CLASS II. AVES. 
9 
than in qnadrupeds. The nasal cavity exhibits but few convolutions, and in some birds the ex- 
ternal nasal apertures are either entirely wanting or reduced to a very small size. The auditory 
apparatus is well developed, and the Hearing is very perfect, though there is no external ear. The 
sense of Taste is enjoyed in a very inferior degree; the Sight surpasses in power any thing with 
which we are acquainted in other animals. The eyes are large, but have little power of motion; 
in some birds, as the owls, they are immovable in their sockets. They are furnished with two 
movable eyelids and a nictating membrane, which performs the process of winking, thus shielding 
and clearing the eyes without closing the sight. The eye is adapted alike to near and distant 
vision, so that a bird a thousand feet in the air is able to see, on the earth beneath, the small quad- 
rupeds or reptiles or insects, or even the grain on which it is to feed. By its gift of vision the 
bird is able to discover at a glance its way amid the mazes of the forest, and to distinguish birds, 
reptiles, and insects Avhose colors blend with the objects of nature around and conceal them from 
the sight of man. 
There is nothing, perhaps, more remarkable in this interesting class of animated beings than 
the voice. The windpipe is wider and stronger in birds than in any other animals, and usually 
terminates in a large cavity, which augments the sound. The lungs, too, have greater extent, 
and as we have stated, communicate with internal cavities which are capable of being expanded 
with air — thus, besides lightening the body, giving additional force to the voice. The scream of 
the eagle seventeen thousand feet in the air, and thus more than three miles distant, may be dis- 
tinctly heard, and the calls of flocks of storks and geese, beyond the reach of sight and equally 
remote, are often audible. And these wonderful powers of voice are infinitely diversified in their 
expression and use, from the simplest call to the most complicated and elaborate song. Every 
species of bird has a peculiarity of voice possessed by no other. By this variety of vocal endow- 
ment they are enabled to express to one another their wants and passions. This power of com- 
munication exists not only between the sexes, but between all individuals of the same species. 
The least experienced observer of nature knows, too, that the approach of danger is expressed by 
a universally intelligible cry, which, if uttered by the wren, for instance, is understood by the tur- 
key-cock, and vice versa. Of whatever species the one may be which first perceives the approach 
of a bird of prey, it is able to excite the attention of all birds in the neighborhood by its peculiar 
cry of warning. As soon as the blue-tit utters her Iss ! so indicative of fear and terror — which, 
nevertheless, she seems sometimes to do from pure love of mischief — the wood is silent in an in- 
stant, and every bird either listens for the enemy's coming, or hastens to the aid of the comrade 
who is attacked. This peculiarity is so marked, that in Europe the fowlers have not failed to 
turn it to purposes of profit. They build a hut, thatch it with green boughs, and cover the roof 
with a plentiful supply of limed twigs. They then display a screech-owl or other bird of prey, 
imitate the sonorous cry of a jay or woodpecker in fear and distress, and birds of every size and 
species flock to the hut and are caught. 
The tones of happiness and joy, by which one bird is able to call forth from another a similar 
expression of feeling, seem to be almost as universally intelligible. Nor is this joy shown by song 
alone, although when one little creature begins to sing, the whole wood, or, among domesticated 
birds, the whole room, soon manifests its sympathy by a general chorus. The same is frequently 
indicated by single notes. In spring and autumn a great variety of species may often be noticed 
in hedges and bushes, which seem to take great delight in the utterance of a common cry. 
Again, when in confinement, birds may often be induced to sing by various noises, loud conversa- 
tion, and above all, by instrumental music, though on wild birds these means would produce no 
other efl'ect than to frighten them away. 
In many cases, also, diff"erent species have a language, which serves for various purposes of mu- 
tual communication. For instance, ravens, crows, jackdaws, &c., understand and respond, both 
by voice and action, to each other's call. By imitating the call of the yellow-hammer, the bird- 
catchers of Europe succeed in taking the ortolan, the snow-bunting, the reed-bunting, the foolish 
bunting, &c. ; the cry of the chafiinch decoys the mountain-finch, and that of the siskin attracts 
the citron-finch and the redpole. 
"Every biixl," says Bechstein, "has received from nature the power of uttering either a. so:ng ©r 
YoL. n.— 2 
