338 TJnwersiiy of California Piiblicaiions in Zoology [Vol. 24 



The adult male collected (no. 42055, Hazelton, September 24) is 

 referred to columbarius, though darker colored than any other adult 

 of that subspecies that T have seen. There are nine adult male pigeon 

 hawks in the several collections housed in the Museum of Vertebrate 

 Zoology, and these exhibit an interesting range of variation. An 

 extreme of darkness is represented by the Hazelton bird above referred 

 to, but slightly removed from that of suckleyi At the opposite extreme, 

 of light coloration, is an example of richardsoni. Between, there are 

 seven specimens, labeled columbarius, illustrating unbroken gradation 

 from one extreme to the other. Thus, in adult birds as in immatures, 

 there is no one character of color or markings that may be taken as 

 absolutely indicative of any one form. The three names, columbarius, 

 suckleyi, and richardsoni, apply to three subspecies of one species, 

 between which no definite lines may be drawn. 



There is this to be said, however, that the above comments are 

 based, not upon breeding birds, but upon specimens collected during 

 the migrations and in winter. The line of nicely graded adults just 

 described was not arranged with regard to geographic continuity. 

 Breeding pigeon hawks are scarce in collections (not one was avail- 

 able to the present writer) and, for the most part, deductions must be 

 drawn as best they may from non-breeding birds. 



The Hazelton series is of interest in that it includes a specimen of 

 suckleyi from what I believe is the northernmost point at which this 

 subspecies has been definitely recorded. This place is at an inter- 

 mediate point between humid coast and arid interior, and most of the 

 pigeon hawks taken there are intermediate in appearance. Of course 

 these birds were not found aetually breeding, but the conclusion does 

 not seem forced that they are representative of the form that does 

 breed in that general region. 



In this discussion I have ignored the recently described Falco 

 columiarJAis hendirei of Swann (1922, p. 66 ; type locality, Fort Walla 

 Walla, Washington). It may be possible eventually to demonstrate 

 the existence of this additional western subspecies, but the two eastern 

 specimens available to me are not to be distinguished from western 

 birds here regarded-as columbarius. 



Falco sparverius sparverius Linnaeus. American Sparrow Hawk 



A fairly common summer visitant to the lowlands. A few were 

 seen in the open country above timber on Nine-mile Mountain, but 

 that was early in August and the birds noted had probably wandered 



