tortuga black-throated sparrow 1003 



Distribution 



Bangs' Black -throated Sparrow (A. h. bangsi) 



Range. — The Bungs' black-throated sparrow is resident in southern 

 Baja California from lat. 26°N. southward, including most of the 

 adjacent islands, 



Cerralvo Black-throated Sparrow {A. h. belvederei) 



Range. — The Cerralvo black-throated sparrow is resident on 

 Cerralvo Island, Baja California. 



AMPHISPIZA BILINEATA TORTUGAE van Rossem 



Tortuga Black -throated Sparrow 

 Contributed by Richard C. Banks 



Habits 



Adriaan J. van Rossem (1930) describes this subspecies of the 

 black- tlu"oa ted sparrow as the darkest of the known races, the back 

 being more slaty and less brown, and the under parts being more 

 extensively and deeply colored. It is resident on Tortuga Island in 

 the Gulf of CaHfornia, an island only a Uttle more than 2 square miles 

 in area. 



A. J. van Rossem (1945b) comments on the density of the population 

 of black-throated sparrows on Tortuga Island as follows; "Through 

 some cause now obscure, but which most likely is connected in some 

 way ^\'ith an abundant, year-round food supply, the density of the 

 population on Tortuga sui-passes anything in my experience with the 

 species." 



In 1930 A. J. van Rossem (op. cit.) visited the island in late March 

 and early April and found that the breeding season was under way. 

 When I visited Tortuga Island on Mar. 30, 1962, breeding had not 

 yet begun (Banks, 1963c); apparently there is some variation in the 

 annual cycle on this island. 



Distribution 



Range. — The Tortuga black-throated sparrow is resident on 

 Tortuga Island off central eastern Baja California. 



