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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
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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.
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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:
- Harris's Hawk
- Scaled Quail
- Verdin
- Cactus Wren
- Rock Wren
- Pyrrhuloxia
Table 2. Chihuahuan Desert Shrub: Priority Species Habitat Factors
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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 |
|
|
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CRTH |
prefers shrubs especially mesquite, not often in creosote |
|
|
|
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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 |
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SCOR |
medium to tall yucca in grass or shrublands |
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