Cactus Ferruginous Pygmy-Owl and Nongame Bird Surveys on the Cabeza Prieta National Wildlife Refuge, 2001
Cactus ferruginous pygmy-owls (Glaucidium brasilianum cactorum, hereafter “pygmy-owl”) are the northernmost subspecies of G. brasilianum and have occurred from lowland central Arizona and southern Texas south to Michoacan, Nuevo Leon, and Tamaulipas, Mexico (Johnsgard, 1988; USFWS, 1997). Historically, pygmy-owls were described as “quite common,” “not uncommon,” and “fairly numerous” in cottonwood (Populus fremontii) forests, mesquite (Prosopis sp.) - cottonwood woodlands, and mesquite bosques along the Salt, Verde, Gila, and Santa Cruz rivers of Arizona (Bendire, 1888; Fisher, 1893; Breninger, 1898; Gilman, 1909; Swarth, 1914). Historical records in desertscrub and xeroriparian vegetation exist (Phillips et. al, 1964; Brandt, 1951) but occurrence in these vegetation communities was thought to be less common and predictable (Johnson and Haight, 1985; USFWS, 1997). This pattern was likely a failure of early naturalists’ to search upland areas adequately and/or because of lower densities. Currently, pygmy-owls are not uncommon in semidesert grasslands and desertscrub vegetation with saguaros in neighboring Sonora, Mexico (Flesch and Steidl, in preparation).
In Arizona, pygmy-owls are federally listed as endangered and have declined to near extirpation (Monson and Phillips, 1981; Millsap and Johnson, 1988; USFWS, 1997), with fewer than 20 confirmed records between 1971 and 1988 (Hunter, 1988). Extensive surveys from 1993 to 1995 resulted in only 7 detections at 5 locations (Lesh and Corman, 1995). More recently in 1999, increased survey effort in Arizona has produced detections at up to 21 sites (Flesch, 1999; Abbate et al., 2000) and 13 documented nests in 2001 (S. Richardson, AZ Game and Fish Dept., personal communication). Despite increased numbers in recent years, no pygmy-owls have been detected west of Organ Pipe Cactus National Monument since 1955 (Monson and Phillips, 1981). The goals of this program were to determine the distribution pygmy-owls on Cabeza Prieta National Wildlife Refuge (CPNWR), describe vegetation in survey and occupied areas, and list all other species of birds detected on the refuge.