SAGE GROUSE NESTING HABITAT IN NORTHEASTERN CALIFORNIA. Gail P. Popham. A Thesis. Presented to. the Faculty of Humboldt State University

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1 SAGE GROUSE NESTING HABITAT IN NORTHEASTERN CALIFORNIA By Gail P. Popham A Thesis Presented to the Faculty of Humboldt State University In Partial Fulfillment of the Requirements for the Degree Master of Science in Natural Resources: Wildlife December, 2000

2 Approved SAGE Ralph T. Floyd Luke GROUSE J. George, by Gutierrez, the Master's NESTING Major Thesis Professor HABITAT Committee Approved W. by Weckerly, the Dean Committee of Graduate Member Studies Director, Natural Resources Graduate Program IN NORTHEASTERN CALIFORNIA By Gail P. Popham 00-W /14 Natural Resources Graduate Program Number Donna E. Schafer

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4 ABSTRACT I studied sage grouse (Centrocercus urophasianus) nesting habitat from mid- March through mid-august of in eastern Lassen County, California. I located nest sites of forty-five radio-marked hens. To evaluate habitat selection I measured vegetation at each nest site and at random sites. Sage grouse avoided low sagebrush (Artemisia arbuscula) cover type for nesting. They used big sagebrush (Artemisia tridentata) cover type and mixed shrub cover type in proportion to their availability. In addition, grouse used diverse sites for nesting as indicated by among nest site variation being similar to variation between nest and random site variables. Likewise, there were habitat differences between successful nests and unsuccessful nests. Mean nest-lek distance was greater for successful nests (K=3588 m, SE=811, n=20, P=0.06) than the nest-lek distance for unsuccessful nests (K=1964 m, SE=386, n=20). Rock cover was greater at successful nests (K=27.67%, SE=4.6%, P=0.04) than at unsuccessful nests (K=14.49%, SE=3.04%). Total shrub height was greater at successful nests (K=65.5 cm, SE=4.7, P<0.01) than unsuccessful nests (K=49.2 cm, SE=1.7). The height of visual obstruction was greater at successful nests (K=40.2 cm, SE=2.6, P=0.02) than at unsuccessful nests (K=32.5 cm, SE=2.0). Greater distance from the lek, total shrub height, rock cover, and visual obstruction appeared to characterize successful nests compared to unsuccessful nests. My results suggest that rangeland managers should strive for both landscape and microsite heterogeneity. iii

5 ACKNOWLEDGEMENTS I owe thanks to the sage grouse of Lassen County for enduring my intrusion into their lives. Their calmness during capture, their resilience in the face of adversity, and their hardiness under harsh environmental conditions were a continual inspiration to me. Without their cooperation this study would have been impossible. I also want to thank California Department of Fish and Game and Sierra Pacific Power Company for funding this project. I thank Marin Rod and Gun Club for their financial assistance. Special thanks goes to Danny Cluck for familiarizing me with the study area. Rick Miller and Gary Schoolcraft helped with plant identification. Other people who helped were Dawn Bush, Frank Hall, Bobette Jones, Matt McDonald, Nancy Nordensten, Tom Rickman, and many others. My most heartfelt appreciation goes to Dave Lancaster who not only assisted in capture and fieldwork but helped keep me aware of the realities of living life. My daughters, Amy and Mariah, gave me lots of encouragement. I am also very grateful to my Aunt Idy (I. N. Langton) for all her support and financial help. I thank my major professor, Dr. R. J. Gutierrez for helping me to make it through graduate school. The other members of my committee were also helpful: Dr. F. W. Weckerly cheerfully fielded my statistical questions; Dr. T. L. George gave my thesis a critical review. iv

6 TABLE OF CONTENTS ABSTRACT. iii ACKNOWLEDGMENTS. iv LIST OF TABLES. vii LIST OF FIGURES. viii INTRODUCTION. STUDY AREA. METHODS. Capture Habitat Measurements. 6 Statistical Analysis. 8 RESULTS. 11 Nesting Activity. 11 Cover Type Selection. 11 Microhabitat Selection. 11 Nest and Random Sites. 11 Successful and Unsuccessful Nests. 14 DISCUSSION. 17 MANAGEMENT IMPLICATIONS. 20 REFERENCES CITED. 21

7 APPENDICES A. Plant species encountered in sage grouse, Centrocercus urophasianus, nest site survey areas in Lassen County, California, March - July B. Descriptions of sage grouse, Centrocercus urophasianus, nest sites in Lassen County, California March - July vi

8 LIST OF TABLES Table. Page 1.Composition of cover types used by nesting sage grouse, Centrocercus urophasianus, in Lassen County, California, March - July Sage grouse, Centrocercus urophasianus, hens radio-marked with survival and reproductive effort in Lassen County, California, March-August Habitat characteristics of successful and unsuccessful sage grouse, Centrocercus urophasianus,nest sites and random sites in Lassen County, California, March-July Plant species associated with successful and unsuccessful sage grouse, Centrocercus urophasianus,nests in Lassen County, California, March-July vii

9 LIST OF FIGURES Figure. Page 1.Sage grouse, Centrocercus urophasianus, study area in Lassen County, California Cover types used by nesting sage grouse, Centrocercus urophasianus, compared to the proportions of cover types available at random sites in Lassen County, California, March-July viii

10 INTRODUCTION Sage grouse (Centrocercus urophasianus) populations have been declining throughout their range since the early 1900's (Braun 1998). This decline is due to a combination of factors, including habitat degradation caused by livestock grazing, conversion of sagebrush (Artemisia spp.) steppe for agriculture, and other human activities (Braun 1998). Sage grouse have also been declining in California (Grinnell and Miller 1944). Sage grouse historically occurred in Siskiyou, Modoc, and Lassen counties of northeastern California (Grinnell and Miller 1944). They have been extirpated in Siskiyou County. In addition, Modoc County populations have been declining. Despite this conservation problem, no habitat use studies have been conducted on sage grouse in northeastern California (Schroeder et al. 1999). However, several nesting habitat studies have been conducted in adjacent southeast Oregon (Gregg 1991, DeLong et al. 1995) and Nevada (Klebenow and Burkhardt 1981). California is along the western edge of sage grouse range, elsewhere in many areas at the periphery of their range this species has been extirpated (Schroeder et al. 1999). Sage grouse no longer occur in British Columbia, Arizona, Kansas, Nebraska, Oklahoma, or New Mexico (Braun 1998). Additionally, a population in Washington has been declining and is being considered for listing under the Endangered Species Act. Because of a paucity of information, declining populations, and edge-ofrange status, I studied sage grouse habitat selection in northeastern California. The objectives of my study were: (1) to examine sage grouse habitat selection by 1

11 2 comparing nesting cover types used to cover types available; (2) to compare habitat characteristics at nest sites with those at random sites to estimate microhabitat selection; and (3) to compare habitat characteristics associated with successful nests to unsuccessful nests.

12 STUDY AREA Eastern Lassen County is primarily a sagebrush steppe community in the Great Basin floristic province of California (Hickman 1993). This area is characterized by volcanic substrates and faulted lava flows (Hickman 1993). It is a basin and range topography. In Lassen County sage grouse can be found in sagebrush steppe habitat north of Honey Lake Valley and east of the Cascade Mountains. The study area (Figure 1) was 273,000 ha bounded on the south by the Amadee and Skedaddle Mountains, on the east by the Smoke Creek Desert in Nevada, on the west by Fredonyer Peak and Horse Lake Mountain, and on the north by Whitinger Mountain and McDonald Peak. Vegetation communities included sagebrush (Artemisia tridentata) scrub, low sagebrush (Artemisia arbuscula), annual and perennial grasslands with some areas of juniper (Juniperus occidentalis) savannah. The northern half of the study area was dominated by the Madeline Plains which had silver sagebrush (Artemisia cana) and other vegetation communities. Extensive alfalfa fields were present in the northern part of the area. Most of the study area south of Madeline Plains was Bureau of Land Management land and was grazed by sheep and cattle. Elevations ranged from 1400 m to 2400 m. Summers were hot and dry. Mean monthly temperatures ( ) taken from a weather station in Termo, California (Figure 1) ranged from -9.7 C in January, to 29.4 C in July. Annual precipitation averaged 27.6 cm., and occured primarily during winter and spring as snow or rain (Western Regional Climate Center 1999). 3

13 4 MODOC COUNTY LASSEN COUNTY m xa z SUSANVILLE HIGHWAY milms==rm. KILOMETERS Figure 1. Sage Grouse, Centrocercus urophasianus, study area in Lassen County, California, (map, G. Popham 2000).

14 METHODS Capture I received approval from the Institutional Animal Care and Use Committee to capture, restrain, and radio-mark sage grouse on 1 December 1998 (IACUC protocol # W.45B). Crews of 2-3 people (California Department of Fish and Game personnel and volunteers) captured birds at night by spotlight trapping (Wakkinen et al. 1992b). We fitted birds with 19-gram battery-powered telemetry transmitters (Advanced Telemetry Systems model 5902N). In 1998, crews placed transmitters on 20 hens. In March-April 1999 and 2000, crews captured and radio-marked 21 and 24 sage grouse hens respectively. We used a total of 50 transmitters and reused some after mortalities occurred. Therefore, we marked 65 individual sage grouse hens over three years. During the nesting season I located birds at 5-7 day intervals in order to estimate time of nest initiation and nest fate. I recorded the locations using a global positioning system receiver (Garmin GPS 12XL). Using a hand-held, 2-element yagi antenna, I avoided disturbing nesting hens by circling them at a distance of m. I marked nests with a stack of rocks, or a dead shrub placed on top of another shrub. Cryptic nest marking, hopefully, lessened the detectablity of nests by predators. I determined nest success by examination of eggshells remaining in the nest. I considered the nest successful if at least one eggshell remained that had membranes detatched from the inside of the shell. If there were no eggshells remaining in the nest, I considered it an unsuccessful nest. 5

15 6 Habitat Measurements The variables I measured at nest sites were: distance from nest to nearest known lek; percentage cover of shrubs, forbs, perennial grasses, annual grasses, litter, bareground, and rock; nest shrub length, width and height; and vertical obstruction. I used the line intercept method to estimate percent cover of shrubs (Canfield 1941). I established the line intercept along two 30-m transects oriented in the cardinal directions (N-S, E-W), with the nest at the center of the transects. I measured the north-south width, east-west width, and maximum foliage height of the nest shrub and recorded its species. I measured the height of the closest shrub within two meters of each five-meter mark on the transect to the nearest centimeter excluding inflorescence (Sveum 1995). If there was no shrub within two meters, I did not record a measurement. I also measured residual grass height of the closest bunch of perennial grass within two meters of each five-meter mark on the transect to the nearest centimeter excluding inflorescence (Sveum 1995). This yielded seven shrub/grass height measurements from each of two transects, giving 14 shrub/grass heights, plus the height of the nest shrub; for a total of up to 15 shrub/grass height measurements. I averaged the shrub height measurements to represent shrub height for the site. Likewise, I averaged the residual perennial grass height measurements to acquire average height for that variable at each site. I used a Daubenmire frame placed at 8 systematic but consistant locations in each vegetation survey area to measure percentage cover of perennial grasses, annual grasses, forbs, litter, bare ground, and rock (Daubenmire 1959). Only rocks of 10 cm or more in diameter

16 7 were included as rock. I placed Daubenmire frame as follows: centered lengthwise over the 1, 5, 10, 20, 25 and 30-m marks on either the north-south or east-west transect (N-S or E-W randomly determined). At the 15 m mark (which was centered on the nest) I centered the Daubenmire frame length-wise on the same transect, and placed it adjacent to the nest (or main stern of the center shrub for random sites) on either side. I identified shrubs to species, and identified forbs and grasses to genus or species. I measured foliage height of residual perennial grasses in the same way as I measured shrub height. To measure visual obstruction at each vegetation plot I used a pole (Robel et al. 1970) marked in 5-cm increments, placed the pole at the center and the mid-point of each of the four transects (7.5 m and 22.5 m) and viewed it from a distance of 15 m and a height of cm. I viewed the pole from four randomly determined directions when it was positioned in the center of the transect. When it was positioned in the midpoints of the four transects, I viewed it from each of two randomly determined directions. From each I of these 12 vantage-points, I recorded the lowest visible height (to the nearest 5 cm). This resulted in twelve visual obstruction measurements at each site, which I averaged to represent over-all visual obstruction at the site. I sampled all nest sites in this same manner within a week after the fate of the nest was determined (failure or hatching). For every nest site I randomly selected another location within a 1-km radius of the nest but greater than 100 m from the original site. At random sites I measured length, width, and height of the shrub nearest the center of the plot to compare to the nest shrub. I used the GIS software "Terrain Navigator" to estimate the distance from the nest to the nearest

17 8 lek. All plant species (or genera) measured at nest sites are included in Appendix A. The three cover types used for nesting were big sage, low sage and mixed shrub (Table 1). Survey sites dominated by shrubs other than Artemisia spp. were considered a mixed shrub cover type (Table 1). I randomly selected one nest site for each of the 45 hens who nested over the three years and categorized it into one of the three cover types to represent habitat used. Habitat available was represented by the cover types of the 88 random sites. Statistical Analysis I used chi-square goodness-of-fit analysis to test the null hypothesis that cover types used for nesting were in proportion to their availability. Additionally, I constructed 95% confidence intervals around the proportion of habitat used to estimate if it was avoided or selected (Neu et al. 1974). I selected samples for analysis of microhabitat selection as follows: Although several birds were monitored for more than one nesting season, and many birds renested within the same year; I used only one nest site per bird in order to maintain statistical independence of samples. Since there were fewer successful nests than unsuccessful nests, I randomly selected a set of successful nests without replacement for individual birds; then I randomly selected one failed nest per bird of the remaining individuals. To minimize multicollinearity and redundancy of variables, I excluded some variables based on their biological significance and extent of correlation with other variables. I omitted total herbaceous cover, forb cover, and annual grass cover but retained perennial grass cover.

18 9 Table 1. Composition of cover types used by nesting sage grouse, Centrocercus urophasianus, in Lassen County, California, March-July Cover Type - Low Sage Canopy cover of 5-24%, dominated by Artemisia arbuscula and Poa secunda Other associated species include Chrysothamnus nauseosus, Purshia tridentata, Pseudoroegneria spicata, Elymus elymoides, Balsamorhiza hookeri, and other forbs. Primarily occurring at elevations of m on flat to gentle slopes with shallow soils and in drainages. Cover Type - Big Sage Canopy cover of 5-40% dominated by Artemisia tridentata, Bromus tectorum. Other associated species include Chrysothamnus nauseosus, Ephedra viridis, Purshia tridentata, Tetradymia glabrata, Pseudoroegneria spicata, Lupinus argentius, Blepharapappus scaber, Helianthus cusackii, Lomatium spp., and other forbs. Occurs at elevations of m, along drainages, lava flows, and flat to moderate slopes. Cover Type - Mixed Shrub Canopy cover of 5-40% dominated by shrub other than Artemisia spp., including Chrysothamnus nauseosus, Tetradymia glabrata, or Purshia tridentatawith under story of Bromus tectorum, and Elymus elymoides. Other associated species include Ephedra viridis, Pseudoroegneria spicata, Lupinus argentius, Blepharapappus scaber, Helianthus cusackii, Lomatium spp., and other forbs. Occurs at elevations of m, on flat to moderate slopes.

19 10 Likewise, I excluded total shrub cover, but retained sagebrush cover and other shrub cover. I also excluded nest shrub height and nest shrub area. Therefore, the variables included in the analysis were distance from nest to lek, perennial grass cover, litter cover, bareground cover, rock cover, sagebrush cover, other shrub cover, total shrub height, residual perennial grass height, and visual obstruction height. I tested the normality of the variables by examining normal probability plots. Several variables were not normally distributed. Therefore, I used the following transformations: distance to lek, log transformation; and all percentage cover variables were arcsin square root transformed (Zar 1996). With the transformed values I used two-factor Multivariate Analysis of Variance (MANOVA) to test for year effect and compare nest sites with random sites. I performed another two-factor MANOVA to compare successful and unsuccessful nests and effects of year. However, I measured vegetation data at nests and random sites each year except 1998 because I changed some vegetation sampling proceedures. I collected 1998 nest site vegetation data in 1999 but on the same date (± one week) that I determined its fate in Therefore, I excluded 1998 data and examined year effects using MANOVA for 1999 and 2000 only. If the resulting Wilks' Lambda test statistic for each of the MANOVAs resulted in a P-value 0.05, I tested each of the individual variables with an ANOVA. I also computed the descriptive statistics for the variables of successful and unsuccessful nests, and the nest and random variables of 1999 and 2000.

20 RESULTS Nesting Activity Between March and August , I monitored sixty-five radio-marked sage grouse hens. I collected one, two, and three years of nesting data for 20, 13 and 4 hens, respectively. Over the three years, twenty hens renested (31%) at least once. In 1999, one hen renested twice. I collected data from a total of eighty-eight nest sites and eighty-eight random sites. Nest success was 35.7, 46.7, and 36.8% for 1998, 1999 and 2000, respectively (R= 40.2%), (Table 2). Cover Type Selection Sage grouse selected low sagebrush, big sagebrush and mixed shrub cover types for nesting (Table 1, Figure 2, and Appendix B). Thirty of forty-five (67%) nest sites were in big sagebrush cover type, thirteen (29%) in mixed shrub, and two nests (4%) were in low sage (Figure 2). Low sage was used less than expected (95% CI: < < 0.118). Big sage (95% CI: < < 0.835) and mixed shrub (95% CI: < < 0.451) were used in proportion to their availability (z=2.393; Chisquare =8.29, P=0.03; Figure 2). Microhabitat Selection Nest and Random sites There was no year effect between years (Wilks' Lambda F-Ratio =0.89; P= 0.48; n=40) nor was there a difference between nest and random sites (Wilks' Lambda F-Ratio=0.96; P=0.54; n=40). 11

21 12 Table 2. Sage grouse, Centrocercus urophasianus, hens radio-marked with survival and reproductive effort in Lassen County, California, March-August, na.% na % na.% RADIO-MARKED CURB. YR. b RADIO-MARKED PREY. YR MISSING PRE-NESTING MORT TOTAL REMAINING DID NOT NEST e c a SUCC. 1st NESTS d d d FAILED 1st NESTS d d d FAILED/NO RENEST d d d SUCC. RENESTS d d d FAILED RENESTS d d d POST-NESTING MORT TOT. NEST ATTEMPTS e SUCC. NESTS f f f FAILED NESTS f f f ANNUAL MORTALITY f f -- BIRDS ALIVE SEPT NEST SUCC.: TELEM. DATAg 5/ / / NEST SUC: WING ANALYSIS h 27/ / a n = number of radio-marked birds in category b a total of 65 sage grouse hens were marked over the 3-year period percentage based on number in category divided by TOTAL REMAINING birds d percentage based on number of birds in category divided by birds that NESTED 5 nests were not located, although the hens did nest, 88 nests had vegetation surveys percentage based on number of birds in category divided by TOT. NEST ATTEMPTS g SUCC. NESTS divided by BIRDS ALIVE SEPT. 01 h NEST SUCCESS estimated from wings collected from hunters.

22 t a Big Sage.Mixed Shrub.Low Sage ri Nest Sites. Random Sites.I 95% CI (Used). (Available) Figure 2. Cover types used by nesting sage grouse, Centrocercus urophasianus, compared to the proportions of cover types available at random sites in Lassen County, California, March-July (Neu et al. 1974).

23 14 Successful and Unsuccessful Nests There was no difference between successful and unsuccessful nests due to year for 1999 and 2000 (Wilks' Lambda=1.55; P=0.18; n=20). However, there were differences among variables comparing successful nests to unsuccessful nests (Wilks' Lambda=2.94; P=0.1; n=20; see Table 3). Successful sage grouse nests were farther (7=3588 m, SE=811 m) from the nearest lek than unsuccessful nests (i=1964 m, SE=386 m), (F=3.85; P=0.06; n=20). Rock cover was greater (i=27.67%, SE=4.6%) at successful nests than at unsuccessful nests (k=14.49%, SE=3.04%), (F=4.70; P=0.04; n=20). Total shrub height was greater at successful nests (7=65.5 cm, SE=4.7 cm) than unsuccessful nests (R=49.2 cm, SE=1.7), (F=10.63; P<0.01; n=20). Visual obstruction height was greater (7=40.2 cm, SE=2.6 cm) at successful nests than at unsuccessful nests (7=32.5 cm, SE=2.0 cm), (F=5.69; P=0.02; n=20), (Table 3). Additionally, sage grouse hens constructed 51.6% of all successful nests beneath big sagebrush, while 63.1% of all unsuccessful nests were also beneath big sagebrush (Table 4, Appendix B). One hen unsuccessfully nested on the graded shoulder of an unpaved, but well-used road under a partially-uprooted big sagebrush. Another successfully nested under a small rock ledge in a rocky drainage beside a 65 cm-tall bluebunch wheat grass plant. A third successfully nested within 15 m of a 10 m-tall western juniper (Juniperus occidentalis).

24 15 Table 3. Habitat characteristics of successful and unsuccessful sage grouse, Centrocercus urophasianus, nest sites and random sites in Lassen County, California, March-July SUCCESSFUL NESTS (n=20) Variable Mean SE Min Max Dist. Nest to Lek (meters)a Proportion perennial grass cover Proportion litter cover Proportion bare ground cover Proportion rock cover' Proportion sagebrush cover Proportion other shrub cover Total shrub height (cm.) a Resid. peren. grass ht. (cm.) Visual obstruction height (cm.) a UNSUCCESSFUL NESTS (n=20) Variable Mean SE Min Max Dist. Nest to Lek (meters)a Proportion perennial grass cover Proportion litter cover Proportion bare ground cover Proportion rock cover' Proportion sagebrush cover Proportion other shrub cover Total shrub height (cm.) a Resid. peren. grass ht. (cm.) Visual obstruction height (cm.) a a Variables significant at P=0.05 (Dist. to Lek, P=0.058)

25 16 Table 4. Plant species associated with successful and unsuccessful sage grouse, Centrocercus urophasianus,nests in Lassen County, California, March-July SHRUBS ALL NESTS SUCC. NESTS UNSUCC. NESTS %b n a %b n a %b na %C %C Artemesia arbuscula Artemesia tridentata Chtysothamnus spp Ephedra viridis Purshia tridentata Tetradymia glabrata PERENNIAL GRASSES Leymus cinereus Pseudoroegneria spicatum TOT. non-a. tridentata nests TOTAL NESTS a total number of nests that were located beneath the plant species listed b percentage of nests located beneath the species in the row category relative to TOTAL NESTS for column category percentage of nests located beneath the row category relative to ALL NESTS, TOTAL

26 DISCUSSION Most habitat studies of sage grouse show that hens place nests under big sagebrush plants most of the time (92-95%; e.g., Patterson 1952, Connelly et al. 1991, Gregg et al. 1994, and Hanf et al. 1994). In contrast, only 59.1% of the nests in my study were placed under big sagebrush (Table 4). In spite of this difference, nest success rates in my study (Table 2) were comparable to success rates in other states (Connelly et al Gregg 1991, Sveum 1995). Moreover, wings collected from Lassen County hunters in 1998 and 1999 were examined by California Department of Fish and Game personnel for moult patterns to estimate nest success rates (Braun et al. 1975, see Table 2). These rates also were comparable to nest success rates in other states. Additionally, my study showed more unsuccessful nests beneath big sagebrush plants than successful nests (Table 4, Appendix B). This contrasts with other studies ( Patterson 1952, Gregg 1991, Sveum 1995, Connelly et al. 1991), where nest success was found to be greater under big sagebrush. My study also showed that the use of specific sagebrush communities was variable. Sage grouse avoided low sagebrush cover types both in my study and in nearby southeastern Oregon (Gregg et al.1994, Hanf et al.1994) whereas most grouse nested in low sage in northwestern Nevada (Klebenow and Burkhardt 1981). Sage grouse habitat studies in other states found differences between nest and random sites (Klebenow 1969, Gregg 1991, Sveum 1995). My study, in contrast, showed that there were no differences between nest and random sites. At the microhabitat level, my findings conflicted with findings for most bird species which showed that habitat structure of used sites differed from structure of available habitat (Block and Brennan 17

27 ). This difference may be due to a high level of landscape diversity as suggested by the use of diverse nest shrubs (Table 4). Although I found no nest versus random site differences, there were differences between the microhabitat components of successful and unsuccessful nests. Sage grouse studies in Nevada, Idaho, southeastern Oregon, and Washington found that cover of tall residual grass was greater at successful nests (Klebenow 1969, Connelly et al. 1991, Gregg et al. 1994, Sveum 1995, respectively). I found no differences in perennial grass cover or height (Table 3). However, I did find over-all visual obstruction to be greater at successful than at unsuccessful nest sites (Table 3). Data from the second year (1993) of Sveum's (1995) two-year study also showed taller visual obstruction at successful nests than at failed nests. In addition, DeLong et al. (1995: page 90) found that "greater amounts of tall grass and medium shrub cover at artificial nest sites were associated with lower probabilities of nest predation." In contrast, Gregg (1991) found no significant differences in visual obstruction between successful and unsuccessful nests. Comparison of shrub height at successful and unsuccessful nest sites in other studies showed that nest success was greater at nest sites where shrub height was taller (Connelly et al. 1991, Gregg 1991, DeLong et al. 1995). Similarly, I found that mean shrub height at successful nest sites was greater than at unsuccessful nest sites (Table 3). Both shrub height and visual obstruction height have biological significance in terms of nest predation because they represent the primary vegetation components at the site that would hide the bird.

28 19 Rock, especially boulders, may also be a component of visual obstruction (Brennan et al. 1987). Accordingly, percentage of rock cover was greater at successful grouse nests. Other investigators did not measure this variable, however, several of my nest sites contained large boulders (>0.5 m in diameter). These large rocks may have been a component of the visual obstruction at the nest. The structural significance of rock might have been more clear if I had included rock height as a measured variable. The question of visual obstruction would be suitable for further investigation; rock height could be a component of visual obstruction. The location of nests relative to leks was studied by Wakkinen et al. (1992a). They found no difference in the nest-to-lek distance between successful and unsuccessful nests. In contrast, I found that the mean distance to the nearest known lek was greater for successful nests than for unsuccessful nests (Table 3). The differential nest success results as related to distance from the lek is an area of this study that needs further investigation. One hypothesis to explain this result is that predators concentrate where grouse density is high and therefore nests far from leks are more successful. Alternatively, habitats may vary away from the lek which might result in hen movement to more variable sites.

29 MANAGEMENT IMPLICATIONS Guidelines for managing sage grouse habitats emphasize the importance of maintaining sagebrush for nest sites (Braun et a1.1977, Connelly et a1.1991, Gregg 1991, Hanf 1994, DeLong et al.1995, and Sveum et al. 1998). Yet, management of sagebrush shrublands for sage grouse as well as other sagebrush obligate species suggests that landscape heterogeneity is desirable (Page and Ritter 1999). My results show that not only sagebrush, but also a diversity of shrubs are relevant to nest success. This has important ecological implications because heterogenity across a landscape enhances overall productivity, resistance to disease, fire, and other forms of environmental stochasticity (Noss 1995). It is significant that the birds in my study displayed habitat selection at the macrohabitat scale; they choose to nest in taller cover types rather than low sage. However, primary analyses of winter habitat selection data from this area indicate that sage grouse prefer low sage cover types for winter habitat use. Therefore, this reinforces the importance of managing the landscape for diversity as well as microhabitat structure diversity. The location of nests relative to leks in my study is consistant with other research although the greater nest-to-lek distance of successful nests in my study adds further emphasis to the importance large scale habitat management. That is, it is important that good nesting habitat be available close to leks as well as far from leks. Additionally, when the winter habitat preference for low sage tracts is considered, and preference for forb-rich areas as brood habitat (Braun et a1.1977, Gregg 1991, Hanf 1994, Sveum 1995) is considered, I recommend that large areas of sagebrush shrubland with both microhabitat and landscape scale diversity be managed for yearround sage grouse habitat. 20

30 REFERENCES CITED Block, W.M. and L.A. Brennan The habitat concept in ornithology. Current Ornithology 11: Braun, C.E., R.B. Gill, and T. Beck Sex and age determination of sage grouse from wing characteristics. Colorado Dept. Nat. Res. Div. Game, Fish and Parks #49. Braun, C. E., T. Britt, and R. 0. Wallestad Guidelines for maintenance of sage grouse habitats. Wildl. Soc. Bull. 5: Braun, C.E Sage grouse declines in western North America: what are the problems? Proc. Western Assoc. State Fish and Wildl. Agencies 78: Brennan, L.A., W. M. Block, and R. J. Gutierrez Habitat use by mountain quail in Northern California. Condor 89: Canfield, R.H Application of the line intercept method in sampling range vegetation. J. For. 39: Connelly, J. W., W.L. Wakkinen, A. P. Apa, and K.P. Reese Sage grouse use of nest sites in southeastern Idaho. J. Wildl. Manage. 55: Daubenmire, R.F A canopy-coverage method of vegetation analysis. Northwest Science. 33: DeLong, A.K., J.A. Crawford, and D.C. DeLong, Jr Relationships between vegetational structure and predation of artificial sage grouse nests. J. Wildl. Manage. 59: Gregg, M.A Use and selection of nesting habitat by sage grouse in Oregon. M.S. Thesis, Department of Fisheries and Wildlife, Oregon State University, Corvallis, Oregon, USA.. Gregg, M. A., J.A. Crawford, M.S. Drut, and A.K. DeLong Vegetational cover and predation of sage grouse nests in Oregon. J. Wildl. Manage. 58: Grinnel, J., and A.H. Miller The distribution of the birds of California. Pacific Coast Avifauna

31 22 Hanf, J.M., P.A. Schmidt, and E.B. Groshens Sage grouse in the high desert of central Oregon: Results of a study Unpublished Report. US Dept. of the Interior, BLM, Prineville, OR. BLM OR/WA/PT-95/ Hickman, J.C., ed Jepson manual of higher plants of California. University of California Press, Berkeley, California, USA. Klebenow, D.A Sage grouse nesting and brood habitat in Idaho. J. Wildl. Manage. 33: Klebenow, D.A. and J. W Burkhardt Sage Grouse on the Sheldon National Wildlife Refuge. Unpublished Report. Univ. of Nevada. No Neu, C.W., C.R. Byers, and J.M. Peek A technique for analysis of utilizationavailability data. J. Wildl. Manage. 38: Noss, R Maintaining ecological integrity in representative reserve networks. Discussion paper. World Wildlife Fund Canada/World Wildlife Fund United States, January Page, C. and S.A. Ritter Birds in a sagebrush sea: managing sagebrush habitats for bird communities. Unpublished Report. Partners in Flight Western Working Group, Boise, ID. Patterson, R. L The Sage Grouse in Wyoming. Sage Books, Inc. Denver, Colorado. Robel, R. J., J. N. Briggs, A. D. Dayton, and L. C. Hulbert Relationship between visual obstruction measurements and weight of grassland vegetation. J. Range Manage. 23 : Schroeder, M.A., J.R. Young, and C.E. Braun Sage Grouse (Centrocercus urophasianus). In The Birds of North America, No. 425 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA. Sveum, C.M Habitat selection by sage grouse hens during the breeding season in south-central Washington. M.S. Thesis, Department of Fisheries and Wildlife, Oregon State University, Corvallis, Oregon, USA.

32 23 Sveum, C.M., W.D. Edge, and J.A. Crawford Nesting habitat selection by sage grouse in south-central Washington. J. Range Manage. 51: Wakkinen, W. L., K. P. Reese, and J. W. Connelly. 1992a. Sage grouse nest locations in relation to leks. J. Wildl. Manage. 56: Wakkinen, W. L., K. P. Reese, J. W. Connelly, and R. A. Fischer. 1992b. An improved spotlighting technique for capturing sage grouse. Wildl. Soc. Bull., 20: Western Regional Climate Center Termo 1 E, California (048873). National Climatic Data Center, Northern California Climate Summaries, 11/15/2000. Zar, J.H Biostatistical Analysis. Third ed. Prentice-Hall, Inc., Upper Saddle River, N.J. 662 p.

33 24 Appendix A. Plant species encountered in sage grouse, Centrocercus urophasianus, nest site survey areas in Lassen County, California, March-July Common name Count Percent a SHRUBS/TREES Artemisia arbuscula low sagebrush 33 39% Artemisia cana silver sagebrush 4 5% Artemisia tridentata big sagebrush 81 95% Atriplex confertifolia shadscale 1 1% Chrysothamnus humilis small rabbitbrush 1 1% Chrysothamnus nauseosus rubber rabbitbrush 23 27% Chrysothamnus vicidiflorus yellow rabbitbrush 10 12% Ephedra viridis Mormon tea 7 8% Greyia spinosa spiney hopsage 12 14% Juniperus occidentalis western juniper 2 2% Purshia tridentata bitterbrush 10 12% Ribes velutinum plateau gooseberry 3 4% Salvia dorrii purple sage 2 2% Tetradymia glabrata little-leaf horsebrush 32 38% PERENNIAL GRASSES/SEDGES/RUSHES Achnatherum hymenoides Indian rice grass 5 6% Achnatherum turberianum Thurber's needlegrass 14 16% Carex spp.. sedge 3 4% Danthonia unispicata one-spike oatgrass 1 1% Elymus elymoides squirreltail 67 79% Festuca idahoensis Idaho fescue 1 1% Juncus spp.. rush 1 1% Leymus cinereus basin wild rye 7 8% Muhlenbergia richardsonis mat muhly 1 1% Pascopyrum smithii western wheatgrass 2 2% Poa secunda one-sided bluegrass 36 42% Pseudoroegneria spicatum bluebunch wheatgrass 13 15% ANNUAL GRASSES Bromus briziformis rattlesnake grass 13 15% Bromus tectorum cheatgrass 81 95% Taeniatherum caput-medusae medusahead 21 25% a Frequency of occurrence in n=88 nest site surveys.

34 Appendix A. Plant species encountered in sage grouse, Centrocercus urophasianus, nest site survey areas in Lassen County, California, March-July (continued). Common name Count Percent a PERENNIAL FORBS Agoseris spp. mountain dandelion 3 4% Allium sp. wild onion 5 6% Antennaria dimorpha low pussy-toes 1 1% Arabis spp. rock cress 3 4% Astragalus filipes thread-leaf astragalus 6 7% Astragalus spp. astragalus 2 2% Balsamorhiza hookerii hooker's balsamroot 11 13% Balsamorhiza sagittata arrowleaf balsamroot 2 2% Camissonia tanacetifolia tansyleaf eve. primrose 1 1% Castilleja spp. paintbrush 7 8% Crepis spp. hawksbeard 22 26% Delphinium spp. larkspur 1 1% Erigeron aphanactis rayless daisy 3 4% Erigeron bloomeri rayless daisy 2 2% Erigeron spp. daisy 3 4% Eriogonum caespitosum mat buckwheat 1 1% Eriogonum spp. buckwheat 1 1% Eriophyllum lanatum wooly sunflower 2 2% Galium multiflorum perennial bedstraw 1 1% Gilia salticola blue anther gilia 3 4% Helianthus cusickii perennial sunflower 10 12% Leucocrinum montanum sand lily 3 4% Linum perenne blue flax 1 1% Lithophragma spp. prairie star flower 7 8% Lomatium macrocarpum large fruit lomatium 10 12% Lomatium triternatum nine-leafed lomatium 6 7% Lomatium vaginatum lomatium 19 22% Lomatium spp. desert parsley 5 6% Lupinus argenteus silvery lupine 11 13% Lupinus spp. lupine 11 13% Muilla spp. muilla 1 1% Penstemon spp. penstemon 9 11% Perideridia bolanderi yampah 4 5% Phlox diffusa spreading phlox 1 1% Phlox speciosia bi-lobed phlox 9 11% Phlox stansburyi long-style phlox 16 19% a Frequency of occurrence in n=88 nest site surveys. 25

35 26 Appendix A. Plant species encountered in sage grouse, Centrocercus urophasianus, nest site survey areas in Lassen County, California, March-July (continued). Common name.count.percent a PERENNIAL FORBS (cont.) Phlox spp.. phlox. 5.6% Scutellaria spp.. skullcap % Sidalcea glaucescens.lobe-leaf sidalcea.4. 5% Taraxacum officinale dandelion. 3.4% Tragopogon dubius yellow salsify.9.11% Trifolium gymnocarpon mat clover. 1. 1% Trifolium macrocephalum big-head clover.8. 9% ANNUAL FORBS Amsinckia tessellata fiddleneck % Blepharipappus scaber blepharipappus.31.36% Cirsium spp.. thistle. 3.4% Cleome platycarpa golden bee plant.1.1% Collinsia sparsiflora blue-eyed Mary.41.48% Cryptantha spp.. cryptantha. 2.2% Descuriania pinnata tansy mustard.3.4% Draba verna draba. 6. 7% Epilobium brachycarpum fireweed % Eriogonum vemineum wick stem eriogonum 1.. 1% Erodium cicutarium storksbill, filaree.10.12% Erysimum repandum wallflower mustard.4. 5% Galium aparine annual bedstraw.1. 1% Helianthus annulus annual sunflower.1.1% Iva axillaris poverty weed. 1. 1% Lactuca serriola prickly lettuce.22.26% Layia glandulosa yellow-center layia.2.2% Lepidium perfoliatum clasping pepperweed.3.4% Lupinus brevicaulis sand lupine. 8.9% Mentzelia albicaulis white-stemmed stickleaf 1. 1% Phlox gracilis common purple phlox % Plectritis brachystemon pouch-flower plectritis.10.12% Polemonium micranthum polemonium. 1. 1% Senecio spp.. butterweed. 3.4% Sisymbrium altissimum tumble mustard.6. 7% Thysanocarpus curvipes lace pod. 2.2% Viola beckwithii great basin violet.6.7% a Frequency of occurrence in n=88 nest site surveys.

36 Appendix B. Descriptions of sage grouse, Centrocercus urophasianus,nest sites in Lassen County, California, March-July ID.Cover type; nest vegetation; terrain; 2 dominant covers 0.957A A 0.294A a 0.016B a a A a a A a A a ' 9.862A a a successful nests Big Sage; ARTR; open flat; bare ground and annual grass Big Sage; ARTR; open flat; bare ground and perennial grass Big sage; ARTR, open flat; annual grass and rock Big sage; ARTR; 2% midslope E; rock and shrubs Big sage; ARTR; 2% midslope N; bare ground and shrub Big sage; ARTR; 2% midslope S; annual grass and shrub Big sage; ARTR; 2% midslope S; bare ground and shrub Big sage; ARTR; 3% midslope SE; shrub and bare ground Big sage; ARTR; 3% midslope SSW; litter and annual grass Big sage; ARTR; 3% upper slope SE; rock and shrub Big sage; ARTR; 4% midslope SW; litter and annual grass Big sage; ARTR; 5% midslope E; rock and annual grass Big sage; ARTR; 5% midslope S; shrub and bare ground Big sage; ARTR; 5% midslope SW; shrub and bare ground Big sage; ARTR; 8% midslope E; bare ground and forbs Big sage; ARTR; 8% midslope SE, drainage; perennial grass, shrub Big sage; ARTR; 10% midslope ESE; shrub and rock Big sage; ARTR; 10% midslope W; bare ground and shrub Big sage; ARTR; flat N of boulder slope; rock and bare ground Big sage; ARTR; flat shoulder of road; bare ground and litter Big sage; ARTR; flat; bare ground, annual grass Big sage; ARTR; open flat, shrub and bare ground Big sage; ARTR; open flat; annual grass and bare ground Big sage; ARTR; open flat; annual grass and forbs Big sage; ARTR; open flat; annual grass and litter Big sage; ARTR; open flat; annual grass and perennial grass Big sage; ARTR; open flat; annual grass and shrub Big sage; ARTR; open flat; annual grass and shrub Big sage; ARTR; open flat; bare ground and annual grass Big sage; ARTR; open flat; bare ground and annual grass Big sage; ARTR; open flat; bare ground and rock Big sage; ARTR; open flat; bare ground and shrub Big sage; ARTR; open flat; bare ground and shrub 27