172 BULLETIN 196, UNITED STATES NATIONAL MUSEUM 



tral Alaska, northwestern Mackenzie, and northern British Columbia 

 eastward to the Atlantic. 



Winter range. — The winter range of the russet-backed thrush group 

 is as yet imperfectly defined owing to the scarcity of carefully identified 

 winter specimens. The russet-backed thrush winters north to central 

 Mexico (Tres Marias, Minca near Mexico City, and Misantla, Vera- 

 cruz); and south to Guatemala (Coban and Los Amates). Some race 

 winters from El Salvador (Colima, Mount Cacaquatique, and Puerto 

 del Triunfo) to southern Costa Rica (Basin of El General and Boruca). 

 These have been recorded as swainsoni but it seems possible that some 

 may be the more recently recognized almae. Specimens from Costa 

 Rica in spring have been identified as this race. 



The olive-backed thrush (H. u. swainsoni) winters in South America 

 from the Santa Marta region of Colombia east to northwestern Brazil 

 (Cocuy and Marabitanas) ; central Bolivia (Buena vista and Entre 

 Rios); and northwestern Argentina (Lules, Tucuman). South to 

 northwestern Argentina. West to Peru (La Merced and Chinchao); 

 western Ecuador (Zamora, Cuenca, and Quito); and western Colom- 

 bia (San Antonio, No vita, and Santa Marta). Since there is as yet 

 no record from Venezuela, it seems probable that a specimen taken 

 at Roraima, British Guiana, on December 6 was a delayed migrant. 



Migration. — In the migration, no attempt has been made to dis- 

 tinguish between the races. Some late dates of spring departure are: 

 Ecuador — San Jos6 de Sumaco, April 18. Colombia — Valparaiso, 

 March 24. Panama — Perine, April 22. Costa Rica — Volcan de 

 Irazu, April 15; Guatemala — Patulul, April 3. British Honduras — 

 Augustine, April 26; Mexico — Presidio, Veracruz, May 6. Florida — 

 Tortugas, May 22. District of Columbia — Washington, June 2. 

 Pennsylvania — Jeffersonville, June 9. Louisiana — Shreveport, May 

 13. Iowa — Sioux City, June 3. Texas — San Antonio, May 18. 

 Kansas — Fort Riley, May 24. North Dakota — Charlson, June 5. 

 Arizona — Tucson, May 30. 



Some early dates of spring arrival are: Georgia — Macon, April 19. 

 North Carolina — Chapel Hill, April 22. District of Columbia — 

 Washington, April 18. Pennsylvania — Pittsburgh, April 24. New 

 York — Rochester, April 22. Massachusetts — Harvard, May 5. 

 Maine — Ellsworth, May 4. Nova Scotia — Wolfville, May 8. New 

 Brunswick — Scotch Lake, May 17. Quebec — Quebec, May 23. 

 Louisiana — New Orleans, April 2. Tennessee — Nashville, April 18. 

 Kentucky — Guthrie, April 3. Ohio — Columbus, April 22. On- 

 tario — Toronto, April 24. Missouri — Columbia, April 16. Iowa — 

 Iowa City, April 17. Wisconsin — Madison, April 25. Minnesota — 

 Minneapolis, April 30. Texas — Austin, March 2. Oklahoma — 

 Norman, April 21. Nebraska — Lincoln, April 28. North Dakota — 



