LAGUNA RUFOUS-CROWNED SPARROW 955 



includes the population on this larger island within the range of the 

 mainland race, A. r. canescens. 



Distribution 



Bange. — The Todos Santos rufous-crowned sparrow is resident on 

 the Todos Santos Islands off northwestern Baja California. 



AIMOPHILA RUFICEPS SORORIA Ridgway 



Laguna Rufous-crowned Sparrow 

 Contributed by Howard L. Cogswell 



Habits 



Robert Ridgway (1898a) describes this subspecies of the Cape 

 district of Baja California as "Similar to^. rujiceps [presumably =^. r. 

 ruficeps and A. r. canescens as now recognized] in coloration of upper 

 parts, but chestnut of pileum somewhat lighter or clearer, supraloral 

 line whiter, and supra-auricular stripe lighter and grayer; smaller 

 than A. ruficeps scottii, \\dth back, etc., less ashy with chestnut streaks 

 darker and much narrower, and the under parts much more strongly 

 tinged with buff; differing from all the other northern forms of the 

 species in much thicker and relatively shorter bill." Robert Ridgway 

 gives the range as "Southern portion of Lower California, in mountains 

 (Laguna; Victoria Mountains)." Joseph Grinnell (1928) gives its 

 status as "Conunon resident locally in the mountains of the Cape 

 district." 



Discussing the probable evolutionary origin of this isolated popu- 

 lation of the rufous-crowned sparrow, John Davis (1959) indicates 

 that it "differs considerably [in morphology] from the nearest popula- 

 tion to the northwest, canescens * * * . in the general pallor of its 

 coloration and in the much greater development of ventral white 

 sororia is much more nearly similar to scottii of Arizona, New Mexico, 

 northeastern Sonora, and northwestern Chihuahua, and to simulans, 

 which ranges in Mexico from southern Sonora to Nayarit and from 

 southern Chihuahua south through Durango and Zacatecas to Guana- 

 juato." 



The emphasis Adriaan J. van Rossem (1934a) placed in his descrip- 

 tion of simulans on its similarity to sororia, which is distinguishable 

 chiefly by its larger bill, is also cited by John Davis (1959) in support 

 of his statement that "The afSnities of sororia are clearly with the 

 populations to its northeast and east, and not with the populations 

 of the Pacific coast to its north." 



For 14 of the 17 endemic forms in the Cape district avifauna 

 John Davis (1959) says that "The available evidence, then, suggests 



