eWestern Birds

Status of the California Gnatcatcher at the Northern Edge of Its Range

Daniel S. Cooper, Jennifer Mongolo, and Chris Dellith

ABSTRACT: At the northern edge of its range, the California Gnatcatcher has long been known to occur from eastern Ventura County east into northwestern Los Angeles County, but the current status of birds in these areas is not well understood. We review historical and recent sources of information and draw two main conclusions: first, that the California Gnatcatcher population that once existed from the lower Santa Clara River Valley in Ventura County east/upstream to Santa Paula and Simi Valley has likely contracted to the southeast. Second, that the current, consistent range of the species in Los Angeles County does not extend north of the San Gabriel Valley. The California Gnatcatcher is evidently extirpated from the San Fernando Valley and never occurred regularly in the Santa Clarita area to the northwest. Dispersing and even occasionally nesting birds in northwestern Los Angeles County have not resulted in a stable, consistent population there. Misinterpretation of seasonal movements and isolated sightings of the California Gnatcatcher here may have led to a misunderstanding of the boundaries of its normal range, as well as the misapplication of critical habitat as defined under the Endangered Species Act. As a result, we recommend that immediate conservation efforts be focused in areas where birds are conclusively known to occur, namely, the Thousand Oaks/Moorpark area of Ventura County, and that coastal sage scrub at low elevations in the Santa Clarita and especially the northeastern San Fernando Valley areas of Los Angeles County be systematically searched to locate any remaining populations.

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