ORDER FIFTH. 
ZYGODACTYLY ( Birds with the toes disposed in 
opposite pairs.} 
The bill of various forms, but more or less arched and 
much hooked, — often also straight and angular (in the 
second family or sub-order.) The toes are always di- 
rected two backward and two forward, the hind exterior 
toe, however, often reversible. 
This order contains birds which have the power of 
directing at will the outer toe backward or forward ; it 
also contains a considerable number (or subordinate 
family) which retain habitually the digits in pairs. This 
conformation, affording a more solid manner of attach- 
ment, furnishes the means for clinging to and scaling the 
trunks and branches of trees ; others also make use of 
this support advantageously for the purpose of prehension 
(as the Parrots.) The European and North American 
genera of this order subsist principally upon caterpillars, 
worms, and the larvae of insects ; other exotic genera, 
with a thick and curved bill, give a preference to soft 
fruits, while others, with very strong and hooked bills, 
derive their subsistence from kernels and nuts. The 
greater number of those birds which have the toes dis- 
posed in pairs, nest in the natural cavities of old trees, 
and some, by the aid of their cutting wedged, bills, form 
