SAN PEDRO BLUEBIRD 275 



variation in the color pattern in 43 adult males from the San Pedro 

 Martir Mountains; 21 have no chestnut whatever on back or scap- 

 ulars; 18 have the back chiefly blue; 4 have the back about equally 

 blue and chestnut; 30 have the chestnut of the breast divided by the 

 blue of the throat, a character of S. m. mexicana; 11 have the chestnut 

 of the breast continuous anteriorly; and 2 do not belong to either 

 category. This analysis shows that the characters of anabelae are 

 not absolutely constant, even in its restricted range. In another 

 footnote he says: "California specimens are not typical of this form, 

 but are much nearer to it than to &. m. occidentalism from which they 

 differ in larger size, more restricted areas of chestnut (though this 

 character varies greatly in both forms), and, on the average, decidedly 

 richer or more violaceous hue of the blue." 



Since the Sierra San Pedro Martir has become the birthplace of so 

 many local subspecies, it seems worth while to include here Mr. 

 Anthony's (1889) description of the region. 



About one hundred and fifty miles south of the United States boundary, and 

 midway between the Pacific Ocean and the Gulf of California, lies a high range of 

 mountains, which is marked upon the later maps of the peninsula as "San Pedro 

 Martir." The region embraces a series of small ranges which rise from an elevated 

 mesa, having a mean elevation of about 8,000 feet, and an extent of sixty by 

 twenty miles. In these mountains are born the only streams that this part of 

 the peninsula affords, and an abundance of pine timber is found throughout the 

 region. Many of the ranges on the eastern side of the San Pedro Martir rise to 

 an elevation of 11,000 feet, or even, in one or two places, to 12,500 (?) feet. 



Arising as the region does from the dry, barren hills of the lower country to an 

 elevation higher than any other on the peninsula or in Southern California, and 

 presenting in its alpine vegetation and clear mountain streams features so different 

 from the dry manzanita and sage-covered hills of the surrounding country, it is 

 not unnatural to suppose that its animal life would be found to differ in some 

 respects from that of the surrounding hills. 



J. Stuart Rowley writes to me: "Near La Grulla in the Sierra San 

 Pedro Martir, of northern Lower California, I took a set of five slightly 

 incubated eggs of this race of bluebird on June 12, 1933. So far as 

 I can determine, the habits of this bluebird are no different from those 

 of the western bluebird of the north." Charles E. Doe, who now has 

 this set in his collection at the University of Florida, in Gainesville, 

 tells me that the nest was in a pine stub 8 feet from the ground. 



Eggs. — The eggs of the San Pedro bluebird are probably indis- 

 tinguishable from those of the species elsewhere. The measurements 

 of 26 eggs average 20.9 by 16.2 millimeters; the eggs showing the four 

 extremes measure 23.1 by 16.5, 20.2 by 16.9, 19.4 by 16.2, and 19.6 

 by 15.2 millimeters. 



