954 U.S. NATIONAL MUSEUM BULLETIN 23 7 paet 2 



crowns I found within a half-mile of trail in good habitat just within 

 the mouth of Fish Canyon, near Azusa, Sept. 27, 1942. 



Distribution 



Range. — The ashy rufous-crowned sparrow is resident in south- 

 western California (Gaviota, Redlands) and northwestern Baja 

 California (south to lat. 30*'30'N.; San Martin Island; east to east base 

 of Sierra San Pedro Mdrtir). 



Egg dates. — California: 18 records, March 11 to June 15. 



AIMOPHILA RUFICEPS SANCTORUM van Rossem 



Todos Santos Rufous -crowned Sparrow 

 Contributed by Howard L. Cogswell 



Habits 



In his description of this insular subspecies of extremely limited 

 range, Adriaan J. van Rossem (1947b), writes: "VentraUy, the 

 darkest and grayest (most plumbeous) of the races of AimopMla 

 riificeps. Dorsally, most nearly similar to the darker and grayer 

 examples of Aimophila ruficeps canescens of southwestern California 

 and northwestern Baja California but averaging stUl darker, the 

 general color of the dorsum and crown close to 'Mars Brown' rather 

 than grayish 'Kaiser Brown,' and with the grayish edgings narrower, 

 darker, and less in evidence. Size somewhat smaller than canescens, 

 particularly in length of taU." 



Van Rossem then comments on the extreme darkness of the Todos 

 Santos birds, although the islands are only 3 miles offshore and hence 

 of similar or identical climate to that experienced by A. r. ''Iambi" 

 of the nearby mainland (now included in A. r. canescens) . He expresses 

 the opinion that isolation in the limited area of the islands and con- 

 sequent inbreeding has "fixed and accentuated tendencies [toward 

 slaty color] already present in mainland populations." The evolu- 

 tionary differences in morphology thus attributed to what is now 

 usually called genetic drift, a weU known phenomenon in small 

 populations, have in this case unfortunately not as yet been accom- 

 panied by any comparison of the habitat or behavior of the birds with 

 those of the nearby mainland populations. 



The only other reference to this race in the literature is in Henry B. 

 Kaeding's (1905) report of his visit to its home in 1897. He remarks 

 only "Noted on Todos Santos Islands, March 10th * * * ." On 

 San Martin Island, 90 miles farther south and much farther offshore, 

 Henry B. Kaeding found the species present but "not common" on 

 Mar. 12, 1897. The fifth edition of the A.O.U. Check-List (1957) 



