234 BULLETIN 16 7, UNITED STATES NATIONAL MUSEUM 



Alila, Paicines, Petaluma, Shasta Valley, and probably Hornbrook) ; 

 Oregon (Swan Lake, Fort Klamath, Prineville, and The Dalles) ; 

 Washington (probably Cleveland, Yakima, probably Tacoma, and 

 probably Bellingham) ; British Columbia (probably Shuttleworth 

 Creek, Okanagan Landing, and probably Kispiox Valley) ; and 

 Alaska (Onslow Island, probably Juneau, and probably Mount 

 Sischu). 



Winte7' range. — The winter range of the Swainson's hawk appears 

 to be located entirely in the Republic of Argentina. Visual winter 

 records for this species in the United States are almost invariably 

 errors in identification for melanistic roughlegs or for one of the 

 races of Buteo horealis. The few specimens taken in North America 

 during this season probably represent disabled birds prevented by 

 their physical condition from performing the migratory flight to 

 normal winter quarters. 



The winter range in Argentina is not fully known, but it extends 

 north at least to Tucuman and south to San Pedro, Cordoba, 

 Platanos, Buenos Aires, and Barracas al Sud. 



Migration. — Because of much misidentification in the field, there 

 is a dearth of authentic data illustrative of the migrations of this 

 hawk. Griscom (1932) refers to the great flights that pass through 

 Central America as "one of the sights of the bird world." He says : 

 "Apparently the great majority of the individuals in existence pass 

 over Central America in a comparatively few days in a few enor- 

 mous flocks which take hours to pass a given point. The birds 

 alight only casualh^, and only three specimens have been collected in 

 Central America." The birds pass south through this region in 

 October and return north in April. 



Spring migration. — Early dates of arrival in the United States 

 and Canada are: Iowa — Sigourney, March 8; Grinnell, March 21; 

 La Porte City, March 23; and Iowa City, March 29. Minnesota — 

 Heron Lake, March 27; Jackson, April 5; Wilder, April 8; and Elk 

 Kiver, April 12. Texas — Corpus Christi, March 16 ; Somerset, March 

 20; Refugio County, March 28; Kerrville, April 3; San Angelo, 

 April 3; and Houston, April 4. Oklahoma — Norman, March 14; 

 and Okmulgee County, April 10. Kansas — McPherson, March 29; 

 and Fort Riley, April 3. Nebraska — Badger, March 16; Lincoln, 

 March 19; and Alda, April 3. South Dakota — Vermillion. April 4; 

 Forestburg, April 4; and Petrodie, April 7. North Dakota — 

 Marstonmoor, March 8; Chase Lake, March 10; Grafton, March 21; 

 and Grand Forks, March 31. Manitoba — Margaret, April 2 ; Awemc, 

 April 5; and Pilot Mound, April 15. Saskatchewan — Eastend, 

 March 31; and Indian Head, April 1. New Mexico — Glenrio, April 

 9. Arizona — Huachuca Mountains, April 3; and Tucson, April 19. 



