Proceedings of 

 the United States 

 National Museum 



SMITHSONIAN INSTITUTION • WASHINGTON, B.C. 



Volume 114 1963 Number 3471 



GEOGRAPHIC VARIATION IN THE THRUSH 

 HYLOCICHLA USTULATA 



By Gorman M. Bond 



Introduction 



Swainson's thrush, Hylocichla ustulata, known also in recent htera- 

 ture as the oUve-backed thrush, is one of the most widely known of 

 its genus. It has an extensive breeding range from Alaska across 

 Canada to Labrador and Newfoundland. In the west it is found 

 south through California and much of the Rocky Mountain area, and 

 in the east it occurs as far south as the mountains of West Virginia. 

 In its migrations it is found in wooded areas to the south of its breed- 

 ing range throughout the United States, Mexico, and Central and 

 South America to northern Argentina. 



Four subspecies are listed in the American Ornithologists' Union 

 Check List (1957, pp. 438-440): H. u. ustulata (Nuttall), the russet- 

 backed form of the Pacific coast; H. u. incana Godfrey, recently 

 named from Yukon; H. u. clarescens Burleigh and Peters, restricted 

 by the authors to Newfoundland and Nova Scotia; and H. u. swainsoni 

 (Tschudi), the olive-backed form of the trans-Canadian spruce belt. 

 In the original descriptions and in most of the standard faunal works 

 these races and others that have been proposed have been treated 



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