264 BULLETIN 19 7, UNITED STATES NATIONAL MUSEUM 



and hindneck, the sides and flanks faintly washed with more grayish 

 olive-yellow; tail and tarsus decidedly longer. Young with under 

 parts pure white, the sides, flanks and under tail-coverts tinged with 

 pale sulphur or primrose yellow ; pileum and hindneck light pinkish 

 gray, approaching ecru drab ; back and scapulars vinaceous-drab," 



Dr. Joseph Grinnell (1914) met with the Arizona vireo at all sta- 

 tions all the way down the Colorado River, it "being one of the most 

 characteristic avifaunal elements in the riparian strip". He says 

 further : 



The bird foraged in all of the component associations, but was perhaps best 

 represented in the willow association, especially where there was an under- 

 growth of guatemote (Baccharis glutinosa). 



On the Arizona side above Bill Williams River, March 14, I was able to make 

 some observations on local distribution. Here the willow association was nai'row 

 but well defined, and the vireos were closely confined to it. A singing male oc- 

 cupied each segment of about 200 yards in this belt, just about the same spacing 

 as the Lucy warbler in the adjacent mesquite belt. Each pair of vireos was 

 closely delimited in the forage beat by that of its neighbor. 



Each pair in its own area actively resented encroachment by others of its own 

 species. The vireos worked a rather low zone of foliage, from the ground up to 

 a height of six or eight feet. 



In Arizona, in 1922, we found this vireo only at the lower levels, 

 in the valley of the San Pedro Eiver, where it frequented the narrow 

 strips of willows, small cottonwoods, and underbrush along the irri- 

 gation ditches, and in the extensive mesquite forest near Tucson. 

 In the former locality the willow association was full of birds, road- 

 runners, Abert's towhees, Sonora yellow warblers, desert song spar- 

 rows, and Sonora redwings. 



W. E. D. Scott (1888), however, found them "breeding throughout 

 the region up to an altitude of 4000 feet. In the Catalinas they 

 arrive about the 25th of March and by April are common. They 

 are apparently mated on arrival, and at once proceed to build nests 

 and lay eggs. Two broods are generally raised and three eggs are 

 commonly found to form the brood. They leave the Catalinas early, 

 by September 5, but are to be found on the plains about Tucson much 

 later." 



Nesting. — The only nest of the Arizona vireo that I collected was 

 taken on May 27, 1922, near Fairbank, in the San Pedro Valley. It 

 was suspended 8 feet from the ground between two twigs and close 

 to the stem of a slender willow near one of the irrigation ditches. 

 The nest, now before me, is a typical vireo basket, none too firmly 

 attached to the two twigs and made of various vegetable fibers, con- 

 spicuous among them being split shreds of sacaton and Johnson 

 grasses, which grew in profusion in the surrounding fields; mixed 

 with these are strips of soft inner bark, finer grasses, bits of willow 

 cotton, plant down, pappus, spider nests, etc., and considerable cattle 



