VOL. XII,. PP. 5-11 JANUARY 27, 1898 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



DESCRIPTIONS OF NEW BIRDS FROM THE TRES 

 MARIAS ISLANDS, WESTERN MEXICO. 



BY E. W. NELSON. 



The specimens upon which the present paper is based were 

 obtained by myself and my assistant, Mr. E. A. Goldman, on the 

 Tres Marias Islands, off the west coast of Mexico, during May, 

 1897. Our visit there was a continuation of the work carried on 

 in Mexico by the Biological Survey of the Department of Agri 

 culture. 



Special efforts were made to secure series of the resident land 

 birds, in which we were quite successful. The study of these 

 series, in connection with our collection from the adjacent main 

 land during the same season, indicates that most of the resident 

 land birds of the islands, not already described, differ in a more 

 or less marked degree from their nearest mainland relatives. In 

 most cases the island birds cannot be considered more than geo 

 graphical races, .although a few differ sufficiently to be treated as 

 species. Not a single species has been found on the islands which 

 has not a closely related form on the mainland. The bird fauna 

 as a whole will be treated in detail in a paper now in course of 

 preparation. 



Previous work on the Tres Marias may be briefly summarized 

 as follows : In 1865-1867 the group was visited three times by 

 Colonel A. J. Grayson, who made extensive collections of birds for 

 the Smithsonian Institution. From these collections a number of 

 new species and subspecies have been described at various times 

 by Baird, Cassin, Lawrence, and Ridgway. In addition, Von 



2-Bioi, Soc. WASH., VOL. XII, 1898 (5) 



