530 BRITISH BIRDS. 
Subfamily CORVIN A, orn CROWS. 
The Crows and their allies are distinguished from all the allied sub- 
families, except the Sylviine, 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 Corvin 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, Bill feathered to the base, but nostrils bare .............+-. ORIOLUS., 
b', Bill feathered to the base and nostrils covered with bristles, or 
base of bill and nostrils bare. 
a’, Bill black or brown. 
a*, Throat spotted; tail black and white.......... ... NUCIFRAGA, 
b*.. Throat unspottedis tall black: a, ke ns ee ce he Corvus. 
Pu, ball orange or yellows...4.. sie os cates t spate oni eee PYRRHOCORAX. 
b. Tail more than three fourths the length of the wing. 
Cee Led wach Sraduatell : 3-5... «akon Mewes at sue ee eee Pica, 
DL ae MOATLY SYED...) cans: PURI REM EM ee  s ek eo nies s GARRULUS, 
Genus CORVUS. 
The genus Corvus was established by Linneus in 1766, in his ‘ Systema 
Nature,’ i. p. 155. Since Linnzeus 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 coraa of 
Linnzeus, which we may accept as the type. 
