Vol. XI"] r IDGWA y, Geographical Variation in Sialia mexicana. 151 



1894 J 



b. Back usually with much chestnut, often wholly so, very rarely 

 with a mere trace ; blue of upper parts varying from rich ultra- 

 marine to light cobalt; wing in adult male averaging 4.07. 

 a 1 . Back with median portion more or less blue, the chestnut 

 sometimes restricted to a mere trace on each side. (Pacific 

 coast, from British Columbia to southern California, east to 

 western Nevada, casually, during migrations, to New Mexico.) 



2. S. m. occidentalis (Towns.). 



b 2 . Back wholly chestnut. (Rocky mountain district south to 

 northern Mexico.) 3- S. m. bairdi Ridgw. 



B. Chestnut color of back and breast greatly reduced in extent, usually 

 wholly wanting or barely indicated on the former, and divided into 

 two lateral patches by backward extension of blue of throat on the 

 latter. Blue of upper parts intermediate between 'smalt' and ultra- 

 marine ; wing in adult male averaging 4.29. (Mountains of Lower 

 California.) 4- S. m. anabeke Anthony. 



1. Sialia mexicana Swainson. 



Mexican Bluebird. 



Sialia mexicana Swains. F. B.-A. II, 1831, 202, foot-note (tableland of 

 Mexico l).— Scl. P. Z. S. 1S56, 293 (Cordova 2 ); 1859, 362 

 (Jalapa 2 ); Catal. 1862, 11 (part, Jalapa).— Sumichr. Mem. Bost. 

 Soc. I, 1869, 544 (alp. reg. of Mt. Popocatapetl).— Scl. and Salv. 

 Norn. Neotr. 1873, 4 (Mexico). —Bouc. Cat. Av. 1876, 149 (Mexico). 

 — Salv. and Godm., Biol. Centr. Am. I, pt. 6, 1S79, 47 (part).— 

 Seebohm, Cat. B. Brit. Mus., V, 1SS1, 331 (highlands of Mexico). 



Geographical Range.— Highest mountains of southern Mexico, 

 (Orizaba, Popocatapetl, etc.) in summer, descending to the tableland in 



winter. 



Adult male in breeding season (i35>70i, Cofre de Perote, Vera Cruz, 

 Mexico, May 30, 1893; E. W.Nelson): Above uniform rich smalt-blue, 

 darker (hyacinth blue) anteriorly; shafts of remiges and rectrices deep 

 black, and tips of the former, especially on inner webs, dull blackish 



1 "Sialia mexicana Sw. Size of S. arctica ; upper plumage bright purple-blue, 

 chin and throat the same ; across the breast a rufous band, which color is continued 

 on the sides and flanks ; middle of the body, vent, and under tail covers light blue, 

 inclining to white. Total length 6 1-2, wings 4 1-2, tarsi 3-4, tail 3 inches. Inhabits 

 Mexico. In Mr. Taylor's collection." 



2 These localities, according to Prof. Sumichrast (1. c), are probably incorrect. 



