In California, the Elf Owl (Micrathene whitneyi) has been found only in riparian habitats and scattered stands of Saguaro (Carnegiea gigantea) along the lower Colorado River and at a few desert oases (Grinnell and Miller 1944). Although the species has never been numerous in California, there has apparently been a population decline. Surveys in 1978 and 1979 located 11 and 6 pairs of Elf Owls, respectively, at two locations along the lower Colorado River (Cardiff 1978, 1979). Cardiff’s (1978) complete record of the 28 Elf Owl sightings made in California prior to 1978 identified eight locations where the species has been found. We gathered 10 additional records made since 1979 (Table 1). All recent records were for either Soto Ranch or near Water Wheel Camp. Since 1979, habitat destruction has continued, resulting in the loss of much of the remaining cottonwood-willow and mesquite bosques (C. Hunter and B. Anderson pers. comm.). This loss is due to the proliferation of tamarisk (Tamarix chinensis), agricultural clearing, bank stabilization projects, urbanization, and recent sustained flooding (Laymon and Halterman 1987). This loss and its potential effect on Elf Owls prompted this survey during the spring of 1987.
The objectives of this study were to (1) identify and survey areas where Elf Owls had been reported during and since the 1979 survey, (2) identify and survey other areas of potential Elf Owl habitat, (3) determine the size and distribution of the breeding population of Elf Owls in California, (4) describe the physiographic features and vegetation of the sites surveyed, (5) assess the condition of the sites, including potential threats, and (6) develop recommendations to halt and possibly reverse the decline of Elf Owls in California.