DISTRIBUTION, ABUNDANCE, AND SEASONALITY

Common, permanent breeding and winter resident and migrant. Breeds throughout California, and winters in all areas without heavy snow cover. Found in almost all habitats, from lowest to highest elevations.

SPECIFIC HABITAT REQUIREMENTS

Feeding: Eats small mammals up to hares in size, small birds, reptiles, amphibians, and some carrion (Orians and Kuhlman 1956). In winter, largely dependent upon mice, but also takes medium to fairly large birds on the ground. Catches small birds during migration. Searches by soaring; also perches and pounces, or pounces on prey from low, quartering flights, sometimes hovering on wind or air currents.

Cover: Feeds in grasslands and grass/shrub stages of most habitats. Roosts in trees; sometimes in dense conifer stands.

Reproduction: Usually nests in large trees near openings, in older, mature forests, especially riparian deciduous habitats. Occasionally nests on cliffs or low ledges. Nests 9-21 m (30-70 ft) above ground in trees, higher on cliffs. Flexible in choice of nest site; occasionally uses human-made structures, shrubs, cacti. Sometimes nests in isolated trees, or in small groves in open habitat.

Water: Requirements probably met from food.

Pattern: Highly adaptable; uses grasslands, open brush habitats, and open stands of deciduous and conifer forests. Also frequents croplands, fields, and pastures.

SPECIES LIFE HISTORY

Activity Patterns: Yearlong, diurnal activity. Most active feeding occurs in early morning and late afternoon.

Seasonal Movements/Migration: Migrates downslope in winter; in summer and fall, some individuals move to open areas at higher elevations.

Home Range: Home ranges vary from less than 1 to 10 km˛ (0.3 to 3.8 mi˛), depending on location, topography, habitat, and prey availability.

Territory: In California, Fitch et al. (1946) calculated that territories varied from 0.3 to 0.8 km˛ (0.1 to 0.3 mi˛). They found 0.8 breeding pairs/km˛ (2/mi˛). Territory defended yearlong.

Reproduction: Courtship begins as early as January. Breeds March through July; peaking in May and June. Clutch of 2-5 eggs, usually 2-3, laid in March and April. Incubates 28-32 days. Semialtricial young fledge in 40-45 days.

Niche: Adaptable, common, and widespread. Scrub jays, and other avian and mammalian predators, take undefended eggs and nestlings (Brown and Amadon 1968). May compete for food with ferruginous, Swainson's, and rough-legged hawks. Great horned owls commonly use old nests, and occasionally golden eagles do. Nestlings may be killed by blood-sucking flies (Fitch et al. 1946). Golden eagles may prey on adult.