Birds of the Greater Otero Mesa Area, New Mexico
By Lawrence A. Sager, Jr.
The Greater Otero Mesa Area
Huge uninterrupted tracts of grasslands characterize the Otero Mesa of south-central New Mexico . The Otero Mesa grasslands have until now, largely escaped degradation by desert scrub plants that has plagued most other regions of Chihuahuan Desert grasslands in the United States and Mexico (Whitford, 2002). These grasslands are an integral part of a continuum of grasslands and grassland types that reaches from Mexico northward through the plains and prairies of the U.S. and into the prairie provinces of Canada . Together these grasslands represent the most endangered ecosystem in North America . Much of the remainder of the Otero Mesa area is, however, typified by a mix of desert scrub and grasses that presents a mosaic of habitats available to the rich avifauna of the region. The grasslands of the Otero Mesa area are an integral part of the North American migratory corridor as well as an important breeding area for several sensitive species.
The Otero Mesa area grasslands provide the habitat and other resource requirements of a large and diverse number of migrating, breeding and/or wintering bird species. The Checklist of Birds, Fort Bliss, Texas lists over 300species of birds (over one million acres administered by Fort Bliss in New Mexico are on the Otero Mesa and adjacent Tularosa Valley). Several of these species are themselves threatened by the disturbance and fragmentation of the fragile grassland ecosystem. This has led to the listing of many bird species present at least part of the year as species of conservation concern reflecting various levels of perceived threats and of a species particular vulnerability. At least three species occurring regularly in the Greater Otero Mesa area are, or have until recently been listed as endangered under the Endangered Species Act (ESA); Bald Eagle (Haliaeetus leucocephalus) , Aplomado Falcon (Falco femoralis septentrionalis) , and Peregrine Falcon (Falco peregrinus) .
Of these, Aplomado Falcon (Endangered at federal, state levels) may be the most significant; having successfully reared three young in southern New Mexico during the summer of 2002 (North American Birds, 2003). The successful fledging was an historic event, marking the first recorded nesting of the birds in the United States in a half-century; the last nest in the U.S. was located near Deming, NM in 1952 (Meyer, 1997). The birds have been reported with increasing frequency on the Otero mesa during the last decade and the possibility of their nesting there in the future cannot be discounted.
Bald Eagles (Threatened at federal, state levels) occupy winter roosts in the Sacramento Mountains from which they make frequent forays onto the grasslands of the Otero Mesa (Meyer, pers. comm.).
Peregrine Falcons (delisted federally; remains Threatened in New Mexico ) are seen mainly in migration with an occasional wintering individual. The birds are also reported sporadically at other times of the year.
From 40 to more than 80 bird species are regularly recorded coincidental to specific surveys in the Otero Mesa area depending on the season (Meyer, 1997, 1999, pers. obs.). Webster, in 1957 found 61 “with a few subsequent additions” species nesting on the Chihuahuan desert grasslands (1974). At that time he noted the decline of several species presumably due to habitat alteration and disturbance of native vegetation (Webster, 1974).
The North American Bird Conservation Initiative (NABCI) has recognized the U.S. portion of Chihuahuan Desert as a single Bird Conservation Region (BCR), within which 31 species are currently listed as Birds of Conservation Concern by the federal government (USFWS, 2002). Among those, about half (15) are known to occur in the Greater Otero Mesa Area (Meyer, 1997,1999)(Table 1). Most are considered to be endemic obligates of the grasslands. The yearly variation in occurrence and density of some grassland birds may be attributed to regional differences of range conditions due to local patterns of land use and weather within the entire ecosystem that forces the animals to seek out an area that best meets their habitat and trophic requirements. Habitat disturbance and fragmentation are believed to be a factor in the decline of virtually all listed grassland bird species, some of which require relatively large tracts of intact habitat free of human activity.
One such species is the Mountain Plover (Charadrius montanus) , a characteristic bird of the prairies that has been proposed as Threatened (USFWS, 2002) due to noted declines in populations throughout their range. Mountain Plovers have long been associated with the Greater Otero Mesa as a migrant as well as a breeding species. Ligon (in Bailey, 1928) listed the grasslands south of the Sacramento Mountains as one of the birds few important nesting areas within the state. In recent decades they have been reported only sporadically; two birds were seen as recently as 18 Mar2003 (R. Meyer, pers. comm.). At least one wintering flock of over 100 plovers was seen immediately south of Otero County , in the vicinity of Dell City , Texas by several observers during 2002 (R. Tafanelli, pers. comm.). Those sightings suggest probable use of the Otero grasslands by the birds during the course of their winter foraging. Mountain Plovers are one of several grassland species that are often associated with Black-tailed prairie dog (Cynomys ludovicianus) colonies.
The Upland Sandpiper (Bartramia longicauda) is, as its name suggests, a grassland species that appears on several watchlists of declining birds. On the Otero Mesa the species has been noted as a regular migrant of late summer (R. Meyer, pers. comm.). Interestingly, Upland Sandpipers are not among the species usually associated with the Otero County grasslands and their noted regular occurrence may be the result of rigorous recent surveys in the region.
The Long-billed Curlew (Numenius americanus) is another species of conservation concern that can be found on the Otero Mesa grasslands in great numbers during migration (R. Meyer, pers. comm.). The birds may summer locally but are not known to breed there, while small numbers may remain in winter (Hubbard, 1978).
Northern Harriers (Circus cyaneus) appear on the federal Species of Concern list (2002) due to documented population declines. In the Greater Otero Mesa area these raptors of open country may be found in varying seasonal abundance with most birds present during migration and in winter and casually in summer.
Swainson’s Hawks (Buteo swainsoni) are long distance migrants that winter in South America , returning to breed on North American grasslands. The hawks are rather common breeders on parts of the Otero Mesa (pers. obs.) and, while lacking protection other than that provided by The Migratory Bird Treaty Act, they are listed by the state as a species of concern in Otero County .
Ferruginous Hawks (Buteo regalis) , another Species of Concern, are usually found in the vicinity of prairie dog towns or other concentrations of ground-dwelling rodents that serve as a prey base for the large Buteos. Several may occur yearly, primarily on the grasslands of the northern Otero Mesa, from fall through the following spring (Meyer 1997). These large, elegant hawks are considered endangered in some western states and “vulnerable” in Canada . The U.S. Bureau of Land Management (BLM) has long considered the Ferruginous Hawk a “Sensitive Species” (Bechard and Schmutz, 1995).
The fortunes of Burrowing Owls (Athene cunicularia) on Otero Mesa, like all populations of the birds statewide, follow closely those of prairie dogs (Cynomys sp.) whose excavations provide most of the birds nesting habitat in New Mexico (pers. obs.). One survey found Burrowing Owls at 68.8% of Black-tailed prairie dog towns on the Fort Bliss area of the Otero Mesa (Meyer, 1997). This is comparable to numbers observed in other grasslands of eastern New Mexico (pers. obs.). The species is listed as endangered, threatened, or a species of concern by the federal government as well as several states including New Mexico .
Loggerhead Shrikes (Lanius ludovicianus) are predatory songbirds of open country. This species is usually seen in grassland areas with scattered shrubs or small trees. The shrikes are year-round residents of the Otero Mesa where their numbers may fluctuate seasonally and annually. Declines in Loggerhead Shrike populations throughout their range has led to inclusion on federal and state species of concern lists.
Several smaller, less conspicuous species of passerines are also known to utilize the Otero Mesa grasslands. Like the birds profiled above, the occurrence of these species on the Otero Mesa may depend on conditions elsewhere within their normal range as well as local conditions, usually related to disturbance and/or precipitation.
While not restricted to southern New Mexico , the Crissal Thrasher (Toxostoma crissale) is, nonetheless, in the heart of its U.S. breeding range in Otero County . This species is not a grassland bird, per se, preferring instead stands of shrubs, often on otherwise bare and rocky ground. The birds are considered a Species of Concern on a federal level (USFWS, 2002).
Sprague’s Pipits (Anthus spragueii) on the other hand, are strict grassland obligates. Usually solitary and somewhat secretive, these birds are detected regularly on the Otero Mesa during fall migration and are often numerous at that time. Some individuals remain throughout the winter (R. Meyer, pers. comm.). This federal, state and Otero County Species of Concern is rarely reported in the remainder of New Mexico .
Six species of sparrows and sparrow-like birds that regularly occur as migrants or breeders on the Otero Mesa grasslands are currently listed as Species of Concern (USFWS, 2002). Other sparrow species such as Savannah , Vesper, and the Spizella group may be abundant in migration, with some individuals remaining over the winter. Some Ammodramus sparrows, notably Grasshopper and Baird’s (Ammodramus bairdii ) are abundant in fall migration following summers with sufficient rains and at such times some individuals may remain throughout the winter (R. Meyer, per. comm.).
Baird’s Sparrows are, with the exception of the conditions noted above, seldom reported in other parts of New Mexico even during spring and fall migrations (Hubbard, 1978). The birds, which nest in the prairie regions of northern states and Canada , are nowhere common and are currently listed as a Species of Concern at both federal and state levels.
Cassin’s Sparrow (Aimophila cassinii) is another species of the desert shrub grasslands whose numbers and occurrence is dependent on breeding season rains. The birds may be quite numerous during years of sufficient rainfall and are present but uncommon during winters (R. Meyer, pers. comm.).
Another wintering sparrow of the Otero Mesa region is the Sage Sparrow (Amphispiza belli) which is listed at the federal level (USFWS, 2002).
The sparrow-like Lark Bunting (Calamospiza melanocorys) gathers in large flocks during migration and, at such times is often abundant on the grasslands of the Greater Otero Mesa.
Both Chestnut-collared (Calcarius ornata) and McCown’s Longspurs (C.mccownii ) occur in winter on the Otero Mesa. Chestnut-collared are usually the more abundant of the two species, often seen in large flocks. During the winter of 2002-2003 however, large numbers of McCown’s (in the hundreds) were present on the Otero Mesa (R. Meyer, pers. comm.). Both species are currently listed as federal Species of Concern.
Table 1: Birds of Conservation Concern in BCR 35 (Chihuahuan Desert-U.S. Portion only) 2002 List.
Common names in Bold =birds of the Greater Otero Mesa Region. *= Proposed Threatened.
Common Black –Hawk
Peregrine Falcon (delisted U.S. , Threatened N.M. )
Snowy Plover
Mountain Plover *
Yellow-billed Cuckoo (ESA Candidate)
Flammulated Owl
Elf Owl
Lucifer Hummingbird
Bell ’s Vireo
Gray Vireo
Bendire’s Thrasher
Sprague’s Pipit
Colima Warbler
Grace’s Warbler
Red-faced Warbler
Black-chinned Sparrow
Lark Bunting
Baird’s Sparrow
McCown’s Longspur
Varied Bunting
Painted Bunting
Hooded Oriole
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Hubbard, J.P. 1978. Revised Check-list of The Birds of New Mexico. New Mexico Ornithological Society Publication No. 6. Albuquerque .
Meyer, R. 1997. 1996-1997 Survey of Endangered Species and Species of Concern at Fort Bliss . Las Cruces .
Meyer, R. 1999. An Aplomado Falcon Survey in Southern Otero County , New Mexico . La Tierra Environmental Consulting. Las Cruces .
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Webster, J.D. 1974. The Avifauna of the Southern Part of the Chihuahuan Desert . U.S. Dept. of the Interior, National Park Service . In Transactions and Proceedings Series. No. 3. Alpine, TX.
Whitford, W.G. 2003. Ecological Characteristics of Otero Mesa and Impacts of Gas Development.