ELEVATIONAL DISTRIBUTION OF CALIFORNIA GNATCATCHERS IN THE UNITED-STATES

Known occurrences of California Gnatcatchers (Polioptila californica) in the United States were mapped relative to the 250-m, 500-m and 750-m elevation contours of southern California. Of 324 sites where this seriously threatened species was recorded from 1960 to 1990, 84% were located below 250 m elevation, and 97% occurred below 500 m. A total of 69 historic (pre-1960) sites showed a similar elevational pattern. These results indicate that previous estimates of the range of the northern, nominate subspecies were probably excessive, and that protection of coastal sage scrub habitat located above 250 m (in regions within 35 km of the coast) or 500 m (inland regions) may not significantly contribute to California Gnatcatcher conservation efforts. Furthermore, using the 250-m and 500-m elevation contours as approximate indices of the potential extent of the species' range in northwestern Baja California, approximately 65-70% of the historic distribution of P. c. californica may have been located in the United States.