Endemic Birds of the Little San Bernardino Mountains, California

Abstract

The Little San Bernardino Mountains which bound the Coachella Valley of California to the northeastward attain heights of somewhat over 5000 feet. Barren in aspect on their southern face, they nonetheless support along their crests and on their northern slopes large tracts of pifion-juniper woodland and open chaparral growth of scrub oak, mountain mahogany, and manzanita. These plant associations mark an Upper Sonoran belt which extends 40 miles southeastward from Morongo Pass. A small area of woodland and chaparral occurs still farther eastward on Eagle Mountain, separated by a gap of at least 20 miles from the area in the Little San Bernardino Mountains. Northwardly the woodland occurs scatteringly over a plateau, which is the heart of the Joshua Tree National Monument, to the mountains immediately south and west of Twentynine Palms, San Bernardino County. The Upper Sonoran area lies between the Colorado and Mohave deserts and adjoins similar areas of coastal southern California only to the westward where, at the eastern flank of the great San Bernardino Mountain mass, there is a narrow connection across Morongo Pass with the chaparral and woodlands of western Riverside and San Bernardino counties. This peninsula of the Upper Sonoran Zone, seemingly because of its constricted base, its length, and the arid, open aspect of its plant growth influenced by desert climate and surrounding desert lowlands, has developed and conserved in partial isolation distinctive races of some permanently resident types of birds. Their degree of distinctness is surprisingly great in view of the imperfect westward barrier to the transfer of individuals between coastal populations and those of the Little San Bernardino Mountains. Three endemic forms, a Mountain Quail, a Plain Titmouse, and a Bush-tit, are herewith described. Further details of their ranges will doubtless be forthcoming as additional biological exploration in the area is conducted. I am indebted to the National Park Service, and particularly to Mr. James Cole, Custodian of Joshua Tree National Monument, for the opportunity to investigate the vertebrate fauna of the Monument area which embraces the ranges of these new subspecies.