This western form of our well-known eastern Nashville warbler, often called the Calaveras warbler, was discovered by Robert Ridgway in the East Humboldt Mountains, Nev., on September 6, 1868, and given the subspecific name _gutturalis_. He (1902) describes it as similar to the eastern bird, "but olive-green of rump and upper tail-coverts brighter, more yellowish, yellow of under parts brighter, lower abdomen more extensively whitish, and greater wing-coverts lighter, more yellowish olive-green." He gives as its range: "Western United States, breeding on high mountains, from the Sierra Nevada (Calaveras Co., California) to British Columbia (Vernon, Nelson, Okanogan district, etc.), eastward to eastern Oregon (Fort Klamath), northern Idaho (Fort Sherman), etc.; southward during migration to extremity of Lower California, and over western and northern Mexico, and southeastward to Texas (San Antonio; Tom Green County; Concho County)." The 1931 A. O. U. Check-List says that this form winters "in Mexico south to Puebla, Oaxaca, Guerrero, Jalisco, and Colima." Dr. Walter K. Fisher wrote to Dr. Chapman (1907): "The Calaveras Warbler is a characteristic denizen of the chaparral and is found on both slopes of the Sierra Nevadas about as far south as Mt. Whitney. It frequents the belts of the yellow, sugar, and Jeffrey pines, and ranges up into the red fir zone. During the height of the nesting season one may see them flitting about among thickets of manzanita, wild cherry, huckleberry, oak and buck brush, almost always in song; and while the female is assiduously hunting among the dense cover of bushes, the male is often singing in a pine or fir, far above mundane cares. * * * I have observed this Warbler at lower altitudes on the west slope among small black oaks, in company with Hermit Warblers." Dr. Wilfred H. Osgood (1896) first saw it in the Sierras at 3,500 feet elevation, but more commonly at 3,700 feet. "At 5,000 feet we found them most common, and from 7,000 to 9,000 feet they gradually disappeared, apparently going as high up as the black oak, in which trees they were generally seen, skipping about in search of insects." Grinnell and Storer (1924) say: "The Calaveras Warbler is common during the summer months in the black oaks and maples along each side of the Yosemite Valley and in similar situations elsewhere on the western flank of the Sierra Nevada. Among all the warblers to be seen in the Yosemite Valley during the summer months the present species is the only one which does not forage and nest in the same niche. The Calaveras seeks its food and does its singing well up in trees, but places its nest immediately upon the ground." C. W. and J. H. Bowles (1906) write of its haunts in Washington: