Written by: D. Gaines
Reviewed by: L. Mewaldt
Edited by: R. Duke
DISTRIBUTION, ABUNDANCE, AND SEASONALITY
A fairly common to common summer resident in
sparse to open forests and other open
habitats from about 1200-3700 m (4000-12,000 ft) in mountains and foothills
of the state.
Most individuals winter below 1500 m (5000 ft), withdrawing from higher,
snowy portions of
breeding range. Locally fairly common to abundant in Central
Valley and surrounding
foothills, in agricultural areas of Owens Valley, Inyo Co., Antelope
Valley, Kern and Los
Angeles cos., and in arid valleys of inner Coast Ranges, as on Carrizo
Plain, San Luis Obispo
Co. Less numerous and occurrence more erratic elsewhere in interior
lowlands of state.
Some years also winters locally throughout Mojave Desert, on coastal
plains of southern
California, and on Channel Islands (Grinnell and Miller 1944, Garrett
and Dunn 1981).
SPECIFIC HABITAT REQUIREMENTS
Feeding: From a low, exposed perch, hovers
and stoops on insects on foliage or ground,
and hawks flying insects. Also eats berries and other small fruits,
especially in winter (Martin
et al. 1961, Power 1966).
Cover: Prefers open terrain with an occasional
tree, rock, fence post, power line, building,
for foraging perch and other cover. Requires suitable cavities
for roosting and nesting,
usually in a snag or dead portion of tree.
Reproduction: Nest of herbaceous stems,
rootlets, grasses, outer bark of shrub placed in
natural cavity or woodpecker hole in snag or dead portion of tree.
Less frequently nests in
crevice or cavity in rock, buiIding or other human structure; also
uses nest box or nest of cliff
swallow or other species (Bent 1949).
Water: No information found. Miller
and Stebbins (1964) suggested that insect food
provided adequate moisture in California deserts.
Pattern: Breeders most numerous where
meadows, grasslands, or other open habitats
edge on woodland or rock formations affording suitable nesting sites.
In winter, occurs in
virtually any open or sparsely wooded habitat, but shows a preference
for agricultural fields
SPECIES LIFE HISTORY
Activity Patterns: Yearlong, diurnal
Seasonal Movements/Migration: Breeders
return to higher portions of nesting range
March to June, depending on elevation and snow conditions, and depart
by October or
November. Usually arrives on wintering areas in November and
departs by March.
Home Range: Estimates of breeding density
include 30 per 40 ha (100 ac) in Wyoming
aspen forest (Salt 1957), 15-18 per 40 ha in Wyoming (Finzel 1964),
and 15.2 pairs per 40 ha
in Sierra Nevada conifer forest (Bock and Lynch 1970).
Territory: Power (1966) found territory
boundary difficult to determine; inferred that 4
territories averaged 4.3 ha each (10.6 ac), range 1.8-6.8 ha (4.5-16.7
ac). These estimates
were minima; some territories "had no clear boundaries at all."
Territory apparently centered
on nest and included suitable flycatching perches and a large area
of open space. At Mt.
Rainier, Washington, Jewett et al. (1953) reported that a nesting female
foraged over about
2.6 ha (6.5 ac).
Reproduction: Monogamous; lays eggs mid-April
to mid-July, depending on elevation.
May be double or triple-brooded. Clutch 5-6 eggs. Incubation
13-14 days by both sexes, and
both sexes care for altricial young. Fledging age 22-23 days
(Bent 1949, Power 1966,
Niche: Tree swallow, house wren, mountain
chickadee, European starling, northern flicker
and other woodpeckers, and rodents compete for nest sites. Predators
include prairie falcon
and sharp-shinned hawk (Munro 1940, Marti and Braun 1975). Numbers
have declined in
recent decades (Ehrlich et al. 1988).
Bent, A. C. 1949. Life histories of North American thrushes,
kinglets, and their allies. U.S.
Natl. Mus. Bull. 196. 454pp.
Bock, C. E., and J. F. Lynch. 1970. Breeding bird populations
of burned and unburned
conifer forests in the Sierra Nevada.
Ehrlich, P. R., D. S. Dobkin, and D. Wheye. 1988. The birder's
handbook. Simon and
Schuster, New York. 785pp.
Finzel, J. E. 1964. Avian populations of four herbaceous
communities in southeastern
Wyoming. Condor 66:496-510.
Garrett, K., and J. Dunn. 1981. Birds of southern California.
Los Angeles Audubon Soc.
Grinnell, J., and A. H. Miller. 1944. The distribution
of the birds of California. Pac. Coast
Avifauna No. 27. 608pp.
Haecker, F. W. 1948. A nesting study of the mountain bluebird
in Wyoming. Condor 50:216-
Harrison, C. 1978. A field guide to the nests, eggs and
nestlings of north American birds. W.
Collins Sons and Co., Cleveland, OH.
Jewett, S. G., W. P. Taylor, W. T. Shaw, and J. W. Aldrich. 1953.
Birds of Washington State.
Univ. Washington Press, Seattle. 767pp.
Marti, C. D., and C. E. Braun. 1975. Use of tundra habitats
by prairie falcons in Colorado.
Martin, A. C., H. S. Zim, and A. L. Nelson. 1961. American
wildlife and plants, a guide to
wildlife food habits. Dover Publ., Inc.,
New York. 500pp.
Miller, A. H., and R. C. Stebbins. 1964. The lives of desert
animals in Joshua Tree National
Monument. Univ. California Press, Berkeley.
Munro, J. A. 1940. Food of the sharp-shinned hawk. Condor
Power, H. W., III. 1966. Biology of the mountain bluebird
in Montana. Condor 68:351-371.
Power, H. W., III. 1974. The mountain bluebird: sex
and the evolution of foraging behavior.
Ph.D. Thesis, Univ. Michigan, Ann Arbor.
Salt, G. W. 1957. An analysis of avifaunas in the Teton
Mountains and Jackson Hole,
Wyoming. Condor 59:373-393.
Compiled from information from California Department of Fish and Game - California Interagency Wildlife Task Group