Endangered Species Recovery Program

San Joaquin Le Conte's thrasher
Toxostoma lecontei macmillanoura

Drawing by Wendy Stevens

Status

California Species of Special Concern (a former U.S.A. Candidate 2)

Life History

The Le Conte's thrasher is a plain gray or brown, medium-sized songbird with a long, dark tail and black down-curved bill. The adult Le Conte's thrasher has an unspotted breast, dark eyes, and pale undertail feathers. Of the other thrashers found in California, the California (Toxostoma redivivum) thrasher and crissal thrasher (T. crissale) are larger in size and darker in color than the Le Conte's thrasher.

The Le Conte's thrasher is a resident, non-migratory species and generally found in open desert scrub, alkali desert scrub, and desert succulent scrub. The San Joaquin Le Conte's thrasher (a distinct population not formally recognized yet as a subspecies) is found primarily in habitats dominated by common saltbush (Atriplex spp.), and areas of desert washes and flats with scattered bushes.

This species forages on the ground by digging 5-7.6 cm (2-3 inches) into the substrate. Their food consists primarily of arthropods, including scorpions, spiders, beetles, grasshoppers, and butterfly and moth larvae. Occasionally, they will feed on seeds, small lizards, or other small vertebrates.

The Le Conte's thrasher nests in tall, robust saltbushes that can support a nest approximately 66-71 cm (26-38 inches) above the ground. Their breeding season begins in late January and extends through early June; however, the pairs remain together year-round. During the breeding season a female thrasher may have up to 3 broods each with 2-4 eggs. The eggs are incubated for 14-20 days by both parents, and the young fledge 14-18 days after hatching.

Distribution

Historical distribution of the San Joaquin Le Conte's thrasher included the west side of the San Joaquin Valley, from the Panoche Mountains, Fresno County, south to Maricopa, Kern County. The current distribution of the San Joaquin Le Conte's thrasher is largely determined by the presence and structure of saltbush, extent of habitat fragmentation, and presence of competitors, which includes the California thrasher, sage thrasher, northern mockingbird, loggerhead shrike, and greater roadrunner. The existing populations are within a set of habitat islands with expansive distances of unsuitable habitat separating them. There are five known and one potentially existing population areas, each containing only unsuitable to fair habitat.

Degradation, fragmentation, and loss of habitat to agriculture, irrigation, urbanization, oil and gas development, fire, and over-grazing are the primary reasons for the decline of the San Joaquin Le Conte's thrasher.

Classification

Order PASSERIFORMES, Suborder OSCINES, Family MIMIDAE, Genus Toxostoma, Species lecontei

Subspecies

Only two subspecies of Le Conte's thrashers (Toxostoma lecontei) are recognized by the American Ornithologist Union: T. l. arenicola, the desert thrasher; and T. l. lecontei, the Le Conte's thrasher. Although the San Joaquin Valley population is apparently isolated from the other populations of Le Conte's thrasher, the San Joaquin Le Conte's thrasher (T. l. macmillanoura) has yet to be officially recognized.

Recent Synonyms

None.

Other Common Names

None.

References

Laudenslayer, W.F., Jr., A.S. England, S. Fitton, and L. Saslaw. 1992. The Toxostoma thrashers of California: species at risk? Trans. West. Sec. Wildl. Soc. 28:22-29.; Phillips, A.R. 1965. Notas sistematicas sobre aves Mexicanus, III. Revista de la Sociedad Mexicana Historia Natural 25:217-242.; Sheppard, J.M. 1970. A study of the Le Conte's thrasher. California Birds 1:85-94.; Sheppard, J.M. 1973. An initial study of the Le Conte's thrasher (Toxostoma lecontei). M.A. thesis, Calif. State Univ., Long Beach, 134pp.

Size

Total length:
24.0-28.0 cm (9.4-11 inches) for both sexes
Weight:
54.5-75.5 g (1.9-2.6 ounces)
Bill length:
~2.7 cm (~1 inch)
Tail length:
~12 cm (~4.7 inches)

Identification

The San Joaquin Valley population is described as having a slightly darker head than back, with lighter sides, flanks, and breast than the desert population of Le Conte's thrasher. Analysis of measurements between the three "subspecies" indicated no significant difference.

Authors of Profile

N. L. Brown