eWestern BirdsThe Quarterly Journal of Western Field Ornithologists
Vol. 43, No. 3
Western Field Ornithologists
A Population Census of the Cactus Wren in Coastal Los Angeles County
Daniel S. Cooper, Robert A. Hamilton,and Shannon D. Lucas
ABSTRACT: The Cactus Wren (Campylorhynchus brunneicapillus) is a polytypic species widespread in the southwestern U.S. and northern Mexico. Though closer in plumage characteristics to the desert subspecies anthonyi, populations resident in coastal sage scrub and alluvial fan scrub on the coastal slope of Los Angeles County occupy an ecological niche more similar to that of the more southerly subspecies sandiegensis. Because of fragmentation of habitat associated with urbanization, the populations on southern California’s coastal slope are almost entirely isolated from those of the deserts, and apparently from each other. They are declining precipitously for reasons not entirely understood but certainly related to loss, fragmentation, and degradation of suitable habitat. In 2009, we organized a volunteer effort to map the entire population on the coastal slope of Los Angeles County and found 155 active, accessible territories. With the addition of scattered groups believed to occupy inaccessible areas, our maximum estimate for the county is around 200 pairs, most of them in the eastern San Gabriel Valley. We also document the loss of several historical populations in the area and present a revised distribution map for the Los Angeles area indicating connectivity among extant populations.