956 U.S. NATIONAL MUSEUM BULLETIN 237 part 2 



strongly that most of the highland endemics of the Cape district 

 colonized that region from the mainland of Mexico and the adjacent 

 inland United States. When one considers the habits of the species 

 concerned, it does not seem likely that such sedentary forms as * * * 

 Rufous-crowned Sparrows * * * would have invaded the Cape region 

 by an overwater, or even island-hopping route from the Mexican 

 mainland." After citing geological and paleobotanical evidence that 

 no significantly greater land connection between the Cape area and 

 the Mexican mainland to the east than now exists has existed since 

 the Miocene, John Davis (1959) concludes: 



It seems most likely that most of the avian endemics of the Cape highlands 

 [including A. r. sororia, as he makes clear elsewhere] have their closest affinities 

 with forms to their northeast and east because the habitat in which these Cape 

 endemics occur today has become relatively little modified from the habitat with 

 which the ancestral stocks of these species were associated in Mexico. In north- 

 western Baja California, the western foothills of the Sierra Judrez and the Sierra 

 San Pedro Martir support a vegetation that is clearly related to the flora of 

 southern California. As might be expected, the highland avian endemics of 

 northwestern Baja California show clear relationships with the populations of 

 the Pacific coast to their north. 



Thus the similarity of Aimophila rvjiceps sororia to ^. r. simulans 

 is of long standing, the form A. r. canescens now interposed between 

 them along the apparent route followed by the species into Baja 

 California being a later evolutionary product. 



Larry Wolf (MS.) notes that this form "may more often retain all 

 the Juvenal primaries than the other races. (Based on small sample 

 to date.)" Nothing more has been published on this form. 



Distribution 



Range. — The Laguna rufous-crowned sparrow is resident in southern 

 Baja California (Triunfo, Sierra Laguna). 



AIMOPHILA AESTIVALIS BACHMANI (Audubon) 



Bachman's Sparrow 

 Contributed by Francis Marion Weston 



Habits 



This sparrow was first named Fringilla Bachmani by John James 

 Audubon (1833) in the folio edition of his Birds oj America. In his 

 Ornithological Biography the follomng year (1834), he described it 

 under the name Fringilla Bachmanii. The earlier spelling has been 

 accepted by the A.O.U. Committee on Nomenclature (A.O.U. Check- 

 List, 1957) as given in the heading of this account. 



