60 



BIRDS OF ILLINOIS. 



Turdus ustulatus swainsonii (lab.) 



OLIVE-BACKED THEUSH. 



Popular synonyms. Swainson's Thrush; Swamp Bobln (New England). 



Turdus swainsonii CABAN. Faun. Per. 1815-46. 187. BAIBD, B. N. Am. 1858. 216; Cat. N. 



Am. B. 1859. No. 153; Review, 1864, 19. COUES, Key, 1872, 72: Check List, 1872. No. 5; 



B. N. W. 1874, 4; B. Col. Yal. 1878. 34.-B. B. & R., Hist. N. Am. B. i. 1874, 14. pi. i. flg. 4. 

 Bylocichla ustulata swainsoni RIDGW. Proc. U. 8. Nat. Mus. iii., 1880. 166; Nom. N. Am. 



B. 1881. No. 4a. 

 Turdus ustulatus swainsoni COUES, 2d Key, 1884,248. 



HAB. Eastern North America, including the Rocky Mountain district, west to the 

 border of the Great Basin; breeding in the British Provinces and far southward in 

 the Rocky Mountains; wintering in southern Union States,* Central America and 

 various parts of South America (Ecuador, Peru, Brazil, etc.). 



SP. CH. Adult. Above uniform olive-brown, more grayish in some examples; 

 a very distinct orbital ring of buff; supraloral stripe, malar region, chin, throat, and jug- 

 ulum, light buff, usually deepest toward sides of head and neck. Jugulum thickly marked 

 with very broad triangular spots of dusky brown (much darker than the color of the 

 crown), these markings more cuneate anteriorly, and continued along sides of the throat 

 in a series of longitudinal dashes, usually blended into a more or less continuous sub- 

 malar stripe, narrower and unbroken anteriorly; chin and upper part of throat immacu- 

 late; sides of breast, sides, and flanks, olivaceous-gray; rest of lower parts pure white; 

 breast marked with distinct transverse spots of deep brownish gray; tibiae light brownish 

 gray. Axillars and lining of wing deep grayish fulvous, mixed with ochraceous. Bill 

 dusky, basal half of mandible pale (dull flesh-color in life); interior of mouth rich yellow 

 (in life); iris dark brown; tarsi and toes palebrownisb, thelatter darker. Length, 7. 7.50; 

 extent of wings, 11.50 12.25; wing. 3.80-4 10 (3.96); tail 2.80 3.10 (2.95): culmen, .50 .55 

 (.52); tarsus, 1.051.18 (1.10); middle toe, .65 .72 (.69).t 



"First plumage: Male. Above much darker than adult, each feather, excepting on 

 rump and tail-coverts, with a tear-shaped spot of rich buff; beneath like adult, but rather 

 more darkly and thickly spotted on the breast, and with narrow terminal bands of dull 

 black on the feathers of the lower breast and sides. From a specimen in my collection 

 shot at Upton, Me.. August 4, 1874." (BBKWSTEB, Bull. Nutt. Orn. Club. Jan.. 1878. p. 18.) 



Among a large series of specimens there is much variation in the 

 precise shade of color of the upper parts, some being much grayer 

 than others. As a rule, examples from the Kocky Mountains are 

 appreciably grayer than those from the East, and in the case of 

 two or three the difference is very decided ; but after a careful com- 

 parison I find that that the difference is not sufficiently constant to 

 warrant varietal distinction, especially since the measurements of 

 the two series coincide very closely. I 



* The only record the author has seen is that of Mr. W. W. Cooke, in the Ornithologist 

 and Oologist, for December, 1883, p. 89, to the effect that this species has been found win- 

 tering in the Mississippi bottom, Illinois. 



t Extreme and average measurements of 14 examples. 



t A series including 5 males and 2 females from the Eastern States and Rocky Moun- 

 tains average as follows: 



