1028 U.S. NATIONAL MUSEUM BULLETIN 237 



feeding grounds. I have yet to determine the exact foraging area a 

 flock of j uncos uses during the winter season. One individual Harry 

 Behrens banded in November in a brushy hollow near the center of 

 Rapid City, S.D., was retrapped 11 days later in the pine woods 3 

 miles northwest of the point of banding. This is unusual; later I 

 started a banding station % mile south of Behrens' station. I banded 

 100 juncos there, while Behrens had banded 30 at his home. While 

 we each had several retraps of our own birds, we did not catch any 

 of each other's. 



For 3 years I made a population study of an area of ponderosa 

 pine forest on the edge of Rapid City. My estimates of the winter 

 population were 61 white-winged juncos per 100 acres the first year, 

 45 the second year, and 35 the third. The cause of this variation 

 was not clear, although it could be correlated with the persistence of 

 snow cover, juncos being more numerous when the ground was bare, 

 and I could not evaluate its significance. 



Distribution 



Range. — Southeastern Montana and western South Dakota south 

 to New Mexico and western Oklahoma. 



Breeding range. — The white-winged junco breeds from southeastern 

 Montana (Rosebud Mountains, Long Pine HUls) and western South 

 Dakota (Short Pine Hills in Harding County; Custer) south to north- 

 eastern Wyoming (near Newcastle) and northwestern Nebraska (Hat 

 Creek). 



Winter range. — Winters in the vicinity of the breeding grounds 

 (chiefly lower elevations in the Black Hills) and south to southwestern 

 Colorado (Plateau Valley, La Plata County), north central New 

 Mexico (Sante Fe), western Oldahoma (Cimarron and Texas counties), 

 and western Kansas; sporadically to northern Arizona (Flagstaff, 

 White Mountains), and central Oklahoma (Fort Reno, Norman). 



Casual records. — Casual in eastern Nebraska (Omaha) and Ontario 

 (Scarborough) . 



Migration. — Early dates of spring arrival are: Wyoming — Laramie, 

 March 10. Montana — Missoula, April 15. 



Late dates of spring departure are: New Mexico — Los Alamos, 

 April 4. Wyoming — Laramie, April 16. 



Early dates of fall arrival are: Wyoming — Laramie, October 13. 

 Arizona — White Mountains, November 21. New Mexico — Los Ala- 

 mos, November 16; Taos County, November 19. Oklahoma — 

 Cimarron County, October 19. 



Late date of fall departure is: Montana — Carter County, December 

 5. 



