530 BRITISH BIRDS. 



Subfamily CORVINE, OR CROWS. 



The Crows and their allies are distinguished from all the allied sub- 

 families, except the Sylviinae, by having a spring moult as well as an 

 autumn one. From the latter subfamily they are principally distinguished 

 by their larger size ; the bill is generally large and conical, though in some 

 groups, as the Choughs, it is long and curved. The emargination of the 

 bill is sometimes well developed and sometimes quite obsolete. The wings 

 are rounded, the first primary being almost always more than half the 

 length of the second. The tail is subject to great variation, being some- 

 times short, sometimes long, sometimes even, and sometimes rounded, and 

 consists of twelve feathers. The feet and claws are strong, and the tarsus 

 is scutellated. The Corvinse are cosmopolitan, and number about two 

 hundred species. About ten species are found in the British Islands, 

 belonging to six genera, which may be distinguished as follows : 



a. Tail less than three fourths the length of the wing. 



a 1 . Bill feathered to the base, but nostrils bare OBIOLUS. 



b 1 . Bill feathered to the base and nostrils covered with bristles, or 



base of bill and nostrils bare. 

 a 2 . Bill black or brown. 



a 3 . Throat spotted ; tail black and white NUCIFHAGA. 



b 3 . Throat unspotted ; tail black COHVITS. 



6 2 . Bill orange or yellow PYEHHOCORAX. 



b. Tail more than three fourths the length of the wing. 



c 1 . Tail much graduated PICA. 



d\ Tail nearly even GARHULUS. 



Genus CORVUS. 



The genus Corvus was established by Linnaeus in 1766, in his ' Sy sterna 

 Naturae/ i. p. 155. Since Linnaeus does not give us the slightest clue as 

 to which species he considers typical, we must fall back upon Brisson, 

 whose Corvus corvus is undoubtedly the Raven and the Corvus corax of 

 Linnaeus^ which we may accept as the type. 



