8 
INTRODUCTION. 
respectively the three most perfect senses, which exercise a general 
influence on the character. 
After sight, the most perfect of the senses in birds appears to be 
hearing , which is even superior to that of the quadrupeds, and 
scarcely exceeded in the human species. We perceive with what 
facility they retain and repeat tones, successions of notes, and even 
discourse ; we delight to listen to their unwearied songs, to the in- 
cessant warbling of their tuneful affection. Their ear and throat 
are more ductile and powerful than in other animals, and their voice 
more capacious and generally agreeable. A Crow, which is scarcely 
more than the thousandth part the size of an ox, may be heard as 
far, or farther ; the Nightingale can fill a wider space with its music 
than the human voice. This prodigious extent and power of sound 
depend entirely on the structure of their organs but the support 
and continuance of their song result solely from their internal 
emotions. 
The windpipe is wider and stronger in birds than in any other 
class of animals, and usually terminates below in a large cavity that 
augments the sound. The lungs too have greater extent, and com- 
municate with internal cavities, which are capable of being expanded 
with air, and, besides lightening the body, give additional force to the 
voice. Indeed the formation of the thorax, the lungs, and all the 
organs connected with these, seem expressly calculated to give force 
and duration to their utterance. 
Another circumstance, showing the great power of voice in birds, 
is the distance at which they are audible in the higher regions of the 
atmosphere. An Eagle may rise at least to the height of 17,000 
feet, for it is there just visible. Flocks of Storks and Geese may 
mount still higher, since, notwithstanding the space they occupy, 
they soar almost out of sight ; their cry will therefore be heard from 
an altitude of more than three miles, and is at least four times as 
powerful as the voice of men and quadrupeds. 
Sweetness of voice and melody of song are qualities, which in 
birds are partly natural and partly acquired. The facility with 
which they catch and repeat sounds, enables them not only to bor- 
row from each other, but often even to copy the more difficult 
inflections and tones of the human voice, as well as of musical 
instruments. It is remarkable, that, in the tropical regions, while the 
birds are arrayed in the most glowing colors, their voices are hoarse, 
grating, singular, or terrific. Our sylvan Orpheus, the Mocking-bird, 
the Brown Thrush, the Warbling Flycatcher ; as well as the Linnet, 
