THE TOXOSTOMA THRASHERS OF CALIFORNIA: SPECIES AT RISK?

Abstract

Four of the 10 described species of Toxostoma thrasher breed in California-California thrasher (T. redivivum), Bendire's thrasher (T. bendirei), Crissal thrasher (T. crissale), and Le Conte's thrasher (T. fecontei). Urbanization, agricultural development, fire management, and livestock grazing are among the land uses that affect large tracts of the habitats occupied by these species. Other uses generally impact smaller areas. None of these species are likely to be eliminated from the California avifauna in the forseeable fiture. However, they are potentially susceptible, in varying degrees, to localized extirpations because (1) they occur at low densities, (2) portions of their ranges are Eragmented, and (3) only the Bendire's thrasher is known to regularly move long distances. Thus, in addition to direct habitat loss and degredation, California, Crissal, and Le Conte's thrashers may be susceptible to population declines following habitat fragmentation. Similarly, other species, subspecies, and populations of the California breeding avifauna with similar life history traits could suffer comparable declines. This potential is especially high among the numerous tam of nonmigratory shrubland birds. Shrubdwelling species have generally been overlooked by wildlife biologists and land managers. A systematic review, survey, and monitoring of the California avifauna is needed to identify taxa and populations that may become threatened.

Citation

LAUDENSLAYER, WILLIAM F.; ENGLAND, A. SIDNEY; FITTON, SAM; SASLAW, LARRY. 1992. THE TOXOSTOMA THRASHERS OF CALIFORNIA: SPECIES AT RISK?. 1992 TRANSACTIONS OF THE WESTERN''SEGTION OF THE WILDLIFE SOCIETY 28:22-29