PACIFIC YELLOWTHROAT 579 



scirpicola the dorsal plumage is greener (less grayish) ; the yellow of 

 the iinderparts extends farther over the abdomen and is, in a series 

 definitely brighter; the flanks are more brownish (less grayish) and 

 the post-frontal band of white in the males is wider." 



The range of the tule yellowthroat "extends along the Pacific slope 

 from about 30° in Lower California north to Santa Barbara, Cali- 

 fornia, the southern San Joaquin Valley and Walker Basin on the 

 south fork of the Kern Kiver. The Colorado River drainage colony 

 which is (apparently) isolated from that on the Pacific extends from 

 the mouth of the Colorado River north along that stream, and its 

 tributary the Virgin River, to Washington, Washington County, 

 Utah, west through the Imperial Valley to Mecca, Riverside County, 

 and east up the Gila and Santa Cruz rivers at least to Tucson, Ari- 

 zona." In California, according to Grinnell and Miller (1944), the 

 altitudes of occurrence are chiefly below 1,500 feet, but birds may 

 range up to 4,200 feet, as at Julian, San Diego County. 



The measurements of 40 eggs average 17.3 by 13.3 millimeters ; the 

 eggs showing the four extremes measure 18.9 by 12.5, 18.0 by 14.0, 

 and 16.0 by 12.5 millimeters. 



The ecology and nesting habits of the tule and western yellowthroats 

 are similar. 



GEOTHLYPIS TRICHAS ARIZELA Oberholser 



PACIFIC YELLOWTHROAT 



HABirS 



Some fifty years after it was originally described, the Pacific race 

 was oificially admitted to the A. O. U. Check-List as a recognizable 

 form. 



The original describer. Dr. Harry C. Oberholser (1899) gives a 

 detailed description of the type, an adult spring male from Fort 

 Steilacoom, Wash., and writes: "From occidentalis the present race 

 may be readily distinguished by its much narrower white frontal 

 band, and also by its appreciably smaller size; though the former 

 character is of course not available for determination of females and 

 young. It differs from trichas as does occidentalis.^ but in dimensions 

 not to so marked a degree. Intermediates between trichas and og- 

 cidentalis such as occur on the Great Plains, come sometimes rather 

 close to arizela^'' 



He gives for this form the following distribution: "Pacific coast 

 region from southern British Columbia to northern Lower California; 

 east to the Cascade Mountains and the west slope of the Sierra Nevada ; 

 south in winter to Cape St, Lucas and Tepic." 



