Brush Cover Research Articles

Mule Deer Habitat Selection Following Vegetation Thinning Treatments in New Mexico

ABSTRACTMule deer (Odocoileus hemionus) survival and population growth in north‐central New Mexico, USA, was previously reported to be limited by nutritional constraints due to poor forage conditions in degraded habitats. Management recommendations suggested thinning of pinyon–juniper to improve habitat quality for mule deer. To evaluate the influence of these vegetation treatments, we monitored habitat selection by 48 adult female mule deer from 2011 to 2013 in a population previously reported to be nutritionally limited. Monitoring occurred 1–4 years after completion of treatments that were intended to improve forage conditions, including mechanical reduction of pinyon pine (Pinus edulis) and juniper (Juniperus spp.) density and senescent brush (Quercus gambelii–Cercocarpus montanus) cover. During the summer season, deer selected recently treated areas, but odds ratios decreased with treatment age. However, during winter, deer avoided more recently treated areas and selected thinned areas >4 years old. Deer selected mixed oak (Quercus spp.) and pinyon–juniper savanna vegetation cover types with a moderately open canopy and ponderosa pine (Pinus ponderosa) forests while avoiding grasslands and montane shrublands across all seasons. Deer selected areas closer to water and developed areas, northeast aspects, on gentle slopes, and at lower elevations. Creating a savanna‐like cover type may elicit a positive deer response as a result of their strong avoidance of dense, closed canopy pinyon–juniper woodlands. © 2020 The Wildlife Society.

Effects of Tanglehead Expansion on Bobwhite Habitat Use in South Texas

Usable space for northern bobwhite (Colinus virginianus) has been reduced across a large portion of South Texas rangelands due to the spread of non-native, invasive grasses. A native grass, tanglehead (Heteropogon contortus) has rapidly expanded its dominance in the western Sand Sheet of South Texas within the last 10-15 years. It has formed high-density monocultures, similar to non-native grasses, which are associated with losses of forb and grass diversity as well as bare ground, which are key components of bobwhite habitat. The objectives of our research were to 1) determine selection-avoidance of habitat features by bobwhites, and 2) determine the effects of tanglehead cover on vegetation characteristics. We detected 488 coveys across 20,103 ha on helicopter surveys conducted December 2014 in South Texas. We measured 6 vegetation characterstics (grass and forb species richness, vegetation height, woody-plant cover, tanglehead cover, and non-native grass cover) at all covey detections and an equal number of random locations. We developed continuous selection ratios based on probability density functions of used and random points derived using Simple Saddlepoint Approximations to determine habitat selection by bobwhites. We also used quantile regression at the 10th, 50th, and 90th quantiles to determine relationships between tanglehead and vegetation factors. Bobwhite avoided areas of high canopy cover (>20%) of all invasive grasses measured. Brush cover was selected for up to 47%, after which it was avoided. We found significant negative relationships between tanglehead cover and forb and grass species richness, bare ground, and shrub cover, and a positive relationship with vegetation height at all quantiles modeled. Our results demonstrate the negative effects of increased tanglehead cover on native rangeland habitats. Further expansion by tanglehead has the potential to significantly reduce usable space for bobwhites in South Texas.

Response of Northern Bobwhites to Habitat Improvement on Private Lands in the Rolling Plains of Texas

Northern bobwhites (Colinus virginianus) in the Rolling Plains of Texas have experienced significant declines in recent years. Examination of the Texas Parks and Wildlife Department Quail Roadside Counts reveals a steep decline since 2007 in the Rolling Plains of Texas. Biologists only detected 2.91 birds/counting route in 2013. This number marked 2 years in a row of record lows (counts started in 1978) below the long-term mean of 19.7 birds/route (Texas Parks and Wildlife 2015). These numbers are not surprising given the historically damaging drought Texas has suffered. Texas Parks and Wildlife Department counts improved to 7.5 bobwhites/counting route in 2014. This increase is linked to improving precipitation levels preceding and during the 2013 and 2014 breeding seasons. Though population growth is controlled primarily by rainfall (Jackson 1962), a reduction in the acreage of suitable habitat has also played a role in the bobwhite decline. Many areas on the Rolling Plains of Texas have become choked with invasive brush species, such as honey mesquite (Prosopis glandulosa) and juniper (Juniperus spp.), because of excessive grazing and a lack of fire (Mcpherson et al. 1988, Ansley et al. 1995). Asner et al. (2003) estimated woody cover increased as much as 500% in some areas of northern Texas between 1937 and 1999. Mesquite and juniper encroachment can occur to the point they become a steady-state, dominant vegetation that shades out grasses and other vegetation (Ansley and Weidemann 2008). Woody cover encroachment exceeding 70% canopy cover is not uncommon (Mirik and Ansley 2012). This heavy brush cover is not suitable habitat for bobwhites and limits population expansion even in years of adequate rainfall (Jackson 1969, Kopp et al. 1998). The millions of acres of brushdominated rangeland in Texas represent areas that can become usable habitat for bobwhites when brush coverage is reduced to suitable levels. Mechanical removal using a dozer or track hoe is a common method of reducing canopy coverage of mesquite and juniper. This method allows a manager to selectively remove brush in the quantity and distribution that is desired while leaving beneficial shrub species such as lotebush (Ziziphus obtusifolia) or skunkbush sumac (Rhus trilobata) undamaged. We received funding from a Texas Parks and Wildlife Habitat Enhancement Grant to mechanically remove excessive brush cover on private lands with the objective of expanding bobwhite populations. We selected treatment sites that were currently inhabited by quail or were adjacent to sites inhabited by quail, but whose populations appeared to be limited by excessive brush cover and unable to expand or increase. These sites were located on ranches enrolled in The Quail-Tech Alliance research program. We treated 404 ha spread across 7 different properties during 2014 and 2015. Depending upon the site, brush removal was accomplished using either a bulldozer or track hoe to mechanically grub mesquite and juniper trees or in some instances a combination of both tree species. In some instances landowners used their own equipment while in others private contractors were hired to accomplish the reduction project. We worked with individual landowners to incorporate their overall wildlife management objectives. Consequently, the pattern and canopy coverage of brush remaining after mechanical reduction varied among projects and was influenced by the brush density of the treatment area. Some landowners removed strips of brush while others left brush mottes throughout the landscape. All projects resulted in increased acreage of suitable bobwhite habitat with a resulting brush canopy coverage ranging from 5% to 30% depending upon the project. The soil disturbance and subsequent beneficially timed rainfall caused treated areas to be revegetated with desirable forbs and grasses within 60 days posttreatment. Bobwhites were observed using the treatment areas within a few months of treatment. Though favorable rains in 2014 and 2015 played a role in this response, it would not have been possible for bobwhites to use the treatment areas before brush reduction. Bobwhite populations will positively respond to mechanical brush removal treatments in the Rolling Plains of Texas. This project increased the acreage of suitable habitat for bobwhites; showing the value of habitat restoration programs.

Habitat Space Used by Northern Bobwhites and Texas Tortoises on South Texas Rangelands

South Texas rangelands are increasingly managed for recreational hunting, particularly northern bobwhite (Colinus virgianus). Effects of habitat management for game species on non-game species are largely unknown. Large private ranches used for recreational hunting could also provide habitat for the threatened Texas tortoise (Gopherus berlandieri). We studied habitat use of Texas tortoises and northern bobwhites on a private ranch in South Texas that undergoes active habitat management. In 2015, tortoises (n = 12) and bobwhite hens (n = 42) were tracked during their active and breeding seasons, respectively, with radio-telemetry. Satellite images were analyzed using ArcGIS 10.3 to delineate habitat through unsupervised classification for relevant habitat categories. Habitats were delineated based on reflectance. Differences in percent habitat composition of observed and random home ranges (100% Minimum Convex Polygon) of tortoises were not significant, but were significant for quail in 3 of 5 habitat categories in only 1 of 2 pastures. These observed quail home ranges included more areas corresponding to light woody cover and moderate herbaceous cover and fewer areas corresponding to sparsely vegetated or bare ground than random home ranges. Tortoise home ranges included more areas with woody brush cover than bobwhite home ranges. Bobwhite home ranges included more areas associated with moderate grass and herbaceous cover than tortoises. This study will continue in 2016 and will include more quail home ranges in areas with tortoises. This research seeks to determine the compatibility of managing for recreational hunting while maintaining landscape characteristics important to Texas tortoises.

A detection probability model for aerial surveys of mule deer

Population estimates derived from aerial surveys of ungulates are biased by imperfect detection, where probability of sighting groups is influenced by variables specific to terrain features and vegetation communities. Therefore, methods for bias-correction must be validated for the region to which they will be applied. Our objectives were to quantify factors affecting detection probability of mule deer (Odocoileus hemionus) during helicopter surveys in Texas, USA, rangelands, and develop a detection probability model to reduce bias in deer population estimates. We placed global positioning system (GPS) collars on 215 deer on 6 sites representative of mule deer range in the southern Great Plains and the Chihuahuan Desert during 2008–2010. We collected data during aerial surveys in January–March and fit logistic regression models to predict detection probability of mule deer based on ecological and behavioral covariates. We evaluated the model using independent estimates of population size derived from a mark-resight procedure. Detection of mule deer was negatively related to distance from the transect, increasing brush cover, sunlight, and increasing terrain ruggedness (P < 0.01). Probability of detection in brush cover was greater if deer were active (P = 0.02). Population estimates corrected for visibility bias using our detection probability model or mark-resight models averaged 2.1 ± 0.49 (SD; n = 50) and 2.2 ± 0.62 times larger, respectively, than uncorrected counts. Estimates of population size derived from the detection probability model averaged 101 ± 26% of mark-resight estimates. However, the detection probability model did not improve precision of population estimates, probably because of unmodeled variation in availability of deer during surveys. Our detection probability model is a simple and effective means to reduce bias in estimates of mule deer population size in southwestern rangelands. Availability bias may be a persistent issue for surveys of mule deer in the Southwest, and appears to be a primary influence of variance of population estimates. © 2016 The Wildlife Society.

Different drivers create spatial vegetation cover and vertical structure in semi-arid African savannas

Important drivers of woody cover in African savannas are rainfall, soil and nutrients, and disturbance factors, such as fire and herbivory. However, very little is known about how these drivers influence woody cover at specific height classes. The main aim of this study was to identify which of these drivers are the best predictors of woody cover at three height classes: shrub (0.75–2.5 m), brush (2.5–5.5 m) and tree (>5.5 m). Percent woody cover estimates were collected using a rapid monitoring technique over 1 700 sites in Kruger National Park, South Africa. Geology (basalt and granite), mean annual rainfall, fire frequency and elephant density were analysed as potential drivers of woody cover. Results indicate that mean annual rainfall was negatively associated with shrub cover, fire frequency was negatively associated with brush cover, and elephant density was negatively associated with tree cover. Patterns of woody cover show that while geology influences the spatial distribution of horizontal woody cover, variation in vertical vegetation structure is created and maintained by top-down disturbance. This provides the first documentation of drivers associated with structurally differentiated woody cover at regional scales. Future studies on woody cover in disturbance-driven environments should not ignore vegetation structure.

Felis nigripes(Carnivora: Felidae)

Abstract: Felis nigripes Burchell, 1824, commonly called the black-footed cat, is the smallest felid in Africa. F. nigripes is a pale tawny cat with dark markings and prominent horizontal stripes on the limbs. It is distributed in the central part of South Africa and mainly occurs in open country often near brush cover. F. nigripes is listed on Appendix I of the Convention for the International Trade of Endangered Species of Fauna and Flora and is listed as “Vulnerable” by the International Union for the Conservation of Nature and Natural Resources.

Is the diet of a typical shredder related to the physical habitat of headwater streams in the Brazilian Cerrado?

Macroinvertebrates are important for processing leaf detritus in temperate streams, but studies about their role in tropical streams often present conflicting results. Via digestive tract analyses, we assessed the diets of Phylloicus sp. larvae (Trichoptera: Calamoceratidae), collected from streams of two southeastern Brazil river basins (Araguari, São Francisco). We classified gut contents as coarse particulate organic matter (CPOM), fine particulate organic matter (FPOM), algae, animal tissue, vascular plant tissue and mineral material. We hypothesized that the diets of Phylloicus larvae would be related to the physical habitat of the streams (e.g., riparian vegetation, organic matter availability and morphological characteristics), larval size and river basin. Although FPOM content predominated in both basins, we found greater CPOM content in Phylloicus larvae of Upper São Francisco sites, and this food item was related to greater riparian vegetation canopy density. The FPOM content was greater in larvae of Upper Araguari sites, and this food item was correlated with greater instream brush cover. Algae, animal tissue, vascular plant tissue and mineral material were very rare in the digestive tracts, and therefore could not be explained. These results indicate the importance of riparian vegetation structure in modulating feeding habitats of macroinvertebrates. We conclude that the Phylloicus larvae had more flexibility in what they eat than we might expect based on their traditional classification as shredders. Therefore, trusting in published classifications, ignoring regional or local differences, may be inaccurate. Instead, regional studies of feeding habits are needed for accurate classifications of invertebrate taxa into trophic guilds.

Online appendix 1:Exploring an extensive dataset to establish woody vegetation cover and composition in Kruger National Park for the late 1980s

Woody plant cover and species composition play an important role in defining the type and function of savanna ecosystems. Approximately 2000 sites in the Kruger National Park (KNP) were surveyed by F.J. Venter over a period from 1985 to 1989, recording vegetation, soil and topological characteristics. At each of these sites (approximately 20 m × 20 m each), woody vegetation cover and species were recorded using a rapid, Braun-Blanquet classification for three height classes: shrub (0.75 m – 2.50 m), brush (2.50 m – 5.50 m) and tree (&gt; 5.50 m). The objective of this study was to re-analyse the vegetation component of the field data, with a specific focus to provide a spatially explicit, height-differentiated, benchmark dataset in terms of species occurrence, species richness and structural canopy cover. Overall, 145 different woody species were recorded in the dataset out of the 458 species documented to occur in the park. The dataset describes a woody layer dominated by a relatively small number of widely occurring species, as 24 of the most common woody species accounted for all woody species found on over 80% of all sites. The less common woody species (101) were each recorded on 20 sites or less. Species richness varied from 12 to 1 species per site. Structural canopy cover averaged 9.34%, 8.16% and 2.89% for shrub, brush and tree cover, respectively. The dataset provides a useful benchmark for woody species distribution in KNP and can be used to explore woody species and height class distributions, as well as comparison with more recent or future woody vegetation surveys.Conservation implications: The results provided evidence that large-scale, woody vegetation surveys conducted along roads offer useful ecosystem level information. However, such an approach fails to pick up less common species. The data presented here provided a useful snapshot of KNP woody vegetation structure and composition and could provide excellent opportunities for spatio-temporal comparisons.

Exploring an extensive dataset to establish woody vegetation cover and composition in Kruger National Park for the late 1980s

Woody plant cover and species composition play an important role in defining the type and function of savanna ecosystems. Approximately 2000 sites in the Kruger National Park (KNP) were surveyed by F.J. Venter over a period from 1985 to 1989, recording vegetation, soil and topological characteristics. At each of these sites (approximately 20 m × 20 m each), woody vegetation cover and species were recorded using a rapid, Braun-Blanquet classification for three height classes: shrub (0.75 m – 2.50 m), brush (2.50 m – 5.50 m) and tree (&gt; 5.50 m). The objective of this study was to re-analyse the vegetation component of the field data, with a specific focus to provide a spatially explicit, height-differentiated, benchmark dataset in terms of species occurrence, species richness and structural canopy cover. Overall, 145 different woody species were recorded in the dataset out of the 458 species documented to occur in the park. The dataset describes a woody layer dominated by a relatively small number of widely occurring species, as 24 of the most common woody species accounted for all woody species found on over 80% of all sites. The less common woody species (101) were each recorded on 20 sites or less. Species richness varied from 12 to 1 species per site. Structural canopy cover averaged 9.34%, 8.16% and 2.89% for shrub, brush and tree cover, respectively. The dataset provides a useful benchmark for woody species distribution in KNP and can be used to explore woody species and height class distributions, as well as comparison with more recent or future woody vegetation surveys.Conservation implications: The results provided evidence that large-scale, woody vegetation surveys conducted along roads offer useful ecosystem level information. However, such an approach fails to pick up less common species. The data presented here provided a useful snapshot of KNP woody vegetation structure and composition and could provide excellent opportunities for spatio-temporal comparisons.

White-tailed deer distribution in response to patch burning on rangeland

Management of rangelands has changed substantially over the past few decades; today there is greater emphasis on wildlife management and increased interest in using natural disturbances such as fire to manage rangeland plant and animal communities. To determine the effect of prescribed fires on the distribution of white-tailed deer ( Odocoileus virginianus), we used Global Positioning System (GPS) collars to monitor the movements of bucks and does during four, month-long, trials before and during the year after implementation of three late summer burns. Deer were expected to increase their use of burned areas to take advantage of fresh plant growth after the disturbance. However, the only increased use of burns occurred 1–2 months after treatment. The presence of cattle did not limit deer use of burns. Low use of burned areas was attributed to drought conditions, which limited vegetation regrowth. Other than a brief flush of fresh grass in autumn, no changes in plant cover could be ascribed to the burns. Thus, in semi-arid areas, use of prescribed burns to reduce brush cover and increase forb production for deer may not be successful, at least in the short-term, if lack of rainfall limits regrowth of vegetation.

A Process for Assessing Wooded Plant Cover by Remote Sensing

The ability to map the extent of wooded vegetation cover over large areas using remote sensing is important for managing and assessing rangelands. Currently, applied techniques are inadequate because they 1) do not directly measure the amount of land covered by woody plants and rely on low-resolution images, 2) require considerable training-area data to train a classifier, and 3) describe only a limited number of land cover types. This paper presents an innovative methodology for creating a landcover map that requires little to no traditional, training-area data collection before classification. The procedure combines both high-resolution aerial photography (resampled to 2.5-m pixels) and lower-resolution satellite imagery (30-m pixels) to produce a detailed and easily producible data set. The resulting data set also categorizes regions into a wide variety of land cover types in addition to differing levels of wooded cover. This new methodology was applied to the Upper Guadalupe River watershed in Texas, which is composed of varying amounts of brush cover between herbaceous range and dense cover. Validation by comparison to aerial imagery demonstrated a 74.4% success rate for all land cover classes. Validation was also performed by ground survey for several brush-covered points and showed a 90.0% success rate. As a result of the ground survey, modifications to the methodology were recommended to reduce classification errors and improve the process.

MODELING EFFECTS OF BRUSH MANAGEMENT ON THE RANGELAND WATER BUDGET: EDWARDS PLATEAU, TEXAS

ABSTRACT: The Soil and Water Assessment Tool (SWAT) was used to evaluate the influence of woody plants on water budgets of semi-arid rangelands in karst terrain. The model was configured for the hydrologic evaluation of the North Fork of the Upper Guadalupe River watershed and was calibrated and verified using measured flow data. Nash and Sutcliffe fit efficiencies for daily and monthly verification periods were 0.09 and 0.50, respectively. Streamflow, baseflow, and evapotranspiration (ET) rates were comparable to published field data. Simulated deep recharge was considerably higher than the published values for the Edwards Plateau. The model was then used to simulate conditions with existing brush cover and four different brush removal scenarios. Scenarios were created to represent existing brush and the removal of brush from only locations that were either covered by heavy brush, were on a moderate slope, or were in shallow soils. Resulting data was compared to previous studies of both field experiments and model simulations. Maximum brush removal resulted in a reduction in ET equal to 31.94 mm/yr depth over the entire basin, or 46.62 mm/yr depth over the treated area. Removal of heavy brush cover resulted in the greatest changes in evapotranspiration, surface runoff, base-flow, and deep recharge. Slope was found to have the greatest effect on lateral subsurface flow.

A Process for Assessing Wooded Plant Cover by Remote Sensing

The ability to map the extent of wooded vegetation cover over large areas using remote sensing is important for managing and assessing rangelands. Currently, applied techniques are inadequate because they 1) do not directly measure the amount of land covered by woody plants and rely on low-resolution images, 2) require considerable training-area data to train a classifier, and 3) describe only a limited number of land cover types. This paper presents an innovative methodology for creating a land-cover map that requires little to no traditional, training-area data collection before classification. The procedure combines both high-resolution aerial photography (resampled to 2.5-m pixels) and lower-resolution satellite imagery (30-m pixels) to produce a detailed and easily producible data set. The resulting data set also categorizes regions into a wide variety of land cover types in addition to differing levels of wooded cover. This new methodology was applied to the Upper Guadalupe River watershed in Texas, which is composed of varying amounts of brush cover between herbaceous range and dense cover. Validation by comparison to aerial imagery demonstrated a 74.4% success rate for all land cover classes. Validation was also performed by ground survey for several brush-covered points and showed a 90.0% success rate. As a result of the ground survey, modifications to the methodology were recommended to reduce classification errors and improve the process.

Tree and shrub invasion in northern mixed-grass prairie: implications for breeding grassland birds

North American grasslands continue to decline in quantity and quality. In the northern mixed-grass prairie, potential edge and fragmentation effects on grassland birds are poorly understood and conclusions are based largely on data from outside the region. Lands in and adjacent to J. Clark Salyer National Wildlife Refuge in north-central North Dakota comprise one of the largest contiguous patches of northern mixed-grass prairie remaining in North America. However, within the region, aspen (Populus tremuloides), willow (Salix spp.), and other woody species have increased, such that continued existence of grasslands is threatened. We examined how breeding grassland birds responded to habitat that has been variably fragmented by encroaching woody vegetation. The probability of occurrence decreased markedly for 11 of 15 bird species (including 3 endemic to the northern Great Plains) as percent woodland, tall shrub, or brush cover increased. Bird species were increasingly affected as the height of woody plants increased from brush to tall shrubs to trees. Grasslands became largely unsuitable for 9 species as woodland cover exceeded 25%. Derived models can be used by land managers to predict the outcome of management actions that alter plant community succession or that restore grasslands degraded by woody invasion.

Landowner willingness to participate in a Texas brush reduction program

Because most of Texas consists of privately owned land and the amount of brush cover on rangelands may affect off-site water yields, there has been increasing interest in publicly funded brush clearing programs aimed at increasing water yield. The Pedernales River was selected as 1 of 8 watersheds to determine the feasibility of implementing such a program. A survey questionnaire was mailed to 720 landowners in Blanco and Gillespie County (containing most of the Pedernales watershed) in June 2000 to identify factors that influence their interest in participating in a brush reduction program. The sample consisted of equal numbers of landowners with 4-20, 21-202, and > 202 ha of land. Fifty eight percent of the survey participants responded, 82% of whom answered questions about their willingness to enroll at least part of their land in a brush reduction program. Property size and income from wildlife were found to be significant positive determinants and level of satisfaction with brush a significant negative determinant of respondents' willingness to enroll. To optimize public investments, it may be preferable to maximize the area enrolled in a brush removal program by targeting larger landowners who appear to be willing to enroll larger portions of their land without requiring compensation that exceeds their net cost of enrollment. Because land in the Edwards Plateau is being subdivided and purchased by people who do not depend on land-based income and who may be more tolerant of brush, public funds required to encourage landowner participation may increase over time.

Landowner willingness to participate in a Texas brush reduction program

Because most of Texas consists of privately owned land and the amount of brush cover on rangelands may affect off-site water yields, there has been increasing interest in publicly funded brush clearing programs aimed at increasing water yield. The Pedernales River was selected as 1 of 8 watersheds to determine the feasibility of implementing such a program. A survey questionnaire was mailed to 720 landowners in Blanco and Gillespie County (containing most of the Pedernales watershed) in June 2000 to identify factors that influence their interest in participating in a brush reduction program. The sample consisted of equal numbers of landowners with 4-20, 21-202, and &gt; 202 ha of land. Fifty eight percent of the survey participants responded, 82% of whom answered questions about their willingness to enroll at least part of their land in a brush reduction program. Property size and income from wildlife were found to be significant positive determinants and level of satisfaction with brush a significant negative determinant of respondents' willingness to enroll. To optimize public investments, it may be preferable to maximize the area enrolled in a brush removal program by targeting larger landowners who appear to be willing to enroll larger portions of their land without requiring compensation that exceeds their net cost of enrollment. Because land in the Edwards Plateau is being subdivided and purchased by people who do not depend on land-based income and who may be more tolerant of brush, public funds required to encourage landowner participation may increase over time.

BIRD COMMUNITIES IN THINNED VERSUS UNTHINNED SIERRAN MIXED CONIFER STANDS

We used point counts and nest monitoring to compare avian community composition and nesting success in thinned and unthinned stands of commercially managed Sierran mixed conifer forest. We conducted point counts and monitored 537 active nests of 37 species on 10 study plots during three consecutive breeding seasons in the northern Sierra Nevada. All 10 study plots had experienced a similar long term man- agement history that included fire suppression and single-tree selection logging, but five of the plots also un- derwent a protocol of combined commercial and biomass thinning 5-8 years prior to the beginning of the study. Pooling species by nest substrate, we found that detections of ground-nesting bird species were similar on thinned and unthinned plots, but we detected canopy-, cavity-, and especially shrub-nesting species much more frequently on the thinned plots. Nest success rates were not statistically different between thinned and unthinned plots for ground-, shrub-, canopy-, or cavity-nesting species. Thinned stands were characterized by significantly less canopy cover, significantly lower density of small and medium conifers, and significantly greater understory cover and deer brush (Ceanothus integerrimus) cover than the unthinned stands. We surmise that the thinning protocol stimulated vigorous shrub growth, and conclude that forest conditions associated with a relatively open canopy and a well-developed shrub understory are highly beneficial to numerous breeding bird species in the Sierran mixed conifer community, including many species that may not nest or forage in the understory. Forest thinning that promotes vigorous shrub growth may correlate with an increased abundance of nesting birds, at least within stands affected by historical fire suppression and single-tree selection logging. Received 1 October 2002, accepted 5 March 2003. Logging practices and human-altered fire regimes have changed forest structure and composition across much of the Sierra Nevada since the mid-Nineteenth Century (Franklin and Fites-Kaufmann 1996, Gruell 2001). Tim- ber harvest practices and fire suppression throughout much of the region generally have reduced the frequency of low intensity fires, reduced the number of large trees, increased the density of smaller trees, and possibly re- duced the extent of shrub cover (Weaver 1974,

A preliminary analysis of Texas ranchers’ willingness to participate in a brush control cost-sharing program to improve off-site water yields

Brush cover of 30% is estimated to be economically optimal for ranches on the Edwards Plateau, Texas. This contrasts with a regional objective to increase off-site water yield, which is maximized if brush cover is removed. Survey research was conducted to assess ranchers' willingness to enter a 10-year easement contract to clear brush to 3%, for a fixed cost-share payment to offset their opportunity costs of participation. Sixty-six percent of the 119 ranchers surveyed were willing to enroll. Ranch size, income from livestock and deer-hunting enterprises, and perceptions about brush control costs were important explanatory variables in statistical analysis using probit and Cragg models.

Landscape requirements of prairie sharp‐tailed grouse Tympanuchus phasianellus campestris in Minnesota, USA

The prairie sharp‐tailed grouse Tympanuchus phasianellus campestris occurs throughout the north central region of North America. It is of management concern because it has decreased in the southeast portion of its range over the past three decades, including marked declines in Minnesota and the Great Lakes region, USA. Although there is general knowledge about the habitat requirements for this species, no quantitative lek site or landscape information has been documented. We quantified landscape composition around active and inactive sharp‐tailed grouse lek sites and random points in brush landscapes in northeast Minnesota at multiple scales (200–3,000 m radii circles). Our objective was to compare landscape composition among these sites. We also developed a model to predict the probability of grouse lek site occurrence in the study area. Landscape composition around active and inactive lek sites differed from each other primarily at the 500 m and 1,000 m radii scales. Inactive sites had higher proportions of upland forest and brush cover types and active sites had a higher percentage of native grass than inactive sites. No differences were found in landscape composition between site types at the 200 m radius scale and only one landscape variable (number of cover types) was different at the 3,000 m radius scale. We found non‐random distributions of this grouse species at four different scales. Random brush land sites differed from both active and inactive sites having higher percentages of forest and brush cover. In contrast, lek sites had more bare ground, emergent aquatic vegetation, bog brush and roads than the random points. A regression model for the grouse at the 3,000 m scale was used to predict the probability of grouse occurrence in the landscape. The model resulted in a spatial map with about 8% of the area having a probability of grouse occurrence of &gt;80%. This information can be used to locate new lek sites and to guide management activities for this species.