Cactus Ferruginous Pygmy-Owl (Glaucidium brasilianum cactorum)
Associated Species in Sonoran Desert: Other species that may use similar habitat components or respond positively to management for the Cactus Ferruginous Pygmy-owl are: Harris’s Hawk, Gila Woodpecker, Gilded Flicker, Gambel’s Quail, Curve-billed Thrasher, Black-tailed Gnatcatcher, Phainopepla, Cactus Wren, Verdin, Elf Owl, Pyrrhuloxia, Ash-throated Flycatcher, Abert’s Towhee, Hooded Oriole, and Scott’s Oriole.
Associated Species in Lowland Riparian: Other species that may use similar habitat components or respond positively to management for the Cactus Ferruginous Pygmy-owl are: Lucy’s Warbler, Bell’s Vireo, Brown-crested Flycatcher, Bewick’s Wren, Hooded Oriole, Gila Woodpecker, Yellow Warbler, Yellow-breasted Chat, Yellow-billed Cuckoo, Ladder-backed Woodpecker.
Distribution: The Cactus Ferruginous Pygmy-Owl occurs from lowland central Arizona south through western Mexico to the States of Colima and Michoacan, and from southern Texas south through the Mexican States of Tamaulipas and Nuevo Leon. South of these regions and through Central America, G.b. ridgwayi replaces G.b. cactorum (Fisher 1893a, Friedmann and others 1950, Johnsgard 1988, Karalus and Eckert 1974, Oberholser 1974, Phillips and others 1964, van Rossem 1937, Schaldach 1963, de Schauensee 1966). In Arizona, its range is limited to Sonoran desertscrub and riparian habitats below 1220 m (4000 ft) in elevation in central and southern Arizona.
Ecology: Pygmy-owls are considered non-migratory throughout their range, having been reported during the winter months at Organ Pipe (Johnson unpubl. data 1976, 1980, T. Tibbitts pers. comm. 1997), Rillito Creek near Camp Lowell at present-day Tucson (Bendire 1888), and Sabino Canyon (USFS unpubl. data). Currently, the earliest nesting record in Arizona is from the collection of five eggs on April 12th , recorded in the United States National Museum (USNM 1996). Due to the small population size and secretive nature of Cactus Ferruginous Pygmy-Owls in Arizona, information is limited. However, recent studies in Arizona have documented copulation on March 31, with egg laying estimated to have taken place between April 6 and April 11, 1996. Working backwards from a confirmed fledging event, the latest record of egg laying is estimated to have been between May 31-June 5 in Tucson, Arizona (Abbate and others 1996). Cactus Ferruginous Pygmy-Owls nest in a large cavity in a tree or large columnar cactus. These cavities may be naturally formed (e.g. knotholes) or excavated by woodpeckers. Nest lining material may or may not be used. Cavities are variously lined with nesting materials or left unlined (Abbate and others 1996, Breninger 1898, Proudfoot 1996). Juveniles remain in close proximity to adults until dispersal. While data is limited, studies indicate that juvenile Cactus Ferruginous Pygmy-Owls have dispersed at least four miles in Texas and two miles in Arizona from their natal sites before establishing their own territories (Proudfoot 1996, S. Richardson pers. comm., AGFD 1997).
Habitat Requirements: In Arizona, the Cactus Ferruginous Pygmy-Owl is primarily associated with the Arizona Upland Subdivision of the Sonoran Desert, below (1220 m) 4000 ft in elevation. Generally, vegetation at these sites includes both species and structural diversity, with well-developed ground cover, mid-story, and canopy layers. The density of the vegetation is likely required to provide an adequate prey base for the Cactus Ferruginous Pygmy-Owl, as well as cover from aerial predators. In riparian areas, plant species may include Fremont cottonwood, willow species, hackberry, and mesquite species. Within Sonoran desertscrub, plant species generally include saguaro, mesquite, paloverde, and ironwood. While the Cactus Ferruginous Pygmy-Owl was historically considered to be a riparian species, little is known about its use of standing water. For Cactus Ferruginous Pygmy-Owls occurring in Sonoran desertscrub, only three observations of direct water use by pygmy-owls for drinking or bathing have been documented (Abbate and others 1996). Cactus Ferruginous Pygmy-Owls within the Tucson, Arizona area, as well as some of those at Organ Pipe Cactus National Monument, occur in close proximity to residential developments in low density housing areas not exceeding one house per 3.3-40 acres where those developments occur adjacent to larger, undeveloped tracks of desertscrub habitat (M. Richardson pers. comm., USFWS 1997).
Habitat and/or Population Objectives:
1. Maintain and increase current population in suitable habitat.
1. Protect known breeding locations from disturbance (i.e. recreation, development etc.).
IMPLEMENTATION RECOMMENDATIONS AND OPPORTUNITIES
Management Issues with Conservation Recommendations
The lack of natural history information for this species has made species management difficult. Riparian and Sonoran desertscrub habitat losses are considered a primary factor in the decline of this species, as well as an on-going threat (Abbate and others 1996, Bahre 1991, Brown and others 1977, Rea 1983, Stromberg 1993, Stromberg and others 1992, Szaro 1989, Willard 1912). Current development pressure around major metropolitan areas, such as the city of Tucson, is resulting in on-going habitat losses (Abbate and others 1996, M. Richardson pers. comm., USFWS 1997). Additionally, increased recreational use and an invasion of nonnative grasses in Organ Pipe Cactus National Monument, increases the risk of habitat loss through wildfire (H. Smith in litt. 1996).
Cactus Ferruginous Pygmy-Owl management issues are listed in italics. Below each issue are Arizona Partners in Flight Conservation Recommendations.
1. Restore, maintain riparian and high quality saguaro, paloverde, ironwood, mesquite habitats.
1. Incorporate owl habitat needs into regional planning.
2. Encourage native landscaping, especially in areas adjacent to natural open space.
3. Maintain larger tracks of existing native habitat.
1. Educate bird enthusiasts and recreationists on possible sensitivity and encourage them to avoid known breeding areas.
1. Implement full fire suppression in suitable habitat.
2. Reduce fuel loads along roadways to lower risk of fire.
1. Increase coordination with local government planning.
2. Identify funding sources for research (especially in Mexico).
EVALUATION OF ASSUMPTIONS: RESEARCH AND MONITORING
1. Increase research in Sonora, Mexico to determine distribution and genetic relationship between the Arizona and the Mexican species.
2. Conduct comprehensive surveys throughout AZ uplands and riparian habitat.
3. Determine the limiting factor in existing riparian habitat.
4. Investigate juvenile dispersal, home breeding range, wintering range, and habitat use by banding and telemetry.
5. Investigate methods to prevent high intensity fires in Sonoran Desert (specifically red brome).
6. Continue to collect natural history information (specifics on prey base).