GREEN-TAILED TOWHEE 559 



the wings and tail — and its gray breast and whitish belly. Immatures 

 are brownish on the back, lack the rufous crown, and are streaked 

 with dusky. 



Enemies. — This towhee is sometimes \-ictimized by the brown - 

 headed cowbird (Molothrus ater), one of the more recent instances 

 having been noted by N. K. Carpenter in Mono County, Calif. 

 (H. Friedmann, 1934). 



While no evidence of predation has come to my attention, probably 

 adults as well as eggs and young of this low-nesting bird occasionally 

 fall prey to mammalian predators, as is suggested by A. H. Miller 

 (1951a) in his discussion of the "rodent-run." 



Other hazards besetting the greentail, in common with other 

 birds, include weather inclemencies such as severe hailstorms, which 

 may destroy sets of eggs (L. Huey, 1936a), and "modern La Brea 

 tar pits," in which the birds may become entrapped (A. E. Borell, 

 1936). 



One specimen examined by C. M. Herman, Jankiewicz and Saarni 

 (1942) was infected with the coccidian parasite, Isospora, which was 

 also found in brown and rufous-sided towhees and several other species 

 of birds. 



Fall. — Prior to faU migration proper, there is an up-mountain scat- 

 tering of birds after the breeding season, and immatm-es are prevalent 

 among these wanderers (Grinnell and Storer, 1924). This well- 

 known phenomenon, as observed in Utah, has been treated by C. L. 

 Hayward (1945) as follows: "This post-nesting up-drift of bird 

 populations is less marked in the Uinta Mountains * * * than it is 

 in the Wasatch, but it is nevertheless evident. The green-tailed 

 towhee, western vesper sparrow, Macgillivray's warbler, western 

 wood pewee, yellow warbler, and Brewer's sparrow are the more 

 common species to foUow this procedure in both the Wasatch and 

 Uintas." 



There is also evidence of downslope scattering of individuals in 

 late summer (J. Grinnell, 1908). 



In many areas migration is well under way in September. Late 

 fall records for localities in Oregon (Jackson County and Rogue 

 River Valley) , Nevada (Carson City and the Charleston Mountains), 

 and Wyoming (Laramie) have been in the last week in September; 

 others for the Yosemite Valley, Utah (Pine Valley), Arizona (San 

 Francisco Mountains), Colorado (Golden), and New Mexico (Silver 

 City), have fallen within the first week in October. In Kern and 

 Inyo counties, Calif., this towhee has been recorded as late as October 

 24 and 25 (see J. Grinnell and A. H. Miller, 1944, who furnish repre- 

 sentative data on migrants in the state). As a transient, the green- 

 tail may be uncommon (Grand Canyon region; R. K. Grater, 1937) 



