THE COMMON RAVENS OF NORTH AMERICA. 



By Harry C. Obekholser. 



The subspecies of the common raven, Corviis cor ax Linnaeus, 

 are among the most difficult birds of the family Corvidae. 

 The differences characterizing them are almost wholly those of 

 size and proportion; and because great individual variation 

 complicates the case, these are largely average distinctions and 

 require series of specimens for proper elucidation. In the Old 

 World some 16 or 17 forms are at present recognized,^ but in 

 North America currently only two, Corvus corax principalis 

 of northern North America, with which the birds of the eastern 

 United States are considered identical, and Corvus corax sinuatus 

 of the western United States and Mexico. Another, however, 

 has been recently described by Doctors Rothschild and Hartert 

 as Corvus corax clarionensis,- from Clarion Island, in the Revilla- 

 gigedo group, western Mexico, and it is now proposed to 

 separate the bird from the eastern United States as a fourth 

 race. By the recognition of these two additional subspecies, 

 the measurements, characters, and distribution of the two 

 original forms are in need of considerable readjustment, and 

 they are, therefore, included in the discussion that follows. 



The material used in the present study consists of about 

 400 specimens. This represents the collections of the United 

 States National Museum, including the Biological Survey; 

 the Academy of Natural Sciences of Philadelphia; the Museum 

 of Comparative Zoology at Cambridge, Massachusetts; the 

 American Museum of Natural History; the Brooklyn Museum 

 of Arts and Sciences; Dr. Louis B. Bishop, Dr. Jonathan Dwight, 

 Dr. L. C. Sanford, Dr. Witmer Stone; Messrs. William Brew^ster, 

 John E. Thayer, A. C. Bent, and E. A. and O. Bangs. To the 

 authorities of these museums and to the individuals here 

 mentioned the writer is indebted for placing their specimens at 

 his disposal. 



^For an excellent account of the Old World forms of Corvus corax, cf. Hartert, 

 Vogel palaarkt. Fauna, Heft I, November, 1903, pp. 2-8; Heft VI, June, 1910, 

 pp. XIII-XIV. 



^Novit. Zool., IX. Xo. 2. July 25, 1902, p. 381. 



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