DISTRIBUTION OF AUUUISOM's THRUSH 29 



larity which some observers, recounting the impressions they 

 received from various transient circumstances of observation, 

 have sought to establish. For all reasonable purposes of biog- 

 raphy, the several races of the Hermit Thrush may be treated 

 as one, as I shall do on the present occasion, saving some par- 

 ticulars of their geographical distribution. Audubon's variety, 

 or the Rocky Mountain Hermit, is specialized in this respect, 

 having an exceptional distribution, both during the breeding- 

 season and at other periods of the year — its special habitat, 

 which subjects it to climatic influences equally peculiar, being 

 beyond doubt the cause of the slight modifications of physical 

 characters it has undergone. Audubon's Thrush haunts the 

 wooded mountainous regions of the West, especially in the 

 area known as the Middle Faunal Province. It has not, to my 

 knowledge, been traced farther north than Fort Bridger, in the 

 Rocky Mountains ; its extension in this direction contrasting 

 strongly with that of either the Dwarf or true Hermit, which 

 reacK the Arctic regions. On the other hand, this variety is the 

 characteristic representative of the species in Mexico, through- 

 out the Alpine regions, up to an altitude of about 2,500 meters. 

 It breeds in that country, and, according to M, Sumichrast, is 

 generally distributed and abundant. Some of the current ref- 

 erences to " Turdus pallasi^' in Mexico doubtless belong to this 



ceous on the rump and tail. Below, pure white, faintly tinged on the breast 

 with bufif, and everywhere except on the throat, middle of belly, and cris- 

 sum marked with numerous large, well-defined, rounded or subtriangular 

 blackish spots. Inner webs and ends of quills fuscous, with a white or 

 buffy edging toward the base. Greater under wing-coverts mostly white. 

 Auriculars sharply streaked with dusky and white. . Bill blackish-brown 

 with flesh-colored or yellowish base. Feet like this part of the bill. Length, 

 7|-8 inches; extent, about 13; wing, 4-Ji; tail, 3-3^; bill, i ; tarsus, IJ; 

 middle toe and claw less. The sexes do not differ appreciably, either in size 

 or coloration. 



Young : For a short tim'e after leaving the nest, the young are speckled 

 or streaked above with pale yellowish or whitish ; usually especially noticea- 

 ble as triangular spots on the wlng-ooverts. But these speedily disappear, 

 when a plumage scarcely different from that of the adult is assumed. 



The present is the most strongly marked species of the subgenus Sylo- 

 ticMa. In T. pallaai, the only other one showing both tawny and olive 

 on the upper parts, the position of the two colors is reversed, the tawny 

 oocupying the rump, the olive the head. In no other species are the spots 

 below so large, sharp, numerous, and generally dispersed, only the central 

 line of the throat, middle of the belly, and the crissum remaining immacu- 

 late. The purity of the white, moreover, only gives way to a faint, some- 

 times almost inappreciable, tinge of buff on the breast. 



