The Cassin Kingbird in San Joaquin County, California
The Cassin Kingbird in San Joaquin County, California
A slight northward extension of the known summer range of the Cassin Kingbird (Tyrannus vociferans) in California is involved in the occurrence of a pair of these birds on July 15, 1937, in Lonetree Canyon, 9 miles south of Tracy, San Joaquin County. A large company of Western Kingbirds (Tyrannus verticalis) was found about a group of eucalyptus trees and tobacco bushes near the mouth of the canyon on this date. In the same grove, but not mixing intimately with the Westerns, were the Cassin Kingbirds. They were at once recognizable by their distinctive notes. Mr. Ernest I. Dyer and I verified plumage characters by repeated observation.
Dawson (Condor, vol. 18, 1916, p. 27) reported Cassin Kingbirds from western Merced County, and similar records are known from San Benito and Santa Cruz counties. It is not unexpeqted that the species should extend northward along the arid coast ranges on the west side of the San Joaquin Valley to the point indicated by the present record. In my experience the species is by no means restricted to the Lower Sonoran Zone, and in Arizona it is principally of Upper Sonoran occurrence. Yet it seems to belong to that considerable aggregation of distinctly austral species which reach their northern limits of tolerance at about this point in the coast region.
Alden H. Miller
Museum of Vertebrate Zoology, Berkeley, California, August 29, 1937
