. Golden eagles are found throughout the range of Gunnison sage-grouse (USGS 2010, p. 1), and golden eagles were found to be the dominant species recorded perching on power poles in Utah in Gunnison sage-grouse habitat (Prather and Messmer 2009, p. 12).

Leks within 0.4 km (0.25 mi) of new powerlines constructed for coalbed methane development in the Powder River Basin of Wyoming had significantly lower growth rates, as measured by recruitment of new males onto the lek, compared to leks further from these lines, presumably resulting from increased raptor predation (Braun

et al.

2002, p. 10). Within their analysis area, Connelly

et al.

(2004, p. 7-26) assumed a 5 to 6.9-km (3.1 to 4.3-mi) radius buffer around the perches, based on the average foraging distance of these corvids and raptors, and estimated that the area potentially influenced by additional perches provided by powerlines was 672,644 to 837,390 km

2

(259,641 to 323,317 mi

2

), or 32 to 40 percent of their assessment area. The actual impact on an area would depend on corvid and raptor densities within the area (see discussion in Factor C, below).

The presence of a powerline may fragment sage-grouse habitats even if raptors are not present. The use of otherwise suitable habitat by sage-grouse near powerlines increased as distance from the powerline increased for up to 600 m (660 yd) (Braun 1998, p. 8). Based on those unpublished data, Braun (1998, p. 8) reported that the presence of powerlines may limit Gunnison and greater sage-grouse use within 1 km (0.6 mi) in otherwise suitable habitat. Similar results were recorded for other grouse species. For example, lesser and greater prairie-chickens (

Tympanuchus pallidicinctus

and

T. cupido

, respectively) avoided otherwise suitable habitat near powerlines (Pruett

et al

. 2009, p. 6). Additionally, both species also crossed powerlines less often than nearby roads, which suggests that powerlines are a particularly strong barrier to movement (Pruett

et al

. 2009, p. 6).

Sage-grouse also may avoid powerlines as a result of the electromagnetic fields present (Wisdom

et al.

in press, p. 19). Electromagnetic fields have been demonstrated to alter the behavior, physiology, endocrine systems and immune function in birds, with negative consequences on reproduction and development (Fernie and Reynolds 2005, p. 135). Birds are diverse in their sensitivities to electromagnetic field exposures, with domestic chickens being very sensitive. Many raptor species are less affected (Fernie and Reynolds 2005, p. 135). No studies have been conducted specifically on sage-grouse. Therefore, we do not know the impact to the Gunnison sage-grouse from electromagnetic fields.

Linear corridors through sagebrush habitats can facilitate the spread of invasive species, such as cheatgrass (

Bromus tectorum

) (Gelbard and Belnap 2003, pp. 424-426; Knick

et al.

2003, p. 620; Connelly

et al.

2004, p. 1-2). However, we were unable to find any information regarding the amount of invasive species incursion as a result of powerline construction.

Powerlines in the Gunnison Basin Population Area

- On approximately 121,000 ha (300,000 ac) of BLM land in the Gunnison Basin, 36 rights-of-way for power facilities, power lines, and transmission lines have resulted in the direct loss of 350 ha (858 ac) of occupied habitat (Borthwick 2005b, pers comm.). As discussed above, the impacts of these lines likely extend beyond their actual footprint. We performed a GIS analysis of transmission line location in relation to overall habitat area and Gunnison sage-grouse lek locations in the Gunnison Basin Population area to obtain an estimate of the potential effects in the Basin. Results of these analyses indicate that 68 percent of the Gunnison Basin population area is within 6.9 km (4.3 mi) of an electrical transmission line and is potentially influenced by avian predators utilizing the additional perches provided by transmission lines. This area contains 65 of 109 active leks (60 percent) in the Gunnison Basin population. These results suggest that potential increased predation resulting from transmission lines have the potential to affect a substantial portion of the Gunnison Basin population.

Powerlines in All Other Population Areas

- A transmission line runs through the Dry Creek Basin group in the San Miguel Basin population, and the Beaver Mesa group has two transmission lines. None of the transmission lines in the San Miguel Basin have raptor proofing, nor do most distribution lines (Ferguson 2005, pers comm.) so their use by raptors and corvids as perch sites for hunting and use for nest sites is not discouraged. One major electric transmission line runs east-west in the northern portion of the current range of the Monticello group (San Juan County Gunnison Sage-grouse Working Group (GSWG) 2005, p. 17). Powerlines do not appear to be present in sufficient density to pose a significant threat to Gunnison sage-grouse in the Pi

non Mesa population at this time. One transmission line parallels Highway 92 in the Crawford population, and distribution lines run from there to homes on the periphery of the current range (Ferguson 2005, pers. comm.).

Summary of Powerlines

The projected human population growth rate in and near most Gunnison sage-grouse populations is high (see discussion under Residential Development). As a result, we expect an associated increase in distribution powerlines. Powerlines are likely negatively affecting Gunnison sage-grouse as they contribute to habitat loss and fragmentation and facilitation of predators of Gunnison sage-grouse. Given the current demographic and economic trends described above, we believe that existing powerlines and anticipated distribution of powerlines associated with residential development will continue at least through 2050, and likely longer. The resulting habitat loss and fragmentation from powerlines, and the effects of avian predators that use them, is a significant threat to Gunnison sage-grouse now and in the foreseeable future.

Fire

The nature of historical fire patterns in sagebrush communities, particularly in Wyoming big sagebrush (

Artemisia

tridentata

var.

wyomingensis)

, is not well understood, and a high degree of variability likely occurred (Miller and Eddleman 2000, p. 16; Zouhar

et al

. 2008, p. 154; Baker in press, p. 16). In general, mean fire return intervals in low-lying, xeric (dry) big sagebrush communities range from more than 100 to 350 years, and return intervals decrease from 50 to more than 200 years in more mesic (wet) areas, at higher elevations, during wetter climatic periods, and in locations associated with grasslands (Baker 2006, p. 181; Mensing

et al

. 2006, p. 75; Baker, in press, pp. 15-16; Miller

et al

., in press, p. 35).

Mountain big sagebrush (

Artemisia tridenata

var.

vaseyana)

, the most important and widespread sagebrush species for Gunnison sage-grouse, is killed by fire and can require decades to recover. In nesting and wintering sites, fire causes direct loss of habitat due to reduced cover and forage (Call and Maser 1985, p. 17). While there may be limited instances where burned habitat is beneficial, these gains are lost if alternative sagebrush habitat is not readily available (Woodward 2006, p. 65).

Herbaceous understory vegetation plays a critical role throughout the breeding season as a source of forage and cover for Gunnison sage-grouse females and chicks. The response of herbaceous understory vegetation to fire varies with differences in species composition, pre-burn site condition, fire intensity, and pre- and post-fire patterns of precipitation. In general, when not considering the synergistic effects of invasive species, any beneficial short-term flush of understory grasses and forbs is lost after only a few years and little difference is apparent between burned and unburned sites (Cook

et al

. 1994, p. 298; Fischer

et al

. 1996, p. 196; Crawford 1999, p. 7; Wrobleski 1999, p. 31; Nelle

et al

. 2000, p. 588; Paysen

et al

. 2000, p. 154; Wambolt

et al

. 2001, p. 250).

In addition to altering plant community structure, fires can influence invertebrate food sources (Schroeder

et al

. 1999, p. 5). However, because few studies have been conducted and the results of those available vary, the specific magnitude and duration of the effects of fire on insect communities is still uncertain.

A clear positive response of Gunnison or greater sage-grouse to fire has not been demonstrated (Braun 1998, p. 9). The few studies that have suggested fire may be beneficial for greater sage-grouse were primarily conducted in mesic areas used for brood-rearing (Klebenow 1970, p. 399; Pyle and Crawford 1996, p. 323; Gates 1983,

in

Connelly

et al

. 2000c, p. 90; Sime 1991,

in

Connelly

et al

. 2000a, p. 972). In this type of habitat, small fires may maintain a suitable habitat mosaic by reducing shrub encroachment and encouraging understory growth. However, without available nearby sagebrush cover, the utility of these sites is questionable, especially within the six small Gunnison sage-grouse populations where fire could further degrade and fragment the remaining habitat. Sagebrush loss as a result of fire is likely to have proportionally more individual bird and population level impacts as the amount of sagebrush declines within each of the remaining populations. As the amount of sagebrush remaining within a population declines, the greater the potential impact is to that population.

The invasion of the exotic cheatgrass increases fire frequency within the sagebrush ecosystem (Zouhar

et al

. 2008, p. 41; Miller

et al

. in press, p. 39). Cheatgrass readily invades sagebrush communities, especially disturbed sites, and changes historical fire patterns by providing an abundant and easily ignitable fuel source that facilitates fire spread. While sagebrush is killed by fire and is slow to reestablish, cheatgrass recovers within 1 to 2 years of a fire event (Young and Evans 1978, p. 285). This annual recovery leads to a readily burnable fuel source and ultimately a reoccurring fire cycle that prevents sagebrush reestablishment (Eiswerth

et al

. 2009, p. 1324). The extensive distribution and highly invasive nature of cheatgrass poses substantial increased risk of fire and permanent loss of sagebrush habitat, as areas disturbed by fire are highly susceptible to further invasion and ultimately habitat conversion to an altered community state. For example, Link

et al

. (2006, p. 116) show that risk of fire increases from approximately 46 to 100 percent when ground cover of cheatgrass increases from 12 to 45 percent or more. We do not have a reliable estimate of the amount of area occupied by cheatgrass in the range of Gunnison sage-grouse. However, cheatgrass is found at numerous locations throughout the Gunnison Basin (BLM 2009, p. 60).

Fire in the Gunnison Basin Population Area

- Six prescribed burns have occurred on BLM lands in the Gunnison Basin since 1984, totaling approximately 409 ha (1,010 ac) (BLM 2009, p. 35). The fires created large sagebrush-free areas that were further degraded by poor post-burn livestock management (BLM 2005a, p. 13). As a result, these areas are no longer suitable as Gunnison sage-grouse habitat. Approximately 8,470 ha (20,930 ac) of prescribed burns occurred on Forest Service lands in the Gunnison Basin since 1983 (USFS 2009, p. 1). A small wildfire on BLM lands near Hartman Rocks burned 8 ha (20 ac) in 2007 (BLM 2009, p. 35). The total area of occupied Gunnison sage-grouse habitat burned in recent decades is approximately 8,887 ha (21,960 ac), which constitutes 1.5 percent of the occupied Gunnison sage-grouse habitat area. Cumulatively, this equates to a relatively small amount of habitat burned over a period of nearly three decades. This information suggests that there has not been a demonstrated change in fire cycle in the Gunnison Basin population area to date.

Fire in All Other Population Areas

- Two prescribed burns conducted in 1986 (105 ha (260 ac)) and 1992 (140 ha (350 ac)) on BLM land in the San Miguel Basin on the north side of Dry Creek Basin had negative impacts on sage-grouse. The burns were conducted for big game forage improvement, but the sagebrush died and was largely replaced with weeds (BLM 2005b, pp. 7-8). The Burn Canyon fire in the Dry Creek Basin and Hamilton Mesa areas burned 890 ha (2,200 ac) in 2000. Three fires have occurred in Gunnison sage-grouse habitat since 2004 on lands managed by the BLM in the Crawford, Cerro Summit-Cimarron-Sims Mesa, and San Miguel Basin population areas. There have been no fires since 2004 on lands managed by the BLM within the Monticello-Dove Creek population. Because these fires were mostly small in size, we do not believe they resulted in substantial impacts to Gunnison sage-grouse.

Several wildfires near or within the Pi

non Mesa population area have occurred in the past 20 years. One fire burned a small amount of occupied Gunnison sage-grouse habitat in 1995, and several fires burned in potential Gunnison sage-grouse habitat. Individual burned areas ranged from 3.6 ha (9 ac) to 2,160 ha (5,338 ac). A wildfire in 2009 burned 1,053 ha (2,602 ac), predominantly within vacant or unknown Gunnison sage-grouse habitat (suitable habitat for sage-grouse that is separated from occupied habitats that has not been adequately inventoried, or without recent documentation of grouse presence) near the Pi

non Mesa population. Since 2004, a single 2.8 ha (7 ac) wildfire occurred in the Cerro Summit-Cimarron-Sims Mesa population area, and two prescribed fires, both less than 12 ha (30 ac), were implemented in the San Miguel population area. There was no fire activity within occupied Gunnison sage-grouse habitat in the last two decades in

the Poncha Pass population area (CDOW 2009a, pp. 125-126) or the Monticello-Dove Creek population area (CDOW 2009a, p. 75; UDWR 2009, p. 5).

Summary of Fire

Fires can cause the proliferation of weeds and can degrade suitable sage-grouse habitat, which may not recover to suitable conditions for decades, if at all (Pyke in press, pp. 18-19). Recent fires in Gunnison sage-grouse habitat were mostly small in size and did not result in substantial impacts to Gunnison sage-grouse, and there has been no obvious change in fire cycle in any Gunnison sage-grouse population area. Therefore, we do not consider fire to be a significant threat to Gunnison sage-grouse or its habitat at this time. It is not currently possible to predict the extent or location of future fire events. However, existing data indicates that climate change has the potential to alter changes in the distribution and extent of cheatgrass and sagebrush and associated fire frequencies. The best available data indicates that fire frequency may increase in the foreseeable future (which we consider to be indefinite) because of increases in cover of cheatgrass (Zouhar

et al

. 2008, p. 41; Miller

et al

. in press, p. 39; Whisenant 1990, p. 4) and the projected effects of climate change (Miller

et al.

in press, p. 47; Prevey

et al.

2009, p. 11) (see Invasive Plants and Climate Change discussions below). Therefore, fire is likely to become an increasingly significant threat to the Gunnison sage-grouse in the foreseeable future.

Invasive Plants

For the purposes of this finding, we define invasive plants as those that are not native to an ecosystem and that have a negative impact on Gunnison sage-grouse habitat. Invasive plants alter native plant community structure and composition, productivity, nutrient cycling, and hydrology (Vitousek 1990, p. 7) and may cause declines in native plant populations through competitive exclusion and niche displacement, among other mechanisms (Mooney and Cleland 2001, p. 5446). Invasive plants reduce and, in cases where monocultures of them occur, eliminate vegetation that sage-grouse use for food and cover. Invasive plants do not provide quality sage-grouse habitat. Sage-grouse depend on a variety of native forbs and the insects associated with them for chick survival, and sagebrush, which is used exclusively throughout the winter for food and cover.

Along with replacing or removing vegetation essential to sage-grouse, invasive plants fragment existing sage-grouse habitat. They can create long-term changes in ecosystem processes, such as fire-cycles (see discussion under Fire above) and other disturbance regimes that persist even after an invasive plant is removed (Zouhar

et al

. 2008, p. 33). A variety of nonnative annuals and perennials are invasive to sagebrush ecosystems (Connelly

et al.

2004, pp. 7-107 and 7-108; Zouhar

et al.

2008, p. 144). Cheatgrass is considered most invasive in

Artemisia tridentata

ssp.

wyomingensis

communities (Connelly

et al.

2004, p. 5-9). Other invasive plants found within the range of Gunnison sage-grouse that are reported to take over large areas include: spotted knapweed (

Centaurea maculosa

), Russian knapweed (

Acroptilon repens

), oxeye daisy (

Leucanthemum vulgare)

, yellow toadflax (

Linaria vulgaris)

, and field bindweed (

Convolvulus arvensis)

(BLM 2009, p. 28, 36; Gunnison Watershed Weed Commission (GWWC) 2009, pp. 4-6). Although not yet reported to create large expanses in the range of Gunnison sage-grouse, the following weeds are also known from the species' range and do cover large expanses in other parts of western North America: diffuse knapweed (

Centaurea diffusa

), whitetop (

Cardaria draba

), jointed goatgrass (

Aegilops cylindrica

), and yellow starthistle (

Centaurea solstitialis

). Other invasive plant species present within the range of Gunnison sage-grouse that are problematic yet less likely to overtake large areas include: Canada thistle (

Cirsium arvense)

, musk thistle (

Carduus nutans

), bull thistle (

Cirsium vulgare

), houndstongue (

Cynoglossum officinale

), black henbane (

Hyoscyamus niger),

common tansy

(Tanacetum vulgare

), and absinth wormwood (

Artemisia biennis

) (BLM 2009, p. 28, 36; GWWC 2009, pp. 4-6).

Cheatgrass impacts sagebrush ecosystems by potentially shortening fire intervals from several decades, depending on the type of sagebrush plant community and site productivity, to as low as 3 to 5 years, perpetuating its own persistence and intensifying the role of fire (Whisenant 1990, p. 4). Connelly

et al

. (2004, p. 7-5) suggested that cheatgrass shortens fire intervals to less than 10 years. As discussed under the discussion of climate change below, temperature increases may increase the competitive advantage of cheatgrass in higher elevation areas where its current distribution is limited (Miller

et al.

in press, p. 47). Decreased summer precipitation reduces the competitive advantage of summer perennial grasses, reduces sagebrush cover, and subsequently increases the likelihood of cheatgrass invasion (Bradley 2009, pp. 202-204; Prevey

et al.

2009, p. 11). This could increase the susceptibility of sagebrush areas in Utah and Colorado to cheatgrass invasion (Bradley 2009, p. 204).

A variety of restoration and rehabilitation techniques are used to treat invasive plants, but they can be costly and are mostly unproven and experimental at a large scale. In the last approximately 100 years, no broad-scale cheatgrass eradication method has been developed. Habitat treatments that either disturb the soil surface or deposit a layer of litter increase cheatgrass establishment in the Gunnison Basin when a cheatgrass seed source is present (Sokolow 2005, p. 51). Therefore, researchers recommend using habitat treatment tools, such as brush mowers, with caution and suggest that treated sites should be monitored for increases in cheatgrass emergence (Sokolow 2005, p. 49).

Invasive Plants in the Gunnison Basin Population Area

- Quantifying the total amount of Gunnison sage-grouse habitat impacted by invasive plants is difficult due to differing sampling methodologies, incomplete sampling, inconsistencies in species sampled, and varying interpretations of what constitutes an infestation (Miller

et al.,

in press, p. 19). Cheatgrass has invaded areas in Gunnison sage-grouse range, supplanting sagebrush habitat in some areas. However, we do not have a reliable estimate of the amount of area occupied by cheatgrass in the range of Gunnison sage-grouse. While not ubiquitous, cheatgrass is found at numerous locations throughout the Gunnison Basin (BLM 2009, p. 60). Cheatgrass infestation within a particular area can range from a small number of individuals scattered sparsely throughout a site, to complete or near-complete understory domination of a site. Cheatgrass has increased throughout the Gunnison Basin in the last decade and is becoming increasingly detrimental to sagebrush community types (BLM 2009, p. 7). Currently in the Gunnison Basin, cheatgrass attains site dominance most often along roadways; however, other highly disturbed areas have similar cheatgrass densities. Cheatgrass is currently present in almost every grazing allotment in Gunnison sage-grouse occupied habitat and other invasive plant species, such as Canada thistle, black henbane, spotted knapweed, Russian knapweed, Kochia, bull thistle, musk thistle, oxeye daisy, yellow toadflax and field bindweed, are found in riparian areas and roadsides

throughout the Gunnison Basin (BLM 2009, p. 7).

Although disturbed areas most often contain the highest cheatgrass densities, cheatgrass can readily spread into less disturbed and even undisturbed habitat. A strong indicator for future cheatgrass locations is the proximity to current locations (Bradley and Mustard 2006, p. 1146) as well as summer, annual, and spring precipitation, and winter temperature (Bradley 2009, p. 196). Although we lack the information to make a detailed determination on the actual extent or rate of increase, given its invasive nature, we believe cheatgrass and its negative influence on Gunnison sage-grouse will increase in the Gunnison Basin in the future because of potential exacerbation from climate change interactions and the limited success of broad-scale control efforts.

Invasive Plants in All Other Population Areas

- Cheatgrass is present throughout much of the current range in the San Miguel Basin (BLM 2005c, p. 62005d), but is most abundant in the Dry Creek Basin group (CDOW 2005a, p. 101), which comprises 62 percent of the San Miguel Basin population. It is present in the five Gunnison sage-grouse subpopulations east of Dry Creek Basin although at much lower densities and does not currently pose a serious threat to Gunnison sage-grouse (CDOW 2005a, p. 101). Invasive species are present at low levels in the Monticello group (San Juan County GSGWG 2005, p. 20). However, there is no evidence that they are affecting the population. Cheatgrass dominates 10-15 percent of the sagebrush understory in the current range of the Pi

non Mesa population (Lambeth 2005, pers comm.). It occurs in the lower elevation areas below Pi

non Mesa that were formerly Gunnison sage-grouse range. Cheatgrass invaded two small prescribed burns in or near occupied habitat conducted in 1989 and 1998 (BLM 2005d, p. 62005a), and continues to be a concern with new ground-disturbing projects. Invasive plants, especially cheatgrass, occur primarily along roads, other disturbed areas, and isolated areas of untreated vegetation in the Crawford population. The threat of cheatgrass may be greater to sage-grouse than all other nonnative species combined and could be a significant limiting factor when and if disturbance is used to improve habitat conditions, unless mitigated (BLM 2005c, p. 6). No current estimates of the extent of weed invasion are available (BLM 2005c, p. 82005d).

Within the Pi

non Mesa Gunnison sage-grouse population area, 520 ha (1,284 ac) of BLM lands are currently mapped with cheatgrass as the dominant species (BLM 2009, p. 3). This is not a comprehensive inventory of cheatgrass occurrence, as it only includes areas where cheatgrass dominates the plant community and does not include areas where the species is present at lower densities. Cheatgrass distribution has not been comprehensively mapped for the Monticello-Dove Creek population area; however, cheatgrass is beginning to be assessed on a site-specific and project-level basis. No significant invasive plant occurrences are currently known in the Poncha Pass population area.

Summary of Invasive Plants

Invasive plants negatively impact Gunnison sage-grouse primarily by reducing or eliminating native vegetation that sage-grouse require for food and cover, resulting in habitat loss and fragmentation. Although invasive plants, especially cheatgrass, have affected some Gunnison sage-grouse habitat, the impacts do not currently appear to be threatening individual populations or the species rangewide. However, invasive plants continue to expand their range, facilitated by ground disturbances such as fire, grazing, and human infrastructure. Climate change will likely alter the range of individual invasive species, increasing fragmentation and habitat loss of sagebrush communities. Even with treatments, given the history of invasive plants on the landscape, and our continued inability to control such species, we anticipate invasive plants will persist and will likely continue to spread throughout the range of the species. Therefore, invasive plants and associated fire risk will be on the landscape for the foreseeable future. Although currently not a significant threat to the Gunnison sage-grouse at the species level, we anticipate invasive species to become an increasingly significant threat to the species in the foreseeable future, particularly when considered in conjunction with future climate projections and potential changes in sagebrush plant community composition and dynamics.

Pi

non-Juniper Encroachment

Pi

non-juniper woodlands are a native habitat type dominated by Pi

non pine (

Pinus edulis

) and various juniper species (

Juniperus

spp.) that can encroach upon, infill, and eventually replace sagebrush habitat. Pi

non-juniper extent has increased 10-fold in the Intermountain West since EuroAmerican settlement, causing the loss of many bunchgrass and sagebrush-bunchgrass communities (Miller and Tausch 2001, pp. 15-16). Pi

non-juniper woodlands have also been expanding throughout portions of the range of Gunnison sage-grouse (BLM 2009, pp. 14, 17, 25). Pi

non-juniper expansion has been attributed to the reduced role of fire, the introduction of livestock grazing, increases in global carbon dioxide concentrations, climate change, and natural recovery from past disturbance (Miller and Rose 1999, pp. 555-556; Miller and Tausch 2001, p. 15; Baker, in press, p. 24). In addititon, Gambel oak invasion as a result of fire suppression also has been identified as a potential threat to Gunnison sage-grouse (CDOW 2002, p. 139).

Similar to powerlines, trees provide perches for raptors, and as a consequence, Gunnison sage-grouse avoid areas with Pi

non-juniper (Commons

et al.

1999, p. 239). The number of male Gunnison sage-grouse on leks in southwest Colorado doubled after Pi

non-juniper removal and mechanical treatment of mountain sagebrush and deciduous brush (Commons

et al.

1999, p. 238).

Pi

non-Juniper Encroachment in All Population Areas

- We have no information indicating that the Gunnison Basin population area is currently undergoing significant Pi

non-juniper encroachment. A significant portion of the Pi

non Mesa population is undergoing Pi

non-juniper encroachment. Approximately 9 percent (1,140 ha [3,484 ac]) of occupied habitat in the Pi

non Mesa population area have Pi

non-juniper coverage, while 7 percent (4,414 ha [10,907 ac)] of vacant or unknown and 13 percent (7,239 ha [17,888 ac]) of potential habitat (unoccupied habitats that could be suitable for occupation of sage-grouse if practical restoration were applied) have encroachment (BLM 2009, p. 17).

Some areas on lands managed by the BLM are known to be undergoing Pi

non-juniper invasion. However, the extent of the area affected has not been quantified (BLM 2009, p. 74; BLM 2009, p. 9). Approximately 9 percent of the 1,300 ha (3,200 ac) of the current range in the Crawford population is classified as dominated by Pi

non-juniper (GSRSC 2005, p. 264). However, BLM (2005d, p. 8) estimates that as much as 20 percent of the population area is occupied by Pi

non-juniper. Pi

non and juniper trees have been encroaching in peripheral habitat on Sims Mesa, and to a lesser extent on Cerro Summit, but not to the point where it is a serious threat to the Cerro Summit-Cimarron-Sims Mesa population area (CDOW 2009a, p. 47). Pi

non and juniper trees are reported to be encroaching throughout the current

range in the Monticello group, based on a comparison of historical versus current aerial photos, but no quantification or mapping of the encroachment has occurred (San Juan County GSWG 2005, p. 20). A relatively recent invasion of Pi

non and juniper trees between the Dove Creek and Monticello groups appears to be contributing to their isolation from each other (GSRSC 2005, p. 276).

Within the range of Gunnison sage-grouse, approximately 5,341 ha (13,197 ac) of Pi

non-juniper have been treated with various methods designed to remove Pi

non and juniper trees since 2005, and nearly half of which occurred in the Pi

non Mesa population (CDOW 2009c, entire). Mechanical treatment of areas experiencing Pi

non-juniper encroachment continues to be one of the most successful and economical habitat treatments for the benefit of Gunnison sage-grouse.

Summary of Pi

non-Juniper Encroachment

Most Gunnison sage-grouse population areas are experiencing low to moderate levels of Pi

non-juniper encroachment; however, Pi

non-juniper encroachment in the Pi

non Mesa population has been significant. The encroachment of Pi

non-juniper into sagebrush habitats contributes to the fragmentation of Gunnison sage-grouse habitat. However, Pi

non-juniper treatments, particularly when completed in the early stages of encroachment when the sagebrush and forb understory is still intact, have the potential to provide an immediate benefit to sage-grouse. Approximately 5,341 ha (13,197 ac) of Pi

non-juniper encroachment within the range of Gunnison sage-grouse has been treated. We expect Pi

non-juniper encroachment and corresponding treatment efforts to continue into the foreseeable future, which we consider to be indefinite for this threat. Although Pi

non-juniper encroachment is contributing to habitat fragmentation in a limited area, the level of encroachment is not sufficient to pose a significant threat to Gunnison sage-grouse at a population or rangewide level either now or in the foreseeable future. Pi

non-juniper encroachment may become an increasingly significant threat to the Gunnison sage-grouse if mechanical treatment of areas experiencing Pi

non-juniper encroachment declines, and if suitable habitat continues to be lost due to other threats such as residential and associated infrastructure development.

Domestic Grazing and Wild Ungulate Herbivory

At least 87 percent of occupied Gunnison sage-grouse habitat on Federal lands is currently grazed by domestic livestock (USFWS 2010c, entire). We lack information on the proportion of Gunnison sage-grouse habitat on private lands that is currently grazed. Excessive grazing by domestic livestock during the late 1800s and early 1900s, along with severe drought, significantly impacted sagebrush ecosystems (Knick

et al.

2003, p. 616). Although current livestock stocking rates in the range of Gunnison sage-grouse are substantially lower than historical levels (Laycock

et al.

1996, p. 3), long-term effects from this overgrazing, including changes in plant communities and soils, persist today (Knick

et al.

2003, p.116).

Although livestock grazing and associated land treatments have likely altered plant composition, increased topsoil loss, and increased spread of exotic plants, the impacts on Gunnison sage-grouse are not clear. Few studies have directly addressed the effect of livestock grazing on sage-grouse (Beck and Mitchell 2000, pp. 998-1000; Wamboldt

et al.

2002, p. 7; Crawford

et al

. 2004, p. 11), and little direct experimental evidence links grazing practices to Gunnison sage-grouse population levels (Braun 1987, pp. 136-137, Connelly and Braun 1997, p. 7-9). Rowland (2004, p. 17-18) conducted a literature review and found no experimental research that demonstrates grazing alone is responsible for reduction in sage-grouse numbers.

Despite the obvious impacts of grazing on plant communities within the range of the species, the GSRSC (2005, p. 114) could not find a direct correlation between historic grazing and reduced Gunnison sage-grouse numbers. While implications on population-level impacts from grazing can be made based on impacts of grazing on individuals, no studies have documented (positively or negatively) the actual impacts of grazing at the population level.

Sage-grouse need significant grass and shrub cover for protection from predators, particularly during nesting season, and females will preferentially choose nesting sites based on these qualities (Hagen

et al.

2007, p. 46). In particular, nest success in Gunnison sage-grouse habitat is related to greater grass and forb heights and shrub density (Young 1994, p. 38). The reduction of grass heights due to livestock grazing in sage-grouse nesting and brood-rearing areas has been shown to negatively affect nesting success when cover is reduced below the 18 cm (7 in.) needed for predator avoidance (Gregg

et al.

1994, p. 165). Based on measurements of cattle foraging rates on bunchgrasses both between and under sagebrush canopies, the probability of foraging on under-canopy bunchgrasses depends on sagebrush size and shape and, consequently, the effects of grazing on nesting habitats might be site specific (France

et al.

2008, pp. 392-393).

Several authors have noted that grazing by livestock could reduce the suitability of breeding and brood-rearing habitat, negatively affecting sage-grouse populations (Braun 1987, p. 137; Dobkin 1995, p. 18; Connelly and Braun 1997, p. 231; Beck and Mitchell 2000, pp. 998-1000). Domestic livestock grazing reduces water infiltration rates and the cover of herbaceous plants and litter, compacts the soil, and increases soil erosion (Braun 1998, p. 147; Dobkin

et al.

1998, p. 213). These impacts change the proportion of shrub, grass, and forb components in the affected area, and facilitate invasion of exotic plant species that do not provide suitable habitat for sage-grouse (Mack and Thompson 1982, p. 761; Miller and Eddleman 2000, p. 19; Knick

et al.

, in press, p. 41).

Livestock may compete directly with sage-grouse for rangeland resources. Cattle are grazers, feeding mostly on grasses, but they will make seasonal use of forbs and shrub species like sagebrush (Vallentine 1990, p. 226), a primary source of nutrition for sage-grouse. A sage-grouse hen's nutritional condition affects nest initiation rate, clutch size, and subsequent reproductive success (Barnett and Crawford 1994, p. 117; Coggins 1998, p. 30). Other effects of direct competition between livestock and sage-grouse depend on condition of the habitat and the grazing practices. Thus, the effects vary across the range of Gunnison sage-grouse. For example, poor livestock management in mesic sites results in a reduction of forbs and grasses available to sage-grouse chicks, thereby affecting chick survival (Aldridge and Brigham 2003, p. 30). Chick survival is one of the most important factors in maintaining Gunnison sage-grouse population viability (GSRSC 2005, p. 173).

Livestock can trample sage-grouse and its habitat. Although the effect of trampling at a population level is unknown, outright nest destruction has been documented, and the presence of livestock can cause sage-grouse to abandon their nests (Rasmussen and Griner 1938, p. 863; Patterson 1952, p. 111; Call and Maser 1985, p. 17; Holloran and Anderson 2003, p. 309; Coates 2007, p. 28). Coates (2007, p. 28) documented nest abandonment

following partial nest depredation by a cow. In general, all recorded encounters between livestock and grouse nests resulted in hens flushing from nests, which could expose the eggs to predation. Visual predators like ravens likely use hen movements to locate sage-grouse nests (Coates 2007, p. 33). Livestock also may trample sagebrush seedlings, thereby removing a source of future sage-grouse food and cover (Connelly

et al.

2004, pp. 7-31). Trampling of soil by livestock can reduce or eliminate biological soil crusts making these areas susceptible to cheatgrass invasion (Mack 1981, pp. 148-149; Young and Allen 1997, p. 531).

Livestock grazing may have positive effects on sage-grouse under some habitat conditions. Evans (1986, p. 67) found that sage-grouse used grazed meadows significantly more during late summer than ungrazed meadows because grazing had stimulated the regrowth of forbs. Greater sage-grouse sought out and used openings in meadows created by cattle grazing in northern Nevada (Klebenow 1981, p. 121). Also, both sheep and goats have been used to control invasive weeds (Mosley 1996

in

Connelly

et al.

2004, pp. 7-49; Merritt

et al.

2001, p. 4; Olsen and Wallander 2001, p. 30) and woody plant encroachment (Riggs and Urness 1989, p. 358) in sage-grouse habitat.

Sagebrush plant communities are not adapted to domestic grazing disturbance. Grazing changed the functioning of systems into less resilient, and in some cases, altered communities (Knick

et al.

, in press, p. 39). The ability to restore or rehabilitate areas depends on the condition of the area relative to the ability of a site to support a specific plant community (Knick

et al.

, in press, p. 39). For example, if an area has a balanced mix of shrubs and native understory vegetation, a change in grazing management can restore the habitat to its potential historic species composition (Pyke, in press, p. 11). Wambolt and Payne (1986, p. 318) found that rest from grazing had a better perennial grass response than other treatments. Active restoration would be required where native understory vegetation is much reduced (Pyke, in press, p. 15). But, if an area has soil loss or invasive species, returning the site to the native historical plant community may be impossible (Daubenmire 1970, p. 82; Knick

et al.

, in press, p. 39; Pyke, in press, p. 17). Aldridge

et al.

(2008, p. 990) did not find any relationship between sage-grouse persistence and livestock densities. However, the authors noted that livestock numbers do not necessarily correlate with range condition. They concluded that the intensity, duration, and distribution of livestock grazing are more influential on rangeland condition than the livestock density values used in their modeling efforts (Aldridge

et al.

2008, p. 990). Currently, there is little direct evidence linking grazing practices to population levels of Gunnison or greater sage-grouse. Although grazing has not been examined at large spatial scales, as discussed above, we do know that grazing can have negative impacts to individuals, nests, breeding productivity, and sagebrush and, consequently, to sage-grouse at local scales.

Public Lands Grazing in the Gunnison Basin Population Area

- Our analysis of grazing is focused on BLM lands because nearly all of the information available to us regarding current grazing management within the range of Gunnison sage-grouse was provided by the BLM. However, this information is pertinent to over 40 percent of the land area currently occupied by Gunnison sage-grouse. A summary of domestic livestock grazing management on BLM and USFS lands in occupied Gunnison sage-grouse habitat is provided in Table 3. The BLM manages approximately 122,376 ha (301,267 ac), or 51 percent of the area currently occupied by Gunnison sage-grouse in the Gunnison Basin, and approximately 98 percent of this area is actively grazed. The USFS manages approximately 34,544 ha (85,361 ac) or 14 percent of the occupied portion of the Gunnison Basin population area. In 2009, within the occupied range in the Gunnison Basin population, 13 of 62 (21 percent) active BLM grazing allotments and 3 of 35 (9 percent) of USFS grazing allotments had Gunnison sage-grouse habitat objectives incorporated into the allotment management plans or Records of Decision for permit renewals (USFWS 2010c, pp. 1-2). Habitat objectives for Gunnison sage-grouse within allotment management plans were designed such that they provide good habitat for the species when allotments are managed in accordance with the objectives. In 2009, 57 percent of the area of occupied habitat in active BLM grazing allotments (45 percent of the entire Gunnison Basin population area) had a recently completed land health assessment (LHA), and 94 percent of the area in occupied habitat in active allotments was deemed by the BLM as not meeting LHA objectives specific to Gunnison sage-grouse. The remainder of the LHA-monitored allotments were deemed to be meeting objectives or as “unknown”. LHAs are assessments of the on-the-ground condition and represent the best available information on the status of the habitat. We are uncertain of habitat conditions on the remaining 55 percent of BLM lands in the Gunnison Basin. Based on the assumption that the same proportion of these lands are also not meeting LHA objectives results in an estimate of 94 percent of BLM lands in the Gunnison Basin not meeting LHA objectives specific to Gunnison sage-grouse habitat. This analysis indicates that, without taking into account habitat conditions on private lands and other Federal and State lands, up to 48 percent of the entire Gunnison Basin population area is not providing optimal habitat conditions for Gunnison sage-grouse.

The fact that most grazing allotments are not meeting LHA objectives indicates that grazing is a factor that is likely contributing to Gunnison sage-grouse habitat degradation. In addition, grazing has negatively impacted several Gunnison sage grouse treatments (projects aimed at improving habitat condition) in the Gunnison Basin (BLM 2009, p. 34). Although these areas are generally rested for 2 years after treatment, several have been heavily used by cattle shortly after the treatment, and the effectiveness of the treatments decreased (BLM 2009, p. 34) and reduced the potential benefits of the treatments.

Table 3. Summary of domestic livestock grazing management on BLM and USFS lands in occupied habitat for each of the Gunnison sage-grouse populations (from USFWS

a

2010c, compilation of data provided by BLM

b

and USFS

c

).

Population

Number of Active USFS Allotments

Number of Active BLM Allotments

Percent

Active Allotments with GUSG

d

Objectives

BLM Allotments with Completed LHA

e

Assessed BLM

Allotments

Meeting LHA

Objectives

Gunnison

34

62

21

66

22

San Miguel Basin

no data

13

0

77

40

Monticello-Dove Creek:

Dove Creek

n/a

3

0

0

0

Monticello

n/a

f

6

100

83

80

Piñon Mesa

no data

15

53

27

100

Cerro Summit-Cimarron-Sims Mesa

n/a

f

10

10

50

40

Crawford

g

n/a

f

7

71

100

86

Poncha Pass

no data

8

13

100

100

Rangewide Averages

34

63

59

a

United States Fish and Wildlife Service

b

Bureau of Land Management

c

United States Forest Service

d

Gunnison sage-grouse

e

Land Health Assessments

f

No United States Forest Service Land in occupied habitat in this population area.

f

Includes allotments on National Park Service lands but managed by the Bureau of Land Management.

Public Lands Grazing in All Other Population Areas

- The BLM manages approximately 36 percent of the area currently occupied by Gunnison sage-grouse in the San Miguel Basin, and approximately 79 percent of this area is actively grazed. Within the occupied range in the San Miguel population, no active BLM grazing allotments have Gunnison sage-grouse habitat objectives incorporated into the allotment management plans or Records of Decision for permit renewals (USFWS 2010c, p. 9). In 2009, 10 of 15 (77 percent) active allotments had LHAs completed in the last 15 years; 4 of 10 allotments (40 percent) were deemed by the BLM to meet LHA objectives. Gunnison sage-grouse habitat within the 60 percent of allotments not meeting LHA objectives and the 5 allotments with no LHAs completed are likely being adversely impacted by grazing. Therefore, it appears that grazing in a large portion of this population area is a factor that is likely contributing to Gunnison sage-grouse habitat degradation.

The BLM manages 11 percent of the occupied habitat in the Dove Creek group, and 41 percent of this area is actively grazed. Within the occupied range in the Dove Creek group of the Monticello-Dove Creek population, no active BLM grazing allotments have Gunnison sage-grouse habitat objectives incorporated into the allotment management plans or Records of Decision for permit renewals (USFWS 2010c, p. 3). In 2009, no active allotments in occupied habitat had completed LHAs. Gunnison sage-grouse are not explicitly considered in grazing management planning, and the lack of habitat data limits our ability to determine the impact to the habitat on public lands.

The BLM manages on 4 percent of the occupied habitat in the Monticello group, and 83 percent of this area is grazed. Within the occupied range in the Monticello group, 6 of 6 active BLM grazing allotments have Gunnison sage-grouse habitat objectives incorporated into the allotment management plans or Records of Decision for permit renewals (USFWS 2010c, p. 6). In 2009, 88 percent of the area of occupied habitat in active allotments had a recently completed LHA. Approximately 60 percent of the area in occupied habitat in active allotments were deemed by the BLM to meet LHA objectives. This information suggests that grazing the majority of lands managed by the BLM is not likely significantly contributing to Gunnison sage-grouse habitat degradation in the Monticello population group.

The BLM manages 28 percent of occupied habitat in the Pi

non Mesa population area, and approximately 97 percent of this area is grazed. Over 50 percent of occupied habitat in this population area is privately owned and, while grazing certainly occurs on these lands, we have no information on its extent. Within the occupied range in the Pi

non Mesa population, 8 of 15 (53 percent) active BLM grazing allotments have Gunnison sage-grouse habitat objectives incorporated into the allotment management plans or Records of Decision for permit renewals (USFWS 2010c, p. 5). In 2009, 23 percent of the area of occupied Gunnison sage-grouse habitat in active allotments in the Pi

non Mesa population area had LHAs completed in the last 15 years, and all of these were deemed by the BLM to meet LHA objectives. Therefore, for the portion of the Pi

non Mesa population area for which we have information, it appears that grazing is not likely significantly contributing to Gunnison sage-grouse habitat degradation.

The BLM manages on 13 percent of the occupied habitat in the Cerro Summit-Cimarron-Sims Mesa population area, and 83 percent of this area is grazed. Within the occupied

range in the Cerro Summit-Cimarron-Sims Mesa population, 1 of 10 (10 percent) active BLM grazing allotments have Gunnison sage-grouse habitat objectives incorporated into the allotment management plans or Records of Decision for permit renewals (USFWS 2010c, p. 7). In 2009, 5 of the 10 active allotments had LHAs completed in the last 15 years and 3 (60 percent) of these were deemed by the BLM as not meeting LHA objectives. Therefore, for the small portion of the Cerro Summit-Cimarron-Sims Mesa population area for which we have information, it appears that grazing is a factor that is likely contributing to some Gunnison sage-grouse habitat degradation.

Lands administered by the BLM and NPS comprise over 75 percent of occupied habitat in the Crawford population, and 96 percent of this area is actively grazed. Grazing allotments on NPS lands in this area are administered by the BLM. Within occupied range in the Crawford population, 1 of 7 (14 percent) active BLM grazing allotments have Gunnison sage-grouse habitat objectives incorporated into the allotment management plans or Records of Decision for permit renewals (USFWS 2010c, p. 8). In 2009, all of the active allotments had LHAs completed in the last 15 years, and 86 percent were deemed by the BLM to meet LHA objectives. Seasonal forage utilization levels were below 30 percent in most Crawford Area allotments, although a small number of allotments had nearly 50 percent utilization (BLM 2009x, p. 68). Based on this information, it appears that grazing is not likely significantly contributing to Gunnison sage-grouse habitat degradation in the majority of the Crawford population area.

The BLM manages nearly half of occupied habitat in the Poncha Pass population area, and approximately 98 percent of this area is actively grazed. Within the occupied range in the Poncha Pass population, 1 of 8 (13 percent) active BLM grazing allotments have Gunnison sage-grouse habitat objectives incorporated into the allotment management plans or Records of Decision for permit renewals (USFWS 2010c, p. 4). In 2009, all active allotments in occupied habitat had completed LHAs, and all were meeting LHA objectives. Based on this information it appears that grazing is not likely significantly contributing to Gunnison sage-grouse habitat degradation in the majority of the Poncha Pass population area.

Non-federal Lands Grazing in All Population Areas -

Livestock grazing on private and other non-federal lands, where present, has the potential to impact Gunnison sage-grouse, but we lack sufficient information to make an assessment. Table 1 summarizes the percentage of land area potentially available to grazing within each of the populations.

As discussed earlier, some private lands are enrolled in the CRP program and provide some benefits to Gunnison sage-grouse. The CRP land in the Monticello group has provided a considerable amount of brood-rearing habitat because of its forb component. Grazing of CRP land in Utah occurred in 2002 under emergency Farm Bill provisions due to drought and removed at least some of the grass and forb habitat component thus likely negatively affecting Gunnison sage-grouse chick survival. Radio-collared males and non-brood-rearing females exhibited temporary avoidance of grazed fields during and after grazing (Lupis

et al

. 2006, pp. 959-960), although one hen with a brood continued to use a grazed CRP field. This indicates that when CRP lands are grazed, negative impacts to their habitat and behavior may result. Since we have very little information on the status of Gunnison sage-grouse habitat on non-federal lands, we cannot assess whether the impacts that are occurring rise to the level of being a threat.

Wild Ungulate Herbivory in All Population Areas

- Overgrazing by deer and elk may cause local degradation of habitats by removal of forage and residual hiding and nesting cover. Hobbs

et al.

(1996, pp. 210-213) documented a decline in available perennial grasses as elk densities increased. Such grazing could negatively impact nesting cover for sage-grouse. The winter range of deer and elk overlaps the year-round range of the Gunnison sage-grouse. Excessive but localized deer and elk grazing has been documented in the Gunnison Basin (BLM 2005a, pp. 17-18; Jones 2005, pers. comm.).

Grazing by deer and elk occurs in all Gunnison sage-grouse population areas. Although we have no information indicating that competition for resources is limiting Gunnison sage-grouse in the Gunnison Basin, BLM observed that certain mountain shrubs were being browsed heavily by wild ungulates (BLM 2009, p. 34). Subsequent results of monitoring in mountain shrub communities indicated that drought and big game were having large impacts on the survivability and size of mountain mahogany (

Cercocarpus utahensis

), bitterbrush (

Purshia tridentata

), and serviceberry (

Amelanchier alnifolia

) in the Gunnison Basin (Jupuntich

et al.

2010, pp. 7-9). The authors raised concerns that observed reductions in shrub size and vigor will reduce drifting snow accumulation, resulting in decreased moisture availability to grasses and forbs during the spring melt. Reduced grass and forb growth could negatively impact Gunnison sage-grouse nesting and early brood-rearing habitat.

Grazing Summary

Livestock management and domestic grazing have the potential to seriously degrade Gunnison sage-grouse habitat. Grazing can adversely impact nesting and brood-rearing habitat by decreasing vegetation available for concealment from predators. Grazing also has been shown to compact soils, decrease herbaceous abundance, increase erosion, and increase the probability of invasion of exotic plant species.

The impacts of livestock operations on Gunnison sage-grouse depend upon stocking levels and season of use. We recognize that not all livestock grazing result in habitat degradation and many livestock operations within the range of Gunnison sage-grouse are employing innovative grazing strategies and conservation actions (Gunnison County Stockgrowers 2009, entire). However, available information suggests that LHA objectives specific to Gunnison sage-grouse are not being met on more than 50 percent of BLM-managed occupied Gunnison sage-grouse habitat in the Gunnison Basin, San Miguel Basin, and the Cerro Summit-Cimarron-Sims Mesa population areas. Cumulatively, the BLM-managed portion of these populations constitutes approximately 33 percent of the entire range of the species. Reduced habitat quality, as reflected in unmet LHA objectives is likely to negatively impact Gunnison sage-grouse, particularly nesting and early brood-rearing habitat, and chick survival is one of the most important factors in maintaining Gunnison sage-grouse population viability (GSRSC 2005, p. 173).

We know that grazing can have negative impacts to sagebrush and consequently to Gunnison sage-grouse at local scales. Available data indicates that impacts to sagebrush are occurring on a significant portion of the range of the species. Given the widespread nature of grazing within the range of Gunnison sage-grouse, the potential for population-level impacts is highly likely. Further, we expect grazing to persist throughout the range of Gunnison sage-grouse for the foreseeable future. Effects of domestic livestock grazing are likely being exacerbated by intense browsing of

woody species by wild ungulates in portions of the Gunnison Basin. We conclude that habitat degradation that can result from improper grazing is a significant threat to Gunnison sage-grouse now and in the foreseeable future.

Nonrenewable Energy Development

Energy development on Federal (BLM and USFS) lands is regulated by the BLM and can contain conservation measures for wildlife species (see Factor D for a more thorough discussion). The BLM (1999, p. 1) classified the area encompassing all Gunnison sage-grouse habitat for its gas and oil potential. Three of the populations have areas with high (San Miguel Basin, Monticello group) or medium (Cra

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