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Grazing system and linear corridor influences on greater sage-grouse (Centrocercus urophasianus) habitat selection and productivity
... We include well pads as a variable as one of the habitat areas, Mesa, has significant oil and gas development (Holloran et al. 2010) and the location of future oil and gas development in this area of Wyoming is an important issue facing land management agencies (Wyoming Game and Fish 2016). All three of the habitat areas have different areal extents of main gravel roads and two-track roads due to differences in local management activities; both road types have been linked to nesting habitat (Lyon 2000;Kuipers 2004). ...
Habitat suitability analysis is complex and requires integration of multiple attributes at a range of spatial scales. We use fine-and broad-scale variables within a spatial modelling framework to determine the suitability of greater sage-grouse nesting habitat using fuzzy logic. Fuzzy theory allows for a landscape component to have full, partial, or no membership in a particular management target. We used seven biophysical and anthropogenic variables correlated with nest site locations to build the fuzzy model. Using field and remotely sensed data and expert opinion, we developed fuzzy functions to define numerical membership values describing relationships between landscape characteristics and nesting habitat suitability. We used a fuzzy gamma overlay function to define five suitability classes in the resulting habitat map. Using a fuzzy logic model, we were able to spatially distinguish the suitability of nesting habitat using fine-and broad-scale attributes and characterise the uncertainty of the habitat model.
... Nests located in drainage features had lower survival rates than nests located on ridges. Drainage features may be used as travel corridors by mammalian predators resulting in a higher probability of detection for nests located within these features (Kuipers 2004). In addition, reduced survival in habitats characteristic of higher variation in shrub cover could be the result of an edge effect where nests become more susceptible to predation based on proximity to edge (Batary and Baldi 2004). ...
... We studied Greater Sage-Grouse at seven sites located in central and southwestern Wyoming in 1994(detailed description in Holloran et al. 2005. Although habitat manipulations (i.e., fire, herbicide application) and livestock grazing occurred in the study area (Holloran 1999, Lyon 2000, Slater 2003, Kuipers 2004, large scale habitat conversions (i.e., cropland, human dwellings) were not present, and areas were dominated by uniformly distributed sagebrush habitats. Areas fragmented by natural gas development were removed from consideration. ...
Degradation of nesting habitat has been proposed as a factor contributing to Greater Sage-Grouse (Centrocercus urophasianus) population declines throughout North America. Delineating suitable nesting habitat across landscapes with relatively contiguous sagebrush cover is difficult but important to identify areas for protection. We used radio-telemetry to locate Greater Sage-Grouse nests in relatively contiguous sagebrush habitats in Wyoming to investigate the spatial arrangement of nests relative to lek and other nest locations. Nest distributions were spatially related to lek location within 3 and 5 km of a lek, and a 5-km buffer included 64% of the nests. There was no relationship between lek size and lek-to-nest distance, suggesting that accurate population trend evaluation might require lek surveys in addition to lek counts. Closest known lek-to-nest distance was greater for successfully hatched compared to destroyed nests, and closely spaced nests tended to experience lower success and have higher probabilities of both nests experiencing the same fate compared to isolated nests, suggesting that a mechanism of enhanced prey detection occurred at higher nest densities. A low probability that a given individual's consecutive-year nest spacing occurred randomly suggested nesting site-area fidelity. Although a grouped pattern of nests occurred within 5 km of a lek, the proportion of nesting females located farther than 5 km could be important for population viability. Managers should limit strategies that negatively influence nesting habitat regardless of lek locations, and preserve adequate amounts of unaltered nesting habitat within treatment boundaries to maintain nest dispersion and provide sites for philopatric individuals.
... In Wyoming, we found that visual predators (birds, such as the Common Raven) and olfactory predators (mammals, such as badgers) depredated the same number of Greater Sage- Grouse nests. Although our method of identifying predators may have led to some error, others studies have also used the remains of the nest, eggshells, scat, tracks, or hair to identify predators that depredated the nests of Greater Sage-Grouse (Slater 2003, kuipers 2004, Moynahan 2004). Our finding that five nests were depredated by avian predators and five by mammalian predators was similar to that of a camera study in Nevada, in which ten nests were depredated by Common Ravens and seven by badgers (Coates et al. 2008). ...
Birds can hide from visual predators by locating nests where there is cover and from olfactory predators where habitat features create updrafts, high winds, and atmospheric turbulence, but sites optimal for hiding from visual and olfactory predators often differ. We examined how Greater Sage-Grouse (Centrocercus urophasianus) balance the dual needs of hiding from both visual and olfactory predators on Parker Mountain, Utah, where the Common Raven (Corvus corax) is the main visual predator and the striped skunk (Mephitis mephitis) and American badger (Taxidea taxus) are the main olfactory predators. By comparing nest sites to random sites during 2005 and 2006, we found that sage-grouse nest at sites where their nests were obscured from visual predators but were exposed to olfactory predators. To validate these findings, we replicated the study in southwest Wyoming during 2008. Again, we found that visual obscurity at nest sites was greater than at control sites but olfactory obscurity was less. Our results indicate that Greater Sage-Grouse select nest sites where they will be concealed from visual predators but at the cost of locating nests where they are exposed to olfactory predators. In southwest Wyoming, we found that olfactory predators (mammals) and visual predators (birds) depredated an equal number of nests. By selecting nest sites with visual obscurity, Greater Sage-Grouse have reduced the threat from visual predators to where it was similar to the threat posed by olfactory predators.
Las aves pueden esconder sus nidos de depredadores visuales localizándolos en sitios con cobertura y de depredados olfatorios donde las características del hábitat crean corrientes de aire, vientos fuertes o turbulencia atmosférica, pero los sitios con características óptimas para esconder los nidos de cada tipo de depredador generalmente son diferentes. Examinamos como Centrocercus urophasianus evalúa las necesidades de esconder sus nidos ante depredadores visuales y olfatorios en las montañas Parker, estado de Utah, donde el cuervo Corvus corax es el principal depredador visual mientras que los mamíferos Mephitis mephitis y Taxidea taxus son los principales depredadores olfatorios. Al comparar las características de los sitios de anidación con las de sitios al azar durante 2005 y 2006, encontramos que los nidos de C. urophasianus se encontraban escondidos de depredadores visuales pero que estaban expuestos a depredadores olfatorios. Para validar estos hallazgos, replicamos el estudio en el sudoeste de Wyoming en 2008. Nuevamente encontramos que la cobertura visual en los nidos era mayor que para sitios al azar, pero que la cobertura olfatoria era menor. Nuestros resultados indican que C. urophasianus selecciona los sitios de anidación con características que esconden los nidos de depredadores visuales pero a costa de localizar los nidos en sitios expuestos a depredadores olfatorios. En el sudoeste de Wyoming, encontramos que los depredadores olfatorios (mamíferos) y visuales (aves) depredaron la misma cantidad de nidos. Al seleccionar sitios de anidación con cobertura visual, C. urophasianus ha reducido el riesgo de depredación por depredadores visuales a un nivel similar al del riesgo impuesto por los depredadores olfatorios.
... Chick survival was commonly reported over different time periods (from hatch to 18-50 days). Numerous studies also reported indices of productivity (e.g., number of chicks per hen in August) rather than estimated chick survival and could not be included in the analysis (e.g., Sveum 1995, Heath et al. 1998, Slater 2003, Kuipers 2004. Time periods for estimates of juvenile survival also varied. ...
Despite decades of field research on greater sage-grouse, range-wide demographic data have yet to be synthesized into a sensitivity analysis to guide management actions. We reviewed range-wide demographic rates for greater sage-grouse from 1938 to 2011 and used data from 50 studies to parameterize a 2-stage, female-based population matrix model. We conducted life-stage simulation analyses to determine the proportion of variation in population growth rate (λ) accounted for by each vital rate, and we calculated analytical sensitivity, elasticity, and variance-stabilized sensitivity to identify the contribution of each vital rate to λ. As expected for an upland game bird, greater sage-grouse showed marked annual and geographic variation in several vital rates. Three rates were demonstrably important for population growth: female survival, chick survival, and nest success. Female survival and chick survival, in that order, had the most influence on λ per unit change in vital rates. However, nest success explained more of the variation in λ than did the survival rates. In lieu of quantitative data on specific mortality factors driving local populations, we recommend that management efforts for greater sage-grouse first focus on increasing female survival by restoring large, intact sagebrush-steppe landscapes, reducing persistent sources of human-caused mortality, and eliminating anthropogenic habitat features that subsidize species that prey on juvenile, yearling, and adult females. Our analysis also supports efforts to increase chick survival and nest success by eliminating anthropogenic habitat features that subsidize chick and nest predators, and by managing shrub, forb, and grass cover, height, and composition to meet local brood-rearing and nesting habitat guidelines. We caution that habitat management to increase chick survival and nest success should not reduce the cover or height of sagebrush below that required for female survival in other seasons (e.g., fall, winter). The success or failure of management actions for sage-grouse should be assessed by measuring changes in vital rates over long time periods to avoid confounding with natural, annual variation. © 2011 The Wildlife Society.
... It is more difficult to spatially quantify the indirect impacts of anthropogenic disturbances on habitat quality than it is to quantify the direct impacts resulting from the conversion of one habitat type into another (Sawyer et al. 2006). The extrapolation of direct habitat loss to indirect impacts is not straightforward because different indirect impacts may be observed in otherwise suitable habitats that are in varying distances from the disturbance (Beck and Mitchell 2000, Lyon and Anderson 2003, Kuipers 2004, Sawyer et al. 2006. For example, Ingelfinger and Anderson (2004) observed lower densities of sagebrush-obligate passerine bird species within 100 m of energy-related developments, whereas Sawyer et al. (2006) noticed that mule deer habitat use was altered in otherwise suitable habitats nearly 4 km away from natural gas wells. ...
Energy development has been occurring in the intermountain western United States for over a century, yet few studies have attempted to spatially quantify the impacts of this disturbance on native ecosystems. We used temporal remotely sensed data for the Pinedale Anticline Project Area (PAPA) in western Wyoming, a region that has experienced increased natural gas development within the past 10 yr, to quantify the spatiotemporal distribution of Wyoming big sagebrush Artemisia tridentata, natural gas development, and other landcover types. Our analyses included 5 Landsat Thematic Mapper (TM) images of the PAPA over a 22-yr period (1985–2006). We determined whether Wyoming big sagebrush spatiotemporal patterns were associated with natural gas development or other landcover types. We also developed a footprint model to determine the direct and indirect impacts of natural gas development on the distribution of Wyoming big sagebrush habitats. Over the 22-yr period, we observed an inverse relationship between the amount of Wyoming big sagebrush habitat and natural gas development. During this time, Wyoming big sagebrush habitat declined linearly at a rate of 0.2% yr−1 (4.5% total net loss), whereas natural gas development increased exponentially at a rate of 20% yr−1 (4800% total net increase). Our evaluation indicated that, by 2006, natural gas development directly impacted 2.7% (1750 ha) of original Wyoming big sagebrush habitat. Indirect impacts, quantified to account for degraded habitat quality, affected as much as 58.5% (assuming 1000-m buffers) of the original Wyoming big sagebrush habitat. Integrating assessments of the direct and indirect impacts will yield a better elucidation of the overall effects of disturbances on ecosystem function and quality.
Degradation of nesting habitat has been proposed as a factor contributing to Greater Sage-Grouse (Centrocercus urophasianus) population declines throughout North America. Delineating suitable nesting habitat across landscapes with relatively contiguous sagebrush cover is difficult but important to identify areas for protection. We used radio-telemetry to locate Greater Sage-Grouse nests in relatively contiguous sagebrush habitats in Wyoming to investigate the spatial arrangement of nests relative to lek and other nest locations. Nest distributions were spatially related to lek location within 3 and 5 km of a lek, and a 5-km buffer included 64% of the nests. There was no relationship between lek size and lek-to-nest distance, suggesting that accurate population trend evaluation might require lek surveys in addition to lek counts. Closest known lek-to-nest distance was greater for successfully hatched compared to destroyed nests, and closely spaced nests tended to experience lower success and have higher probabilities of both nests experiencing the same fate compared to isolated nests, suggesting that a mechanism of enhanced prey detection occurred at higher nest densities. A low probability that a given individual's consecutive-year nest spacing occurred randomly suggested nesting site-area fidelity. Although a grouped pattern of nests occurred within 5 km of a lek, the proportion of nesting females located farther than 5 km could be important for population viability. Managers should limit strategies that negatively influence nesting habitat regardless of lek locations, and preserve adequate amounts of unaltered nesting habitat within treatment boundaries to maintain nest dispersion and provide sites for philopatric individuals.
Populations of Greater Sage-Grouse (Centrocercus urophasianus) have been declining throughout their range since the 1960s. Productivity, which includes production and survival of young, is often cited as a factor in these declines. We monitored radio-equipped Greater Sage-Grouse at 3 sites in western Wyoming to assess early brood-rearing habitat use (through 14 days post-hatch) and productivity. Logistic and linear regression analyses with Akaike's Information Criterion were used to evaluate early brooding habitat use and to examine relationships between productivity and vegetation, insect size and abundance, and weather parameters. Females with broods were found in areas with greater sagebrush canopy and grass cover, and fewer invertebrates compared to random areas. The number of juveniles per female (estimated from wing barrel collections during fall harvest) was positively related to the abundance of medium-length Hymenoptera and grass cover, and the proportion of females with confirmed chicks 14 days post-hatch was positively related to abundance of medium-length Coleoptera and total herbaceous cover. Although the specific parameters varied slightly, Greater Sage-Grouse productivity in Wyoming appeared to be associated with a combination of insect and herbaceous cover elements. Managing for abundant and diverse insect communities within dense protective sagebrush stands should help ensure high-quality early brood-rearing habitat and increased Greater Sage-Grouse productivity.
ABSTRACT Sagebrush (Artemisia spp.)-dominated habitats in the western United States have experienced extensive, rapid changes due to development of natural-gas fields, resulting in localized declines of greater sage-grouse (Centrocercus urophasianus) populations. It is unclear whether population declines in natural-gas fields are caused by avoidance or demographic impacts, or the age classes that are most affected. Land and wildlife management agencies need information on how energy developments affect sage-grouse populations to ensure informed land-use decisions are made, effective mitigation measures are identified, and appropriate monitoring programs are implemented (Sawyer et al. 2006). We used information from radio-equipped greater sage-grouse and lek counts to investigate natural-gas development influences on 1) the distribution of, and 2) the probability of recruiting yearling males and females into breeding populations in the Upper Green River Basin of southwestern Wyoming, USA. Yearling males avoided leks near the infrastructure of natural-gas fields when establishing breeding territories; yearling females avoided nesting within 950 m of the infrastructure of natural-gas fields. Additionally, both yearling males and yearling females reared in areas where infrastructure was present had lower annual survival, and yearling males established breeding territories less often, compared to yearlings reared in areas with no infrastructure. Our results supply mechanisms for population-level declines of sage-grouse documented in natural-gas fields, and suggest to land managers that current stipulations on development may not provide management solutions. Managing landscapes so that suitably sized and located regions remain undeveloped may be an effective strategy to sustain greater sage-grouse populations affected by energy developments.
We tested how edges affect nest survival and predator distribution in a native tallgrass prairie system in southwestern Missouri using artificial nests, natural nests of Dickcissels (Spiza americana) and Henslow's Sparrows (Ammodramus henslowii), and mammal track stations. Survival of artificial nests was lower within 30 m of forest edge. Nesting success of Dickcissels and Henslow's Sparrows was lower within 50 m to a shrubby edge than at greater distances, whereas fates of nests were not related to distances to roads, agricultural fields, or forests. Evidence from clay eggs placed in artificial nests indicated that mid-sized carnivores were the major predators within 30 m of forest edges. Furthermore, mid-sized carnivores visited track stations most frequently within 50 m of forest edges. Because proximity of woody habitat explained more variation in nest survival and mammal activity than did fragment size, it appears that edge effects were more pronounced than area effects. Edge effects appeared to be caused mainly by greater exposure of nests to mid-sized carnivores. We argue that, based on edge avoidance behavior, “grassland-interior” species such as the Henslow's Sparrow respond to edge effects mainly by a decrease in density, whereas habitat generalists such as the Dickcissel are affected mainly by a decrease in nesting success.
During the 1980's short-duration grazing attracted much attention based on the claims it would accelerate range improvement while at the same time accommodating higher stocking rates. On many ranches it was contended that stocking rates could be doubled or even tripled while at the same time improving both range and livestock productivity. We will summarize present knowledge on short-duration grazing, focusing on a few recent studies that are fairly complete in terms of evaluating soil, vegetation, livestock, and financial responses over time and space. The managerial implications of these studies and their relevance to Savory's ideas will be given particular emphasis. Reviews of various grazing studies from Africa will be included in our discussion.
We studied sagebrush (Artemisia spp.) exposure above snow and topographic distribution of sage grouse (Centrocercus urophasianus) foraging sites in winter (Jan-Mar) in the Gunnison Basin, Colorado. Sage grouse feeding activity (n = 157 foraging sites) was not proportionally distributed among 5 topographic categories (P < 0.001). Most (46 and 75% of foraging sites in 1985 and 1986, respectively) feeding activity occurred in drainages and on slopes with south or west aspects. Use of slopes with north or east aspects was less than expected. Distribution of sage grouse feeding activity was influenced by topographic variation in snow depth and mountain big sagebrush (A. tridentata vaseyana) exposure above snow. During a severe winter in 1984, <10% of the sagebrush vegetation in the Gunnison Basin was exposed above snow and available to sage grouse. During milder winters in 1985 and 1986, exposure of sagebrush was 84 and 79%, respectively. We recommend that sagebrush be maintained in drainages and on slopes with south or west aspects.
We estimated survival rates of greater sage-grouse (Centrocercus urophasianus) in North Park, Colorado, USA, from band-recovery data of 6,021 birds banded during spring, 1973-1990, with recoveries through 1993. Average annual adult female survival (S̄ = 0.59, SE = 0.011) was greater than average adult male survival (S̄ = 0.37, SE = 0.007), and average subadult (<1 yr old at time of banding) female survival (S̄ = 0.77, SE = 0.030) was greater than average subadult male survival (S̄ = 0.63, SE = 0.034). Four weather covariates (spring and winter precipitation and temperature) did not contribute to predicting annual survival.
Mammalian predation is a major cause of mortality for breeding waterfowl in the U.S. Northern Great Plains, and yet we know little about the selection of prairie habitats by predators or how this influences nest success in grassland nesting cover. We selected 2 41.4-km2 study areas in both 1996 and 1997 in North Dakota, USA, with contrasting compositions of perennial grassland. A study area contained either 15-20% perennial grassland (Low Grassland Composition [LGC]) or 45-55% perennial grassland (High Grassland Composition [HGC]). We used radiotelemetry to investigate the selection of 9 landscape cover types by red fox (Vulpes vulpes) and striped skunk (Mephitis mephitis), while simultaneously recording duck nest success within planted cover. The cover types included the edge and core areas of planted cover, wetland edges within planted cover or surrounded by cropland, pastureland, hayland, cropland, roads, and miscellaneous cover types. Striped skunks selected wetland edges surrounded by agriculture over all other cover types in LGC landscapes (P-values for all pairwise comparisons were
Predation on bird eggs and nestlings on this sandplain grassland in S Maine, was positively correlated with foraging for invertebrates by striped skunks Mephitis mephitis in plots of primary skunk usage. The hypothesis that skunk predation was incidental, rather than targeted towards birds' nests, was also supported by the absence of skunk foraging behavior consistent with active nest searching, absence of a relationship between nest success and vegetative cover or promixity to a forest/grassland edge, the low density of breeding birds (<2.0 territories ha-1) on these grasslands, and the small proportion of avian material, 1.5% reported in the summer skunk diet. Although nest predation was high (58.0% overall), its unpredictability probably limits the utility of certain antipredator behaviors by birds nesting at this site. -from Authors
Improved carrying capacity of grasslands has been attributed to the effect of time-controlled grazing with high animal density, which can be achieved by increased stocking rates as well as by fencing. Therefore, a study was conducted to test the hypothesis that time-controlled grazing with high animal densities and high stocking rates will improve grassland condition. The study was made over a 6-year period on 3 sites with time-controlled grazing imposed. One site was on native grassland in the Fescue Prairie and 2 sites, 1 on seeded and the other on native grassland, were in the Mixed Prairie. On each site, stocking densities averaged 3,6, and 15 cow-calf pairs/ha, respectively, and stocking rates averaged 1.65,4.45, and 2.72 animal unit months/ha, respectively. Species composition and root mass and distribution were compared on grazed and protected areas within each site. Utilization averaged about 80% of available forage over the study period. Range condi-tion was less on grazed areas than on protected areas in the Fescue Prairie (38 vs 53% of climax) and in the Mixed Prairie (49 vs 53%). Average ash-free root mass, throughout the sampling profile, tended to be greater on the ungrazed vs the grazed area of the native Mixed Prairie site but not on the seeded Mixed Prairie or Fescue Prairie sites. The grazed areas of the Mixed Praiie sites tended to have more available phosphorus, possibly due to the application of manure, but less nitrogen and organic matter. The results led to a rejection of the hypothesis and a conclusion that high animal density and high stocking rates with time-controlled grazing would result in range deterioration.
Number and kinds of cattle trails may have a dramatic impact on relative amount of bare soil and subsequently on amount and rate of soil erosion. The objective of this study was to quantify the effect of a cell-designed, rotational grazing treatment (RG) on density and kinds of cattle trails. Density of cattle trails in the RG treatment was compared to those in heavy continuous (HC), moderate continuous (MC), and deferred rotation (DR) treatments at 4 distances from water. There were no differences among the HC, MC, and DR treatments in density of trails. Trail densities ranged from 14/km near water sources to 9/km at the far end of the pastures. This compares to the RG treatment where trail densities ranged from 164/km near the cell center to 24/km at the far end of the paddock. The effect of increasing the RG treatment from 14 to 42 paddocks was also investigated. Subdivision of paddocks increased trail densities near the center from 32/km to 57/km with no increase noted at the far ends of the paddocks. It is concluded that implementation of a cell-designed, RG system will cause a significant increase in density and number of cattle trails particularly near the cell center.
The effects of fall and spring sheep use on cover components and recovery following a change in seasonality of grazing prac-tices, were studied within long-term grazing treatments of three-tip sagebrush (Artemisia tripartitu Rydb.) steppe on the U.S. Sheep Experiment Station near Dubois, Ida. Few significant dif-ferences existed among treatments within the litter, moss, lichen, and soil components, but several differences in vegetational cover categories occurred. More live shrub and annual grass cover were observed in the long-term (since 1924) and new spring (since 1950) treatments than in the long-term fall (since 1924), new fall (since 1950), old exclosure (since 1940), and new exclo-sure (since 1950) (P < 0.01). More perennial grass and forb cover, and less dead shrub cover existed in fall-grazed treatments (P < 0.01). The new fall-grazed treatment previously grazed in the spring failed to reach a more uniform mixture of perennial growth forms after 46 years such as was evident in the long-term fall, which suggests low resilience following spring grazing. The exclosure which was heavily spring and fall-grazed prior to 1950 had even less perennial forb cover than the new fall treatment, indicating that the cessation of sheep grazing did not promote herb recovery any better than continued fall use. The direct impact of sheep herbivory and its indirect effects on the competi-tive relationships among major plants appear to have affected the cover of sagebrush steppe components at thii study site.
We quantified predation on artificial nests in Iowa roadsides and examined the relationships between nest predation and characteristics of roadsides. Transects consisting of 10 nests (five in the foreslope and five the in backslope) were set up in 136 roadsides in six watersheds in south-central Iowa. Most roadsides had herbaceous vegetation with fences (67%); fewer were wooded (18%) or had herbaceous vegetation without fences (15%). Most roads were gravel (80%), and most roadsides were adjacent to row crops (63%). Average total nest predation per transect was 23% (SE = 2), ranging from 0 to 100%. Nest predation was categorized into one of three outcomes; disappearance of eggs without disturbance to the nest bowl (39%), disappearance of eggs with disturbance to the nest bowl (17%), and broken or crushed egg shell fragments in or near the nest bowl (44%). Wooded roadsides and herbaceous roadsides with fences had significantly greater nest predation than herbaceous roadsides without fences for disappearance of eggs without disturbance to the nest bowl. Backslopes had significantly greater nest predation than foreslopes for all outcome categories except the disappearance of eggs with disturbance to the nest bowl. Wooded roadsides and herbaceous roadsides with fences along the backslope may provide cover and travel corridors for mammalian predators or elevated perches for avian predators.
ID for their valuable comments and criticisms. The mission of the Policy Analysis Center for Western Public Lands is to help rural communities, policy makers, resource managers and users, and others understand, analyze and engage effectively in the public land policy process. The Center will provide relevant, science-based information and analysis of ongoing and proposed public land management policies.
Available data indicate that sage grouse Centrocercus urophasianus have declined throughout their range. This species presently occurs in 11 U.S. States and in two Canadian provinces. In nine states having long-term data, breeding populations have declined by 17-47% (̄ = 33%) from the long-term average. Six states have long-term information on sage grouse production. In five of these states, production has declined by 10-51% (̄ = 25%) from the long-term average. Habitat deterioration, loss, and fragmentation have reduced the quantity and quality of nesting and early brood-rearing habitat causing population declines. Factors appearing to be largely responsible for the changes in habitats and, ultimately, sage grouse populations over wide areas of western North America are discussed, and hypotheses that could be tested to provide better insight into sage grouse population declines are suggested. Once these changes are better understood, conservation strategies that address protection and rehabilitation of sagebrush Artemisia spp. rangelands should be developed and implemented in each state and province to halt the decline of sage grouse and initiate recovery.
We tested how edges affect nest survival and predator distribution in a native tallgrass prairie system in southwestern Missouri using artificial nests, natural nests of Dickcissels (Spiza americana) and Henslow's Sparrows (Ammodramus henslowii), and mammal track stations. Survival of artificial nests was lower within 30 m of forest edge. Nesting success of Dickcissels and Henslow's Sparrows was lower within 50 m to a shrubby edge than at greater distances, whereas fates of nests were not related to distances to roads, agricultural fields, or forests. Evidence from clay eggs placed in artificial nests indicated that mid-sized carnivores were the major predators within 30 m of forest edges. Furthermore, mid-sized carnivores visited track stations most frequently within 50 m of forest edges. Because proximity of woody habitat explained more variation in nest survival and mammal activity than did fragment size, it appears that edge effects were more pronounced than area effects. Edge effects appeared to be caused mainly by greater exposure of nests to mid-sized carnivores. We argue that, based on edge avoidance behavior, “grassland-interior” species such as the Henslow's Sparrow respond to edge effects mainly by a decrease in density, whereas habitat generalists such as the Dickcissel are affected mainly by a decrease in nesting success.
Greater sage-grouse (Centrocercus urophasianus )populations have declined from 6 6 to 92% during the las t 3 0 years in Canada, where they are listed as endangered. We used radiotelemetry to examine greater sage-grous e nest and brood habitat use in Alberta and assess the relationship between habitat and the population decline. W e also identified the patch size at which sage-grouse were selecting nest and brood-rearing sites. Nest areas were i n silver sagebrush (Artemisia can a) stands that had greater amounts of tall cover ( P ≤ 0 .00 1 ) at a patch size of 7 . 5 t o 1 5m in radius. Within those sagebrush stands, nests were located beneath the densest sagebrush present. Area s used for brood rearing had greater amounts of taller sagebrush cover in an area ≥1 5 m in radius than at random locations. Brood locations were not selected based on forb content; mesic areas containing forbs (20% -40% cover ) as a food resource for chicks were limiting (only 12% cover available). Overall cover of sagebrush is considerabl y lower in Canada ( 5 -11% ) compared with sagebrush (Artemisi aspp.) cover in other areas throughout the range o f greater sage-grouse (1 5 -25% ). If management goals are to provide suitable nesting and brood-rearing habitat , efforts should be directed toward protecting and enhancing sagebrush stands ≥3 0 m 2and increasing overall sag e - brush cover. Management strategies also should focus on increasing the availability of mesic sites and increasin g the abundance of sites with >10% forb cover, to enhance brood rearing habitat .
The status of sage grouse populations and habitats has been a concern to sportsmen and biologists for >80 years. Despite management and research efforts that date to the 1930s, breeding populations of this species have declined throughout much of its range. In May 1999, the western sage grouse (C. urophasianus phaios) in Washington was petitioned for listing under the Endangered Species Act because of population and habitat declines (C. Warren, United States Fish and Wildlife Service, personal communication). Sage grouse populations are allied closely with sagebrush (Artemisia spp.). Despite the well-known importance of this habitat to sage grouse and other sagebrush obligates, the quality and quantity of sagebrush habitats have declined for at least the last 50 years. Braun et al. (1977) provided guidelines for maintenance of sage grouse habitats. Since publication of those guidelines, much more information has been obtained on sage grouse. Because of continued concern about sage grouse and their habitats and a significant amount of new information, the Western States Sage and Columbian Sharp-tailed Grouse Technical Com- mittee, under the direction of the Western Association of Fish and Wildlife Agencies, request- ed a revision and expansion of the guidelines originally published by Braun et al. (1977). This paper summarizes the current knowledge of the ecology of sage grouse and, based on this information, provides guidelines to manage sage grouse populations and their habitats.
Food habits of prairie skunks are not well understood, yet such knowledge might provide insight into factors influencing nest depredation. We studied food habits of radiocollared adult striped skunks (Mephitis mephitis) during 1976-78 in North Dakota, where skunks are regarded as important predators of ground-nesting birds. Plant foods, primarily grain and sunflower seeds, occurred in a larger percentage of scats in spring (15 Apr-31 May) than summer (1 June-15 July, P=0.04), but overall, plant foods were a minor part of skunk diets. Animal foods, primarily birds (including eggs), small rodents, and insects, occurred annually in a large percentage of the scats of all skunks. These foods were acquired nearly exclusively in grasslands. Percentage of scats containing animal foods was similar, irrespective of sex, season, or year (P>0.45). In spring, vertebrates occurred in a smaller percentage of scats of females than males (P<0.01). Among females, vertebrates also occurred in a smaller percentage of scats in spring than summer (P<0.01). Among all skunks, birds occurred in a smaller percentage of scats in spring than in summer (P<0.01). Both birds (P<0.02) and mammals (P<0.01) occurred in a smaller proportion of scats when wetland conditions were poor. Percentage of scats containing insects, the primary invertebrate food of skunks, did not vary by sex, season, or year (P>0.15). Insects were mostly adult and larval Coleoptera, larval Lepidoptera, and adult and nymph Orthoptera.
Heavy grazing continues to be an important problem on rangelands in the United States and other parts of the world. This is somewhat puzzling in view of the fact that 25 long term grazing studies are consistent in showing it to be a losing proposition, financially, as well as biologically. Torell et al. (1991) using a Colorado prairie study (Sims et al. 1976), found profit-maximizing stocking rates were well below those that would deteriorate the rangeland resource. Workman (1986), as well as several studies we reviewed, drew the same conclusion. Therefore we believe ignorance, rather than monetary incentive, is the main reason why overgrazing is still such a serious problem. Rotation grazing systems have been widely recommended by various government agencies concerned with range management. However research shows stocking rate reductions from heavy to conservative, have much higher probability of increasing grazing capacity, reducing risk, increasing financial returns, and reducing erosion. Many of the rotation grazing systems were studied using heavy stocking rates. Moderate continuous grazing typically gave better vegetation, livestock, and financial performance than rotation grazing at heavy stocking rates. However under moderate stocking rates there is evidence that some rotation grazing systems give equal or superior vegetation, livestock, and financial performance to continuous grazing. The Merrill 3 herd/4 pasture system has proven superior to continuous grazing on Texas rangelands. The Merrill 3 herd/4 pasture system differs from all others in that it involves multiple herds and only 25% of the rangeland receives non-use at any time. We have talked to many ranchers outside of Texas who have had considerable success with the Merrill multi-herd approach. We believe this approach should receive experimental evaluation in other range types.
Road reserves provide habitat for wildlife. Roadside vegetation has greatest value as a wildlife habitat when it comprises remnant or regenerated strips of indigenous vegetation. Road, roadside habitats and the aerial space above roads can facilitate the movement of animals along the direction of the road reserve. Road reserves can act as a filter or barrier to the movements of wildlife through the landscape, thus dividing and isolating populations to varying extents. Roads are a source of mortality for wildlife. For some species, particularly those that are large, rare, or are regularly brought into contact with busy roads, road-kills can have a significant effect on conservation status. Road systems are a source of biotic and abiotic effects on the surrounding landscape. -from Author
Diet, dietary selection, and nutritional composition of the foods of sage grouse (Centrocercus urophasianus) hens were determined during the pre-laying period in southeastern Oregon in 1990 and 1991. We collected 42 female sage grouse during a 5-week period preceding incubation (4 March-8 April). Sagebrush (Artemisia spp.) was the most common among 21 foods consumed but forbs composed 18 to 50% of the diet by weight. Desert-parsley (Lomatium spp.), hawksbeard (Crepis spp.), long-leaf phlox (Phlox longifolia Nutt.), everlasting (Antennaria spp.), mountain-dandelion (Agoseris spp.), clover (Trifolium spp.), Pursh's milk-vetch (Astragalus purshii Dougl.), buck wheat (Eriogonum spp.), and obscure milk-vetch (A. obscurus) were the primary (≥1% of the diet by weight) forbs consumed. Forbs were used selectively over sagebrush in both low and big sagebrush cover types. All forbs were higher in crude protein and phosphorus and many were higher in calcium than sagebrush. Consumption of forbs increased nutrient content of the composite diet. Substantially fewer forbs were present in the diet in 1991 than in 1990, which coincided with reduced sage grouse productivity on the study area. These results suggest that consumption of forbs during the pre-laying period may effect reproductive success by improving nutritional status of hens.
Livestock production from grazing is an integrated measure of the quantity and quality of forage produced and consumed. Research was conducted over 6-yr to assess the effects of four yearlong grazing treatments on cow-calf production (382 cows Bos taurus) and economic returns under extensive rangeland conditions (4637 acres). Treatments were heavy (HC) and moderate (MC) stocked continuous (1-pasture; 1-herd), a moderate stocked 4-pasture, 3-herd deferred rotation (DR); and a very heavily stocked 16-pasture, 1-herd rotation (RG). Averaged across years, stocking rates were approximately 12, 16, 15, and 10 acres/cow-year for the HC, MC, DR, and RG treatments, respectively. From 1982 through 1987, conception rates averaged 89, 93, 95, and 89%; weaned calf crops averaged 80, 83,86, and 80%; weaning weights averaged 579, 574, 593, and 550 lb; production/cow averaged 466, 467, 508, and 439 lb; production per acre averaged 40, 31,35, and 45 lb; and residual returns to land, management and profit averaged $60.81, $69.57, $93.12, and $62.72/cow and $5.35, $4.46, $6.47, and $6.63/acre for the HC, MC, CR, and RG treatments, respectively. Results show that stocking rate was the major factor affecting differences among grazing treatments in cow/calf production and economic returns and that, as stocking rate was increased, production stability decreased.
Please view the pdf by using the Full Text (PDF) link under 'View' to the left. Copyright © 1990. . Copyright © 1990 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, 5585 Guilford Rd., Madison, WI 53711 USA
Studies of Capercaillie Tetrao urogallus and Black Grouse T. tetrix in Northern Europe have found that juvenile males of these sexually size dimorphic species suffer higher mortality than juvenile females during adverse conditions. This difference may be due to the more rapid growth rates among males. Differences in the juvenile survival of the dimorphic Sage Grouse Centrocercus urophasianus and the monomorphic Gray Partridge Perdix perdix were studied in western North America. Juvenile male Sage Grouse survive less well than juvenile females during years unfavorable for juvenile survival and in poorer habitats. Juvenile male Gray Partridge showed little or no such trend. These results are consistent with those obtained in the European studies. Pressures of sexual selection may have led to a growth rate in juvenile males of highly dimorphic grouse species which is near the upper limit of that which can be sustained by their ecological niche.
Movements and nesting cover of sage grouse (Centrocercus urophasianus) hens were studied in central Montana during the springs of 1969, 1970, 1971, and 1972. Thirty-one sage grouse hens were radio-equipped resulting in 22 nests being located. Nineteen additional nests were located during nest searches and work incidental to telemetry. Adults laid larger clutches than yearling hens and aldo were more successful in bringing off a brood. Sixty-eight percent of the 22 nests of radio-equipped hens occurred within 1.5 miles (2.5 km) of the strutting ground where the h ens were captured. Sagebrush (Artemisia tridentata) formed the nesting cover over all of the nests located. Successful nests werre located in sagebrush stands with a higher average canopy coverage than those of unsuccessful nests, and had significantly greater sagebrush cover with 24 inches (60 cm) of nest and within a 100-square foot (9-m2) plot around nest. Consideration fo the ecological requirements animals affected by publicy funded programs in important. This is especially true of sage grouse since extensive areas of sagebrush have already been eliminated or modified by such programs with little apparent regard for the welfare of this unique game bird.
Trampling by cattle on simulated ground nests were compared between continuous (CONT) grazing at 8.0 ha/steer and short duration grazing (SDG) at 5.3 ha/steer. Trampling losses were similar under CONT grazing (15%) and SDG (9%) at a nest density of 1/ha. Percentage trampling loss did not increase at higher nest densities under either grazing regime. Nest survival curves indicated a loss rate of 2.21%/wk under CONT grazing and 2.09%/wk under SDG. The data from this study suggest there is no reason for concern that SDG with cattle will increase trampling loss of ground nests over CONT grazing.
The habitat use and movements of sage grouse (Centrocercus urophasianus) broods were studied with the aid of radiotelemetry in central Montana during the summers of 1968 and 1969. Five hundred and eleven locations were obtained on 13 radio-marked sage grouse broods. In both summers big sagebrush (Artemisia tridentata) in scattered (1-10 percent) and common (10-25 percent) densities received the greatest utilization by broods. Sagebrush heights at brood sites ranged mainly between 6 and 18 inches. For the 2 years combined, sagebrush canopy coverage averaged 14 percent for June, 12 percent for July, 10 percent for August, and 21 percent for September. Broods utilized sagebrush-grassland benches early in the summer (June and July) and shifted to greasewood (Sarcobatus vermiculatus) bottoms and/or alfalfa (Medicago sativa) fields as the forbs on the higher elevations became desiccated. Broods remained in these bottom types until late August and early September and then shifted back into sagebrush. Sizes of areas used by broods averaged 213 acres in sagebrush in early summer (June and July), 144 acres in alfalfa fields (July and August), 91 acres in greasewood bottoms (July and August), and 128 acres in sagebrush in late summer (August and September). Availability of food appeared to be the factor that determined the vegetational types utilized by broods during different periods of the summer.
A review of pertinent literature shows that grazing systems and grazing intensities both influence herbage production on Western ranges. Mean annual herbage production increased by 13% when grazing systems were implemented at a moderate stocking intensity. Increases were larger (35% and 27%) when continuous livestock use was reduced from heavy to moderate, and moderate to light, respectively. This suggests that adjustments in livestock numbers have a greater effect on herbage production than do grazing systems.
Twenty-nine journals and diaries were reviewed for their vegetation descriptions of the sagebrush-grass area in an attempt to assess the relative importance of herbaceous plants and woody brush in the northern Intermountain West. The early writings suggest a pristine vegetation visually dominated by shrubs. Stands of grass apparently were largely confined to wet valley bottoms, moist canyons, and mountain slopes, with more extensive areas in eastern Oregon near the Cascade Range. The major area was apparently covered by thick stands of brush.
Linear right-of-ways are ubiquitous in the United States and may alter vertebrate populations, yet they remain little studied. We examined the relationship between these areas and common raven (Corvus corax) and red-tailed hawk (Buteo jamaicensis) populations in the Mojave Desert of California by flying helicopter transects along paved highways, transmission powerlines, and control areas (i.e., no highways nor powerlines within 3.2 km). Ravens were equally (P > 0.10) common along highway and powerline transects, but were more (P < 0.02) abundant along these transects than along controls. Raven nests were more (P < 0.0001) abundant along powerlines than along either highways or controls. Red-tailed hawks and their nests were more (P < 0.0001) abundant along powerlines than along either highway or control transects. Neither species used potential nest or perch sites in proportion to their availability. Ravens used power poles as nest sites more (P < 0.001) than expected based on availability, but not (P > 0.10) as perch sites. Red-tailed hawks used power poles for both nesting and perching more (P < 0.001) than expected based on availability. Our data suggest that ravens are more abundant along highways because of automobile-generated carrion, whereas both ravens and red-tailed hawks are more common along powerlines because of the presence of superior perch and nest sites. We recommend that land managers evaluate possible changes in vertebrate populations and community-level interactions when assessing the effects of future linear right-of-way projects.
We tested 2 predictions about the locations of nests of lek-forming species to evaluate a guideline developed to protect sage grouse (Centrocercus urophasianus) nesting habitat. Sage grouse (n = 37) in southeastern Idaho did not attempt to nest midway between leks, as 1 hypothesis suggests. Neither was there evidence indicating that areas surrounding a lek are important for nesting, as a second hypothesis suggests. Because distribution of sage grouse nests was random with respect to lek location, nesting habitat protection based on either hypothesis affords no special protection for nests.
Heavy late-fall grazing by sheep following spring deferment improves deteriorated sagebrush-grass ranges by reducing sagebrush and increasing the production of grasses and forbs. Fall grazing as a method for range improvement is more effective and practical than complete protection from grazing and is less expensive than mechanical or chemical means of sagebrush control. Heavy spring grazing damages good-condition ranges by increasing sagebrush and reducing herbaceous production.
A study of the seasonal movements, productivity, and management of sage grouse (Centrocercus urophasianus) was undertaken by the Idaho Cooperative Wildlife Research Unit from August, 1952, to May, 1960, on an area in Fremont and Clark counties in Idaho, directly west of Yellowstone National Park. Nineteen individual strutting grounds 1/10-10 acres in size were located along 12 miles of the Red Road. Summer brood range was found to be 13-27 miles north and northeast of the Red Road strutting grounds. Flocks of sage grouse began migrating west and southwest in October and November and traveled 30-50 miles, depending upon the depth of the snow. Winter concentrations were usually found where snow was less than 6 inches deep. Dispersal and return east and northeast to the breeding grounds began in late winter for a yearly round trip of 50-100 miles. The number of adult males increased quickly on strutting grounds, and the peak of breeding occurred April 7-21. Strutting grounds were abandoned early in May if there was a high ratio of adults to subadults. A late season peak of subadult males was often seen on strutting grounds after all other grouse had departed. Interstrutting movements of adult males varied from 22 to 53 percent and up to 4.3 miles from original banding sites. Sexing criteria included plumage differences on chin, throat, breast, undertail coverts, and minor marginal tectrices; size of feet; wing length and length of primaries; weights of adults. Identification of gonads provided the only ready internal diagnostic characteristics of sex. Aging criteria included measurement of bursa, and characteristics of outer two primaries, second primary covert, undertail coverts, and sternum. The mandible test is not reliable for adult sage grouse. The high counts of males on strutting grounds has provided a reasonably accurate method of determining breeding population trends. The method may be as much as 20 percent conservative because of cocks which are not on strutting grounds. The reproductive potential cannot be fully assessed without knowledge of the relative proportion of adult to subadult females. Ovulated-follicle counts as a measure of the number of eggs laid are unreliable, but are useful in determining the relative laying effort between yearlings and adult females. Adverse weather during hatching appreciably lowered number of grouse available for fall hunting. Brood census on summer range is useful in determining reproductive success and is reliable until the third week in July, when brood structure begins to deteriorate.
We investigated nest site selection by sage grouse (Centrocercus urophasianus) in southeastern Idaho from 1987 to 1989. During 3 breeding seasons, 79% of 84 nest sites were found under sagebrush (Artemisia spp.). Nest success averaged 53% for grouse that used sagebrush and 22% for birds that used nonsagebrush nest sites. Total vegetative cover for sagebrush and nonsagebrush nest sites was similar. However, grass height was shorter (P = 0.01) at sagebrush compared to nonsagebrush nest sites. Herbaceous cover was important to nesting sage grouse but the relatively low nest success of nonsagebrush nest sites indicated they might provide less than optimal nesting habitat.
Productivity of Sage Grouse (Centrocercus urophasianus) was studied in north-central Washington during 1992-1996. Nest timing and success, clutch size, proba-bility of nesting and renesting, and variation associated with age and year were examined for 84 females monitored with the aid of radio telemetry. Although date of nest initiation varied annually, yearling females (hatched in previous year) consistently nested later than adults; mean date of initiation of incubation was 22 April overall. The average nest contained 9.1 eggs and was incubated for 27 days. Clutch size was smaller for renests than for first nests; clutch size also varied annually. Although the overall rate of nest success was only 36.7%. all females apparently nested at least once, and at least 87.0% of females renested following predation of their first nests. As a result of renesting, annual breeding success was estimated as 61.3%. Percent of all females that produced a brood at least 50 days old was 49.5%; at least 33.4% of 515 chicks survived 2 50 days following hatch. Although the rates of nesting and renesting appear to have been under-estimated in other studied populations, Sage Grouse in north-central Washington display more reproductive effort overall; they lay more eggs and are more likely to nest and renest.
Because of high nest predation and long-term declines in sage grouse (Centrocercus urophasianus) productivity in Oregon, we assessed the effects of vegetational cover and height on predation of artificial sage grouse nests (n = 330). Artificial nest fate was positively associated with tall grass cover and medium-height shrub cover collectively (P = 0.01). No other vegetation, predator, temporal, or spatial variables explained any additional variation in the probability of predation. This study supports the hypothesis that greater amounts of tall grass and medium-height shrub cover at nest sites lower risk of nest predation for sage grouse. Management practices that increase cover and height of native grasses in sagebrush communities with medium-height shrubs are recommended to enhance sage grouse productivity.
Vegetation canopy cover on upland and lowland sites inside and outside a 22-year-old exclosure in big sagebrush (Artemisia tridentata tridentata) range was evaluated by sampling for canopy cover. The area outside the exclosure had received moderate use of grazable forage by cattle in the late winter and spring for the past 22 years. The two sites did not show a consistent response to grazing. Big sagebrush canopy cover was higher inside the exclosure on the upland site and higher outside the exclosure on the lowland site. Big sagebrush dominated the canopy cover both inside and outside the exclosure on both sites and relatively little understory was present. Forbs were nearly absent from the area, which is attributed to a past history of heavy sheep grazing. Elimination of grazing had little effect on vegetation composition on both sites studied.
F ew subjects in recent years have stirred up more con-troversy in the range profession than the issue of using utilization guidelines in public rangeland man-agement. Herbage utilization is now becoming a part of management goals on Forest Service and Bureau of Land Management rangelands in some western states. Arguments against herbage use as a primary range man-agement tool are given by Sharp et al. (1994), Frost et al. (1994), McKinney (1997) and Burkhardt (1997). Collectively these papers develop the case that percent use is difficult to determine and grazing timing is more important to plant welfare than degree of use. We believe that these papers make some valid points, but can be misleading and fail to consider all aspects of the situation. Therefore, we have prepared a response along with suggestions on how graz-ing intensity can be appropriately used in range manage-ment decisions. Grazing Intensity Defined Grazing intensity and percent utilization are often used in-terchangeably but actually differ in what they describe. We define grazing intensity as the cumulative effects grazing animals have on rangelands during a particular time period. In contrast utilization is the percentage of the current year's herbage production consumed or destroyed by herbivores. Percent herbage use provides only one measure of grazing intensity. Others include amount of forage standing crop re-maining at the end of the grazing cycle, percentages of grazed and ungrazed plants, plant stubble heights, litter, or carry over vegetation from previous years and visual ap-pearance. For important backgrounding on the advantages and disadvantages of these approaches we refer the read-er to Jasmer and Holechek (1984). In our discussion we will address grazing intensity recognizing that there are several ways it can be evaluated. How Important is Grazing Intensity to Rangeland Health? We believe many ranchers and range managers are probably confused because some range experts have writ-ten that grazing timing and/or frequency are of primary im-portance in grazing outcomes (Frost et al. 1994, Sharp et al 1994, Burkhardt 1997) while others have emphasized graz-ing intensity (Pieper and Heitschmidt 1988, Heady and Child 1994, Holechek et al. 1998). This issue has emerged as an important controversy in range management. This controversy has created a serious dilemma for public range managers. Should they base their management around prescribed numbers of animals for prescribed peri-ods of time for prescribed seasons or should they use flexi-ble systems that continually attempt to keep animal num-bers in balance with forage resources? Basically, the case for use of grazing intensity as a prima-ry tool in range management decisions centers around 30 long term grazing management studies conducted at vari-ous locations in the United States and Canada. These stud-ies generally show that financial returns from livestock pro-duction, trend in ecological condition, forage production, watershed status, and soil stability are all closely associat-ed with grazing intensity.
Sage Grouse (Centrocercus urophasianus) brood-habitat use was examined during 1992 and 1993 at the Yakima Training Center in Yakima and Kittitas counties, Washington. During the 2 yr we followed 38 broods, of which 12 persisted to 1 August ($\bar x$ = approximately 1.5 chicks/brood). Food forb cover was greater at all brood locations than at random locations. Hens with broods in big sagebrush/bunchgrass habitat (Artemisia tridentata/Agropyron spicatum) selected for greater food forb cover, total forb cover, and lower shrub heights; broods in altered big sagebrush/bunchgrass habitats selected greater tall grass cover and vertical cover height; broods in grassland showed no preference for any measured vegetation characteristics. During the early rearing period (post-hatching-6 wk) each year, broods selected sagebrush/bunchgrass. Broods in 1993 made greater use of grasslands than in 1992 and selected grassland during the late brood-rearing period (7-12 wk). Broods selected for sagebrush/bunchgrass during midday, but 52% of brood locations in the afternoon were in grassland. Tall grass cover was greater at morning (0500-1000 h) and afternoon (1501-2000 h) brood locations than at midday (1001-1500 h) and random locations. Midday brood locations had greater shrub cover and height than morning and afternoon locations. Selection of habitat components was similar to the results of other studies, but habitat conditions coupled with a possible lack of alternate brood-rearing cover types resulted in low survival of chicks.
We evaluated the influence of insect reductions on survival of sage grouse (Centrocercus urophasianus) chicks with 148 captive individuals aged 2-45 days when treatment began. Captive sage grouse chicks 21 days old required insects for optimum development. Quantity of insects in the diet was correlated with sage grouse chick survival and growth.
Medium height (40-80 cm) shrub cover was greater at nonpredated (mean 41%) and predated (29%) nests than in areas immediately surrounding nests (mean 15 and 10%, non-predated and predated, respectively) or random locations (8%). Tall (>18 cm), residual grass cover was greater at nonpredated nests (mean 18%) than in areas surrounding nonpredated nests (6%) or random (3%). Nonpredated nests had greater cover of tall, residual grasses (mean 18%) and medium height shrubs (41%) than predated nests (5 and 29% for grasses and shrubs, respectively). Removal of tall grass cover and medium height shrub cover may negatively influence Centrocercus urophasianus productivity. -from Authors
Steppe larks are rare species in Europe, and several reserves have been established in Spain to promote their conservation. Little is known, however, about the benefits these reserves provide for Iberian larks. At Las Amoladeras Bird Reserve predation of lark nests was high according to the Mayfield method: 68–99% of nests were preyed upon, primarily by red foxes (Vulpes vulpes) and feral dogs. A negative correlation between canid abundance and daily nest survival was detected, but there was no relationship between predator abundance and lark density. There was a positive correlation between canid track abundance and rabbit density. Evidence indicated that lark nest predation in the Iberian shrubsteppes was an example of incidental predation (Vickery et al. 1992), which nevertheless has caused serious conservation problems for the larks. Lark densities in some areas decreased 80% during the 3 years of our study. Incidental predation, which is determined by rabbit abundance, is a complicating factor for the conservation of these ground-nesting birds and should be taken into account in the management of reserves for steppe birds.