Cactus Ferruginous Pygmy-owl
Cactus Ferruginous Pygmy-owl
Glaucidium brasilianum cactorum
|Listed||March 10, 1997|
|Description||Small, yellow-eyed owl with out ear tufts and usually reddish-brown overall.|
|Habitat||Subtropical, scrub, and woodland communities.|
|Food||Birds, lizards, insects, small mammals, and amphibians.|
|Reproduction||Three to six eggs, which incubate for 28 days.|
|Threats||Urban and agricultural encroachment; woodcutting; water diversion and impoundment; channelization; livestock overgrazing; groundwater pumping; hydrologic changes resulting from various land-use practices.|
The cactus ferruginous pygmy-owl, Glaucidium brasilianum cactorum, is a small bird approximately 6.75 in (17 cm) long. Male ferruginous pygmy-owls average 2.2 oz (62 g), while female owls average 2.6 oz (74 g). This yellow-eyed owl without ear tufts is usually reddish-brown overall with a cream-colored belly streaked with reddish-brown, although some individuals are more grayish than reddish-brown. The crown is lightly streaked, and paired black-and-white spots on the nape suggest eyes. The tail is relatively long for an owl and is colored reddish-brown with darker brown bars. The call of this diurnal owl, heard primarily near dawn and dusk, is a monotonous series of short notes.
The cactus ferruginous pygmy-owl is one of four subspecies of the ferruginous pygmy-owl. It occurs from lowland central Arizona south through western Mexico to the states of Colima and Michoacán, and from southern Texas south through the Mexican states of Tamaulipas and Nuevo León. South of these regions and through Central America, G. b. ridgwayi replaces G. b. cactorum. G. b. brasilianum is the resident subspecies throughout South America, although a fourth subspecies of pygmy-owl from central Argentina was identified as G. b. stranecki in 1995.
The cactus ferruginous pygmy-owl is distinguished from G. b. ridgwayi and G. b. brasilianum by its shorter wings, longer tail, and generally lighter coloration. G. b. cactorum occurs in several color phases, with distinct differences between regional populations. Some researchers have suggested that further taxonomic investigation may be needed, but G. b. cactorum has been widely recognized as a valid subspecies by at least six authorities in the field. The U. S. Fish and Wildlife Service (FWS) accepted G. b. cactorum as a subspecies in 1991, reaffirmed this in 1993, and has also recognized this taxon as the only subspecies of cactus ferruginous pygmy-owl in Arizona.
The cactus ferruginous pygmy-owl, nonmigratory throughout its range, begins nesting activities in late winter to early spring. This bird nests in cavities in trees or large columnar cacti—although it has also been known to nest in fabricated nest boxes—and such cavities may be either natural openings such as knotholes or holes excavated by woodpeckers. The pygmy-owl uses no nest-lining materials before it lays three, four, five, or even six eggs, which are then incubated for approximately 28 days. The young fledge about 28 days after hatching. The pygmy-owl's diverse diet includes birds, lizards, insects, small mammals, and amphibians.
The cactus ferruginous pygmy-owl occurs throughout its range at elevations generally below 4,000 ft (1,200 m) in a variety of subtropical, scrub, and woodland communities. These include river bottom woodlands, woody thickets called bosques, coastal plain oak associations, thorn scrub, and desert scrub. These communities have the unifying habitat characteristics of being quite densely wooded, either with thickets or woodlands, with enough trees and large cacti to provide nesting cavities. Both riparian and desert scrub habitats are likely to meet several requirements of the pygmy-owl ecology. The commonly occurring trees and large cacti provide cavities for nesting and roosting, while those habitats along watercourses are noted for their high density and diversity of animal species that constitute the pygmy-owl's prey base.
Pygmy-owl habitat in southern Texas is confined to coastal plain oak associations and the Tamaulipan thorn scrub of the lower Rio Grande Valley region, which consists of mesquite (Prosopis glandulosa ), hackberry (Celtis spp.), oak (Quercus spp.), and Texas ebony (Pithecellobium ebano ). The primary historical habitats of the pygmy-owl in central and southern Arizona were riparian cottonwood (Populus spp.) forests, mesquite bosques, and Sonoran desert scrub, but the subspecies now occurs mostly in southern and southwestern Sonoran desert scrub associations of palo verde (Cercidium spp.), bursage (Ambrosia spp.), ironwood (Olneya tesota ), mesquite (Prosopis juliflora ), acacia (Acacia spp.), and giant columnar cacti such as saguaro (Cereus giganteus ) and organ-pipe (Cereus thurberi ). The pygmy-owl also was noted to occur at isolated desert oases supporting small pockets of riparian and xeroriparian vegetation. The pygmy-owl occurs in northeastern Mexico on lowland thickets, thorn scrub communities, riparian woodlands, and second-growth forest; in northwestern Mexico, it occurs in Sonoran desert scrub, Sinaloan thorn scrub, and Sinaloan deciduous forest, as well as river bottom woodlands, cactus forests, and thorn forest. The use of cypress trees by pygmy-owls along the Rio Grande has also been noted.
The northernmost record for the cactus ferruginous pygmy-owl is from New River, approximately 35 mi (56 km) north of Phoenix, where in 1893 it was common in thickets of intermixed mesquite and saguaro cactus. Prior to the mid-twentieth century, the pygmy-owl also was described as "not uncommon, of common occurrence, and a fairly numerous" resident of lowland central and southern Arizona in cottonwood forests, mesquite-cottonwood woodlands, and mesquite bosques along the Gila, Salt, Verde, San Pedro, and Santa Cruz Rivers, as well as their various tributaries including the Rillito Creek near Fort Lowell, in the vicinity of Tucson.
The available information strongly indicates that the pygmy-owl is divided into an eastern population occurring along the lower Rio Grande, the coastal plain of southern Texas, and northeastern Mexico and a western population occurring in lowland areas of northwestern Mexico and southern Arizona. The pygmy-owl's elevational distribution, the distribution of habitat, and recorded locations indicate that these eastern and western ranges of the bird are geographically isolated from each other and are ecologically distinct. In the United States, eastern and western portions of the pygmy-owl's range are separated by the basin-and-range mountains and intervening Chihuahuan Desert basins of southeastern Arizona, southern New Mexico, and western Texas.
The eastern and western populations in Mexico are separated by the highlands of the Sierra Madre Oriental, the Sierra Madre Occidental, and the Mexican Plateau. The pygmy-owl is considered rare on the Mexican Plateau at elevations of more than 4,000 ft (1,200 m) on the west and more than 1,000 ft (300 m) on the east. Some sources describe the eastern and western ranges as contiguous at the southern end of its range, near the southern end of the Mexican Plateau in central Mexico, while others describe these two ranges as disjunct. In a 1937 description of the subspecies, it was noted that Texas specimens exhibited characteristics of both G. b. cactorum and G. b. ridgwayi. The species was not ultimately assigned to G. b. cactorum, although it was noted that, 23 years earlier, the species had been considered distinct from G. b. ridgwayi.
The pygmy-owl's eastern and western populations, as well as being geographically separated, also occupy different habitats. These eastern and western locations are very dissimilar floristically, although they share the previously mentioned dense woodland/thicket broad habitat physiognomy. The desert scrub and thorn scrub associations in Arizona and western Mexico are unlike any habitats occupied by the pygmy-owl in eastern Mexico and southern Texas. The oak association habitat occupied on coastal plains in southern Texas is also unlike any habitat available in the western portion of the pygmy-owl's range. The Tamaulipan thorn scrub habitat of the east and the river bottom mesquite-cottonwood bosque habitat in Arizona, however, are more similar in physiognomy and to a slight degree in floristic makeup.
The potential for genetic distinctness further supports a distinction between eastern and western pygmy-owl populations. The fact that the pygmy-owl is nonmigratory throughout its range suggests that genetic mixing across wide areas may be infrequent. In addition, considerable variation in plumage between regional populations has been noted, including specific distinctions between Arizona and Texas pygmy-owls. The above information indicates that the Arizona (western) and Texas (eastern) populations of the cactus ferruginous pygmy-owl are each discrete groups based on geographic isolation; floristics, distribution, and status of habitat; and potential morphological and genetic distinctness. A population segment is "discrete" if it is markedly separated from other populations of the same taxon as a consequence of physical, physiological, ecological, or behavioral factors. A population also can be considered discrete if it is delimited by international boundaries across which exist differences in management control of the species. As discrete subspecies populations, the Arizona and Texas pygmy-owl populations can therefore be considered separately for listing under the Endangered Species Act. This is why the Arizona population can be listed as endangered, while the Texas population is not currently listed. The loss of either population would decrease the genetic variability of the taxon and would result in a significant reduction of its range.
The primary threat to the cactus ferruginous pygmy-owl is habitat destruction and modification, although the severity of habitat loss and future threats to remaining habitats varies across its range. It is estimated that 85-90% of low-elevation riparian habitats in the southwestern United States have been altered or eliminated, mostly through urban and agricultural encroachment, woodcutting, water diversion and impoundment, channelization, livestock overgrazing, groundwater pumping, and hydrologic changes resulting from various land-use practices.
Pygmy-owl numbers have been drastically reduced in Arizona, which once constituted its major U. S. range, and it has also experienced a significant decline in Texas. This decline in Texas has been mostly confined to the lower Rio Grande Valley, while larger populations persist in oak associations on the coastal plain north of the Rio Grande Valley. Status information for pygmy owls in Mexico is very limited, but some observations suggest that, although habitat loss and reductions in numbers are likely to have occurred in northern portions of the two subspecies in Mexico, the pygmy-owl persists as a locally common bird in southern portions of the country. Historical presence, habitat loss, and current population status for the populations of the pygmy-owl are summarized below. The western and eastern populations each include Mexican sub-populations, so four distinct pygmy-owl groups will be discussed.
The pygmy-owl now occurs mostly in areas quite different from where it historically predominated in Arizona. It is not only very rare in the riparian areas where it used to flourish, it also appears more frequently in Sonoran desert scrub. It was more often found historically in xeroriparian habitats—very dense desert scrub thickets bordering dry desert washes—rather than more open, desert uplands.
The trend of Sonoran desert scrub habitats and pygmy-owl occupancy is not as clear. Historical records from this habitat in Arizona are few. While historical records of pygmy-owls do exist for Sonoran desert scrub in areas such as the Santa Catalina foothills, they generally note that the birds are rare in these areas. This may be due to disproportionate collecting along the rivers where people congregated, while the less-frequented upland deserts were not as intensively surveyed. It has also been suggested that the pygmy-owl adapted to upland associations and xeroriparian habitats in response to the demise of Arizona's river bottom woodlands, although conclusive evidence to support this hypothesis is not available. It may be that desert scrub habitats simply are of lesser quality and have always been occupied by pygmy-owls at lower frequency and density.
The pygmy-owl has declined so markedly throughout Arizona that it is now extremely limited in distribution there. A brief examination of the historical processes at work in the state reveal just how much prime pygmy-owl habitat has been destroyed or damaged. River bottom forests and bosques, which supported the greatest abundance of pygmy-owls, have been extensively modified and destroyed by clearing, urbanization, water management, and hydrological changes. Cutting for domestic and industrial fuelwood was so extensive throughout southern Arizona that riparian forests within tens of miles of towns and mines had been decimated by the late nineteenth century. Mesquite was a favored species because of its excellent fuel qualities. The famous vast forests of giant mesquites along the Santa Cruz River in the Tucson area and the heavy mesquite thickets along Rillito Creek, a Santa Cruz River tributary, were felled for fuel in the early twentieth century. Only remnant fragments of these bosques remain. Cottonwoods also were felled for fuelwood, fenceposts, and even for the bark, which was used as cattle feed. In recent decades, the pygmy-owl's riparian habitat has continued to be modified and destroyed by agricultural development, woodcutting, urban expansion, and general watershed degradation. Sonoran desert scrub has been affected to varying degrees by urban and agricultural development, woodcutting, and livestock grazing.
The pumping of groundwater and the diversion and channelization of natural watercourses are also likely to have reduced pygmy-owl habitat. Diversion and pumping diminish surface flows, and consequent reductions in riparian vegetation are very likely. Channelization often alters stream banks and fluvial dynamics necessary to maintain native riparian vegetation. The series of dams along the Colorado, Gila, Salt, and Verde Rivers have altered riparian habitat downstream of dams through hydrological and vegetational changes and have inundated former habitat upstream.
Livestock overgrazing in riparian habitats is one of the most common causes of riparian degradation. Effects of overgrazing include changes in plant community structure, species composition, relative species abundance, and plant density. These changes are often linked to more widespread changes in watershed hydrology, and are likely to affect the habitat characteristics critical to the pygmy-owl.
A study published in 1988 found less than 20 verified records of pygmy-owls in Arizona for the period 1971-88. Although pygmy-owls are diurnal and frequently vocalize in the morning, the species was not recorded or reported in any breeding bird survey data in Arizona. Formal surveys for the pygmy-owl began in 1990 and have been done periodically since then, with consistently grim results. One bird was located in 1990, three in 1992, and three in 1993. During 1993-94 surveys, one pair of owls was detected in north Tucson near the sightings in 1992 and 1993. Two individual owls were found in northwest Tucson during 1995 surveys. In 1966 a focused survey in northwest Tucson and Marana detected a total of 16 birds, 2 of which were a pair and 2 of which were fledglings. Three additional pygmy-owls were detected in 1996, with three additional unconfirmed reports.
Potential threats to pygmy-owl habitat in Arizona persist. There are at least five specific housing and development projects operating or in the planning stages that would affect habitat where the majority of birds in Arizona exist. In 1996, 54,400 acres (22,000 hectares) of suitable pygmy-owl habitat existed in the northwest Tucson area, the very region where most of the remaining birds in the state are concentrated. But housing and industrial developments continue to expand in the Tucson area, and the northwest region is experiencing rapid growth. Even though 60% of this area is in state trust or U.S. Bureau of Land Management (BLM) ownership, much of it could become subject to development, as the town of Marana is developing a general plan for future growth that may incorporate these areas. The BLM is also evaluating a proposal to exchange all of its land within this area to a developer.
Potential threats at Organ Pipe Cactus National Monument include the increased risk of wildfire associated with an invasion by non-native grasses such as red brome (Bromus tectorum ) and buffelgrass (Pennisetum ciliare ). Sonoran desert scrub is not generally considered fire-adapted, and fire can lead to loss of saguaros. An additional threat in this area is the increasing visitation and through-traffic from the international port of entry at Lukeville.
The pygmy-owl is now listed as endangered in Arizona because the population there exists in extremely low numbers, the vast majority of its former habitat can no longer support the species, and much of the remaining habitat is under immediate and significant threat.
The cactus ferruginous pygmy-owl—absent or rare in the highlands of Mexico's central plateau, where the least (G. minutissima ) and northern (G. gnoma ) pygmy-owls appear—occurs in the generally more arid elevations of western Mexico below 4,000 ft (1,200 m), in riparian woodlands and communities of thorn scrub and large cacti.
This taxon was generally described in the mid-twentieth century as common in western Mexico. Fifty years ago the pygmy-owl was considered fairly common in the lower elevations of western Sonora, and as abundant at the southern extreme of its range in Colima in 1963. Information on the late twentieth century status of the pygmy-owl and its habitat in western Mexico, although incomplete, suggests that trends vary within different geographic areas. The pygmy-owl could still be located fairly easily in southern Sonora, but its distribution was somewhat erratic. Data from 1972-95 from Alamos in Sonora and San Blas in Nayarit indicated that the pygmy-owl was common, but detections varied widely from year to year, possibly due to variations in the time spent per count and the number of searchers participating in the count. The count for Alamos never exceeded four individuals, and no sightings were recorded in 10 out of 14 years. In the late 1990s, pygmy-owls were found in abundance in some areas but not observed in locations of apparently similar habitat. This bird also appeared to be more abundant in thorn forest than cactus forest.
The pygmy-owl is now rare or absent in northern Sonora, within 150 mi (240 km) of the U. S.-Mexican border. Extensive conversion of desert scrub and thorn scrub to buffelgrass, an exotic plant introduced for livestock forage, is now taking place, although the quantity of land converted is not available. It is possible that the factors causing declines in Arizona also are affecting western Mexico. Immediately south of Organ Pipe Cactus National Monument is the Sonita region, an area currently undergoing extensive urban and agricultural development that may result in modification or destruction of movement corridors for the pygmy-owl between southern Arizona and northern Sonora. There is not enough information available, however, to determine if this subspecies should be listed in western Mexico.
The pygmy-owl's historical range in Texas included the lower Rio Grande Valley, where it was considered a common resident of dense mesquite, cottonwood-ebony woodlands, and Tamaulipan brushland. Pygmy-owls also occur in coastal plain oak associations between Brownsville and Corpus Christi; it was here that researchers in the early 1990s found greater numbers of this bird than previously known. Prior to the formal and systematic surveys done in the late twentieth century, pygmy-owls were generally reported as occurring in the Rio Grande floodplain below Falcon Dam and north of the lower Rio Grande Valley along U. S. highway 77. Pygmy-owls have been reported almost annually from the Rio Grande floodplain downstream of Falcon Dam to the Santa Ana National Wildlife Refuge in Starr and Hidalgo Counties. Two pygmy-owls were reported below the dam in April 1993. These records generally are for 1 bird or 1 pair of birds, with the exception of a report of 10 birds from below the dam in 1989. Pygmy-owls were found in 1993 in Kenedy, Brooks, and adjacent south Texas counties.
A larger population of pygmy-owls occurs on the King Ranch and surrounding ranches, located approximately 70 mi (110 km) north of Brownsville. The most consistently used owl habitat in this region, historically known as the Wild Horse Desert, is a 1,800 sq mi (4,650 sq km) oblong area of deep and sandy soil, which supports live oak (Quercus virginiana ) and honey mesquite (Prosopis glandulosa ), with the live oaks clustered into small groups or mottes. This area constitutes a 50 mi (80 km) intrusion of coastal sands from the Laguna Madre that covers portions of northern Willacy, Kenedy, and Brooks Counties. This habitat was recognized in 1950 as a distinct Texas vegetational region. It was noted that brush in this area thins out as available moisture declines inland, and that there was a difference in plant composition in this region due to the extensive sand strip.
A 1993 study of 27 sites in Mexico and 11 sites in Texas, yielded only 12 positive responses, all from Mexico. Additional survey results from work completed later in 1993 found 116 individual, nonredundant pygmy-owl records on and around the King Ranch in mature mixed live oak-mesquite habitats, with the highest density of birds on the Norias Division. A 1996 study recorded 166 responses during 1994 and 1995 on the King, Kenedy, Canelo, and Runnels ranches.
One hundred eleven pygmy-owls were trapped and banded on the Norias Division of the King Ranch, focusing on a 71,393 acre (28,892 hectare) portion that supports a live oak-honey mesquite forest. All but one small parcel of the estimated 250,000 acres (101,200 hectares) of live oak habitat surrounding the King, Kenedy, and other nearby ranches has been surveyed for pygmy-owls.
While the high end number of known individuals found in these surveys ranges from 111 to 166, the estimated population of this bird is much higher; a 1966 estimate was between 745 and 1,823 pygmy-owls just on the Norias Division of the King Ranch. Three years earlier, 1,308 birds were estimated in the habitat available in Kenedy, Brooks, and Willacy Counties. The Caesar Kleberg Institute of Texas A&M University believes that pygmy-owl numbers in Texas probably exceed 1,300 birds, with most of the populations being viable.
The FWS believes that the habitat for pygmy-owls along the coastal plain of southern Texas is stable, and may be increasing as former grasslands are invaded by oaks and the oaks mature to form the structural characteristics favored by pygmy-owls. Furthermore, large tracts of habitat on privately owned ranches in this area are largely managed for hunting and birding, conversion for agricultural use is considered uneconomical and unlikely, and other threats to this habitat are low or nonexistent. Finally, habitat acquisition and rehabilitation underway in the lower Rio Grande Valley could provide substantial habitat for future pygmy-owl populations. Since a significant population of pygmy-owls in the Texas coastal plain persists and a substantial amount of relatively unthreatened owl habitat still exists in the state, the FWS has determined that the cactus ferruginous pygmy-owl in Texas is not likely to become endangered in the foreseeable future throughout all or a significant portion of its range.
The pygmy-owl occurs in regions below 1,000 ft (300 m) along the Gulf Coast of Mexico, in the states of Tamaulipas and Nuevo León. Its primary habitat in this region is Tamaulipan thorn scrub, forest edge, riparian woodlands, thickets, and lowland tropical deciduous forest. The pygmy-owl is absent or rare in the highlands of Mexico's central plateau, where the least and northern pygmy-owls occur.
This bird was generally described in the middle of the twentieth century as having been common in eastern Mexico. Current information on the status of the pygmy-owl and its habitat in eastern Mexico is incomplete. The pygmy-owl was reported in 1976 to be fairly common in the Sierra Picachos of Nuevo León. Pygmy-owls were located at 13 of 27 survey sites in northeastern Mexico in 1991. Data from 1972 through 1996 from Rancho Los Colorados, Río Corona, and Gomez Farias, all in Tamaulipas, indicate the pygmy-owl was common, but detections varied widely from year to year, probably due to time spent per count and the number of individuals involved in the count effort.
The pygmy owl is also menaced throughout its range by threats other than habitat degradation and destruction, of which overzealous attention by birders, a foodborne disease, animal predation, competition for nesting sites with another bird, pesticides, and a lack of genetic variability in its small population are the most likely to be dangerous.
The pygmy-owl is highly sought by birders who concentrate at several of the remaining known locations of pygmy-owls in the United States. Limited and careful birding is probably not harmful; excessive attention by birders may at times, however, harass and affect the occurrence, behavior, and reproductive success of the pygmy-owl. An example of excessive, perhaps harmful, attention can be cited from early 1993, when one of the few areas in Texas known to support the pygmy-owl continued to be widely publicized. The resident pygmy-owls were detected at this highly visited area only early in the breeding season and not thereafter. Five birds initially detected in southern Texas in 1990 failed to respond after repeated visits by birding tours, and birding may disturb owls at highly visited areas in southern Texas.
One disease identified by the Arizona Game and Fish Department as potentially affecting the pygmy-owl is trichomoniasis. Because owls prey on finches, sparrows, and other seed-eating birds known to carry trichomoniasis, they are at risk of contracting the disease. According to a 1996 study, raptors in urban areas experience a higher exposure rate to trichomoniasis, and the result is high mortality of raptor nestlings. No studies have been completed to date on the pygmy-owl in urban or other areas to determine if pygmy-owls have been affected by this disease.
Snake predation may be an additional factor adversely affecting the pygmy-owl population on the Norias Division of the King Ranch. A lack of egg shell remaining in depradated nest boxes indicates that snakes rather than long-tailed weasels (Mustela frenata ), which also occur in the study area, were the probable plunderers. The indigo snake (Drymarchon corais ) has been observed climbing trees on the King Ranch; this snake is known to prey on green-cheeked Amazon parrots (Amazona viridigenalis ) that nest in cavities similar to the ones preferred by the pygmy-owl. Eggs were not disturbed in those nest boxes whose trees had protective flashing installed. The number of young successfully raised per year for eggs and owls in natural cavities was approximately one-third that of fecundity in protected nest boxes. This lower natural cavity fecundity rate was likely to have been caused by both snake and long-tailed weasel depredation. It is not known, however, what effect nest predation has on pygmy-owl mortality rates, or even if predation rates are unnaturally high.
The pygmy-owl nests in cavities excavated by woodpeckers in trees or large cacti. Some sources believe that increasing competition for nest cavities with the European starling (Sturnus vulgaris ), an exotic first reported in Arizona in 1946, may be a threat to cavity-nesters such as the pygmy-owl.
Pesticides, when used in floodplain habitat areas that are now largely agricultural, may pose an additional threat to the pygmy-owl. The accumulation of slowly degradable and resistant pesticides may result from repeated application of these chemicals on cotton and other crops that are grown year after year. Pesticide contamination, described as widespread throughout the inland waters of the lower Rio Grande Valley, includes concentrations of DDT, dieldrin, endrin, lindane, endosulfan, Guthion, and PCBs that exceed 1976 U. S. Environmental Protection Agency criteria for propagation of fish and wildlife. Without appropriate precautions, these agents may potentially affect pygmy-owls through direct toxicity or effects on their food base. No quantitative data on the effects of this potential threat are known at this time. While the effects of pesticides such as DDT on the reproductive success of other bird species are well known, there are no data on whether pesticides are currently affecting the pygmy-owl.
The relatively scant available information indicates low levels of genetic variation within each of the pygmy-owl populations, as well as probably between the individual populations themselves. Small populations without genetic variation are often considered imperiled due to the combined effects of low numbers of individuals in the group, the increased chances of inbreeding, and the relative vulnerability to sudden extirpation through the agency of random natural events.
Conservation and Recovery
No conservation plans or habitat restoration projects specific to the cactus ferruginous pygmy-owl currently exist for lands managed by the U. S. Government, Indian Nations, state agencies, or private parties. The U. S. Forest Service, the BLM, and the U. S. Bureau of Reclamation have focused some attention on modifying livestock grazing practices in recent years, particularly as they affect riparian ecosystems. Several of these projects are in the former range of the pygmy-owl, including some historical nesting locations. In addition, some private landowners in southern Texas are accommodating and funding research and have expressed an interest in carrying out conservation measures to benefit the pygmy-owl.
Located in Arizona, the Barry M. Goldwater Range, which overlaps the historical distributional range of the pygmy-owl, has an existing policy stating that any species that have been identified as state or federal species of concern will have its range inventoried and potential impacts to those species analyzed in the light of any other information gathered. Projects can then be modified to avoid or minimize impacts to the species. The Goldwater Range also has identified any habitats that are unique or significant on the range, including desert washes, bajadas, and dunes. The Goldwater Range has the flexibility to create management plans for any species of concern; at the turn of the millennium, however, no such policy existed for the pygmy-owl.
Through the Santa Ana/Lower Rio Grande Valley National Wildlife Refuge Complex in Texas, the FWS has started a Wetlands Reserve Program with the Natural Resources Conservation Service; using grant monies, the FWS will pursue the purchase of easements with willing landowners. The focus of the easement agreements will be on habitat protection and restoration. Additional tracts of land are being evaluated for purchase in river frontage areas in Starr and Hidalgo Counties. These efforts will result in a corridor of riparian woodlands, which may serve as pygmy-owl habitat in the future.
U. S. Fish and Wildlife Service
Arizona Ecological Services Field Office
2321 West Royal Palm Rd., Suite 103
Phoenix, Arizona 85021-4915
Telephone: (602) 640-2720
Fax: (602) 640-2730
U. S. Fish and Wildlife Service
Corpus Christi Ecological Services Field Office
c/o Texas A & M University at Corpus Christi
6300 Ocean Dr., Campus Box 338
Corpus Christi, Texas 78412-5599
Telephone: (361) 994-9005
Fax: (361) 888-3189
U. S. Fish and Wildlife Service. 10 March 1997. "Determination of Endangered Status for the Cactus Ferruginous Pygmy-Owl in Arizona." Federal Register 62 (46): 10730-10747.