76 University of California PuHicaUons in Zoology [Vol. 21 



INTRODUCTION 



The genus Passerella contains but one species, Passerella iliaca, 

 the fox sparrow, confined to North America, and distributed over 

 the greater part of the continent. In the eastern two-thirds of the 

 general habitat, from northern Alaska to Newfoundland, the fox 

 sparrow occurs as one relatively uniform subspecies, in the Pacific 

 Coast and Rocky Mountain regions as a number of more or less 

 widely differentiated local races. Sixteen subspecies are formally 

 recognized in the present paper. All the forms of Passerella are 

 migratory, most of them traveling long distances between their 

 summer and winter homes. The eastern race, iliaca, occurs in Cali- 

 fornia as a rare straggler in winter ; each of the other fifteen subspecies 

 occurs more or lesss abundantly in California at one season of the 

 year or another. 



The Museum of Vertebrate Zoology has gradually acquired a fairly 

 extensive representation of fox sparrows, mostly collected by various 

 field expeditions. This collection consists in part of series of most 

 of the subspecies collected upon their breeding grounds, in part of 

 miscellaneous non-breeders of various subspecies, taken as migrants 

 and winter visitants. Of late years it has become increasingly difficult 

 to coordinate the museum arrangement of many of these specimens 

 with current classifications and descriptions. Inconsistencies were 

 apparent but the remedy was not so readily seen. At the same time 

 the Museum was being called upon constantly to identify specimens, 

 sometimes single birds, sometimes extensive series, sent in for this 

 purpose by collectors in various parts of the state ; while every effort 

 was made to satisfy such requests, the questions asked could not 

 alwaj^s be satisfactorily answered. 



It seemed desirable to bring together as large a series of Passerella 

 as was to be had, in expectation that careful study of material known 

 to be available would, among other things, peniiit of a clearer defini- 

 tion of the subspecies and their characteristics than had yet been put 

 forth. This study has proven far more complicated than was at first 

 apparent, and while I feel that it has resulted in a much clearer 

 perception of the nature of the problem, I cannot assume to have 

 finally disposed of many of the questions involved. 



In this connection my attention has been frequently called to the 

 desirability of supplying bird students with a "key" or some similar 



