Strix occidentalis lucida - (Nelson, 1903)
Mexican Spotted Owl
Taxonomic Status: Accepted
Related ITIS Name(s): Strix occidentalis lucida (Nelson, 1903) (TSN 177928)
Unique Identifier: ELEMENT_GLOBAL.2.101065
Element Code: ABNSB12012
Informal Taxonomy: Animals, Vertebrates - Birds - Other Birds
 
Kingdom Phylum Class Order Family Genus
Animalia Craniata Aves Strigiformes Strigidae Strix
Genus Size: C - Small genus (6-20 species)
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Concept Reference
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Concept Reference: American Ornithologists' Union (AOU). 1957. The A.O.U. Check-list of North American Birds, 5th ed. Port City Press, Inc., Baltimore, MD. 691 pp.
Concept Reference Code: B57AOU01HQUS
Name Used in Concept Reference: Strix occidentalis lucida
Conservation Status
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NatureServe Status

Global Status: G3G4T3T4
Global Status Last Reviewed: 21Aug2013
Global Status Last Changed: 21Aug2013
Ranking Methodology Used: Ranked by calculator
Rounded Global Status: T3 - Vulnerable
Reasons: Occurs disjunctly in the southwestern U.S. and the northern half of Mexico; fairly large number of occurrences; total adult population size probably is at least a couple thousand; current population trend is uncertain but apparently varies among different regions; negatively affected by historical loss, degradation and/or fragmentation of habitat, especially even-age timber management; threatened in some areas by the potential for catastrophic fire.
Nation: United States
National Status: N3N4 (21Aug2013)

U.S. & Canada State/Province Status
United States Arizona (S3S4), Colorado (S1B,SUN), Navajo Nation (S2S3), New Mexico (S2B,S2N), Texas (S1B), Utah (S2)

Other Statuses

U.S. Endangered Species Act (USESA): LT: Listed threatened (16Mar1993)
Comments on USESA: In 1993, the Board of Supervisors of Apache County, Arizona, petitioned to have the Mexican spotted owl delisted (on the basis of loss of jobs, business, education, recreation, wildlife, fisheries, and forest health, as well as fire danger and watershed concerns), but USFWS (1993) found that the petition action was not warranted. See also Federal Register, 1 April 1994, for a fairly detailed USFWS response to delisting petition.
U.S. Fish & Wildlife Service Lead Region: R2 - Southwest
Convention on International Trade in Endangered Species Protection Status (CITES): Appendix II

NatureServe Global Conservation Status Factors

Range Extent: 200,000-2,500,000 square km (about 80,000-1,000,000 square miles)
Range Extent Comments: Under the taxonomic concept followed by USFWS (2012), the range extends from Utah and Colorado south through the mountainous regions of Arizona, New Mexico, western Texas (Guadalupe Mountains), northern Sonora, Chihuahua, and Nuevo Leon south to central Mexico, including Michoacan and Puebla (Kertell 1977, Marti 1979, AOU 1983, Webb 1983, Ganey and Balda 1989; USFWS 1994, 1995, 2012). Many populations occur disjunctly in relatively isolated mountain ranges or canyon systems.

Area of Occupancy: 501-2,500 4-km2 grid cells
Area of Occupancy Comments: Area of occupancy is much less than the range extent but likely includes well over 1,000 grid cells (2 km x 2 km).

Number of Occurrences: 81 - 300
Number of Occurrences Comments: This subspecies is represented by a large number of occurrences (subpopulations) and locations (as defined by IUCN) (see map, USFWS 2012:167).

In the United States, this subspecies is represented by more than 1,300 known sites (a site is an area with a high probability of being used by a single or a pair of adult or subadult owls for nesting, roosting, or foraging); some of these sites (recorded since 1989) may not be currently occupied (USFWS 2012). The vast majority of known sites are in the United States, with only 34+ sites known in Mexico (USFWS 2012).

Population Size: 1000 - 10,000 individuals
Population Size Comments: Based on the number of known owl sites, the total adult population may be roughly a few thousand, assuming a pair at each srte.

Number of Occurrences with Good Viability/Integrity: Unknown

Overall Threat Impact: Medium
Overall Threat Impact Comments: Primary threat in the past was alteration of habitat in Arizona and New Mexico as a result of even-aged timber management (USFWS 1995).

The current primary threat in the U.S. (but likely not in Mexico) is increased risk of stand-replacing wildland fire. Southwestern forests have experienced larger and more severe wildland fires from 1995 to the present than previous to 1995. Climate variability combined with current forest conditions (e.g., heavy accumulations of ground and ladder fuels) may synergistically result in increased loss of habitat from fire. The intensification of natural drought cycles and the ensuing stress placed upon forested habitats could result in even larger and more severe wildland fires in owl habitat. Source: USFWS (2012).

Grazing by domestic and wild ungulates is a potential threat to spotted owls when managed insufficiently as to its effects on prey species habitat (e.g., reducing herbaceous ground cover), nest/roost habitat (e.g., limiting regeneration of important tree species, especially in riparian areas), and the capacity for resource managers to restore and maintain conditions supporting natural fire regimes within an array of habitat types. Grazing by domestic and wild ungulates is prevalent and recurring within most Mexican spotted owl habitat types. This potential threat occurs throughout the owl's range and often during periods of its reproductive cycle when prey availability is most critical. The magnitude of the threat is greatly dependent on the duration, timing, and intensity of grazing, and if insufficiently managed, both short-term and long-term adverse affects on the owl's habitat and that of its prey species may occur in the future. Source: USFWS (2012).

Land development poses a potential threat to Mexican spotted owls primarily through habitat fragmentation, alteration of ecological processes (e.g., predation, fire regimes), and increased potential for disturbance. Land development probably threatens foraging and wintering
habitat more than nest/roost habitat, although the level of threat is unknown. Source: USFWS (2012).

The extent and severity of threat posed by water develoment warrants additional study (USFWS 2012).

Climate change will likely influence spotted owl habitat significantly, but the nature of such influence is difficult to predict (USFWS 2012).

Habitat loss, alteration, and fragmentation probably are the main threats in Mexico. Habitat modifications include land-use changes for agriculture and cattle production, wildland fires, and illegal logging (see USFWS 2012).

Short-term Trend: Decline of <30% to relatively stable
Short-term Trend Comments: Trend over the past 10 years or three generations is uncertain, but distribution and abundance probably have been relatively stable or slowly declining.

Long-term Trend: Decline of 10-50%
Long-term Trend Comments: Distribution in the United States has declined to a small degree over the long term, particularly in lowland riparian areas along major rivers (USFWS 2012). Distributional trends in Mexico are largely unknown (USFWS 2012). A few studies have found population declines in the recent past, but long-term trend in overall abundance of this subspecies is unknown (USFWS 2012).

Seamans et al. (1999) studied the demography of a population in Arizona and another in New Mexico from 1991 to 1997. Survival and fecundity estimates indicated that both populations were declining at more than 9 percent per year. These estimates were corroborated by observed declines in abundance. With four additional years of data on these same populations, Gutiérrez et al. (2003; cited by USFWS 2004) concluded that the decline observed by Seamans et al. (1999) on the Arizona study area was temporary, whereas the decline in New Mexico appeared to be continuing. Wide population fluctuations may be common for populations of owls (Gutierrez et al. 2003, cited by USFWS 2004).

Intrinsic Vulnerability: Moderately vulnerable
Intrinsic Vulnerability Comments: Small clutch size, temporal variability in nesting success, and delayed onset of breeding all contribute to the relatively low fecundity of this species (Gutiérrez 1996).

Other NatureServe Conservation Status Information

Inventory Needs: Obtain up-to-date information on occurrences throughout range, especially in Mexico.

Protection Needs: Protection of large contiguous tracts of habitat, capable of supporting multiple pairs, is the most important management need; this includes both occupied habitats and unoccupied areas approaching characteristics of nesting habitat (USFWS 1995).

Distribution
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Global Range: (200,000-2,500,000 square km (about 80,000-1,000,000 square miles)) Under the taxonomic concept followed by USFWS (2012), the range extends from Utah and Colorado south through the mountainous regions of Arizona, New Mexico, western Texas (Guadalupe Mountains), northern Sonora, Chihuahua, and Nuevo Leon south to central Mexico, including Michoacan and Puebla (Kertell 1977, Marti 1979, AOU 1983, Webb 1983, Ganey and Balda 1989; USFWS 1994, 1995, 2012). Many populations occur disjunctly in relatively isolated mountain ranges or canyon systems.

U.S. States and Canadian Provinces
Color legend for Distribution Map
NOTE: The maps for birds represent the breeding status by state and province. In some jurisdictions, the subnational statuses for common species have not been assessed and the status is shown as not-assessed (SNR). In some jurisdictions, the subnational status refers to the status as a non-breeder; these errors will be corrected in future versions of these maps. A species is not shown in a jurisdiction if it is not known to breed in the jurisdiction or if it occurs only accidentally or casually in the jurisdiction. Thus, the species may occur in a jurisdiction as a seasonal non-breeding resident or as a migratory transient but this will not be indicated on these maps. See other maps on this web site that depict the Western Hemisphere ranges of these species at all seasons of the year.
Endemism: occurs (regularly, as a native taxon) in multiple nations

U.S. & Canada State/Province Distribution
United States AZ, CO, NM, NN, TX, UT

Range Map
No map available.


U.S. Distribution by County Help
State County Name (FIPS Code)
AZ Apache (04001), Cochise (04003), Coconino (04005), Gila (04007), Graham (04009), Greenlee (04011), Maricopa (04013), Mohave (04015), Navajo (04017), Pima (04019), Pinal (04021), Santa Cruz (04023), Yavapai (04025)
CO Custer (08027), Douglas (08035), El Paso (08041), Fremont (08043), Huerfano (08055)*, Montezuma (08083), Pueblo (08101), San Miguel (08113)
NM Catron (35003), Cibola (35006), Colfax (35007)*, Dona Ana (35013), Eddy (35015), Grant (35017), Hidalgo (35023), Lincoln (35027), Los Alamos (35028), Luna (35029)*, Mckinley (35031), Mora (35033), Otero (35035), Rio Arriba (35039), San Juan (35045), San Miguel (35047), Sandoval (35043), Santa Fe (35049), Sierra (35051), Socorro (35053), Taos (35055)*, Torrance (35057), Valencia (35061)*
TX Jeff Davis (48243)
UT San Juan (49037)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
10 Upper South Platte (10190002)+
11 Upper Arkansas (11020002)+, Fountain (11020003)+, Huerfano (11020006)+*, Cimarron (11080002)+*, Mora (11080004)+
13 Alamosa-Trinchera (13010002)+*, Upper Rio Grande (13020101)+, Rio Chama (13020102)+, Rio Grande-Santa Fe (13020201)+, Jemez (13020202)+, Rio Grande-Albuquerque (13020203)+, Rio Puerco (13020204)+, North Plains (13020206)+, Rio San Jose (13020207)+, Plains of San Agustin (13020208)+, Rio Salado (13020209)+, Elephant Butte Reservoir (13020211)+, Caballo (13030101)+, El Paso-Las Cruces (13030102)+*, Mimbres (13030202)+, Western Estancia (13050001)+, Tularosa Valley (13050003)+, Salt Basin (13050004)+, Pecos headwaters (13060001)+, Rio Hondo (13060008)+, Rio Penasco (13060010)+, Upper Pecos-Black (13060011)+, Toyah (13070003)+, Barrilla Draw (13070005)+
14 Upper Dolores (14030002)+, Lower Lake Powell (14070006)+, Upper San Juan (14080101)+, Blanco Canyon (14080103)+, Middle San Juan (14080105)+, Chaco (14080106)+, Mancos (14080107)+, Lower San Juan-Four Corners (14080201)+, Chinle (14080204)+, Lower San Juan (14080205)+
15 Lower Colorado-Marble Canyon (15010001)+, Grand Canyon (15010002)+, Havasu Canyon (15010004)+, Little Colorado headwaters (15020001)+, Upper Little Colorado (15020002)+, Carrizo Wash (15020003)+, Zuni (15020004)+, Upper Puerco (15020006)+, Middle Little Colorado (15020008)+, Chevelon Canyon (15020010)+, Canyon Diablo (15020015)+, Lower Little Colorado (15020016)+, Dinnebito Wash (15020017)+, Moenkopi Wash (15020018)+, Big Sandy (15030201)+*, Santa Maria (15030203)+, Upper Gila (15040001)+, Upper Gila-Mangas (15040002)+, Animas Valley (15040003)+, San Francisco (15040004)+, Upper Gila-San Carlos Reservoir (15040005)+, San Simon (15040006)+, Middle Gila (15050100)+, Willcox Playa (15050201)+, Upper San Pedro (15050202)+, Lower San Pedro (15050203)+, Upper Santa Cruz (15050301)+, Rillito (15050302)+, Black (15060101)+, Upper Salt (15060103)+, Carrizo (15060104)+, Tonto (15060105)+, Lower Salt (15060106)+, Upper Verde (15060202)+, Lower Verde (15060203)+, Agua Fria (15070102)+, Hassayampa (15070103)+, Rio De La Concepcion (15080200)+, Whitewater Draw (15080301)+, San Bernardino Valley (15080302)+*, Cloverdale (15080303)+*
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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Basic Description: Medium-sized, dark-eyed owl lacking ear tufts.
General Description: A large, dark-eyed, round-headed, brown owl with whitish spotting on the head, back, and underparts (spotted breast, barred belly).
Diagnostic Characteristics: Differs from other subspecies in being generally paler and having the lighter markings of the underparts more whitish (Ridgway 1914).
Reproduction Comments: Egg dates: peak in April in Arizona and New Mexico, sometimes as early as early March. Clutch size is 2-4, usually 2. Incubation, by female (fed by male), lasts about 30 days. Hatching generally occurs in early to mid-May. Young leave nest at about 5 weeks (June), fly at about 6-7 weeks, stay near nest for several weeks, fed by adults until late summer, independent by early fall (dispersal of young occurs in September-October). First breeds at 2-3 years; may not breed every year. Reproductive success generally is low (USFWS 1993); average number of young fledged per pair is about 1.0 (USFWS 1995).
Ecology Comments: Density generally is less than 0.4/sq km (mostly about 0.1-0.2/sq km) (USFWS 1995). Annual survival rate appears to be about 80-90% in adults, 6-29% in juveniles (White et al. 1995, USFWS 1995).
Non-Migrant: Y
Locally Migrant: Y
Long Distance Migrant: N
Mobility and Migration Comments: In the southwestern U.S., these owls are apparently largely nonmigratory, with some vertical migration at higher elevations (Ganey et al. 1988) (i.e., owls move to lower elevations for winter, with some exceptions). Some owls remain year-round in the same general areas but exhibit seasonal shifts in habitat use pattern (USFWS 1995). Some migrate 20-50 km between summer and winter ranges (see USFWS 1995). Some Mexican spotted owls undergo elevational migrations to winter in areas where habitat structure and composition differ from that used during breeding (USFWS 2012).

Mexican spotted owls appear to be obligate dispersers, with all juveniles dispersing from natal
areas. Distance from the natal site to the last observed location for radio-marked juveniles may exceed 100 kilometers (USFWS 1995), but probably most successfully dispersing juveniles occupy territories near their natal territories (USFWS 2012).

In Utah, seven juveniles dispersed 24-145 km (USFWS 1995). In New Mexico, five juvenile females dispersed 8-56 km (mean 22 km), five juvenile males dispersed 2-13 km (mean 6 km); some females, including an adult, made intermountain movements (Gutierrez et al. 1996).

Home range size apparently varies with location and habitat; generally the smallest home ranges are a few hundred hectares and the largest ones are about 1500 ha (minimum convex polygon) (see USFWS 1995). In northern Arizona, mean home range of three pairs was 847 ha; owls shifted seasonally such that year-round home range was larger than the range used during any one season (Ganey and Balda 1989). Mean home range size of four pairs in the Lincoln National Forest was 1180 ha; mean home ranges in Utah varied from 242 ha in Zion National Park to 625 ha for two owls elsewhere (see USFWS 1993). In Utah, some home ranges shifted seasonally, others did not (see USFWS 1994). In general, fidelity to territories is apparently high (USFWS 1995).

Palustrine Habitat(s): Riparian
Terrestrial Habitat(s): Cliff, Forest - Conifer, Forest - Hardwood, Forest - Mixed
Special Habitat Factors: Standing snag/hollow tree
Habitat Comments: Nesting and roosting occurs in both forested and rocky-canyon habitats. Forests used for roosting and nesting often contain mature or old-growth stands with complex structure; typically they are uneven-aged, multistoried, and have high canopy cover; nest trees are typically large Douglas-fir, though other species sometimes are used. In parts of its range, Mexican spotted owls occupy a variety of steep, rocky-canyon habitats. The owls appear to use a wider variety of cover types for foraging than for roosting or nesting. Source: USFWS (2012).

Highest densities occur in mixed-conifer forests that have experienced minimal human disturbance (USFWS 1995, Ganey and Dick 1995). In the southwestern U.S., these owls are most common where unlogged closed canopy forests occur in steep canyons; uneven-aged stands with high basal area and many snags and downed logs are most favorable. In Arizona, owls occur primarily in mixed-conifer, pine-oak, and evergreen oak forests; also in ponderosa pine forest and rocky canyonlands (Ganey and Balda 1989). In Arizona, spotted owls generally foraged more than or as frequently as expected (based on availability) in virgin mixed-conifer and ponderosa pine forests, and less than expected in managed forests; they roosted primarily in virgin mixed-conifer forests; both foraging and especially roosting sites had more big logs, higher canopy closure, and greater densities and basal areas of both trees and snags than did random sites (Ganey and Balda 1994). In southern Utah, spotted owls commonly used mesa tops, benches and warm slopes above canyons in fall and winter; relatively cool canyons were the primary summer habitat (see USFWS 1994). In New Mexico, breeding and roosting occurred in mixed-conifer forests that contained an oak component more frequently than expected by chance; generally did not use pinyon pine-alligator juniper woodlands for nesting or roosting; selected roost and nest sites in forests characterized by mature trees with high variation in tree heights and canopy closure greater than 75% (Seamans and Gutierrez 1995).

Mexican spotted owls are basically intolerant of even-age forest management practices (USFWS, Federal Register, 1 April 1994). They require cool summer roosts (Barrows 1981, Ganey et al. 1993), such as near canyon bottoms, in dense forests, on shady cliffs or in caves (Ganey et al. 1988). Sometimes they occur in deep canyons in areas that lack extensive forests. Sometimes they winter in comparatively open habitats at lower elevations. Breeding formerly occurred in desert riparian habitat, but occurrences are rare in this habitat today. In general, foraging habitat requirements are not well known (USFWS 1995). See USFWS (1993, 1994, 1995) for further details on habitat.

Nests are on broken tree tops, cliff ledges, in natural tree cavities, or in trees on stick platforms, often the abandoned nest of a hawk or mammal; sometimes in caves. In Utah and Colorado, most nests are in caves or on cliff ledges in steep-walled canyons; elsewhere, nests apparently most often are in trees, especially Douglas-fir (USFWS 1995, Seamans and Gutierrez 1995). Mexican spotted owls exhibit a high level of nest site fidelity. Typically they select cool, shady sites with high canopy closure and at least a few old-growth trees, usually on moderate to steep slopes (USFWS 1993). In New Mexico, 61% of nest structures were on clumps of limbs caused by dwarf mistletoe infections; nest trees averaged 164 years old and 60.6 cm in diameter (Seamans and Gutierrez 1995). See also USFWS (1995).

Adult Food Habits: Carnivore
Immature Food Habits: Carnivore
Food Comments: Diet varies with location and often includes small- and medium-sized rodents such as woodrats, deer mice, pocket gophers, and voles, but may also include bats, birds, reptiles, and arthropods (Kertell 1977; Ganey et al. 1988; Ganey 1992; USFWS 1995, 2012; Ward and Block 1995). Mexican spotted owls generally hunt from a perch and may cache prey.
Adult Phenology: Crepuscular, Nocturnal
Immature Phenology: Crepuscular, Nocturnal
Phenology Comments: Roosts during the day; hunts at dusk and at night. May leave roost during day to capture prey beneath roost, retrieve cached prey, or to drink or bathe in stream. In northern Arizona, calling peaked in late spring and during 2-hour period following sunset (Ganey 1990).
Length: 45 centimeters
Economic Attributes Not yet assessed
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Management Summary
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Stewardship Overview: Key recovery criteria (USFWS 2012) include : 1. Owl occupancy rates must show a stable or increasing trend after 10 years of monitoring. 2. Indicators of habitat conditions (key habitat variables) are stable or improving for 10 years in roosting and nesting habitat.

Conservation actions needed for recovery include the following, as described by USFWS (2012):

1. Management. Given that the owl is a widespread subspecies with a disjunct and somewhat fragmented distribution, management of the owl and its habitat must be conducted at the landscape scale. Three levels of management are recommended:

(a) Protected Activity Centers (PACs). PACs encompass a minimum of 600 acres surrounding known owl nest/roost sites. Management recommendations are most conservative within PACs, but by no means advocate a "hands-off" approach. PACs are the only form of protected habitat included in the revised recovery plan.

(b) Recovery habitat. This habitat is primarily ponderosa pine-Gambel oak, mixed-conifer, and riparian forest that either currently is, or has the potential for becoming, nest/roost habitat or does or could provide foraging, dispersal, or wintering habitats. Nesting/roosting habitat typically occurs either in well-structured forests with high canopy cover, large trees, and other late seral characteristics, or in steep and narrow rocky canyons formed by parallel cliffs with numerous caves and/or ledges within specific geologic formations. Ten to 25 percent of forested recovery habitat should be managed as recovery nest/roost habitat. This habitat should be managed to replace nest/roost habitat lost due to disturbance (e.g., fire) or senescence and to provide additional nest/roost habitat to facilitate recovery of the owl. The remainder of forested recovery habitat should be managed for other needs (such as foraging, dispersing, or wintering) provided that key habitat elements are retained across the landscape.

(c) Other forest and woodland types, such as ponderosa pine forest, spruce-fir forest, and pinyon-juniper woodland. No specific management is suggested for these habitat types, recognizing that current emphasis for sustainable and resilient forests should be compatible with needs of the owl.

2. Monitoring. As management proceeds, monitoring assesses the efficacy of management actions. It is critically important to monitor owl populations and habitat to determine whether both are stable or improving. Monitoring population trends provides a real-time assessment of the owl's status, whereas habitat monitoring indicates if there will be adequate habitat to support a viable owl population in the future. As a surrogate for evaluating trends in actual owl numbers, owl occupancy will be monitored at a sample of fixed sites randomly selected throughout the U.S. range of the Mexican spotted owl. USFWS (2012) also recommend that Mexico undertake a monitoring effort consistent with the one recommended for the U.S. No specific design is proposed for monitoring habitat, although Forest Inventory and Assessment data might have application to the owl. Combining owl occupancy and habitat monitoring provides an opportunity to examine relationships between habitat features and owl populations to assess whether a review of current management is warranted.

3. Research. Four general areas require additional research: habitat relationships, biological interactions, population structure, and ecosystem structure. This research would increase our understanding of the effects of the recovery plan management recommendations on the owl and ecosystem composition, structure, and function.

4. Implementation. The recovery plan includes an implementation schedule that details recovery tasks, the entities responsible for implementing them, and the estimated costs. The recovery team recommends that a working teams be assembled to oversee implementation and to provide feedback on successes and failures of the recovery plan.

Preserve Selection & Design Considerations: This subspecies probably exists as more or less discrete clusters of populations, reflecting the patchiness of the habitat; each cluster of populations (e.g., the Mogollon Rim cluster and the Southern Rockies cluster) apparently can be regarded as a classical metapopulation; owls disperse frequently within clusters but only rarely between clusters (Keitt et al. 1995).
Population/Occurrence Delineation Not yet assessed
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Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 21Aug2013
NatureServe Conservation Status Factors Author: Hammerson, G.
Element Ecology & Life History Edition Date: 21Aug2013
Element Ecology & Life History Author(s): Hammerson, G.

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

References
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  • American Ornithologists' Union (AOU). 1957. The A.O.U. Check-list of North American Birds, 5th ed. Port City Press, Inc., Baltimore, MD. 691 pp.

  • American Ornithologists' Union (AOU). 1983. Check-list of North American Birds, 6th edition. Allen Press, Inc., Lawrence, Kansas. 877 pp.

  • Barrowclough, G. F., and R. J. Gutierrez. 1990. Genetic variation and differentiation in the spotted owl (STRIX OCCIDENTALIS). Auk 107:737-744.

  • Barrows, C.W. 1981. Roost selection by spotted owls: an adaptation to heat stress. Condor 83:302-309.

  • Bond, M. L., R. J. Gutiérrez, A. B. Franklin, W. S. LaHaye, C. A. May, and M. E. Seamans. 2002. Short-term effects of wildfires on spotted owl survival, site fidelity, mate fidelity, and reproductive success. Wildlife Society Bulletin 30:1022-1028.

  • Bosakowski, T. 1987. Census of barred owls and spotted owls. Pages 307-308 in Nero, R. W., et al., eds. Biology and conservation of northern forest owls. USDA For. Serv., Gen. Tech. Rep. RM-142.

  • Bull, E. L., et al. 1987. Nest platforms for great gray owls. Pp. 87-90 in Nero, R. W., et al., eds. Biology and conservation of northern forest owls. USDA Forest Service, Gen.Tech. Rep. RM-142.

  • Bull, E.L. 1987. Capture techniques for owls. Pages 291-293 in R.W. Nero, R.J. Clark, R.J. Knapton, and R.H. Hamre, editors. Biology and conservation of northern forest owls. USDA Forest Service, Gen. Tech. Rep. RM-142.

  • Campbell, L. 1995. Endangered and Threatened Animals of Texas: Their Life History and Management. Texas Parks and Wildlife Department, Endangered Resources Branch, Austin, Texas. ix + 129 pp.

  • Dawson, W. R., J. D. Ligon, and J. R. Murphy. 1987. Report of the Scientific Advisory Panel on the Spotted Owl. Condor 89:205-229.

  • Forsman, E. D. 1983. Methods and materials for locating and studying spotted owls. U.S.D.A. Forest Service, Gen. Tech. Report PNW-162. Portland, Oregon. 8 pp.

  • Forsman, E., and E. C. Meslow. 1986. The spotted owl. Pages 742-761 in R. L. Di Silvestro, editor. Audubon Wildlife Report 1986. National Audubon Society, New York. 1094 pp.

  • Ganey, J. L. 1990. Calling behavior of spotted owls in northern Arizona. Condor 92:485-490.

  • Ganey, J. L. 1992. Food habits of Mexican spotted owls in Arizona. Wilson Bull. 104:321-326.

  • Ganey, J. L. et al. 1988. Mexican spotted owl. Pages 145-150 in Glinski et al., eds. Proc. Southwest raptor management symposium and workshop. Nat. Wildl. Fed. Sci. and Tech. Ser. No. 11.

  • Ganey, J. L., R. P. Balda, and R. M. King. 1993. Metabolic rate and evaporative water loss of Mexican spotted and great horned owls. Wilson Bull. 105:645-656.

  • Ganey, J. L., and J. L. Dick, Jr. 1995. Habitat relationships of the Mexican spotted owl: current knowledge. Pages 1-42 in U.S. Fish and Wildlife Service. Mexican spotted owl recovery plan. Volume II. Albuquerque, New Mexico.

  • Ganey, J. L., and R. P. Balda. 1989a. Distribution and habitat use of Mexican spotted owls in Arizona. Condor 91:355-361.

  • Ganey, J. L., and R. P. Balda. 1989b. Home-range characteristics of spotted owls in northern Arizona. J. Wildlife Management 53:1159-1165.

  • Ganey, J. L., and R. P. Balda. 1994. Habitat selection by Mexican spotted owls in northern Arizona. Auk 111:162-169.

  • Gutierrez, R. J., M. E. Seamans, and M. Z. Peery. 1996. Intermountain movement by Mexican potted owls (STRIX OCCIDENTALIS LUCIDA). Great Basin Naturalist 56:87-89.

  • Keitt, T., A. B. Franklin, and J. P. Ward, Jr. 1995. Landscape analysis and metapopulation structure. Pages 1-16 in U.S. Fish and Wildlife Service. Mexican spotted owl recovery plan. Volume II. Albuquerque, New Mexico.

  • Kertell, K. 1977. The spotted owl at Zion National Park, Utah. Western Birds 8:147-150.

  • Lefranc, M. N., Jr., and R. L. Glinski. 1988. Southwest raptor management issues and recommendations. Pages 375-392 in Glinski et al., eds. Proc. Southwest raptor management symposium and workshop. National Wildlife Federation Science and Tech. Ser. No. 11.

  • Marti, C. D. 1979. Status of owls in Utah. Pages 29-35 in P. Schaeffer and S. Ehlers, eds. Owls of the West: their ecology and conservation. National Audubon Society, Western Education Center, Tiburon, California.

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