CASSIN'S FINCH 287 



vigorously and sweetly as those in the adult livery. On several 

 occasions purple finches were heard singing while in flight." 



Field marks. — The adult male Cassin's finch can be distinguished 

 readily from the house finch by its larger size, faint rose throat and 

 breast, and by the absence of dusky streaks on the flanks and belly. 

 From the adult male California purple finch it differs in having a 

 much paler rose on the throat and breast and by the fact that the 

 top of the head is crimson and sharply defined from the back of the 

 neck and back which are brown with but a faint rosy tinge. 



The female and immatm-e male may be distinguished from the 

 house finch in comparable plumages by larger size and more sharply 

 defined ventral streaking. From the California purple finch in female 

 or immature male plumage Cassin's finch differs in having less of an 

 olive tinge on the back and more sharply defined streaks on the 

 ventral surface. 



Enemies. — No doubt the Cassin's purple finch, like other small 

 passerine birds that frequently forage on the ground, is subject to 

 attack by a number of bird and mammal enemies. Clabaugh (1933) 

 records collecting a pigmy owl with a freshly caught Cassin's finch in 

 its claws on Aug. 18, 1930, near Hat Creek, Shasta County, Calif. 

 Dixon and Dixon (1938), after listing a number of species of birds, 

 including a pair of Cassin's finches, that were found nesting within 

 100 yards of a goshawk nest in Mono County, Calif., wondered "if 

 these nesting birds did not gather there for the protection afforded 

 from other predators which might be driven off by the hawks." 



Late spring and summer storms are undoubtedly a serious hazard 

 to birds of the high mountains. De Groot (1935) records finding a 

 Cassin's finch frozen to death on her nest and three eggs one morning 

 in the latter part of June, 1934, at Echo Lake in the Tahoe region. 

 There had been a freak snowstorm the night before. Hanford (1913) 

 comments as follows on the effect of heavy rain and hail in midsummer 

 in the central Sierra Nevada at Lake of the Woods: "A mother Cassin 

 Purple Finch continued to feed her young in a nest high up in a 

 hemlock during a few hours of rain; at the first crashing downpour 

 of the hail, the nestlings were silenced and the parent was seen no 

 more." 



Fall. — Throughout many parts of the range of this species, especially 

 in the Great Basin region, there appears to be a downward migration 

 after the flocks are formed in fall. Taylor and Shaw (1927) mention 

 a flock of 25 to 50 seen August 21 flying over Mount Ruth (8, 700 feet) 

 in Mount Rainier National Park, Wash. They beheved that these 

 birds were either migrating or preparing to do so. A downward 

 movement of Cassin's finches was noted by van Rossem (1936) in the 

 Charleston Mountains of southern Nevada in the autumn. 



