Mountain Bluebird (Sialia currucoides)
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 and Pastures.
SPECIES LIFE HISTORY
Activity Patterns: Yearlong, diurnal activity.
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, Harrison 1978).
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. Condor 72:182-189.
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. 408pp.
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 50:216-219.
Harrison, C. 1978. A field guide to the nests, eggs and nestlings of north American birds. W. Collins Sons and Co., Cleveland, OH. 416pp.
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. Condor 77:213-214.
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. 452pp.
Munro, J. A. 1940. Food of the sharp-shinned hawk. Condor 42:168-169. 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. 405pp. Salt, G. W. 1957. An analysis of avifaunas in the Teton Mountains and Jackson Hole,
Wyoming. Condor 59:373-393.