This is the palest of all the yellow warblers, one of the many pale races of the southwestern desert regions. Its breeding range extends from southeastern California, southern Utah, Arizona, and New Mexico to central western Texas, Sonora, and Chihuahua; and it winters from Mexico southward to Guatemala, Nicaragua, and Costa Rica. It is best described by Ridgway (1902) as "similar to _D. æ. æstiva_, but much paler; adult male lighter and much more yellowish olive-green above, the back frequently (usually?) streaked with chestnut, pileum usually wholly clear yellow, lower rump and upper tail-coverts yellow, faintly streaked with olive-greenish; wing edgings all yellow; under parts lighter yellow than in _D. æ. æstiva_, and with chest and sides much more narrowly (often faintly) streaked with chestnut; adult female conspicuously paler than in _D. æ. aestiva_, the upper parts often largely pale grayish, the under parts usually very pale buffy yellow." Woodbury, Cottam, and Sugden (MS.) say of its status in southern Utah: "This race of yellow warbler is a breeder of the streamside fringes of willows, tamarix, and brush of various kinds along the San Juan and lower Colorado Rivers. It undoubtedly extends up the Colorado above the mouth of the San Juan, but how far it extends before yielding to _morcomi_ has not been determined. Data available are not sufficient to determine its nesting or migration dates or the length of its stay in Utah." Swarth (1914) calls it "a common summer visitant in southern and western Arizona, apparently confined almost entirely to the Lower Sonoran river valleys, the Colorado and the Gila, with their tributaries. * * * I know of no breeding record of a yellow warbler from any point in Arizona north of the Mogollon Divide." Mrs. Bailey (1928) says that "the lower Rio Grande in New Mexico apparently marks the most northern extension of the range of the Sonora Yellow Warbler. It is a common breeder at Mesilla," which is in the southwestern part of the State. We found the Sonora yellow warbler breeding commonly in the San Pedro Valley, near Fairbank, Ariz., and found several nests in a row of willows along an irrigation ditch. The nests, from 12 to 15 feet above the ground in slender trees, were not very different from those of the eastern bird, being made mainly of willow cotton interwoven with fine strips of inner bark, fine grasses, and plant fibers. The eggs do not differ greatly from those of the species elsewhere, though what few I have seen are more faintly and finely speckled. The measurements of 40 eggs average 16.9 by 12.8 millimeters; the eggs showing the four extremes measure =18.4= by 13.1, 17.0 by =13.6=, =14.9= by 12.5, and 17.8 by =11.4= millimeters (Harris). DENDROICA PETECHIA GUNDLACHI Baird CUBAN YELLOW WARBLER HABITS