Hawks Aloft, Inc.
New Mexico
Partners in Flight

Chihuahuan Desert Shrub
Description, importance and conservation status:

This shrubland occurs solely within the Chihuahuan Desert Physiographic Area, which roughly covers the southern third of the state. This habitat extends across the southern border of the state east through southern Lea County. In the Pecos Valley, it extends north to Roswell; in the Tularosa Basin north to White Sands Missile Range and to San Acacia in the Middle Rio Grande Valley. The Sierra-Socorro county line, west to the Gila River on the border with Arizona defines the northwestern area. It spans elevations from 2800 to roughly 5000 feet.

Much of this habitat consists of creosotebush (Larrea tridentata) and tarbush (Flourensia cernua). In some zones, whitethorn acacia (Acacia constricta, A. neovernicosa) codominates. Mesquite (Prosopis glandulosa) dominates in other areas. These zones may be quite organized and consistent within the overall desert habitat, depending on elevation and soil composition. In general, areas dominated by whitethorn acacia are characterized by a high diversity of shrubs, while grasslands that have converted to mesquite contain the lowest diversity of plants.

Other Chihuahuan Desert shrubs such as cacti (various spp.), squawbush (Condalia spathulata), allthorn (Koeberlinia spinosa), fourwing saltbush (Atriplex canescens), lechuguilla (Agave lechuguilla), and ocotillo (Fouquieria splendens) are found scattered or in local patches (Dick-Peddie 1993). On rocky hillsides, little-leaf sumac (Rhus microphylla) may be found.

Chihuahuan Desert Shrub occurs in basins, outwash plains, low hills, and bajadas (Brown 1982). This habitat may be relatively secure and expanding as a result of desertification. Overgrazing in grassland areas may allow invasion of shrubland species. Where shrubs and cacti dominate, grasses are sparse or patchy. It is difficult for fire to spread, especially in creosote-dominated areas.

Creosotebush is used rarely by Chihuahuan Desert birds for nesting (Anderson and Anderson 1946). The presence of other shrubs such as cacti, yuccas (Yucca spp.), mesquite, javelina bush (Condalia warnockii), white-thorn acacia and Ephedra spp., however, will increase usage by birds in this habitat (Naranjo and Raitt 1993, Kozma and Mathews 1997). The Black-throated Sparrow, in particular, nests where grasses and other small shrubs are found near the base of creosote.

Arroyos and Dry Washes

Arroyos and dry washes are established in areas that receive periodic, concentrated pulses of water due to heavy rainfall events. These habitats are dry between rains.

Chihuahuan Desert Shrub is characterized primarily by desert willow (Chilopsis linearis) and honey mesquite. Occasionally additional shrubs codominate, especially where arroyo beds widen. These include burrobrush (Hymenoclea monogyra), Apache plume (Fallugia paradoxa), littleleaf sumac, and brickellia (Brickellia laciniata). Other shrubs may include torrey yucca (Yucca torreyi), javelina bush, catclaw acacia (Acacia gregii), iodinebush (Allenrolfea occidentalis), arrowweed (Pluchea sericea), and seepwillow (Baccharis glutinosa).

In the Chihuahuan Desert of Fort Bliss in south-central New Mexico, Kozma and Mathews (1997) found that the nesting density of breeding birds in arroyos was greater than twice the density of nests on surrounding uplands. Of breeding neotropical migrants, 33% nested more frequently in arroyos. However, of the non-migratory birds, 62% nested equally or more frequently in arroyos. Peak nest initiation for all species occurred between 18 and 24 May in each of the three years of the study.

Kozma and Mathews found that littleleaf sumac, mesquite, desert willow, and javelina bush were preferred for nesting in this habitat, even though these shrubs were less abundant overall, relative to other species. They concluded that desert birds may be strongly influenced, when selecting nest sites, by shrubs that have spines, are denser, have more foliage, and are larger with stiff branches. This may be because they offer greater protection, provide shade, and protect from heat generated by the soil.

Another structural component of arroyos are the walls comprising the edges. These walls can provide important nesting areas in the form of cavities for such species as Rock Wren, American Kestrel, Burrowing Owls and even Barn Owls.

Desert Shrub habitat occurs within a matrix of government-managed and privately held lands. Most of the lands east of the Sacramento Mountains are privately owned. Land east of the Guadalupe Mountains is managed by the BLM or the Department of Energy. Patches of this habitat may be leased to oil and gas companies. Habitat in the Tularosa Basin is primarily located on military lands. In the Rio Grande Valley, most of this habitat north of Elephant Butte Lake is BLM managed, while lands in the Hatch, Mesilla, and Las Uvas Valleys, as well as the Deming-Columbus corridor are primarily private. Agricultural lands are intermixed with this habitat in these areas. Much of the land west of Deming and Columbus is BLM managed.

Physiographic Areas covered: Chihuahuan Desert

Associated priority species from Appendices B and C:

Table 1. Chihuahuan Desert Shrub Priority Species

Highest Priority	Priority	High Responsibility
Gambel's Quail Costa's Hummingbird Northern Beardless-Tyrannulet Black-tailed Gnatcatcher Bendire's Thrasher Crissal Thrasher Varied Bunting Scott's Oriole	Loggerhead Shrike Gray Vireo Verdin Cassin's Sparrow	Scaled Quail Greater Roadrunner Common Poorwill Lesser Nighthawk Black-chinned Hummingbird Ladder-backed Woodpecker Ash-throated Flycatcher Cactus Wren Rock Wren Canyon Towhee Black-throated Sparrow Pyrrhuloxia
Additional Representative Species: Harris's Hawk

Bird Habitat Requirements, Population and/or Habitat Objectives:
(in taxonomic order)

Harris's Hawk _{(Bednarz 1995)}

Associated Species: Great Horned Owl, Greater Roadrunner, Mourning Dove, Ladder-backed Woodpecker, Ash-throated Flycatcher, Chihuahuan Raven, Verdin, Cactus Wren, Northern Mockingbird, Crissal Thrasher, Blue Grosbeak

semi-open, desert shrub with scattered large trees or shrubs, providing perches and branches for nesting

primarily in shrub areas with mesquite bushes greater than 12ft (4m) in height

uses areas with greater density of large mesquite, more sagebrush and less litter and grass

there are questions about the importance of open water for these birds; they travel up to 6.2mi (10km) to cattle tanks

interbrood period (for those attempting a second brood) negatively correlated with cottontail availability. They are more likely to breed and double clutch in the same year. May not nest at all during periods of low prey availability.

mesquite used for nesting over 50% of the time; 7 other species also used, including hackberry and Spanish dagger

average nest height above ground in 8.2ft (2.7m)

known to hunt in pairs or family groups

Distribution: Found from Carlsbad east and south to the Texas border, rarely north to Roswell, rarely in the Rio Grande Valley north to Truth or Consequences, and west to the Arizona border, south of I-10.

Population and/or Habitat Objectives:

in Region 2, T = -5.0%, p = 0.02, N = 32, RA=0.95 (Sauer et al. 1997)
reduce loss of rangeland habitat due to oil and gas development
reduce human activity near nest sites, especially during heat of the day
establish raptor-management areas where human disturbance is greatly limited
control hunting and off-road vehicle use during prime nesting seasons (Feb - Oct)
restore disturbed rangeland

Gambel's Quail _{(Brown et al. 1998)}

Associated Species: Lesser Nighthawk, Ash-throated Flycatcher, Verdin, Cactus Wren, Northern Mockingbird, Curve-billed Thrasher, Pyrrhuloxia, Black-throated Sparrow, House Finch

brushy and thorny vegetation in the Chihuahuan Desert
also river valleys, especially those close to agricultural lands
key plants include mesquite, Acacia sp., prickly pear (Opuntia sp.), other chollas, several Lycium spp., burroweed and snakeweed
drainages and arroyos are very important in extremities of range
need dense shrub perches for nighttime roosting
generally nests on the ground; may occasionally use shrubs
numbers often highly dependent upon winter rainfall

Distribution: Occurs in the Chihuahuan Desert from the Guadalupe Mountains west, in riparian areas of the Rio Grande Valley, north to the Espanola area. Also found in the San Juan River watershed.

Population and/or Habitat Objectives:

in NM, T = 0.4%, p = 0.86, N = 19, RA=4.78 (Sauer et al. 1997)
restore 2 populations to the Rio Grande Valley north of Cochiti Lake
maintain appropriate habitat in known areas of occurrence
limiting grazing in areas where populations need to rebound may be helpful (Brown et al. 1998)
may require lower bag limits at edges of towns and cities
use of spring call counts as population indicator for setting fall bag limits

Costa's Hummingbird _{(Baltosser and Scott 1996)}

Associated Species: Common Poorwill, Gray Vireo, Rufous-crowned Sparrow

uses lowland desert shrub usually associated with canyon walls and rocky slopes
often chooses more xeric areas even when adjacent to riparian areas in Arizona. This may not be true in New Mexico
nests in shrubs generally 3-7ft (1-2m) above the ground in either living or dead material
early breeder, generally starting in March and leaving breeding areas by June (NM PIF)
may breed only in years with a wet spring (S. Williams pers.comm.)
appears to have limited adaptability to non-native vegetation and hummingbird feeders

Distribution: Occurs most regularly in Guadalupe Canyon and side canyons along the lower Gila River from Cliff south; may be irregular in other small desert ranges, especially in the San Andres mountains in Dona Ana county.

Population and/or Habitat Objectives:

in the West, T = 4.0%, p = 0.31, N = 53, RA=0.57 (Sauer et al. 1997)
maintain current known breeding birds, especially in Guadalupe Canyon
encourage maintenance of native vegetation, especially tubular flowering forbs
discourage use of fire in shrub areas with high amounts of non-native grasses
encourage fencing to keep cattle out of Costa’s habitat

____________________ Guadalupe Canyon only:

Northern Beardless-Tyrannulet_{(Williams 1999)}

Associated Species: Black-chinned Hummingbird, Ladder-backed Woodpecker, Bell's Vireo, Verdin, Blue Grosbeak, Varied Bunting,

dense thickets of mesquite, acacia, hackberry, and other thorny species
found either at edges of groves or the understory of larger trees
territories are near pools of water
nests from 4.5-50 ft (1.4 - 15m) above ground often in mistletoe clumps
maximum spacing in Guadalupe Canyon is 5 territories in a 2mi (3.2km) transect

Distribution: Guadalupe Canyon

Population and/or Habitat Objectives:

no BBS data available
maintain the current breeding populations
maintain habitat in Guadalupe Canyon
cool-season only grazing, or cattle exclusion, in this canyon
Prescribed burns in this particular canyon will not result in a net benefit. Riparian woodlands are not well-adapted to fire. Any fire in this area will likely also burn through much of the shrub area here as well.

____________________

Loggerhead Shrike _{(Yosef 1996)}

Associated Species: Scaled Quail, Greater Roadrunner, Mourning Dove, Common Nighthawk, Ash-throated Flycatcher, Western Kingbird, Northern Mockingbird, Cassin's Sparrow, Black-throated Sparrow

shrub component within a grassland complex critical
shrubs with spines, or barbed wire fenceline, critical for impaling vertebrates before eating
nests often found in shrubs, usually thorny or dense shrubs
nest height above ground depends on shrub height
diet includes birds, insects, and small mammals

From anecdotal information, this species does not appear to be having much trouble in the state. However, current BBS trends in New Mexico are showing a decrease. This species is of intense interest in Canada as well as in many areas of the United States. New Mexico currently has a large breeding population and, therefore, may be extremely important to this species.

Distribution: Found statewide.

Population and/or Habitat Objectives:

in NM, T = -5.9%, p = 0.001, N = 49, RA=3.72 (Sauer et al. 1997)
stabilize BBS trends in the state
maintain or enhance grassland areas with large shrub component

Verdin _{(DeGraaf et al.1991)}

Associated Species: Gambel's Quail, Greater Roadrunner, Ladder-backed Woodpecker, Ash-throated Flycatcher, Rock Wren, Northern Mockingbird, Pyrrhuloxia, Blue Grosbeak

nests in shrubby arroyos but also on slopes and in wider valleys with acacias, mesquite, hackberry, hawthorn, cholla and other shrubs
nests anchored to twigs in a ball-shaped mass up to 8in (21cm) in diameter
diet includes insects, spiders and fruits

Distribution: Closely tied to the Chihuahuan Desert. Occasionally found further north in the Rio Grande Valley to Belen.

Population and/or Habitat Objectives:

in Region 2, T = -4.2%, p = 0.02, N = 102, RA=4.56 (Sauer et al. 1997)
stabilize current negative population based upon BBS routes
maintain areas with diverse shrubs, especially areas with acacias

Black-tailed Gnatcatcher _{(DeGraaf et al. 1991)}

Associated Species: Mourning Dove, Verdin, Cactus Wren, Northern Mockingbird, Bendire's Thrasher, Pyrrhuloxia, Canyon Towhee, House Finch

low elevation washes in southwestern New Mexico
desert brush and shrub areas, especially with allthorn or mesquite-dominated areas
an open-cup nester primarily in thorny shrubs in south-central New Mexico (Kozma and Mathews 1997)
cowbird parasitism can be as high as 50% (Kozma and Mathews 1997)
negatively correlated with creosotebush

Distribution: Found only in Chihuahuan Desert, from the Sacramento Mountains west, south, and north to Bosque del Apache NWR, occasionally east of the Sacramentos.

Population and/or Habitat Objectives:

in Region 2, T = -1.6%, p = 0.41, N = 39, RA=3.56 (Sauer et al. 1997)
stabilize trend data from BBS and/or develop additional BBS routes that appropriately monitor this species in the Chihuahuan Desert
maintain buffer zone of 330ft (100m) on either side of arroyo banks, especially within urban or suburban areas
reduce Brown-headed Cowbird parasitism when possible

Bendire's Thrasher _{(England and Laudenslayer 1993)}

Associated Species: Mourning Dove, Loggerhead Shrike, Black-tailed Gnatcatcher, Cactus Wren, Bewick's Wren, Northern Mockingbird, Black-throated Sparrow

relatively open grassland, shrubland or juniper savanna with scattered shrubs or trees, may use fringes of dense vegetation areas such as riparian woodland or desert washes
large individuals of one or more of the following are usually present: cholla, Spanish bayonet, mesquite, acacia, desert-thorn or agave
may breed in degraded desert-grassland and desert shrublands supporting various xeriphytic, microphyllous shrubs with little grass
avoids cholla in the south but uses it in the north
nest placed in semi-dense shrubs, cacti or trees typically 2.5-5.0ft (0.7 - 1.5m) above the ground but can be as high as 21.3ft (6.5m)

Distribution: Found in the Chihuahuan Desert from Deming west to the Arizona border and north to the Colorado line. Also found in juniper savanna areas around Corona, north to the Caja del Rio west of Santa Fe. Especially prevalent in degraded grasslands of northwestern New Mexico.

Population and/or Habitat Objectives:

in NM, T = -7.1%, p = 0.19, N = 14, RA=0.80 (Sauer et al. 1997)
stabilize then reverse current BBS trend in New Mexico
maintain continued presence at known nesting areas
maintain edge habitat with a slight grass component in shrubland
maintain large shrubs from 3-6ft (0.9-1.8m) in grassier habitats

Crissal Thrasher _{(NM PIF)}

Associated Species: Greater Roadrunner, Western Kingbird, Loggerhead Shrike, Verdin, Northern Mockingbird, Pyrrhuloxia, Canyon Towhee, House Finch

prefers shrubby habitat, especially mesquite
much less common in creosote-dominated habitats
occurs in juniper near desert washes
a very early nester; may initiate nests as early as February

Distribution: Found regularly as far north as the southern Sandia Mtns. in the Middle Rio Grande Valley, in the east north to Roswell and in the west north to Silver City and Pleasanton.

Population and/or Habitat Objectives:

in Region 2, T = 20.3%, p = 0.17, N = 26, RA=0.29 [recent trends from '80-'96 in AZ are T = -5.4%, p = 0.10, N = 14, RA=0.29 (Sauer et al. 1997)]
maintain at least stable trends in New Mexico using BBS as an indicator

Varied Bunting _{(Groschupf and Thompson 1998)}

Associated Species: Gambel's Quail, Broad-billed Hummingbird, Black-chinned Hummingbird, Ladder-backed Woodpecker, Bewick's Wren, Black-chinned Sparrow

thick, arid, thorny brush in canyons and along washes, at the edge of more mesic riparian areas
often in areas surrounded by densely vegetated hillsides with abundant annual grasses
does not tolerate residential or non-native habitat
in New Mexico, found in areas below 5000ft (Williams 1999)
nests near outer edge of thorny shrubs; exposed on one side shaded by overhanging or adjacent vegetation; nests are about 2-5 ft (0.6-1.5m) above ground (Lockwood 1995)
often nests on slopes, or on the edges of a wash. In dense vegetation, nesting often occurs following growth of plains love-grass, forget-me-not and Muhlenbergia microsperma, which are used for nest construction

Distribution: Occurs regularly in some canyons in Carlsbad National Park in the southeast, in Dona Ana County in the San Andres Mtns in south-central New Mexico, and at Guadalupe Canyon in the southwest (Williams 1999).

Population and/or Habitat Objectives:

no BBS data available
maintain known populations in Guadalupe Canyon (2-4 pair), the San Andres Mtns. and at Carlsbad Caverns National Park
maintain dense arroyo riparian vegetation, especially in areas closely surrounded by canyon walls or hillsides
maintain tall, dense grasses on hillsides, in canyons or draws where dense riparian vegetation is present
maintain structure of habitat in known areas of occurrence

Scott's Oriole _{(NM PIF)}

Associated Species: Scaled Quail, Mourning Dove, Western Kingbird, Cactus Wren, Northern Mockingbird

in Chihuahuan Desert, most often found in areas with yuccas; yuccas should be at least 3.3ft (1m) in height
found most frequently in torrey yucca by Kozma and Mathews (1997)

Distribution: From southern New Mexico as north as the northeastern corner of San Miguel county in the east, north to Santa Fe in central New Mexico and north to Mt. Taylor in the west.

Population and/or Habitat Objectives:

in NM, T = 1.2, p = 0.57, N = 27, RA=1.17 (Sauer et al. 1997)

maintain current populations in yucca shrubland based upon BBS data

Overall Habitat Strategies:

Vegetative cover - Reduce or eliminate non-native grasses in this habitat. Maintain larger, denser, spiny, shrubs with dense foliage.

Fire - Discourage fires, especially in areas with non-native grasses. Maintain low fire frequency in yucca grasslands.

Arroyo maintenance - Maintain the integrity of arroyos. Maintain water sources outside of arroyos. Reduce grazing in arroyos, and to the extent possible, graze in arroyos only during the non-breeding season. Maintain buffer zones on either side of arroyos in developed areas.

Research and monitoring needs:

1. Determine limiting factors for Costa's Hummingbird in New Mexico. Revisit historic known nest sites and survey for additional sites based on known habitat.

2. Establish and run additional BBS routes designed specifically for monitoring species such as Black-tailed Gnatcatcher, Verdin, Pyrrhuloxia and other desert shrub species.

3. Survey and determine population estimates for Black-tailed Gnatcatcher.

4. Determine nesting success required to sustain populations of Varied Bunting. Survey for additional populations based on known habitat.

5. Study the effects of fire on vegetation and bird populations in this habitat.

Additional species for which monitoring is recommended:

Table 2. Chihuahuan Desert Shrub: Priority Species Habitat Factors

Species	Vegetation Composition/ Structure	Abiotic Factors	Landscape Factors	Special Factors
HRSH	Desert shrublands; tall shrubs (>=12 ft) dominated by mesquite; only moderate grass cover or litter needed			often hunts in pairs or larger family groups
GAQU	highly shrubby desert scrub and river valleys		tends to avoid areas with fewer shrubs and Pinyon-Juniper	numbers fluctuate wildly with amount of winter rainfall
COHU	shrubby habitat; nests in shrubs averaging 3-7ft.	rocky slopes and canyon walls		often found in more xeric areas even when riparian is available
NBTY	dense thickets of mesquite, acacia, hackberry, and other thorny species	territories are near pools of water	found either at edges of groves or the understory of larger trees	nests from 4.5-50 ft above ground often in mistletoe clumps
VERD	mesquite, hackberry, acacia or other thorny shrubs		sometimes on slopes or flood plains
BTGN	desert scrub, especially mesquite and creosote	associated with denser dry wash areas
BETH	open shrubland with spanish bayonet, mesquite, desert-thorn often with degraded grass
CRTH	prefers shrubs especially mesquite, not often in creosote
VABU	dense, mesic riparian edges or desert thorn scrub; often nests following growth of forget-me-not, plains love-grass and Muhlenbergia microsperma	nests on slopes or edges of wash; surrounding areas are dense, grassy hillsides	nests below 5000 ft. uses arroyos
SCOR	medium to tall yucca in grass or shrublands