Hawks Aloft, Inc. New Mexico Partners in Flight

This is the most extensive grassland in the state (Dick-Peddie 1993), this habitat type comprises two distinct regions: the Eastern Plains and Great Basin grasslands.

The Eastern Plains start along the Texas border and run west to the bajadas of the Sangre de Cristo Mountains in the north, the Sandia and Manzano mountain ranges in central New Mexico and the Sacramento Mountains in the south, excluding the Pecos Valley below Roswell. Great Basin grasslands, or Mesa Shortgrass areas, are found in the northwest quadrant of the state and the Rio Grande valley. These include the Plains of San Agustin and mix with Plains grassland over a large area of northwestern and north-central New Mexico (Brown 1994).

In climax condition, these grasslands are composed almost entirely of grasses. The few shrubs and forbs constitute less than 10% of the vegetation. The transition area from grassland to grassland-scrubland ecotone is often subtle and extensive. Blue grama (Bouteloua gracilis) is the most common component of these grasslands in New Mexico. It codominates with buffalo grass (Buchloe dactyloides) in the northeast and east-central plains and with western wheatgrass (Agropyron smithii) or galleta (Hilaria jamesii) on northern mesas. On fine-textured soils in the north, indian ricegrass (Oryzopsis hymenoides), New Mexico feathergrass (Stipa neomexicana), and needle and thread (Stipa comata) may be important components/codominants. Other areas may be dominated by threeawns (Aristida spp.) or side-oats grama (Bouteloua curtipendula). Tobosa (Hilaria mutica) swales occur within this type of grassland. These are dominated by Hilaria spp. and, in some areas, alkali sacaton (Sporobolus airoides). Galleta and indian ricegrass are the primary grasses in the northwest.

Shrubs often occur where the soil is calcareous. Shrubs that may occur scattered through eastern shortgrass communities are soapweed yucca (Yucca glauca) and fringed sage (Artemisia frigida). Winterfat (Ceratoides lanata) and bigelow sage (Artemisia bigelovii) can be found in western areas. Broom snakeweed (Gutierrezia sarothrae) increases in overgrazed areas in eastern grassland as do clumps of low-growing honey mesquite (Prosopis glandulosa) and chollas (Opuntia spp.). Rabbitbrush (Chrysothamnus spp.) and sagebrush (Artemisia spp.) replace broom snakeweed in the disclimax communities caused by overgrazing in Great Basin Grasslands. Livestock grazing in the early part of the century resulted in extensive and rapid succession of these grasslands toward shrubland. Great Basin grasslands tend to be more arid than Plains Grasslands and mix with Great Basin desert shrub at lower elevations.

In the past, high temperatures and summer winds contributed to lightning-set grass fires where grasses from prior growing seasons provided ample fuel. A natural succession to climax grass-forb associations followed. As a result of grazing in most areas, less residual grass is available for fuel, and the incidence of fire is less frequent. Natural successions are now usually arrested and replaced by fire disclimax associations of shrubs.

In healthy grasslands, fire will suppress mesquite and other shrubs. Areas with little grass initially, sometimes as a result of overgrazing, lack sufficient fuel to carry a fire. Fire is often prescribed in eastern New Mexico, mostly in swales. Fire is being reintroduced into the Middle Rio Grande valley at Sevilleta National Wildlife Refuge and the Kiowa National Grasslands in eastern New Mexico (Mike Means pers. comm.).

Ford (1999) resummarizes several studies on grasses and response to fire, which have been used to promote fire suppression in shortgrass prairies. Upon reanalysis, Ford concludes that "Most of the literature ... reviewed was primarily interested in the use of fire as a tool to increase the forage value of the grassland vegetation. Perception and the value of fire in shortgrass steppe may have been colored by a desire for rapid recovery or for increases in grassland productivity to benefit domestic livestock." Ford continues, "the use of fire in shortgrass steppe need not be perceived in a negative light. Regardless of fire type, buffalograss and blue grama response to fire was predominantly neutral or positive, and it depended largely on precipitation and possibly season of fire."

Ford and McPherson (1996) state that "there is general agreement that fire is necessary (though usually not sufficient) to control the abundance of woody plants and maintain most grasslands". However, there is some disagreement about the succession of shrubs in healthy non-burned grasslands. Bahre (1991 in Ford and McPherson 1996) concluded through the use of historical accounts that "fire size and frequency have diminished greatly in desert grasslands since the 1880's".

In a summary of grassland fire studies, Ford and McPherson (1996) state that many macroarthropod herbivores increase after fire, as do soil-dwelling microarthropods. Other reports effects of fire include increased habitat heterogeneity.

"Fires ... affect [bird] population levels indirectly by altering habitat structure, abundance of competing species, and food levels (Bock and Bock 1990;Dickson 1981; Rotenberry et al. 1995 in Ford and McPherson 1995). In shrub-grass complexes, bird diversity and abundance are enhanced if shrub cover and nesting sites are interspersed with open grassy areas maintained by fire (Baldwin 1968; Kramp et al. 1983; Pulliam and Mills 1977 in Ford and McPherson 1995) ... Many bird species that inhabit grasslands have been documented to increase habitat use in shrublands or grasslands after fire." They include American Kestrel, Scaled Quail, Mourning Dove, Greater Roadrunner, Eastern Kingbird, Western Kingbird, Loggerhead Shrike, Horned Lark, Sprague’s Pipit, Lark Bunting, Savannah Sparrow, Baird’s Sparrow and Western Meadowlark. "Far fewer bird species are reported to be negatively affected by fire. These species are generally closely associated with shrubby habitat, and [are] more abundant in unburned areas (Ford and McPherson 1995)."

"Summer fires can stimulate seed yields of native grasses more than fires in winter or early spring (Biswell and Lemon 1943; Paton et al. 1988). ... In general, plant species in semi-arid grasslands are more strongly influenced by fire season and frequency than fire behavior (intensity, percent of area burned, fuel consumption)(Steuter and McPherson 1995) (Ford and McPherson 1995)". "Plant growing season and fire season, along with other biotic and abiotic environmental variables, including grazing and rainfall, are important factors in determining the response of plants to disturbance by fire. (Ford 1999)"

Shrubby habitat (usually mesquite in the east) is now extensive due to grazing that generally took place in the last century. A combination of overutilization, changes in fire frequency, and poor soils has contributed to the current abundance of shrub habitat. It should be noted that shrub encroachment dynamics in northeast New Mexico, north of the mesquite range, may differ from areas south of the Canadian Escarpment (Dick-Peddie 1993).

There is clearly a dynamic balance between the distribution and abundance of grass and shrub conditions in eastern New Mexico. Grass conditions are suitable for Grasshopper Sparrow and other grass-preferring birds. Shrub conditions are more suitable for Cassin=s Sparrow and Loggerhead Shrike.

Urban areas exist within this habitat and are considered to be a subhabitat. This section is being developed and will appear in a later version of this Bird Conservation Plan.

The vast majority of eastern plains lands are privately owned. Some areas near Clayton, comprising the Kiowa National Grasslands, are managed by the U.S. Forest Service. Three National Wildlife Refuges are in this habitat: Grulla (near Portales), Las Vegas and Maxwell. Of the privately owned lands, most are ranches rather than agricultural lands. A high proportion of agricultural lands exist around Clovis/Portales, the Tucumcari Basin to the Texas border, along the Texas border near Clayton, and the Estancia Valley.

Many portions of western grasslands are managed by the Bureau of Land Management: the majority of the Plains of San Agustin and grasslands further north, including the Bisti/De-na-zin Wilderness areas. Chaco Canyon National Monument, managed by the National Park Service includes small areas of this habitat, as does Sevilleta National Wildlife Refuge. A large area of former grassland has been converted to agriculture at the Navajo Agricultural Products area south of Farmington. Other portions are privately owned.

Physiographic Areas covered: Colorado Plateau and Pecos and Staked Plains

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

Associated Species: Scaled Quail, Mountain Plover, Mourning Dove, Common Nighthawk, Ladder-backed Woodpecker, Say=s Phoebe, Loggerhead Shrike, Bendire=s Thrasher, Vesper Sparrow, Western Meadowlark,

Associated Species: American Kestrel, Prairie Falcon, Scaled Quail, Western Kingbird, Lark Bunting, Vesper Sparrow, Say=s Phoebe, Western Meadowlark

• short- or mid-grass prairie, mid-grass grasslands, sagebrush grasslands
• late succession grasslands 4-12 in (10-31cm) high
• Nesting generally in sites with grass <3. 9in (10 cm) tall. However, grasses are taller in the immediate vicinity (within 20 ft or 6m) of nest sites. Grass within 50 ft (15m) was significantly shorter overall than random vegetation heights in Utah. (Paton and Dalton 1994)
• some taller shrubs (~ 5%) for protection and shade for young
• avoids areas with excessive bare ground (Cochran and Anderson 1987 in Paton and Dalton 1994)
• flat to Amoderate@ topography
• 5ac (2ha) needed per breeding pair; nests can be as little as 750ft (229m) apart
• abundant invertebrate prey
• sensitive to habitat fragmentation
• some grazing prior to breeding may be beneficial; in Utah, Curlews initiated nesting from mid-April to mid-May (Paton and Dalton 1994); may occure earlier in New Mexico (NMPIF)

• uses savannas, with occasional trees, shrubs, and brush patches, but also towns, agricultural areas, and landscaped areas such as golf courses
• density decreases with increased presence of grama-buffalo grass associations
• needs sufficient number of perches (trees, shrubs, fences, wires) ranging from just above ground to 32ft (10m) in height
• nests in isolated trees or shrubs, often honey mesquite: average distance of 45ft (13.8m) to next nearest shrub, 15.4 ft (4.7m) in height, and 225 yd; (172m;) in volume; shrubs had less vertical cover from 0-9.8ft (0-3m) and more from 9.8-19.7ft (3-6m) (Nolte and Fulbright 1996 in Regosin 1998)
• needs wide shrubs as nest placement can average 6.2ft (1.9m) from main stem

• relatively open grassland with scattered shrubs or trees, may use fringes of dense vegetation areas such as riparian woodland or desert washes
• large shrubs of one or more of the following species are usually present: cholla, junipers or sagebrush
• may breed in relatively open, degraded grasslands with moderate to dense shrubs
• avoids cholla in the south but uses it in the north
• nest placed in semi-dense shrubs, cacti or trees typically 2.3 - 4.9 ft (0.7 - 1.5m) above the ground but can be as high as 2ft (6.5m)

• dry grasslands above 6000 feet, also in open shrublands and occasionally open pinyon-juniper woodland
• needs sparse shrub brush for perches
• requires low percentage of grass cover and corresponding high percentage of bare ground
• less than 40% shrub canopy cover is required in sagebrush areas
• territory size averages around 5ac (2ha)
• nests on ground at base of grass tussocks or forbs; no apparent need for shrub canopy concealment
• will not recolonize a grassland until three years after burning
• frequent cowbird host

Associated Species: Long-billed Curlew, Cassin=s Sparrow, Grasshopper Sparrow, Western Meadowlark

• primarily found in shortgrass grasslands
• occasionally in sagebrush shrublands, weedy agricultural areas, and other shrubby grassland areas
• on the Pawnee Grasslands in CO, preferred habitat had high (>70%) grass cover and only 10-16% bare ground
• preferred grass was 5.2in (13.4cm) tall and relatively dense (32.2 plants/0.1 m5)
• 5-15% of vegetative canopy cover was taller than average surrounding areas
• less than 15% bare ground considered optimal with corresponding 60-90% grass cover, will not use if >60% bare ground (Finch et al. 1987 in Yanishevsky and Petring-Rupp 1997)
• territory size is only 1.2-2ac (0.5-.75ha) however, Finch et al. (1987) consider patch size to be much larger due to the species social nature
• nests on ground and needs 10-30% cover (shrubs and midgrasses) for nest shading and protection from solar radiation, which may be critical (Pleszcynska and Hansell 1980 in Yanishevsky and Petring-Rupp 1997)
• in NM, may breed only in higher rainfall years (NM PIF)
• main diet is grasshoppers
• breeding beginsin late May. 21 days from egg-laying to fledging (Baicich and Harrison 1997)

• in Region 2, T = 0.6%, p = 0.31, N = 173, RA = 17.05; in the U.S., T = -1.6%, p = 0.00, N = 783, RA = 16.29 (Sauer et al. 1997)
• maintain current known nesting populations near Fort Sumner, Clovis and Maxwell NWR
• maintain habitat: early successional weedy fields, mid-grass prairie and shrubby shortgrass
• reduce grazing in mid to shortgrass areas
• delay haying until after breeding season (beginning of August)
• maintain early successional, weedy fields and perches rising above average height of vegetation

Associated Species: Prairie Falcon, Long-billed Curlew, Loggerhead Shrike, Cassin=s Sparrow, Vesper Sparrow, Grasshopper Sparrow

Over time and a large landscape managers should address the following issues:

Even in healthy grasslands, 100% grass canopy coverage does not occur. Managers should try to achieve a 50-65% grass canopy cover on an overall basis. Bare ground should be kept to a minimum. Canopy cover is important for grass-utilizing species and a lack of adequate cover will cause species to abandon an area. Bare ground is important for such birds as Horned Lark, which should not be the dominant bird, although it is an important component of most grassland bird assemblages. Avoid seeding of exotic grasses and cultivation of habitat where possible (Janes 1985)

Managers should work toward maintenance of grass heights averaging 4-8 in (10-20cm) or more. Depending on soil conditions, grazing regimes, and other factors, this is not possible in every area. However, an average can be maintained over an entire landscape. In areas that are slightly more mesic, i.e. drainages in grassland areas, swales, etc., grasses should be maintained at an average of 1ft (30cm).

Fire should be prescribed during early spring or late summer, as a tool to reduce shrub and litter cover. It appears to be beneficial to many grassland species (Ford and McPherson 1996), excepting those needing denser, taller grasses, such as Dickcissel.

ATiming of prescribed burns should be a major consideration to resource managers concerned with declining [bird] populations that breed in the southern Great Plains. ... Birds in general, are most vulnerable to fire during nesting and fledging periods. Fires can be devastating to ground-nesting birds because they destroy existing nests, remove protective cover and eliminate insect food resources (Daubenmire 1968 in Ford and McPherson 1995) that may be associated with ground litter and vegetation (Ford and McPherson 1995).@

True grasslands contain few shrubs. Healthy grasslands generally allow minimal shrub encroachment. Encroachment is an indication that a grassland is not maintaining its integrity. Some shrub cover is a part of grasslands, but generally at considerably lower densities than found in most grasslands today. Managers should work towards maintaining no more than 10-20% shrubs in the overall landscape. While shrub habitat is used by many birds, the xerification of grasslands over the last century and a half has caused an increase in the abundance of birds utilizing shrubs. This has occurred at the expense of those species which require pure or primarily grass habitats.

The use of rest-rotation methods or the Savory method, appears to be a more effective method for maintaining grassland integrity, and the health of the herd, than many historic methods of grazing, particularly those that allow cattle to graze one area throughout the year. "In short-grass types, grazing results in a dramatic increase in percent of bare ground and reduces food, shade, and nest site availability (Finch et al. 1987 in Yanishevsky and Petring-Rupp 1997)."

Prairie dog control:

Prairie dogs currently inhabit a small percentage of their historic range. Burrowing Owls largely depend on burrows created by prairie dogs. They can also be an important food source for raptors such as Golden Eagles, Ferruginous Hawks, and in New Mexico, Bald Eagles. Managers should refrain from controlling prairie dog populations whenever possible.

Additional species for which monitoring is recommended:

• Scaled Quail
• Burrowing Owl
• Common Nighthawk
• Cassin's Kingbird
• Vesper Sparrow
• Western Meadowlark