The Olive-sided Flycatcher 
No. 177 
Olive-sided Flycatcher 
A. 0. U. No. 459. Nuttallornis borealis (Swainson). 
Description.— Adult: Upperparts brownish slate with a just perceptible tinge 
of olivaceous on back; top of head a deeper shade, and without olivaceous; wings and 
tail dusky blackish, the former with some brownish gray edging only on tertials; flank- 
tufts of fluffy, yellowish or white feathers, sometimes spreading across rump and in 
marked contrast to it, but usually concealed by wings; throat, belly, and crissum, and 
sometimes middle line of breast, white or yellowish white (naphthaline yellow on belly); 
heavily shaded on sides and sometimes across breast with brownish gray or olive- 
brown—the feathers with darker shaft-streaks. Bill black above, pale yellow below; 
feet black. Immature: Similar to adult, but coloration a little brighter; wing-coverts 
fulvous or buffy. Length about 177.8 (7.00); wing 105.7 (4.16); tail 70 (2.756); bill 
17 (.67); tarsus 15 (.59). 
Recognition Marks.— Sparrow size; heavily shaded sides; bill yellow below; 
tew-tew note; keeps largely to summits of conifers. 
Nesting. — Nest: A rather shallow cup of twigs, bark-strips, and, rarely, 
grasses—or moss (northerly); lined with coarse rootlets (or, exceptionally, with moss 
and fine grass), settled upon horizontal spreading branch of conifer or other tree, often 
at great heights. Eggs: 3, very rarely 4; creamy white, cartridge buff, or pale pinkish 
buff; handsomely and rather sparingly spotted, chiefly in wreath about larger end, 
with chocolate, walnut-brown, pecan-brown (exceptionally sayal brown), and vinaceous 
gray. Av. of 22 eggs in the M. C. O. coll.: 22 x 16 (.866 x .63); index 72; range 20- 
24.1 by 14.5-17 (.79-.95 by .57 x .67). Season: June 1-15; one brood. 
General Range.— North and South America; breeds in Transition and Canadian 
zones from central Alaska and southern Mackenzie east to central Quebec and Cape 
Breton Island, south in the coniferous forests of the West to southern California, 
Arizona, and Texas; and in the East south in the mountains to North Carolina; passes 
through Mexico and Central America in migrations; and winters in northwestern 
South America to Peru. 
Distribution in California.— Common summer resident in Transition and 
Canadian zones, practically throughout the State, save in the eastern desert ranges, 
south to Cuyamaca Mountains and Santa Barbara. Near Carpinteria breeds almost 
to sea-level in pure Upper Sonoran, non-coniferous associations. In humid coastal 
strip breeds down to sea-level from Monterey County north. Of wide occurrence 
during migrations. 
Migrations.— Spring arrivals: Santa Barbara, May 6, 1911; May 7, 1912; 
Apr. 29, 1913; Apr. 29, 1914; Apr. 29, 1919; May 3, 1920. 
Authorities.—Gambel ( Tyrannus borealis ), Proc. Acad. Nat. Sci. Phila., vol. 
iii., 1847, p. 157 (Monterey )\ Bendire, Life Hist. N. Am. Birds, vol. ii., 1895, p. 282, 
pi. 2, figs. 15, 16 (eggs); Grinnell, Univ. Calif. Pub. Zool., vol. v., 1908, p. 76 (San 
Bernardino Mts.; habits, desc. nest and eggs); Beal , U. S. Dept. Agric., Biol. Surv. 
Bull., no. 44, 1912, p. 41 (food); Dixon , Condor, vol. xxii., 1920, p. 200, figs. (desc. 
nest, eggs, taken at Berkeley); Bangs a 7 id Penard, Proc. Biol. Soc. Wash., vol. xxxiv., 
1921, p. 90 ( Nuttallornis borealis majorinus, new subsp.; type locality, Pine Flats, 
Los Angeles Co.). 
