VERTEBRATA. 321 
tween the terrestrial and perching Birds, as the Flamin- 
goes link the aquatic and 
terrestrial. They differ from 
the typical Rasores in havy- 
ing wings for prolonged 
flight, and slender legs, fit- 
ted rather for an arboreal 
life, with toes not united, 
and the hind toe on a level 
with the rest. 
C. Aértat Brrpos.— This 
highest and largest group 
includes all those Birds 
whose toes are fitted for we 1 
grasping or perching, the Fre. 306.—Ring-dove (Columba palumbus). 
hind toe being on a level Hhelende 
with the rest. The knee is free from the body, and the 
leg is generally feathered to the heel. The wings are 
adapted for rapid or long flight; and they hop, rather 
than walk, on the ground.” They always live in pairs; 
and the young are hatched helpless. 
8. Raptores, or Birds of Prey, differ from all other 
rye Birds, except Parrots, in having a 
strongly hooked bill and a waxy 
membrane (cere) at the base of the 
upper mandible; and from Parrots, 
Fig. 307.—Barn-owl (Strix flam- Fig. 308,—Fish-hawk (Pandion Carolinensis). 
mea). Both hemispheres. United States. 
