From the pages of
The Sublette County Journal
Volume 4, Number 14 - 12/2/99
brought to you online by Pinedale Online

"The Sage Grouse: Natural History, Wyoming Studies, Current Issues and Management Considerations"

by Wyoming Cooperative Research Unit

The Sage Grouse:

Natural History, Wyoming Studies, Current Issues, and Management Considerations

Matt Holloran and Stanley H. Anderson

Wyoming Cooperative Wildlife Research Unit

University of Wyoming, Laramie, WY 82071

Matt Holloran / (307) 766-2602 /

Sage grouse distribution in Wyoming:

1. Sage grouse were historically distributed throughout the western United States and southern Canada wherever sagebrush occurred.

2. Compared to any other western state, Wyoming historically contained a higher population of sage grouse, and still possesses some of the best sage grouse habitat. However, no large-scale studies have been conducted since Patterson's work in the 1950s.

3. Ten years of harvest data suggest that statewide sage grouse harvests have declined while hunter numbers have remained constant. This indicates a numerical population decline assuming constant hunter efficiency.

4. In January 1993, the Wyoming Game and Fish Department funded an enhancement to investigate factors responsible for low productivity and survival of Wyoming sage grouse. The goal of this project was to identify limiting habitat components and provide management recommendations to address these habitat inadequacies.

Sage Grouse Life-History Information:

Shrubsteppe Ecosystems:

1. Sage grouse depend on sagebrush for most of their life history requirements; they feed, nest, raise their broods and winter in sagebrush habitats.

2. The predominate reasons for sage grouse declines in abundance and reduction in distribution throughout their historical range are: permanent loss, degradation, and/or fragmentation of shrubsteppe ecosystems.

Sage Grouse Strutting Grounds (Leks):

1. Sage grouse leks are situated in areas with minimal shrub cover where strutting males are easily seen from the ground and are visible for great distances to birds flying 5-10 m above the ground.

2. Adult male lek fidelity (attendance within and between years) is absolute, while subadult males may visit several leks before establishing a territory.

1. Average male reproductive success is maximized when yearlings visit several strutting grounds to find one suitable for territory establishment and retain that territory until reaching the mating center as an adult.

3. Males display in early morning and evening hours, traveling 0.3-2.1 km from the lek to day-use feeding and resting areas.

Nesting Habitat:

1. Sage grouse females retire into the vicinity of their nest location within a few days of being bred, and remain relatively sedentary until they nest (Patterson 1952).

2. No concealment strategies are attempted except that afforded by natural cover and the hen's cryptic plumage coloration pattern.

3. Egg laying takes 7-10 days, incubation lasts approximately 22-27 days, and average clutch sizes are between 7-9 eggs (Patterson 1952).

4. Sage grouse nesting habitat is often a broad area between winter and summer range, typically within a 3 km radius of the lek (Braun et al. 1977).

5. Over 90% of nests are located under sagebrush with average patch shrub heights varying from 17-79 cm and 18-40% shrub canopy coverage (Patterson 1952, Wallestad and Pyrah 1974, Autenrieth 1981).

6. Hatching success in sage grouse ranges from 10-86% (Trueblood 1954, Gregg 1991), with an average of approximately 35% (Bergerud 1988).

7. Herbaceous vegetation has been identified as a critical component of nest site selection and hatching success (the chance of a sagebrush nest successfully hatching will increase 30% if it is in combination with residual herbaceous vegetation exhibiting 20% cover and is (15cm high).

8. Black-billed magpies, common ravens, Richardson's and striped ground squirrels, foxes and badgers are the predominant nest predators.

Early Brood-rearing Habitat:

1. Chicks are precocial and move immediately following hatch to search for food.

2. Hens rear their broods in low sagebrush types in the immediate vicinity of the nest (within 1-2 miles) for the first month post hatch.

3. Areas with sagebrush in scattered densities and clumps are preferred as early brood-rearing habitat.

4. Broods use open areas to feed and dense shrub clumps as escape and thermal cover.

5. During early brood-rearing periods (through 3 weeks of age), chicks require a high protein diet consisting of forbs and insects for survival and growth.

1. Insect matter averages 60% of dietary constituents during the first week, 33% in the second and remains constant (at a lower level) from 3 to 11 weeks of age.

2. Darkling beetles and harvester ants are preferred sage grouse insect foods.

6. Stand structure and forb and insect availability are characteristics most associated with habitat selection by brooding hens.

Late Brood-rearing Habitat:

1. Sage grouse broods remain in sagebrush habitats until range desiccation induces them to move to more mesic habitats still supporting succulent vegetation.

2. Food habits of juveniles begin to parallel those of adults while on the summer range (at approximately 3 months of age).

3. Juvenile females achieve maturity in the fall (mid-November) of their first year, while males reach maturity early in the following spring (April); both sexes are able to breed successfully as yearlings.

4. Beginning in September, brood flocks shift back to big sagebrush cover types. This shift coincides with forb reduction due to desiccation and frost and with juvenile dietary shifts from forbs to sagebrush.

5. The golden eagle is the number one predator of adult and juveniles greater than one month of age on both summer and winter range.

Winter Habitat:

1. A precipitation event (usually snow) or a drop in the temperature initiates migration, which begins in late August (in advance of snow accumulation) and continues until December.

2. Winter habitat is probably the most limiting seasonal habitat, with sage grouse over a broad summering area congregating on traditional wintering grounds.

3. Winter ranges are characterized by large expanses of dense sagebrush on land with south- to west-facing gentle slopes, or windblown ridges.

4. Sage grouse distribution during the winter is primarily a reflection of sagebrush exposure and topographic categories (slope and aspect).

5. Sage grouse feed during almost all weather conditions and subsist on a diet consisting solely of sagebrush during the winter.

6. Drainages are sheltered from the wind and contain taller sagebrush stands, snow drifts (used for roosting to escape extreme cold) and closed shrub canopies, which combined provide food and reduce thermoregulatory costs.

Wyoming Studies: (Funding provided by the Wyoming Game & Fish Department, the 3-shot sage grouse foundation, Ultra Petroleum, and the Bureau of Land Management)

Farson (sage grouse seasonal habitat use) - 1993 - 1995

Rawlins (sage grouse seasonal habitat use with an emphasis on livestock grazing) - 1996 - 1997

Bates Hole (sage grouse seasonal habitat use) - 1997 - 1998

Pinedale (effects of gas well development on sage grouse seasonal habitat use and movements) - 1998 - 1999

The critical seasonal periods for sage grouse, based on survival and productivity data collected throughout Wyoming, are nesting (hatching success), extreme early brood-rearing (chick survival from hatch through two weeks post hatch), and fall (adult hen survival).

1. Annual nest success estimates throughout Wyoming range from 25% (Farson, 1995) to 79% (Rawlins, 1996), with an average over 4 study sites and 7 years of 51%.

2. 87% of chick mortalities throughout the 4 studies occurred during the early brood-rearing period (hatch through 2 weeks post hatch); and 73% of the hens who successfully hatched their clutches in Pinedale (1999) lost entire broods prior to 2 weeks post hatch.

3. 45% of recorded adult hen mortalities occurred during September and October; and 62% of the 1994 annual mortality in Farson occurred during September.

Nesting Results:

Overall: 318 collared females - 290/352 (82%) initiated nests - 139/274 (51%) successful - 136/144 (94%) unsuccessful nests predated

1. Farson - Nesting - 78/90 (87%) initiated nests - 29/83 (35%) successful

Nests in areas with higher sagebrush density and canopy cover, grass height, and grass, residual grass, and total herbaceous cover compared to available habitat.

Successful nests located in areas with higher residual grass height, and higher residual grass and forb cover compared to unsuccessful nests.

2. Rawlins - Nesting - 40/53 (75%) initiated nests - 30/42 (71%) successful

Nests in areas with higher sagebrush density, total shrub canopy cover, grass and residual grass height, and residual grass and litter cover compared to available habitat.

No vegetative differences between successful and unsuccessful nests.

3. Bates Hole - Nesting - 108/118 (92%) initiated nests - 62/99 (63%) successful

Nests in areas with higher sagebrush canopy cover and height, residual grass height, and non-food forb cover, and lower bare ground compared to available habitat.

Successful nests located in areas with higher food forb cover compared to unsuccessful nests.

4. Pinedale - Nesting - 52/79 (66%) initiated nests - 25/63 (40%) successful

Nests in areas with higher total shrub and dead sagebrush canopy cover, average sagebrush height, residual grass height, and grass, residual grass, total forb, and total herbaceous cover; and lower live sagebrush density and bare ground compared to available habitat.

Successful nests had higher residual grass and total herbaceous cover; and lower bare ground compared to unsuccessful nests.

Sage grouse throughout Wyoming are consistently selecting denser patches of sagebrush with increased herbaceous understories as nesting habitat. The selection of nesting habitat exhibiting increased sagebrush canopy cover is well documented throughout the literature. Nesting habitat is generally located within upland expanses of sagebrush. However, hens typically locate their nests near a habitat edge, presumably to minimize distances between nesting and suitable early brood-rearing habitat. The interior of large, contiguous patches of dense sagebrush are rarely selected for nesting.

Recently, the herbaceous understory has surfaced as a critical component in nest site selection. As nests are initiated prior to the growing season for most grasses and forbs, residual grass height and cover as a screening element beyond that afforded by sagebrush is important. Sage grouse nest sites throughout Wyoming had increased residual grass height and, Bates Hole withstanding, residual grass cover compared to available nesting habitat.

Nest fate appears to be determined by the herbaceous component. Increased residual grass height and cover and food forb cover are directly correlated with increased probability of a successful hatch. As overall nest success rates decline (Farson and Pinedale), residual vegetative height and cover becomes increasingly important. Theoretically, increased forb cover within nesting habitat will decrease the effort required for incubating hens to find food. This will minimize the activity associated with the nest, and the spatial extent of the area inundated with the hen's scent, thereby reducing the probability that a predator will detect the nest.

Red foxes, ravens, and badgers were the most prevalent nest predators identified throughout Wyoming. A study initiated on the Jackson Hole, Wyoming sage grouse population (results not included in above summary due to small initial season sample sizes) is used here to illustrate nest predation issues. Seven sage grouse nests were identified in Grand Teton National Park (GTNP) during the 1999 field season, and four successfully hatched. All three failed nests were predated. Raven breeding density within GTNP is substantially greater than other studied populations. Ravens have been previously identified as sage grouse nest predators, and were probably responsible for the three failed sage grouse nests (based on the eggs' appearance and the lack of physical evidence).

Mammalian nest predation was not observed during 1999 in GTNP. Because of increased carrion and the lack of exploitation, coyote densities in the Jackson Hole area are potentially maintained at a higher level than encountered elsewhere. It has been suggested that control efforts throughout the central United States have disrupted the ecological hierarchy existing among canids, resulting in dense populations of red foxes. Red foxes were responsible for 64% of the mammalian predated sage grouse nests in Bates Hole. Elevated coyote numbers in GTNP could be reducing mammalian nest predation by restricting densities of more proficient nest predatory species.

Although predators are the agent responsible for the majority of nest failures, the ultimate cause probably relates to habitat inadequacies, and not overall predator numbers. Sage grouse nesting habitat is characterized by dense sagebrush patches, with hatching success hinging on a healthy residual and forb herbaceous understory.

Brood-Rearing Results:

Overall: 87/127 (69%) successfully nesting hens raised (1 chick through 2 weeks post hatch (successful early brood-rearing) - 78/84 (93%) hens that had (1 chick after the initial 2 weeks fledged (1 chick on August 15 (successful fledging) - 3.2 fledged chicks/successful brooding hen - 2.0 fledged chicks/successful nesting hen

1. Farson - Brood-Rearing - 23/29 (79%) successful early brood-rearing - 22/23 (96%) successful fledging -

1.2 fledged chicks/successful hen

Early brood-rearing habitat had higher dead sagebrush density compared to available early brood-rearing habitat.

Late brood-rearing habitat had higher vertical obstruction, and food forb, total forb, and litter cover; and lower grass cover compared to available summering habitat.

2. Rawlins - Brood-Rearing - 18/30 (60%) successful early brood-rearing - 17/18 (94%) successful fledging -

2.9 fledged chicks/successful hen

Early brood-rearing habitat had higher grass and total herbaceous cover; and lower vertical obstruction and bare ground compared to available early brood-rearing habitat.

No vegetative differences between late brood-rearing and available summering habitats.

3. Bates Hole - Brood-Rearing - 32/43 (74%) successful early brood-rearing - 27/29 (86%) successful fledging -

3.6 fledged chicks/successful hen

Early brood-rearing habitat had higher residual grass, total forb, food forb, and total herbaceous cover; and lower total shrub and live sagebrush canopy cover, and litter cover compared to available early brood-rearing habitat.

Late brood-rearing habitat had higher food forb cover; and lower residual grass height compared to available summering habitat.

4. Pinedale - Brood-Rearing - 14/25 (56%) successful early brood-rearing - 12/14 (86%) successful fledging -

2.6 fledged chicks/successful hen

BUT 1999 early brood survival = 3/11 (27%)

Early brood-rearing habitat had higher grass and total herbaceous cover; and lower live sagebrush density and canopy cover, total shrub canopy cover, litter cover, and bare ground compared to available early brood-rearing habitat.

Late brood-rearing habitat had higher live sagebrush density and canopy cover, total shrub canopy cover, and average live sagebrush height compared to available summering habitat.

Sage grouse broods throughout Wyoming (during the initial two weeks post hatch) are selecting more open habitats with an increased herbaceous component. Tactics used by brooding hens to improve the survival of progeny should include frequenting areas where young chicks can optimally forage. Sage grouse chicks (10 days old require insects in their diets for survival, after which insects are required for normal growth and development. After the first week, forbs replace insects as the major diet constituent. Survival rates, growth rates, and long-term productivity increase as the quantity of insects in the juvenile diet increases.

Early brood-rearing habitat was not identified until two weeks post hatch (to allow hens to become established with their broods before disturbance). This was past the critical first 10 days when insects are imperative for survival and into the time period when forbs dominate diets. Although shrub measurements were consistently lower at early brood sites compared to available habitat throughout Wyoming, we believe that selection was based on forb and insect availability, not for the decreased shrub component.

Causative factors resulting in high chick mortality rates during the initial two weeks post hatch, including actual causes of death (starvation or predation) and early brood-rearing habitat inadequacies, were not identified. Current sage grouse research in Wyoming is investigating extreme early brood-rearing (hatch through 10 days post hatch) habitat selection (both vegetative and insect variables). The causes of chick mortality will be investigated during a project beginning in the spring of 2000.

Late brood-rearing habitat does not appear to be limiting sage grouse chick survival and subsequent productivity throughout Wyoming, substantial drought conditions not withstanding (Farson, 1994, when 4/5 brooding hens who had (1 chick 2 weeks post hatch fledged (1 chick). The selection of summer brood-rearing habitat based on forb availability is well documented throughout the literature.

Fall Adult Hen Survival Results:

Overall: 198/271 (73%) adult hens survived the summer - 38/84 (45%) adult hen mortalities occurred during September and October

Adult hen mortalities that occurred during September and October

1. Farson - 16/36 (44%); BUT 60% of the successfully nesting hens were killed in September; and in 1994,

100% of successfully nesting hens and 62% of annual mortality occurred during September.

2. Rawlins - 7/14 (50%)

3. Bates Hole - 7/16 (44%)

4. Pinedale - 8/18 (44%)

Fall mortality was caused by hunting and predation, the majority of which occurred during September. In 1994, 62% of the annual mortality occurred during September, presumably because drought conditions concentrated birds on riparian areas. Results from Bates Hole indicated that sage grouse preferred to remain within sagebrush dominated habitats throughout the summer, and resorted to concentrating on riparian corridors only after upland forb desiccation. The drier summers increased the importance of riparian area distribution and extent.

Current and Future Studies in Wyoming:

Sage Grouse Seasonal Habitat Selection

2 year project funded by the Wyoming Game & Fish Dept., and the USGS begun spring 1999 in Jackson Hole, Wyoming

The Jackson Hole sage grouse population has experienced a 73% decline since 1990, based on maximum rooster counts on known leks. The current population is estimated at less than 220 individuals. Since Grand Teton National Park's conception in the 1930's and expansion in 1950, natural ecosystem processes have been emphasized. This policy has resulted in an ecosystem shaped by relatively natural pressures, and offers a unique opportunity to study sage grouse habitat selection in an ecosystem influenced almost exclusively by native large ungulate grazing pressure.

1. Concentrating on extreme early brood-rearing habitat selection (vegetation and insects)

2. Differences between natural (elk) and livestock grazing on shrubsteppe ecosystems

3. Winter survival (population within Wyoming where winter could potentially be a bottleneck)

4. Direct responses of roosters and hens to construction disturbance during the breeding season (Airport extension)

Impacts of Gas / Oil drilling activity and Distance on sage grouse strutting activity and hen seasonal habitat selection

3 year project funded by the BLM beginning spring 2000 near Farson, Wyoming

Project Goal: Determine the effects of drilling activity (all aspects in combination) within specified distances from active sage grouse strutting grounds.

Question of Concern: What is the distance from an active sage grouse lek where the impacts of spring drilling activity on the strutting behavior of males and seasonal habitat selection of females minimized or eliminated?

The impacts drilling has on rooster strutting activity, hen habitat selection, and overall productivity will be assessed.

An Examination of Varying Domestic Cattle Grazing Intensities on Sage Grouse Seasonal Habitat Use and Productivity

15 year project (initial 5 years continuous - follow-up studies as necessary) beginning spring 2000 near Lander, Wyoming

Ranchers: Tony Malmberg and Bob Thompson

Project Goals: 1. Provide scientifically credible data that would assist managers in ascertaining the impacts

grazing has on sage grouse population sustainability.

2. Determine livestock grazing practices that will lead to healthy overall sagebrush steppe

ecosystems and provide sage grouse habitat conducive to sustainable populations.

Sage grouse seasonal habitat selection and overall shrubsteppe ecosystem condition will be assessed in relation to different grazing intensities, durations, and seasonality.

1. Cattle grazing management manipulation study on 2 ranches with sage grouse habitat ranging from summering areas [relatively high precipitation (11" - 15" mountain big sagebrush communities)] to winter habitat [lower precipitation (5" - 9" wyoming big sagebrush communities)].

2. Manipulation of grazing management schemes is achievable due to progressive characteristics of selected ranches and corresponding owners and managers.

Management Concerns and Questions:

1. Nesting and extreme early brood-rearing (hatch through 2-3 weeks post hatch) the critical periods for sage grouse. Although currently populations are doing well, we need to manage for maintenance of populations during downswings (i.e. drought periods).

2. Dense sagebrush stands are typically in late successional stages (especially Wyoming Big sagebrush stands), while forb cover within nesting habitat is important (early successional stage). How to manage for both early and late successional conditions within the same patch of sagebrush?

3. Again, nesting and extreme early brood-rearing (hatch through 2-3 weeks post hatch) the critical periods for sage grouse. Although currently populations are doing well, we need to manage for maintenance of populations during downswings (i.e. drought periods).

4. NESTING HABITAT: Dense sagebrush stands are typically in late successional stages (especially Wyoming Big sagebrush stands), while forb cover within nesting habitat is important (early successional stage). How to manage for both early and late successional conditions within the same patch of sagebrush?

5. Another issue is pro-active sagebrush management and manipulation

6. Dense stands of sagebrush provide adequate fuel for burning, but also important as nesting habitat and thermal protection during the winter.

7. Sage brush reestablishment is a long process (sprayed with 2,4-D in 1971).

8. Sage grouse are using the sprayed area and old burns throughout the Bates Hole study area for nesting and brooding, but only those areas in close proximity to sagebrush.

9. Large expanses without sagebrush are not consistently used by sage grouse.

10. However, we are not advocating no habitat manipulation.

11. Hens typically select nesting habitat on an edge. The proximity of suitable early brooding habitat could be an important variable in nest site selection? / Why are certain nest sites chosen when "better" concealing cover exists in close proximity (often within meters) if habitat structure is the sole selection criterion? (Would explain the extensive use of edges when selecting nesting habitat, and have implications for the new guidelines no burn policy in large tracts of sagebrush)

12. A mosaic within nesting habitat is extremely important

13. EXAMPLE: If a 40% burn is proposed in a given area, 60% of available nesting habitat has to remain, not 60% of the overall landscape.

14. It is important to remember that sage grouse require sagebrush, the eradication of sagebrush will do nothing but exclude birds from an area.

15. Grazing is the single dominant use of sagebrush dominated lands. Management of livestock needs to be concerned with restoring and maintaining herbaceous understory cover in nesting and early brood-rearing areas.

16. CHICK SURVIVAL: Weather was not a direct factor contributing to very low chick survival in 1999 (during early brood-rearing stages). The hatch occurred in 2 peaks this year (1 the beginning of June, 1 the end of June) and chick survival was low during both early brood periods (weather, especially during the second hatch peak, was not severe).

17. Losing entire broods during the early brood-rearing stages logically indicates a food shortage (insects) resulting in starvation, however brood loss appears to occur during the initial 2-5 days, when the broods are clumped around the hen, thus mammalian predation of the entire brood at this juncture is not out of the question. If chicks are being predated, then the extended hatching season in 1999 theoretically would have reduced the effectiveness of a synchronized hatch (dumping effect).

18. The proximity of suitable early brooding habitat could be an important variable in nest site selection? / Why are certain nest sites chosen when "better" concealing cover exists in close proximity (often within meters) if habitat structure is the sole selection criterion? (Would explain the extensive use of edges when selecting nesting habitat, and have implications for the new guidelines no burn policy in large tracts of sagebrush)

Additional Points of Discussion:

Grazing: The ultimate question is how to manage areas for nesting habitat that provide a dense canopy of sagebrush and a healthy grass component (both indicators of a late successional stage) as well as an abundance of food forbs (early successional stage species)? Grazing disturbs the interstitial spaces between sagebrush plants, which would provide areas for weedy forb invasion. However, nesting habitat cannot be grazed to a point that grass cover is compromised (especially late season grass cover and height that carries over into the following nesting season as residual herbaceous cover).

This leads us into the next dilemma: How do we combine economically feasible stocking rates with the need to ensure residual stubble height and cover, especially during drought conditions? Stocking rates throughout the state do not appear to compromise sage grouse productivity during wet years (sage grouse populations in Rawlins and Bates Hole increased during the study). But, if stocking densities were determined during drought conditions, cattle numbers would probably be too low to ensure the economic survival of many ranches. Current stocking levels would require that herbaceous cover be monitored annually, and livestock removed when heights and coverage reach a predetermined level. In certain years, livestock removal could be early in the summer. Supplemental feeding would then become a necessity.

Cycling Populations: A ten-year population cycle has been basically confirmed in sage grouse populations throughout Wyoming (data dating to the early 1930's). Clait Braun (Colorado Division of Wildlife) has also indicated that populations cycle every ten years within Colorado. However, each population peak has been lower than the previous, indicating a long-term population decline.

Sage grouse hunting seasons were closed throughout Wyoming from 1937 through 1948. Based on my understanding of public perception as it related to wildlife during this period in U.S. history, for the Game and Fish Department to restrict hunting, populations must have been exceptionally low. Harvest data collected throughout the state indicates that sage grouse populations peaked in the late 1960's and early 1970's (unfortunately, no population data is available for the perceived peak prior to the 1937 low). The possibility of a 30 to 40 year cycle exists.

This leads us to two questions: (1) Is the current population low a natural cyclic low? Which would indicate that we are not considering an important variable or condition which has influenced the decline (populations possibly cycling with sagebrush decadence). And, (2) Grazing pressure on sagebrush dominated ecosystems throughout the 1950's and 60's was less progressive and more intense than during the 1980's. If grazing is the reason behind the population decline, how were populations able to rebound from the 1940's low? A thought: recent BLM grazing management has centered around reestablishing healthy riparian areas. This has resulted in increased grazing pressure on sagebrush uplands. Sage grouse require grass cover in sagebrush uplands for nesting success (less grazing), and forb cover in riparian areas for summer feeding (more grazing). Historical grazing pressure (bison) probably concentrated around riparian zones. Has this shift to grazing uplands been a factor in the sage grouse decline?

Fragmentation: There are several questions dealing with this issue in Wyoming, where most of the sagebrush dominated habitat throughout the state has not been fragmented, in the classic sense of fragmentation.

A. Are Wyoming's sagebrush landscapes fragmented? And, what is causing this fragmentation?

Example: Sage grouse appear to avoid power lines that could potentially be used by raptors as perch sites (based on anecdotal observations in Bates Hole). This avoidance pattern has effectively fragmented the landscape, although the habitat under the power lines is suitable.

B. When sagebrush canopies are eliminated through fire or management, at what spatial point is a portion of that area not used by sage grouse?

Sage grouse prefer to remain close to sagebrush cover, but will use these burns, especially as summer feeding sites. Yet, if the area is large, birds tend to stay out of the middle. The question is, at what point is the disturbance large enough to exclude birds, thereby causing fragmentation?

Sage grouse exhibit remarkable site fidelity, often nesting and rearing their broods in the same sagebrush patch year after year. If that patch is destroyed, and the nearest suitable habitat is outside of the typical area that the hen will search, what happens? Probably one of two things: (1) she will continue her search until suitable habitat is found. If sage grouse concentrate in the remaining suitable habitat, this could theoretically result in a sink (concentrated prey). Or, (2) she will nest in sub-par habitat. Eventually, this will result in the elimination of her and her lineage.

Which leads to more questions: (1) How close does a persistent population have to be to colonize an area that has become reestablished with suitable habitat? (2) How large does an undisturbed area have to be to ensure that the reservoir population persists? (3) How important are corridors for colonization? (4) Etc. These questions are important as the slow reestablishment rate of sagebrush (30-40 years) requires a sage grouse re-colonization event.

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