FOX sparrow 1393 



Nevada, and south central California, in these birds the grays pre- 

 dominate, especially toward the south, the tail is equal to or usually 

 longer than the wing, and the large, swollen bill increases in size to 

 the westward and southward. Included are the races schistacea, 

 olivacea, swarthi, canescens,fulva, megarhyncha, brevicauda, monoensis, 

 and stephensi. 



Many of these races are rather weakly differentiated. Allan R. 

 Phillips et al. (1964), for instance, consider canescens and swarthi 

 indistinguishable from schistacea, and call the California races "gen- 

 erously oversplit." However Swarth (1920) claims: "I believe it to 

 be possible, at the present state of our knowledge, to arrive at a solu- 

 tion of the fox sparrow problem that will enable anyone to identify 

 accurately perhaps ninety per cent of the specimens taken," but he 

 warns in the same breath "it is to be doubted if diagnoses can be 

 prepared enabling anyone positively to identify all specimens of 

 Passerella secured. * * * Intergrades between two forms may re- 

 semble a third and, taken in their winter home, may have their char- 

 acters wrongly interpreted. Also immatures of one form may bear 

 some resemblance to adults of another * * *. Intergradation of 

 characters apparently occurs wherever two races come together. 

 Thus * * * there are intergrades to be found between any two 

 contiguous forms." 



The morphological variation in the species, though extensive, is 

 almost entirely geographical in nature. As Swarth (1920) points out: 



In this species variation due to age, sex and season of the year is extremely 

 slight. The juvenal plumage is essentially the same as in the following stages, 

 with regard to color and markings, the distinguishing features of the first men- 

 tioned being mainly due to the different texture of the feathers. Where color 

 differences are concerned as of subspecific value, the young birds show these 

 differences just as do the adults. As regards the later stages, I am unable to 

 distinguish any differences between immatures in first winter plumage and adults 

 a year or more old. As to sexual differences, males average slightly larger than 

 females, but in color and markings there is no discernible variation. Seasonal 

 differences arc shown solely as the result of wear and fading of the feathers. 

 There is but one annual molt, after the juvenal stage is passed, occurring in the 

 late summer and including the entire feather covering, with no assumption of a 

 special breeding dress such as is seen in so many species of birds. Consequently, 

 a study of variation in this group is narrowed down quite closely to a consideration 

 of but one category of differences, namely, geographic variation. 



Swarth's analysis of the species' external morphology encouraged 

 Jean M. Linsdale to examine its internal structure. During the next 

 decade he completed an exhaustive study of the species' osteology, 

 based on a comparison of 465 skeletons representing 14 of the 16 sub- 

 species Swarth recognized. From this Linsdale (1928) claims: " 

 nificant geographic variation was found in every part of the skeleton 

 that was examined. The various geographic populations do not vary 



