Strigidae (Typical Owls)

Western Screech-Owl,Otus kennicottii. (Fig. 11.12) Male length 8 1/2 in (22 cm), female length 9 in (22.5 cm); male weight 4 3/4 oz (133 g), female weight 5 1/2 oz (155 g). Uncommon permanent resident in the White-Inyo Range; recorded from 7,200 to 8,200 ft (2,200 to 2,500 m) elevation.

Although this species is locally common in old-growth cottonwoods and tree willows in Owens Valley, only small numbers occur in the White-Inyo mountains. There they prefer the warmer portions of the Singleleaf Pinyon belt. Western Screech-Owls dwell in the lower stretches of canyons in mature trees on gently sloping ground. Natural or woodpecker-excavated cavities in large pinyon trunks are used for roosting and nesting. Foraging takes these owls into more open habitats, but at least some scattered pinyons or junipers seem essential for the presence of this species. Western Screech-Owls feed on a variety of insects, including grasshoppers, crickets, beetles, moths, caterpillars, and spiders. Vertebrates are occasionally eaten, especially during the winter months. The bouncing-ball song of the local subspecies (O. k. inyoensis ) is shorter and composed of fewer notes than the vocalizations of related forms. Like all small owls, the Western Screech-Owl has suffered from fuel-wood cutting in the Singleleaf Pinyon Woodland and from the removal of riparian trees generally. Numbers nearly everywhere have been declining over the past several decades. Reference: Miller and Stebbins (1964).

Great Horned Owl,Bubo virginianus. (Fig. 11.13) Male length 18 in (45.75 cm), female length 19 1/2 in (49.75 cm); male weight 2 lb (914 g), female weight 2 1/2 lb (1,142 g). Fairly common permanent resident in the White-Inyo Range; occurs at all elevations up to approximately 9,500 ft (2,896 m).

The Great Horned Owl is widespread through the region in a variety of habitats. Mammals of small to medium size predominate in their diet, but birds such as quail,

Figure 11.12
Western Screech-Owl.

woodpeckers, and passerines are also taken. To a lesser extent, the species may eat reptiles or amphibians, large insects (e.g., crickets, beetles), and carrion found along highways. Great Horned Owls are most active at night, but they can be seen abroad during the day under overcast conditions. However, most days are spent roosting in large pinyons, in other conifers or aspens, or in cavities in canyon walls. Stick nests abandoned by other raptors, either on cliff shelves or in trees, serve as the primary nesting sites. This species breeds in late winter or early spring. Toward the onset of the nesting season and during the breeding period, both sexes emit deep, resonant hoots. These hoots are deeper pitched in males despite their smaller size relative to females. Great Horned Owls are generally shy and difficult to approach, even at night. References: Burton (1973), Fitch (1947).

Long-eared Owl,Asio otus. (Plate 11.2) Male length 13 in (33.25 cm), female length 13 in (33.5 cm) male weight 8 5/8 oz (245 g), female weight 97/8 oz (279 g). Uncommon permanent resident throughout the White-Inyo region, occurring up to 9,500 ft (2,900 m).

Although in this region the Long-eared Owl favors dense pinyon forest, it also frequents stands of cottonwoods, tree willows, aspens, and Mountain Mahogany. At night, the owls hunt through woodland and along the edges of clearings in search of prey, which consists primarily of small mammals. These owls also feed occasionally on

Figure 11.13
Great Horned Owl.

small birds and, more rarely, on reptiles or amphibians. During the day, the species roosts in dense clumps of Singleleaf Pinyon, Mountain Mahogany, cottonwoods, or aspens. Long-eared Owls are generally solitary except during the winter, when they form loose roosting aggregations in riparian thickets in the foothills and lowlands. Breeding takes place in abandoned nests of other large birds, particularly Red-tailed Hawks, Common Ravens, and, in the lower valleys, Black-billed Magpies. The Long-eared Owl is shy and difficult to attract by means of imitated calls. References: Grinnell and Storer (1924), Marti (1976).

Northern Saw-whet Owl,Aegolius acadicus. (Fig. 11.14) Male length 7 in (17.75 cm), female length 7 1/2 in (18.75 cm); male weight 2 5/8 oz (75 g), female weight 3 1/4 oz (91 g). Uncommon resident in the White Mountains. Winter status is uncertain; at that time, individuals from other regions may augment the local population. Recorded up to approximately 9,000 ft (2,740 m).

This owl occurs in dense riparian thickets and on remote canyon slopes far from water. They forage at the edges of meadows or clearings, particularly among open

Figure 11.14
Northern Saw-whet Owl.

stands of small to medium-sized conifers. There, mice and an occasional bird are taken. Nest sites consist of abandoned woodpecker holes or natural cavities at medium heights in trees. During the day, individuals roost in the dense foliage of small trees, commonly within 10 ft (3.0 m) of the ground. Mated males call infrequently. In contrast, unmated Northern Saw-whet Owls call steadily in the late winter and spring. These calls carry up to 0.5 mi (0.8 km), and thus the owls can easily be detected. They are difficult to locate, however, because the steady whistles quaver in pitch and fade in and out in intensity. Once a Northern Saw-whet Owl is found, either during the day or at night, commonly it can be closely approached. Reference: Earhart and Johnson (1970).