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Home/Species/ Cactus Ferruginous Pygmy-owl

Glaucidium brasilianum cactorum

van Rossem, 1937

Cactus Ferruginous Pygmy-owl

T2T2 (G5T2) Found in 20 roadless areas NatureServe Explorer →
T2T2Global Rank
Very high - highThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.101546
Element CodeABNSB08041
Record TypeSPECIES
ClassificationSubspecies
Classification StatusStandard
Name CategoryVertebrate Animal
CITESAppendix II
Endemicoccurs (regularly, as a native taxon) in multiple nations
KingdomAnimalia
PhylumCraniata
ClassAves
OrderStrigiformes
FamilyStrigidae
GenusGlaucidium
Concept Reference
American Ornithologists' Union (AOU). 1957. The AOU check-list of North American birds, 5th ed. Port City Press, Inc., Baltimore, MD. 691 pp.
Taxonomic Comments
A thorough, rangewide taxonomic analysis of the species would be useful in clarifying patterns of variation and the status of the nominal subspecies. Western and eastern segments of the population exhibit plumage differences. In the original description of subspecies cactorum (van Rossem 1937), Texas populations were found to exhibit characteristics of both cactorum and subspecies ridgwayi and were not assigned to subspecies cactorum. Most subsequent authors have included Texas populations in cactorum. Form intermedium is synonymized with cactorum, but probably worthy of recognition (Proudfoot and Johnson 2000).
Conservation Status
Rank MethodLegacy Rank calculation - Excel v3.1x
Review Date2017-12-09
Change Date2017-12-09
Edition Date2017-12-09
Edition AuthorsDavidson, A.D. and Flesch, A.D. (2017)
Threat ImpactVery high - high
Range Extent20,000-200,000 square km (about 8000-80,000 square miles)
Number of OccurrencesUnknown
Rank Reasons
Resident in extreme southwestern U.S. and northern Mexico; many U.S. populations have been eliminated, mainly the result of loss and degradation of habitat as a result of human activities. May be more abundant in Mexico, but population declines and habitat destruction occurring there as well.
Range Extent Comments
This subspecies occurs in Arizona, U.S., and Sonora and Sinoloa, Mexico. The subspecies G. r. ridgwayi occurs in Texas and other localities in Mexico (Proudfoot et al. 2006).
Occurrences Comments
Unknown for full subspecies range. All occurrences near Tucson have gone extinct since the early 2000s, and in Maricopa City since the early 1970s.
Threat Impact Comments
USFWS (2011) details a suite of interacting and compounding threats facing G. r. cactorum. Decline in the U.S. resulting from destruction and modification of riparian, desertscrub and grassland habitats via urban development, agriculture, wood cutting, water diversion, channelization, livestock overgrazing that causes loss of saguaros and reductions in prey species such as lizards, introduction of non-native buffelgrass that increases fire occurrence and kills cacti that owls rely on for habitat, groundwater pumping, and hydrological changes resulting from various land-use practices (USFWS 2011); Threats appear to be comparatively less significant throughout other parts of Mexico, but habitat impacts occurring there as well (USFWS 2011). Climate change in the American Southwest is also a major threat to owl populations, and threats from climate change are magnified in landscapes with higher levels of anthropogenic disturbance (Flesch 2014; Flesch et al 2015; Flesch et al. 2017)
Ecology & Habitat

Description

A small, long-tailed, yellow-eyed owl, with gray-brown upperparts; tail is reddish with dark or dusky bars; white underparts are streaked with reddish-brown; crown is faintly streaked; two white-margined black spots on nape resemble eyes; mass of female usually 64-87 g (mean around 75 g), mass of male usually 46-74 g (mean 61 g) (NGS 1983, Johnsgard 1988). Occurs in several color morphs, with distinct differences between regional populations (see USFWS 1994).

Diagnostic Characteristics

Differs from adjacent subspecies RIDGWAYI in having the upperparts and tail bands cinnamon-rufous rather than grayish with white tail bands (Johnsgard 1988). Phillips et al. (1964) stated that CACTORUM is "a well-marked pale grayish extreme for the species" (this seems to contradict the information presented by Johnsgard).

Habitat

Arizona: at present mainly associated with Sonoran desertscrub, especially along washes with dense xeroriparian mesquite, palo verde, desert ironwood, desert hackberry, and catclaw acacia; in Tuscon area in low density residential areas dominated by saguaro and foothill palo verde, ironwood, and velvet mesquite, and augmented by irrigation and exotic vegetation. Formerly more common in riparian cottonwood-willow forests intermixed with mesquite bosques (Cartron et al. 2000).

Northwestern Mexico: Sonoran desertscrub, Sinaloan thornscrub, Sinaloan deciduous forest, riverbottom woodlands, cactus forest, and thornforest (see USFWS 1994).

Texas: Formerly common in coastal plain oak associations and Tamaulipan thornscrub of the lower Rio Grande valley region (mesquite, hackberry, oak, Texas ebony). Now the largest population is in coastal sand plains dominated by mixed live oak and honey mesquite forest (Wauer et al. 1993).

Northeastern Mexico: lowland thickets, thornscrub communities, riparian woodlands, and second-growth forest.

Nests usually in natural tree or columnar cactus cavity or abandoned woodpecker hole; reported sites 3.3-9 m above ground. May re-use old nest site. Has used fabricated nest boxes (Proudfoot et al. 2000).

Ecology

Occurs singly or in pairs, except when caring for dependent young.

Reproduction

Egg dates: mainly May in Texas (eggs collected as early as late March); mainly April-May in Mexico; sometimes late March or June. Clutch size is 2-5, usually 3-4. Incubation lasts about 28-30 days (also reported as 22 days), by female. Young are tended by both parents, can fly at about 27-30 days.
Terrestrial Habitats
Forest - HardwoodWoodland - HardwoodShrubland/chaparralSavannaDesert
Palustrine Habitats
Riparian
Other Nations (1)
United StatesN3
ProvinceRankNative
ArizonaS1Yes
TexasS2Yes
Threat Assessments
ThreatScopeSeverityTiming
1 - Residential & commercial developmentRestricted (11-30%)Serious - moderateHigh (continuing)
1.1 - Housing & urban areasRestricted (11-30%)Serious - moderateHigh (continuing)
2 - Agriculture & aquaculturePervasive - largeSerious - moderateHigh (continuing)
2.3 - Livestock farming & ranchingPervasive - largeSerious - moderateHigh (continuing)
2.3.3 - Agro-industry grazing, ranching or farming———
4 - Transportation & service corridors——High (continuing)
4.1 - Roads & railroads——High (continuing)
5 - Biological resource useRestricted - smallModerate - slightHigh (continuing)
5.3 - Logging & wood harvestingRestricted - smallModerate - slightHigh (continuing)
7 - Natural system modificationsLarge - restrictedSerious - moderateHigh (continuing)
7.1 - Fire & fire suppression———
7.1.1 - Increase in fire frequency/intensity———
7.2 - Dams & water management/useLarge - restrictedSerious - moderateHigh (continuing)
11 - Climate change & severe weatherPervasive - largeSerious - moderateHigh (continuing)
11.1 - Habitat shifting & alteration———

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Roadless Areas (20)
Arizona (20)
AreaForestAcres
Black CrossTonto National Forest5,966
BoulderTonto National Forest40,359
Butterfly Roadless AreaCoronado National Forest42,296
Catalina St. Pk. Roadless AreaCoronado National Forest951
Cdo WsaCoronado National Forest1,955
GaliuroCoronado National Forest28,333
GoldfieldTonto National Forest15,257
Happy ValleyCoronado National Forest7,972
Horse MesaTonto National Forest9,146
Lower RinconCoronado National Forest3,278
Lower Romero WSRCoronado National Forest10
Middle Romero WSRCoronado National Forest60
Oracle RoadlessCoronado National Forest22,365
PinalenoCoronado National Forest130,920
Santa RitaCoronado National Forest6,078
Santa TeresaCoronado National Forest8,929
TumacacoriCoronado National Forest44,594
Upper Rincon RoadlessCoronado National Forest2,991
Upper Romero WsrCoronado National Forest150
WhetstoneCoronado National Forest20,728
References (35)
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  2. American Ornithologists' Union (AOU). 1983. Check-list of North American Birds, 6th edition. Allen Press, Inc., Lawrence, Kansas. 877 pp.
  3. AviList Core Team. 2025. AviList: The Global Avian Checklist, v2025. https://doi.org/10.2173/avilist.v2025
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  5. Cartron, J.-L. E., W. S. Richardson, and G. A. Proudfoot. 2000a. The Cactus Ferruginous Pygmy-Owl: taxonomy, distribution, and natural history. Pp. 5-16 IN J.-L. E. Cartron and D. M. Finch (tech. eds.). Ecology and conservation of the cactus Ferruginous Pygmy-Owl in Arizona. General Technical Report RMRS-GTR-43. Ogden, UT: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 68pp.
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  13. Mays, J. L. 1996. Population size and distribution of Cactus Ferruginous Pygmy-Owls in Brooks and Kenedy Counties, Texas. M.S. thesis, Texas A&M University-Kingsville, Kingsville, Texas.
  14. Millsap, B. A., and R. R. Johnson. 1988. Ferruginous pygmy-owl. Pages 137-139 in Glinski et al., eds. Proc. Southwest raptor management symnposium and workshop. Natural Wildlife Federation Science and Technology Ser. No. 11.
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  17. Nicholls, T. H., and M. R. Fuller. 1987. Owl telemetry techniques. Pages 294-301 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.
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  27. U.S. Fish and Wildlife Service (USFWS). 1994. Proposed rule to list the cactus ferruginous pygmy-owl as endangered with critical habitat in Arizona and threatened in Texas. Federal Register 59(237):63975-63986.
  28. U.S. Fish and Wildlife Service (USFWS). 1997. Determination of endangered status for the cactus ferruginous pygmy-owl in Arizona. Federal Register 62:10730-10747.
  29. U.S. Fish and Wildlife Service (USFWS). 1998. Proposed determination of critical habitat for the Cactus Ferruginous Pygmy-Owl in Arizona. Federal Register 63:71820-71838.
  30. U.S. Fish and Wildlife Service (USFWS). 1999. Designation of critical habitat for the Cactus Ferruginous Pygmy-owl (<i>Glaucidium brasilianum cactorum</i>). Federal Register 64:37419-37440.
  31. U.S. Fish and Wildlife Service (USFWS). 2023. Endangered and Threatened Wildlife and Plants; Threatened Species Status With Section 4(d) Rule for Cactus Ferruginous Pygmy-Owl. Federal Register 88(138):46910-46950.
  32. U.S. Fish and Wildlife Service (USFWS). 2025. Endangered and Threatened Wildlife and Plants; Review of Species That Are Candidates for Listing as Endangered or Threatened; Annual Notification of Findings on Resubmitted Petitions; Annual Description of Progress on Listing Actions. Candidate notice of review (CNOR). Federal Register 90(209):48912-48937.
  33. U.S. Fish and Wildlife Service (USFWS). Endangered and Threatened Wildlife and Plants; Threatened Species Status With Section 4(d) Rule for Cactus Ferruginous Pygmy-Owl. Proposed rule. Federal Register 86(243):72547-72573.
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