Best Management Practices

Wyoming Partners In Flight Best Management Practices for Shrub-steppe to Benefit Birds In Wyoming. (Excerpted from “Birds in a Sagebrush Sea”, Paige and Ritter 1999.)

Introduction

Sagebrush country symbolizes the wild, wide-open spaces of the West. While the first impression may be a monotony of low shrubs, the over-reaching sky, a scattering of little brown birds darting away through the brush, and that heady, ever-present sage perfume, a closer look reveals just how complex and variable sagebrush landscapes can be. From shrublands to grasslands, wet meadows and woodland edges, a mosaic of habitats supports an abundance of birds, other animals, and native plants, some of them specially adapted to these semi-deserts.

Sagebrush habitats across the West have been greatly altered by a century of settlement, livestock grazing, agriculture, weed invasion, and changes in wildfire frequency. Across the United States, the populations of 63% of shrubland and shrub-dependent bird species and 70% of grassland species are declining. In the Intermountain West, more than 50% of grassland and shrubland species show downward trends. The lack of quantitative information on many species’ habitat needs reflects a severe shortage of ecological studies in sagebrush habitats. Thoughtful land management can help rejuvenate native sagebrush habitats and reverse the declines of sagebrush-dependent species.

These Best Management Practices have one purpose: to help anyone who is a steward of sagebrush shrublands include management practices that help support a thriving community of wild birds. Not all of the suggestions in this document will be appropriate in all places, depending on local conditions and management needs, but birds can benefit even if only a few suggestions are adopted.

Ecology of Sagebrush Habitats

Sagebrush occurs in cold semi-deserts across the Intermountain West. In much of this region, winters are long, summers are hot and dry, and winds are persistent. In these semi-deserts, most of the annual precipitation comes as snow and early spring rain. Summer storms are brief and intense, and most summer rain runs off or evaporates.

The entire sagebrush region covers approximately 155.5 million acres (63 million ha) of the West. This broad zone is divided into two general vegetation types. The true “sagebrush steppe” type covers the northern portion of the Intermountain region, where sagebrush is co-dominant and grasses are few and sparse [44.5 million acres (18 million ha)]. Across the sagebrush region, sagebrush habitat ranges from semi-arid grasslands with a scattering of sagebrush to arid sagebrush-dominated shrublands with few grasses.

Several species and subspecies of sagebrush grow in the West, but the species big sagebrush predominates, and has five known subspecies. It is often important to differentiate between sagebrush species and subspecies in order to classify rangeland types; understand site potential, palatability to livestock and wildlife, and response to fire; and manage vegetation. However, for many birds, the species of sagebrush is less important than its height, density, cover, and patchiness.

A wide variety of vegetation community types exist within the sagebrush landscape due to differences in soil, climate, topography, and other physical processes, and natural and human-induced disturbances. Usually a single species of sagebrush is dominant in a community, but communities differ widely in understory plants. Understories are usually dominated by one or more perennial bunchgrasses, such as bluebunch wheatgrass, Idaho fescue, Sandberg bluegrass, Thurber needlegrass, needle-and-thread grass, bottlebrush squirreltail, or Indian ricegrass. Forbs, such as phlox, milkvetch, and fleabane, are less common, but can be abundant in moist areas.

Stands of sagebrush may be dense, patchy, or sparse. In tall sagebrush types, sagebrush cover may range from 5 to 30% or greater on some sites. Stands may vary from expanses of single species to multi-species mosaics where sagebrush is intermixed with other shrubs, most commonly rabbitbrush and antelope bitterbrush, but also greasewood, shadscale, Mormon tea, winterfat, and spiny hopsage. Other shrub communities often occur adjacent to sagebrush shrublands, especially at higher elevations, such as those dominated by serviceberry, mountain mahogany, ceanothus, and snowberry. Grassy openings, springs, seeps, moist meadows, riparian streamsides, juniper woodlands, stands of aspen, and rock outcrops also add to the sagebrush mosaic, and these habitats help attract a diversity of birds and wildlife.

Biological soil crust is an integral and usually overlooked component of sagebrush shrublands. It creates a rough crust on the soil surface in semi-arid habitats. Biological soil crust (also known as “cryptobiotic crust”, “microbiotic crust”, or “cryptogamic soil”) is a fragile microfloral community composed of blue-green algae, bacteria, fungi, mosses, and lichens. The diversity and function of crust communities has been little understood and under appreciated. This crust may play an important role in dry regions by stabilizing soils from wind and water erosion, contributing to soil productivity, influencing nutrient levels, retaining moisture, altering soil temperature, and aiding seedling establishment. Where crust communities are well established in a healthy shrubland, they help prevent the invasion of cheatgrass and, because crusts do not provide much fuel, they slow the spread of wildfire.

Approximately 100 bird species and 70 mammal species can be found in sagebrush habitats. Some of these are sagebrush obligates (restricted to sagebrush habitats during the breeding season or year-round) or near obligates (occur in both sagebrush and grassland habitats). Sagebrush obligates include the Sage Sparrow, Brewer’s Sparrow, Sage Thrasher, Greater Sage-Grouse, pygmy rabbit, sagebrush vole, sagebrush lizard, and pronghorn antelope.

Changes in Sagebrush Country

Early explorers of the Intermountain West encountered a landscape dominated by shrubs and found grasslands chiefly limited to hillsides and moist valley bottoms. Sagebrush was widespread and dominant, and the boundaries of sagebrush habitats before European settlement were about the same as they are today.

Over time, many areas of sagebrush steppe have become more densely packed with sagebrush as livestock eliminated understory grasses and wildfires were suppressed, tipping the competitive advantage toward shrubs. Evidence also suggests that fire suppression and heavy grazing have contributed to the invasion of junipers and other conifers in some sagebrush areas.

Explorers’ reports of abundant and widespread sagebrush probably indicate that fires were relatively infrequent in sagebrush habitats. Because bunchgrasses generally do not provide a continuous fuel layer to carry fire long distances, fires in presettlement times were probably patchy and small except in very dry years. Presettlement fire intervals have been estimated at 20 to 25 years in wetter regions, and 60 to 110 years in the arid sagebrush steppe of southern Idaho. After a fire, big sagebrush must be reestablished by wind-dispersed seed or seeds in the soil. Depending on the species, sagebrush can reestablish itself within 5 years of a burn, but a return to pre-burn densities can take 15 to 30 years. Before European settlement, then, spotty and occasional wildfire probably created a patchwork of young and old sagebrush stands across the landscape, interspersed with grassland openings, wet meadows, and other shrub communities.

Since presettlement times, sagebrush communities have suffered severe degradation and loss. The ecology, natural disturbance patterns, and vegetation communities have been altered by agricultural conversion, invasion of non-native plants, extensive grazing, development, sagebrush eradication programs, and changes in fire regimes.

The arrival of cattle and sheep in the Great Basin in the late 19^th century triggered a rapid change in sagebrush plant communities. Sites may have lost their native perennial grasses less than 15 years after livestock introduction. In addition, settlers burned off sagebrush to produce more grass for horses, sheep, and cattle and to clear the land for farming. Today, grazing pressure has decreased considerably compared to the early 1900s. However, less than 1% of the sagebrush steppe remains untouched by livestock; roughly 20% is lightly grazed, 30% is moderately grazed and has remnants of native herbs, and 30% is heavily grazed with the native understory replaced by introduced annuals. Sagebrush steppe can take time to recover from excessive grazing, especially on drier sites.

The effect of grazing in any region depends on season of use, intensity, type of livestock, and the plant species themselves. In the Great Basin, for example, perennial bunchgrasses must grow quickly to set seed over the short growing season, so intensive spring grazing prevents the plants from reproducing, eventually eliminating the palatable native bunchgrasses. Where grazing removes the herbaceous understory altogether, the balance is tipped in favor of shrubs, allowing sagebrush to spread and creating overly dense sagebrush stands with a sparse understory of annuals and unpalatable perennials.

Excessive grazing in the 19^th and early 20^th centuries also likely reduced crust communities throughout the Intermountain West, and it is difficult now to piece together their original extent and role in sagebrush habitats.

As well as affecting vegetation, grazing can influence bird communities in another way. The presence of livestock (particularly cattle and horses) creates feeding habitat for the Brown-headed Cowbird, a “nest parasite” that lays its eggs in the nests of other songbirds for the host parents to raise. This reduces the number of young that the host species population can produce in a year. Cowbirds feed on insects stirred up by grazing herbivores, and parasitize nests in nearby shrublands and woodlands. A native of the Great Plains, the Brown-headed Cowbird adapted to follow the herds of migratory bison. With settlement and the spread of livestock throughout the West, the cowbird’s range expanded, exposing new populations and species of songbirds to brood parasitism pressure. Cowbird parasitism may be a significant factor in the decline of some songbird populations.

From the 1930s through the 1960s, and to a much lesser extent today, land managers controlled sagebrush on degraded rangeland by burning, plowing, chaining, disking, and spraying herbicides to increase livestock forage on sites where the native grasses had been lost. Many areas were seeded with crested wheatgrass, a nonnative perennial bunchgrass, to provide forage. In addition to the thousands of acres where nonnative grasses are mixed with sagebrush, approximately 10% of native sagebrush steppe has now been completely replaced by invasive annuals or by intentionally seeded nonnative grasses. Another 10% of the sagebrush steppe has been converted to dryland or irrigated agriculture.

The greatest change to sagebrush plant communities came with the invasion of nonnative annual grasses and forbs. Inadvertently introduced in the late 19^th century, cheatgrass spread like an epidemic across the Intermountain West along transportation corridors and in the wake of grazing and agriculture, and reached its present geographic range by about 1928. Today, cheatgrass threatens to dominate 62 million acres (25 million ha)—more than half of the West’s sagebrush region.

Cheatgrass readily invades and rapidly colonizes disturbed sites and is a persistent resident, replacing native species. Other non-native species, such as medusahead, yellow star-thistle, knapweed, tumble mustard, and halogeton, are also becoming increasing problems. The presence of these invasive weeds also affects biological soil crusts.

Cheatgrass invasion fundamentally alters fire and vegetation patterns in sagebrush habitats by creating a bed of continuous, fine fuel that readily carries fire. Where cheatgrass dominates the understory, it carries fire over great distances, and the range burns far more frequently—at intervals of 3 to 5 years. Cheatgrass matures and dries earlier than native bunchgrasses, increasing the chance of fire earlier in the season. Because sagebrush may take several years to mature before producing seed, repeated, frequent fires can eliminate sagebrush entirely. Cheatgrass dominance eventually creates a uniform annual grassland perpetuated by large, frequent fires and void of remaining patches of native plant communities. Native shrubs, perennial grasses, and forbs can reestablish on a cheatgrass-dominated site over the course of several years if fire is suppressed, rainfall is low, and there is a seed source for native species.

How to Help Birds in Sagebrush Habitats

The maintenance and restoration of sagebrush bird habitats depend on our ability to provide a mosaic of native plant communities across the landscape. This goal goes hand-in-hand with sustainable rangeland management.

Wildlife species respond to their environment at different scales—“landscape ”, “stand”, and “patch”. The size of a landscape can be thousands to hundreds of thousands of acres, a stand can be one acre to thousands of acres, and a patch can be less than one acre to hundreds of acres. Each habitat patch provides some of the resources needed by individual birds, from feeding to nesting sites. Combined into stands, these habitat patches provide enough total habitat for a pair to survive and raise its young. Many stands across a landscape can support a population of a particular species. The exact size of patches, stands, and landscapes depends on the needs of each species. Thus, changes to a patch can affect the specific needs of individuals and pairs (food, water, shelter, nest site, and escape cover); changes to a stand can affect the home ranges of individual birds and pairs of birds; and changes to a landscape can affect entire populations of birds.

Managing a single site for all sagebrush wildlife species is not possible because practices that benefit some species may be detrimental to others. Management for a particular site will depend on that site’s potential. The idea is to strike a balance so that all habitats originally occurring (such as young and old sagebrush stands, grassland openings, wet meadows, springs, and riparian habitat) are represented across a large area.

The following management recommendations are voluntary and are meant to aid the land manager in enhancing habitat for sagebrush birds. These are based on our current knowledge of habitat requirements of sagebrush birds. Our main goal is to describe what birds need. Most of these suggestions will also benefit other wildlife species. You may find that certain recommendations are not appropriate for your situation, depending on your management goals, vegetation types, site potential, costs, and opportunities. But even if you can implement only a few of the recommendations, you can help improve habitat for birds.

General Sagebrush Habitat Management

We recommend no net loss of sagebrush steppe habitat on a landscape scale. No net loss does not preclude management activities. Future habitat conversions should be mitigated by restoration or conservation elsewhere, and range managers should plan for a dynamic pattern of different aged stands across a landscape.

1) Identify and protect those habitats that still have a thriving community of native understory and sagebrush plants. These may be managed as conservation easements (which do not necessarily exclude economic land uses), refuges, protected areas, sanctuaries, or research areas. Management should focus on restoring natural disturbance processes, such as fire, and removing invasive nonnative plants.

2) Where possible, restore or rehabilitate degraded and disturbed sites to native plant communities.

3) To benefit area-sensitive species such as Greater Sage-Grouse, Sharp-tailed Grouse, and Sage Sparrows, maintain sagebrush in large, continuous areas composed of a mosaic of open to moderate shrub densities (5 to 20%) and multiple age and height classes. An area-sensitive species is one that requires a large block of unfragmented habitat to successfully breed and survive. For Sage Sparrows, continuous areas should be greater than 320 acres (130 ha).

4) Within extensive areas of sagebrush habitat, manage for a patchwork or mosaic of native plant communities across the local landscape. This may include stands of young and old sagebrush, openings (ranging from bare ground to short vegetation to high grass density), wet meadows, seeps, healthy riparian vegetation, and other interspersed shrub and woodland habitats. Mosaics support many bird species with different needs. Young, sparse stands support Vesper Sparrows and Lark Sparrows. Older, denser stands benefit Greater Sage-Grouse, Long-billed Curlews, and Burrowing Owls. Broad-leaved shrub thickets and riparian areas provide winter habitat for Sharp-tailed Grouse. Forested streamsides provide nest sites for Swainson’s Hawks, and interspersed juniper woodlands supply nesting areas for Loggerhead Shrikes, Gray Flycatchers, Ferruginous Hawks, and Green-tailed Towhees.

5) Openings of short vegetation surrounded by sagebrush are particularly important for Sage-Grouse leks and for ground foraging by Sage Thrashers, Loggerhead Shrikes, Brewer’s Sparrows, and Sage Sparrows. Openings of short vegetation [2 to 8 inches (5 to 20 cm)] with wide visibility provide Long-billed Curlew and Burrowing Owl breeding habitat.

6) Maintain remaining biological soil crust communities by minimizing sources of soil disturbance, such as off-road vehicle travel or heavy grazing.

7) Maintain seeps, springs, wet meadows, and riparian vegetation in a healthy state for young Greater Sage-Grouse and other species that depend on the forbs and insects available in moist places.

8) Maintain ground squirrel and prairie dog colonies to provide nesting burrows for Burrowing Owls, and maintain small mammal populations as prey for many bird and mammal predators.

9) Regularly monitor birds to see how the management plan is working, and redirect efforts if necessary (with special emphasis for species that seem to be declining). Implement shrub-steppe habitat monitoring programs to establish baseline data and identify changes in habitat quality (both positive and negative) through time. Use standardized methods to monitor the habitats and sensitive species in an area, before and at several-year intervals after treatments are applied, to aid in making proper land management decisions in the future.

Sagebrush

1) Avoid practices that permanently convert sagebrush shrubland to nonnative grassland or farmland.

2) Manage existing stands of sagebrush steppe for a balance between shrub and perennial grass cover and for open to moderate shrub cover (5 to 25%) and multiple height classes.

3) Extensive, overly dense, and crowded sagebrush stands that have lost much of the native herbaceous understory and plant diversity may require selective removal of shrubs to reestablish a balance between shrub cover and perennial grass and forb cover. Only use prescribed fire in areas not threatened by cheatgrass or medusahead invasion.

4) In large disturbed areas, sagebrush and perennial grasses may need to be reseeded to shorten the recovery time and prevent dominance by nonnative grasses and forbs.

5) Use Tables 12 and 13 below to determine the sagebrush habitat components needed and nesting substrates used by sagebrush shrubland bird species of concern. These tables can help guide landowners and land managers in efforts to provide necessary habitat characteristics for sagebrush obligate and dependent species on patch, stand, and landscape scales.

Table 12. Habitat components used by 17 sagebrush shrubland bird species of concern.
					Short
	Tall,	Open,	Grass		grass,	Seeps,
Species	dense	patchy	cover		bare	wet	Dry
	sagebrush	sagebrush	for nests	Grassland	ground	habitat	woodland	Riparian

*Sagebrush*
*Obligate*
*Species*
Sage Grouse	X	X	X	X	X	X
Sage Thrasher	X	X	X		X
Sage Sparrow	X		X		X
Brewer’s Sparrow	X	X	X		X

*Shrubland*
*Species*
Black-throated Sparrow		X	X
Green-tailed Towhee	X	X	X				X
Lark Sparrow		X	X	X			X

*Shrubland and*
*Grassland*
*Species*
Swainson’s Hawk		X		X	X	X		X
Ferruginous Hawk		X		X	X