°s" I Ridgway, Geographical Variation i?i Sialia mexicana. 1 4^ 



ON GEOGRAPHICAL VARIATION IN SIALIA 

 MEXICANA SWAINSON. 



BY ROBERT RIDGWAY. 



In October, 1SS9, Mr. A. W. Anthony, of San Diego, Cali- 

 fornia, described, in the 'Proceedings' of the California Academy 

 of Sciences (2d Ser., Vol. II, p. 79), under the name Sialia 

 ?nexica?ia anabelce, a supposed new race of Sialia mexicana, 

 resident on the San Pedro Martir Mountains, Lower California. 

 A small number of specimens were sent to me by Mr. Anthony 

 for examination, and upon this insufficient evidence an unfavor- 

 able opinion was formed as to the validity of the form. It was 

 accordingly considered by the A. O. U. Committee on Publica- 

 tions ineligible for admission to the Check List on the ground 

 that its characters were "deemed not sufficiently constant." (See 

 'The Auk,' Jan. 1890, p. 66.) 



Not satisfied with the disposition made of it by the A. O. U. 

 Committee, Mr. Anthony again visited the San Pedro Mountains 

 and collected a large number of specimens, which he forwarded 

 to me, early in November, 1S93, for examination by the Com- 

 mittee ; but the question of its status not having been raised 

 during the year no action could properly be taken concerning it. 

 It is for the purpose, therefore, of having this question avail- 

 able for consideration by the Committee at its next session that 

 this paper has been prepared ; for I am now convinced that an 

 error was committed in rejecting the new subspecies which Mr. 

 Anthony had described. 



In order to clearly understand the nature and value of the 

 characters presented in the resident birds of this species from 

 Lower California, it has been found necessary to bring together 

 for comparison as many specimens of the species, from all parts 

 of its range, as possible. No difficulty has been experienced in 

 getting a pretty good series of the common form of the western 

 United States (S. mexicana occidental is) and, thanks to Mr. 

 Anthony, of the resident race of the Lower California mountains 

 (S. m. anabelce) ; but of the bird resident in southern Mexico 

 (true S. mexicana), very few specimens — only 10 — could be 



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