174 University of California Puhlications in Zoology [Vol. 21 



number compared witli the abundance of certain other subspecies 

 associated with them that there seems no doubt that the places of 

 capture of these scattered individuals do not represent the main 

 winter home of the race. Then, too, some of these winter birds are 

 not absolutely typical of 'nvariposae, though most nearly resembling 

 that form. Altogether, it is evident that the winter metropolis of 

 mariposae is still to be discovered. In this connection it may be 

 pointed out that we are similarly ignorant of the winter homes of 

 the other Sierran fox sparrows, stephensi and monoensis, and of their 

 neighboring relatives fulva and canescens. In each case there are 

 scattering winter birds and migrants at hand, but nothing to show 

 where the bulk of the populations winter. It is not to be supposed 

 that all five of these subspecies necessarily depart to the same place, 

 but it seems possible that their modes of departure and arrival are 

 very similar, and that the explanation of the puzzle in each case lies 

 in the existence of a relatively restricted winter habitat, and one that 

 has not been thoroughly scrutinized for these birds at that season. 

 It may be, of course, that mariposae winters in some parts of the 

 Sierran foothills, but there is little evidence of this either in the avail- 

 able specimens, or in published literature. Belding (1890, p. 170), 

 speaking of the Sierran bird (under the name niegarhynchus) , says: 

 "Not at Alta and Colfax November 17-21, nor at Red Bluff in warm 

 winter of 1884—85. I never see it in the lower foothills of Calaveras 

 County in winter, though P. unalaschcensis is common there at that 

 time." 



That the detailed mapping of summer ranges of the forms of 

 Passer ella breeding in the Sierra Nevada will yield interesting and 

 valuable results is indicated by the general facts already gathered. 

 The habitats of stephensi and ruariposae are each known to be inter- 

 rupted along certain lines where thorough exploration has been prose- 

 cuted, and as there are other parts of the Sierras presenting similar 

 conditions it is evident that at these places also there must be breaks 

 in distribution, and that each of these subspecies in summer is scat- 

 tered into a number of colonies of varying extent. 



The Kings River Caiion section of the Sierra Nevada may be cited 

 in its bearing on the fox sparrow problem. This caiion runs far back 

 into the mountains, a broad, gently sloping valley, Transition zone 

 clear to its uppermost confines and therefore not inhabited in sum.mer 

 by Passerella. The surrounding walls are high and steep, and drop 

 from plateaus, zonally of high Transition, Canadian and higher. In 



