The Russet-backed Thrushes 
extensively white, with lighter, more creamy-buffy, wash on breast and sides. Size of 
last, save for wing, which averages mm 3 longer. 
Recognition Marks. —As in preceding; grayer above, lighter buffy below. 
Nesting. — Nest and Eggs indistinguishable from those of typical form, H. u. 
ustulata. 
Range of H. u. swainsoni. —North and South America. Widely distributed 
during migrations save along Pacific coastal strip. Breeds chiefly north of the United 
States nearly to the limit of trees, from northwestern Alaska to Newfoundland; south 
in the mountains of the West to east-central California and Colorado; and in the East 
to Pennsylvania and West Virginia. Winters from southern Mexico through South 
America to Argentina. 
Distribution in California. —Sparingly resident in summer in the mountains 
of the northeastern plateau section, and along the east slopes of the Sierra Nevada, at 
least to Mono Lake (June 6, 1919) and Mammoth Camp (June 11-July 5, 1919). 
Authorities.—Belding ( Turd/us ustulatus swainsonii ), Proc. Calif. Acad. Sci., 
ser. 2, ii., 1889, p. 60 (biog., song, etc.); Fisher, N. Am. Fauna, no. 7, 1893, p. 145 
(Panamint Mts.); Grinnell, Pac. Coast Avifauna, no. 11, 1915, p. 170 (status in Calif.); 
Swarth, Univ. Calif. Pub. Zool., vol. xxiv., 1922, p. 301 (life hist., desc. nest and eggs, 
etc.; n. British Columbia). 
THE MORE OPEN WOODS and more abundant suns of the interior 
districts effect that reduction of color in the “burnt” Thrush, which 
henceforth characterizes the species clear through to the Atlantic. It 
would be idle to trace in detail all accompanying changes of manner and 
habit, but we can hardly fail to note the improved quality of the Olive- 
back’s song. This is most nearly comparable to that of the Wilson 
Thrush, and has something of the same rolling, vibrant quality. It is, 
however, less prolonged and less vehement. It may or may not retain 
the liquid l’s, but it discards outright the rich r’s which the Veery rolls 
under his tongue like sweet morsels; and the pitch of the whole rises 
slightly, perhaps a musical third, as the volume of sound diminishes 
toward the end: We-e-o, we-e-o, we-o, we-o, weee. 
The Olive-backed Thrush was recorded first by the M. V. Z. party 
of 1911, from the Warner Mountains, where I, also, found them breeding 
in the summer of 1912. Whether or not this race overlaps ustulata in its 
distribution further west, has not been determined, but even if it did so, 
it would probably be found that the two forms are maintaining their 
distinctness, as they are known to do elsewhere. Indeed, it is not even 
certain that ustulata and swainsoni, although resembling each other so 
closely, do really occupy a conspeciffc relation. Perhaps the two groups 
were separated, and so differentiated, during the Ice Age, and have not 
reunited within the brief time since elapsed. 
