EFFECTS OF LAND-USE PRACTICES

Past and current uses of public lands have impacted virtually all sagebrush ecosystems (Bock et al. 1993, West and Young 2000, Miller and Eddleman 2001). Livestock grazing, conversion to agriculture or urban areas, energy and natural resource development, habitat treatment, and even restoration activities, have had direct as well as indirect consequences. The magnitude of these effects is difficult to quantify. Direct effects, such as extent of fragmentation or total area lost, rarely have been linked to specific land uses (Dobler et al. 1996, Hann et al. 1997, Knick and Rotenberry 1997) and cumulative effects have not been estimated over the large geographic extent of sagebrush. These analyses have been hindered because large-scale maps have been unavailable, inconsistent across administrative boundaries, or limited by coarse spatial and thematic resolution. Similarly, an assessment of landscape changes caused by land use has been precluded by lack of maps depicting habitats at comparable resolutions to contrast different times.

Other effects, such as altered or depleted understories, have been well documented in local site-specific contexts but are difficult to quantify for large areas because of our inability to translate local events into broad-scale dynamics (Allen and Starr 1982, Wiens 1989a). Technological challenges also limit mapping these conditions in semiarid regions using remote sensing (Knick et al. 1997). As a result, the wide geographic distribution of sagebrush in maps depicting only a dominant cover type (Fig. 1) provides a deceptive mask and false sense of security. Land uses influence site-specific factors as well as landscape features to form a complex mosaic of varied conditions and histories. Thus, analyses of additional landscape metrics, such as fragmentation (Fig. 2), may be necessary to identify the potential consequences for disturbance regimes, invasions of exotic plants, and trajectories of future vegetation dynamics (Turner et al. 2001).

LIVESTOCK GRAZING

Livestock grazing and associated habitat alterations have had the most widespread impact on western ecosystems of any land use (Bock et al. 1993, Fleischner 1994). Virtually all sagebrush lands are managed principally for livestock grazing. In 2001, 15 000 permits were issued for >10.2 million animal unit months of forage consumption on lands managed by the U.S. Bureau of Land Management (Bureau of Land Management 2002b). (One animal unit month = the quantity of forage required by 1 mature cow weighing 454 kg and calf, or equivalent, for 1 month.) Livestock grazing can change habitat features that directly influence birds; for example, by reducing plant species diversity and biomass (Reynolds and Trost 1981, Bock and Webb 1984, Saab et al. 1995). Alternatively, changes in water and nutrient cycling caused by grazing can promote the spread of invasive species, which then degrade native bird habitats by altering fire and disturbance regimes (Rotenberry 1998). In addition, activities associated with livestock production, such as feedlots, can facilitate nest predators or parasitism by Brown-headed Cowbirds (Molothrus ater; Vander Haegen and Walker 1999, Goguen and Matthews 2000).

Many areas of sagebrush steppe in western North America historically did not support herds of large ungulates. Large native herbivores had disappeared by 12 000 years BP, and native vegetation communities developed in the absence of significant grazing pressure (Grayson 1994). Because of semiarid climate and the absence of grazing in their recent evolutionary history, sagebrush systems are particularly sensitive to grazing disturbance (Mack and Thompson 1982). Excessive grazing by domestic livestock during the late 1800s and early 1900s, coupled with severe drought, significantly impacted sagebrush ecosystems (Yensen 1981, Young and Sparks 2002). Long-term effects persisting today include widespread changes in plant community composition and soils that have increased the spread of exotic vegetation and altered natural disturbance regimes (Yensen 1981, Young 1994, Miller and Rose 1999).

Manipulation of sagebrush landscapes to increase forage production for livestock has dominated our perspective and shaped our use of sagebrush ecosystems (Holechek et al. 1998). Large expanses of sagebrush have been eradicated and reseeded with non-native grasses (primarily crested wheatgrass [Agropyron cristatum]) to increase production of forage for livestock grazing (Hull 1974, Evans and Young 1978, Shane et al. 1983). An estimated 2–6 million ha of sagebrush lands were treated to reduce or eliminate sagebrush cover by the 1970s (Schneegas 1967, Vale 1974). Thinning or prescribed burning to reduce cover density of sagebrush and promote forb and grass production continues to be practiced widely (Olson and Whitson 2002, Bureau of Land Management 2002a, Wambolt et al. 2002).

AGRICULTURE AND URBANIZATION

Crop production on lands previously dominated by sagebrush has completely converted vast tracts of sagebrush habitats and fragmented many remaining landscapes (Wisdom et al. 2000; Fig. 3). Similarly, urbanization, roads, and powerlines continue to fragment ecological systems (Trombulak and Frissell 2000, Wright et al. 2001). This loss represents a major challenge for restoration (and may be irreversible) because essential components of the system are disrupted or lacking entirely.

Lands converted to agriculture occur primarily at low elevations in areas containing deep, highly productive soils (Dobler et al. 1996, Scott, Murray, et al. 2001). In central Washington, 75% of the shrubsteppe regions containing loamy soils have been converted to agriculture or other land uses, compared to <15% of the shrubsteppe communities on shallow soils (Vander Haegen et al. 2000). An estimated 99% of the basin big sagebrush habitats in the Snake River Plain now are used for cropland (Hironaka et al. 1983).

Development of the agricultural landscape has fragmented sagebrush steppe regions at multiple scales (Fig. 2, 3). Fragments of intact sagebrush habitats in Washington now exist within a matrix of agriculture (Vander Haegen et al. 2001). The mean patch size of sagebrush in Washington decreased from 13 420 ha to 3418 ha and the number of patches increased from 267 to 370 between 1900 and 1990 (Hann et al. 1997, McDonald and Reese 1998). Nest predation also increased in fragmented habitats dominated by agriculture (Vander Haegen et al. 2002). Cowbird parasitism increased in agricultural landscapes and in the presence of feedlots for livestock, although the rate of cowbird parasitism on shrubsteppe birds generally remains low (Vander Haegen and Walker 1999). At broader scales, conversion of the Snake River Plain to agriculture disconnected regions north of the Snake River from sagebrush in southern Idaho and northern Nevada (Fig. 1, 3).

NATURAL RESOURCE DEVELOPMENT

Approximately 2.7 million ha of western lands administered by the U.S. Bureau of Land Management currently are in production status for oil, gas, or geothermal energy (Bureau of Land Management 2002b). An estimated 9.3 million ha in five basins of federal lands (includes habitats in addition to sagebrush) in Montana, Wyoming, Colorado, Utah, and New Mexico, are available for oil and gas leasing with standard stipulations (U.S. Departments of Interior, Agriculture, and Energy 2003). Approval for 29 000 new oil and gas leases is anticipated by 2005 (Bureau of Land Management 2003).

Energy development and natural resource extraction directly alter sagebrush habitats at the site of operation (Braun et al. 2002). In Wyoming, existing oil and gas wells were located primarily in landscapes dominated by sagebrush (Fig. 4). Associated road networks, pipelines, and powerline transmission corridors also influence vegetation dynamics by fragmenting habitats or by creating soil conditions facilitating the spread of invasive species (Fig. 4; Braun 1998, Gelbard and Belnap 2003). Density of sagebrush-obligate birds within 100 m of roads constructed for natural gas development in Wyoming was 50% lower than at greater distances (Ingelfinger 2001). Increased numbers of corvids and raptors associated with powerlines (Steenhof et al. 1993, Knight and Kawashima 1993, Vander Haegen et al. 2002) also increase the potential impact of predation on sage-grouse and other sagebrush-breeding birds.

HABITAT TREATMENT

Land managers burn or otherwise treat large areas of sagebrush habitats on public lands every year. In 2000 and 2001, prescribed fires were used to treat 50 000 ha managed by the Bureau of Land Management; nonfire treatments (e.g., herbicides, biocontrols, mechanical alteration) were used on an additional 96 000 ha (Bureau of Land Management 2001, 2002b). The preferred alternative presented by the Bureau of Land Management in the Final Vegetation Environmental Impact Statement (Bureau of Land Management 1991) recommended treating 919 212 ha in the 13 western states annually. The appropriateness of these actions and their effects on habitats and the associated avifauna are widely debated (Connelly, Reese, et al. 2000, Wambolt et al. 2002).

Prescribed fire, herbicides, and numerous mechanical and biological means are used to thin or reduce biomass of woody vegetation, improve forage production for livestock, control invasive weeds or insects, or obtain a desired seral condition. Our understanding of the effects of these habitat treatments on diversity, density, or productivity of shrubland birds most often has been derived from studies of specific, fine-scale management actions (Best 1972, Schroeder and Sturges 1975, Castrale 1982, Petersen and Best 1987, Howe et al. 1996). With few exceptions (Kerley and Anderson 1995), most studies address short-term effects immediately post-treatment. Of 35 papers investigating perturbation effects, 94% did not sample pretreatment conditions, had no controls, or were of short duration (Petersen and Best 1999). Planned experiments that incorporate habitat manipulations are rare (Wiens and Rotenberry 1985, Winter and Best 1985, Wiens et al. 1986, Fischer et al. 1997, Connelly, Reese, et al. 2000) but provide greater insights into mechanisms underlying habitat change and bird response.

EXOTIC PLANTS IN SAGEBRUSH ECOSYSTEMS

Exotic plant species, such as cheatgrass (Bromus tectorum), yellow starthistle (Centaurea solstitialis), spotted knapweed (C. biebersteinii [= maculosa]), tamarisk (Tamarix ramosissima), medusahead wildrye (Taeniatherum caput-medusae), and rush skeleton-weed (Chondrilla juncea), are rapidly invading breeding and wintering ranges of birds. Invasion of alien plants causes changes in the vegetation composition and structure and alters disturbance regimes (Brooks and Pyke 2001). The area infested by exotic plants increased from 1.1 million ha in 1985 to 3.2 million ha in 1994 on lands managed by the Bureau of Land Management (Bureau of Land Management 1996). Rate of spread for noxious weeds has been estimated to be approximately 931 ha day⁻¹ on BLM lands and 1862 ha day⁻¹ on all public lands in the West (Bureau of Land Management 1996).

SAGEBRUSH REHABILITATION AND RESTORATION

The accelerating frequency of large wildfires in sagebrush ecosystems has resulted in extensive rehabilitation efforts to control erosion, return stability to the system and, in some cases, reestablish a shrubland landscape (Roundy et al. 1995). During 2000–2001, $91 million was approved to treat 755 000 ha of lands managed by the Bureau of Land Management in the emergency fire rehabilitation program, whose primary objective is to stabilize soils (Bureau of Land Management 2001, 2002b). Federal agencies encourage the use of native seeds (Richards et al. 1998), but in reality the use of non-native grasses (such as crested wheatgrass) will continue to increase because of the demand caused by large fires coupled with low availability of native seeds from commercial seed sources (Asay et al. 2001). The effects of non-native grasses on dynamics of birds in sagebrush communities have not been well studied (Reynolds and Trost 1981, McAdoo et al. 1989), particularly in the context of the landscape in which the rehabilitation project is embedded.

Land-management agencies are developing major programs for restoration of sagebrush ecosystems (Beever and Pyke 2002, Bureau of Land Management 2002a). Restoration will be difficult, expensive, and may require decades or even centuries (U.S. Department of Interior 1996, Hemstrom et al. 2002). The process of recovery is relatively unknown, although we have extensive documentation of deterioration in sagebrush ecosystems (Allen-Diaz and Bartolome 1998). Not all areas previously dominated by sagebrush can be restored because alteration of vegetation, nutrient cycles, topsoil, cryptobiotic crusts, and disturbance processes have pushed these systems past critical thresholds from which recovery is unlikely (Allen 1988, Belnap and Lange 2001, McIver and Starr 2001) or because we lack the political agenda and economic incentives (Allen and Jackson 1992).

LIFE-HISTORY ATTRIBUTES OF BIRDS IN SAGEBRUSH HABITATS

Sagebrush ecosystems support few bird species compared to other ecosystems due to relatively low floristic structure and diversity coupled with low productivity and seasonal environments (Rotenberry 1998, Vander Haegen et al. 2001). Perhaps 18 bird species associated with sagebrush ecosystems are of conservation concern (Appendix; Paige and Ritter 1999). Our understanding of bird and habitat relationships in sagebrush systems, however, is based largely on studies of three game species (Greater Sage-Grouse, Gunnison Sage-Grouse, Sharp-tailed Grouse) and three passerines (Sage Thrasher, Brewer's Sparrow, Sage Sparrow). We know little basic life history of other bird species that use sagebrush habitats.

BIRD-HABITAT RELATIONSHIPS

The relationship of vegetation characteristics to bird distribution and abundance has been the most widely investigated aspect of birds associated with sagebrush habitats (Rotenberry and Wiens 1978, Wiens and Rotenberry 1981, Rotenberry 1985, Wiens et al. 1987, Schroeder et al. 1999, Connelly, Schroeder, et al. 2000, Vander Haegen et al. 2000). Most studies of bird and habitat relationships have been site specific. However, additional insights into composition and disturbances structuring habitats used by shrubsteppe birds might be obtained from a meta-analysis of multiple sites. For example, we used data collected in Oregon, Nevada, Idaho, and Washington (Rotenberry and Wiens 1980b, Wiens and Rotenberry 1981, Dobler 1994, Knick and Rotenberry 1995) in a detrended correspondence analysis to determine the primary habitat and disturbance gradients along which shrubsteppe birds were distributed (Fig. 5). The first axis captured the primary distribution of bird species along a gradient from grassland to shrubland. We inferred an increasing fire frequency associated with greater amounts of grassland. The second axis contrasted a vegetatively open to dense habitat structure, which resulted from increasing likelihood of invasion by juniper and other woody vegetation correlated in part with decreasing fire frequency. By developing models of bird and habitat relationships at multiple scales of investigation, we can attempt to understand and predict the response of shrubsteppe bird communities to habitat changes.

Statistical models used to derive relationships between animals and their habitats may fit a high proportion of the variation in the sample (Verner et al. 1986, Morrison 2001, Scott et al. 2002), but often these models do not perform well in regions or times outside of the sampling space (Rotenberry 1986, Knick and Rotenberry 1998). We may need to develop a different paradigm in the way we assess habitats. Instead of deriving habitat characteristics that are highly correlated with bird abundance, we might seek to identify a minimum or constant set of habitat characteristics required by a species to be present (Knopf et al. 1990). By modeling basic or minimum requirements, we may develop a better understanding of components necessary to maintain bird populations, as well as improve capability to predict response of populations to habitat changes (Rotenberry et al. 2002).

SCALES OF BIRD-HABITAT RELATIONSHIPS

Most research on response to habitat change by birds, conducted at fine spatial and temporal scales, suggests that cumulative effects of local changes significantly influence population dynamics of birds in sagebrush habitats. Site-specific studies have provided a good understanding of components of sagebrush habitats associated with breeding birds. However, we recently have noted the relationship between landscape-level habitat variables and local abundances of birds (Knick and Rotenberry 1995, Knick and Rotenberry 1999, Vander Haegen et al. 2000). Occupancy of a home range is based on multiple variables operating at different scales: local vegetation coupled with landscape characteristics much larger than individual home ranges (Rotenberry and Knick 1999). The answer to how much habitat or how many resources are required to sustain a population is not trivial and differs among species. Development of regional vegetation maps (Comer et al. 2002) and GIS-based analyses should permit identification of broad-scale variables that affect species distribution. By integrating technological advances and field research, we might better understand the relative contribution of broad- and fine-scale habitat features to dynamics of shrubland birds.

Historical information on long-term changes in bird distribution (Brown and Davis 1995) would improve our understanding of habitat relationships as well as increase our ability to predict consequences of management decisions or global dynamics such as climate change. A long-term perspective of past fire regimes in sagebrush regions (Miller and Wigand 1994, Miller and Tausch 2001), coupled with vegetation changes (Tausch 1999, Thompson and Anderson 2000, Miller and Eddleman 2001), climate fluctuations, and anthropogenic impact, provide an important context in which to interpret current dynamics of sagebrush habitats and birds.

MECHANISMS OF BIRD RESPONSE TO HABITAT CHANGE

The processes by which birds respond to changes in habitat composition and configuration remain elusive, and identifying them requires knowledge of local population dynamics and their variations across the landscape (Knick and Rotenberry 2002). Local abundance derives from a complex interaction of habitat characteristics coupled with variation in survival, productivity, and dispersal (Wiens 1989b, 1989c, 2002). In sagebrush ecosystems, we do not understand how habitat fragmentation influences productivity, density of breeding adults, size of home range, or probability of predation or Brown-headed Cowbird parasitism.

We lack the necessary demographic information to reliably model population growth and to ascertain source-sink status for birds dependent on sagebrush habitats. Much of the focus of productivity studies for shrubsteppe passerines has been on regional and annual variation (Rotenberry and Wiens 1989). Clutch size, nest success, and fledging rates vary significantly among years (Petersen and Best 1987, Rotenberry and Wiens 1989) and may be related to weather before and during the nesting season (Rotenberry and Wiens 1991). More recently, the effect of large-scale habitat fragmentation on productivity of shrubland birds has been studied by integrating satellite imagery with field studies in Washington state, with the conclusion that nest success decreases in more-fragmented landscapes (Vander Haegen et al. 2002). Ultimately, criteria defining source-sink habitat gradients need to be based on measures of productivity per area or on population growth rates (Van Horne 1983, Morrison 2001, Misenhelter and Rotenberry 2000).

EFFECTS OF LAND-USE PRACTICES

Accurate rangewide estimates of total area degraded, fragmented, converted to agriculture, or invaded by exotic weeds are needed to grasp fully the magnitude of changes and their impact on birds. For some pervasive land uses, such as livestock grazing, empirical data to test the effects on bird populations are limited (Bock and Webb 1984, Saab et al. 1995). We need experiments having strong statistical designs that include treatments and controls at spatial and temporal scales relevant to the impacts to vegetation and soils and the dynamics of recovery (Fleischner 1994, Tewksbury et al. 2002, Wambolt et al. 2002). Long-term studies incorporating a widespread system of exclosures (Bock et al. 1993) and ability to control treatment levels are necessary to determine effects of land use on habitats and birds. The treatment projects planned by management agencies and the large number of areas to be treated represent a tremendous opportunity to design a sound experimental approach. In addition, a commitment to monitoring at appropriate scales would provide feedback to evaluate treatment effects and provide a basis for adaptive management strategies (Walters 1986, Morrison 2002).

Implementation of sound management based on an understanding of the effects of land-use practices, and enforced accountability to those policies, may be the only way to ensure long-term survival of sagebrush habitats and their birds. Protection from economic use (as national parks or monuments) is not viable for all sagebrush lands but could be an option in specific areas that retain native plants or are important regions for biodiversity. Purchasing lands for protection (Shaffer et al. 2002) also is not a complete solution because the areas required to encompass natural disturbance patterns are too large. Approximately 4.3 million ha of sagebrush lands would need to be placed in nature reserves if we are to meet the conservation goal of protecting 10% of the distribution. To develop this network of reserves, we need to prioritize the landscape by identifying and providing protection or other appropriate management to those relatively large areas of sagebrush in good condition. We then need to enlarge existing protected blocks, increase connectivity in the landscape, and employ basic principles of landscape management to ensure long-term survival of sagebrush habitats and birds.

Complete restoration of habitats requires that we understand critical patterns and processes at the appropriate spatial scales (Whisenant 1993). For sage-grouse, which may use ranges encompassing >2500 km² (Schroeder et al. 1999), creating suitable habitats will require that we focus efforts to restore entire landscapes rather than pursue individual unconnected efforts (Dobkin 1995, Wisdom, Rowland, et al. 2002, Wisdom, Wales, et al. 2002). However, the ecological foundation for development of overarching management prescriptions based on sage-grouse (Dobkin 1995, Rich and Altman 2002) or other single-taxon approaches (such as birds) needs to be tested for its capability to accommodate all species associated with sagebrush ecosystems.

In the absence of active restoration, exotic grasses will continue to invade sagebrush landscapes and degrade habitat (Hemstrom et al. 2002, Wisdom, Rowland, et al. 2002). To counter this disastrous scenario, we strongly recommend a federal policy to require use of ecologically appropriate native plant species in all shrubsteppe restoration projects on public lands. Such a policy will provide the incentive for the private sector to create sufficient commercial sources of native seed. Mandatory use of native seed in public-land restoration is a relatively simple step with great potential for redirecting the ecological trajectory of these landscapes away from ecological dysfunction and toward ecological resiliency.

BIRD RESPONSE TO HABITAT CHANGE

Questions about basic life history for birds living in sagebrush habitats should form an integrated foundation for testing broader hypotheses about relationships between birds and their habitats (Noon and Franklin 2002, Wiens 2002). Because of their increasing dominance in sagebrush systems, we need to focus research on the influence of exotic plants on habitat dynamics and bird response. Understanding mechanisms underlying bird response to habitat characteristics will require that we determine population information across a range of habitat conditions. We recommend establishing a coordinated network of study sites across a gradient of habitat conditions at which demographic information, such as reproductive success, adult and juvenile survival, adult return rates, and patterns of juvenile dispersal, can be obtained. An intensive program to mark birds at such sites could yield great insight into population dynamics (Sherry and Holmes 2000) but will require a long-term commitment to maintain. Long-term studies involving marked individuals also could assess the potential for birds' site fidelity to delay population response to habitat changes, a possible cause of confounded bird-habitat models (Wiens et al. 1986). Ultimately, development of population models based on life-stage information collected from such a network of sites (Caswell 2001) could yield significant insights into critical life stages, survival during breeding, migration, and wintering periods, and the influence of habitat on population dynamics.

MONITORING AND SURVEY ISSUES

Robust sampling over spatial and temporal scales that we view as necessary must involve methods that permit detectability estimates and describe sources of variation. Existing large-scale bird-monitoring programs, such as the North American Breeding Bird Survey (Robbins et al. 1986, Peterjohn and Sauer 1999) and the Christmas Bird Count (Root 1988) may not adequately sample many of the species in sagebrush ecosystems (Saab and Rich 1997). These surveys also have come under increasing criticism because of their inability to estimate biases in detectability of birds, which vary with respect to species, observers, and vegetation type, and their subsequent failure to incorporate differential detectabilities into trend analyses (Johnson 1995, Anderson 2001). For some species, targeted surveys (i.e., lek counts for sage-grouse) and new methods may be required to estimate population trends.

Almost all sampling of shrubsteppe bird populations has been based on counts of singing males on survey plots. Yet, the relationship between singing males and population parameters has not been established. Seasonal variation also may be critical in adjusting estimates based on large regions sampled throughout the breeding period (Best and Petersen 1985). Estimates based on counts of singing males may actually overestimate the breeding segment of the population by including nonbreeding territorial males, confounding our conclusions about habitat associations or population trends.

Sampling effort of current monitoring programs is distributed unevenly within sagebrush habitats among individual states. Even though many Breeding Bird Survey routes in western states sample sagebrush habitats, the proportion of sagebrush area sampled varies greatly compared to the proportion within the states (Table 2). Thus, Breeding Bird Survey routes likely capture neither the large-scale habitat features nor the smaller-scale dynamics along the gradient of habitat configurations available to shrubsteppe birds. Similar to most other habitats, surveys based on road networks may limit our ability to estimate abundance over the full range of available landscapes (Anderson 2001). Small-scale bias due to presence of unpaved or little-used roads on bird counts was insignificant in sagebrush habitats (Rotenberry and Knick 1995). Therefore, development of a new survey network that samples the existing sagebrush distribution but using unpaved roads still may be the most practical means to survey large areas. To address gradients in habitat and bird dynamics, surveys need to be based on a standard set of sampling methods for habitats and birds that incorporate local efforts into a broader program in a hierarchical design. Ultimately, counts, indexes, or density estimates need to be related to habitat components and translated into estimates of fitness or productivity per unit of area or habitat to understand source-sink dynamics and mechanisms underpinning population trends (Morrison 2001, Noon and Franklin 2002)

MIGRATION AND WINTERING-GROUND PROCESSES

Improving our ability to track migrating birds, identify wintering areas, and estimate mortality during the nonbreeding period may be the most significant contributions that we can make toward understanding population dynamics of shrubsteppe birds. Because population dynamics of birds may be strongly influenced by mortality during the nonbreeding period (Fretwell 1972), focusing our attention solely on sagebrush breeding areas risks overlooking the importance of migration routes and wintering grounds. Wintering areas for some species breeding in sagebrush habitats have been identified in the southwestern United States and Mexico (Fig. 6). However, we do not know the migration pathways these birds use or their yearly fidelity to wintering ranges.

We need a new system of surveys designed to identify the spatial and temporal distribution of wintering birds. From these surveys, we can determine habitats or regions important to wintering birds, determine the influence of weather on seasonal or yearly variation in areas used, and assess risks to birds from contaminants or habitat loss.

The ability to link habitat and population components of shrubsteppe birds during breeding, migration, and wintering periods may provide insights into annual fluctuations in populations and area-specific productivity (Wiens and Dyer 1975). To achieve this, technological advances in marking and tracking individuals and populations will be necessary. Banding information is limited because banded birds are rarely recovered. Most species, such as Sage and Brewer's Sparrows, are too small (<25 g) to carry radio-transmitters that currently are available. For larger birds, such as Sage Thrasher (35–50 g), battery life of radio-transmitters and detection distances are too short to track between breeding and wintering ranges. We only now are developing transmitters sufficiently small for attachment to small birds and powerful to track their movements over large distances and for longer periods. Other techniques that do not distinguish individuals, such as stable isotopes (Marra et al. 1998), may hold potential to determine the extent to which breeding populations mix or concentrate during the wintering period as well as link wintering ranges of birds to their breeding ranges in northern sagebrush ecosystems.