16 
FOOD OF BIRDS. 
eluded in each of these classes, while no great difference of form and 
structure separate them, we find that the structure of birds is not so 
modified in accordance with their food habits as to be available for pur- 
poses ot systematic classification, and we thus arrive at, though indi- 
rectly and in part, the same conclusion which has been reached by Prof. 
Gil!, who finds that among recent (existing) birds divisions cannot be 
tormed ot equivalent value to those which constitute orders iu other 
classes, as, tor instance, Rodents aud Carnivora among Mammals. 
The reason for this will be more evident if we consider that birds are 
wanting in one very important element iu the classification of Mam rivals — 
teeth. The mouth of birds presents but little modification throughout 
the class, and this only such as is required for the taking and suitable 
division of food preparatory to its being immediately swallowed. Lack- 
ing fleshy lips and tongue tor tasting, teeth, and to a great extent salivary 
glands tor masticating, the food is simply reduced to a proper size and 
swallowed. The stomach is obliged to lake upon itself the mechanical 
offices which are usually performed by teeth, aud iu so far as the food of the 
bird consists ot hard substances, whether animal or vegetable, it will be 
found a strong muscular gizzard. A moment’s reflection, then, accounts 
ter so many birds using so many aud so diverse articles of food ; not 
that they are specially adapted to each kind, but because they are not so 
differenced as to prevent them from eating many kinds. 
Having shown what constitutes the food of each of our birds, we 
mi glit rest the case with those most interested, were it not that popular 
opinion regards insectivorous biids as beneficial and gramnivorcus birds 
injurious to agriculture. This is almost equivalent to saying that all i i 
sects are injurious and ail vegetables beneficial to agriculture, which is 
not the case either as regards the one or the other. Birds which feed 
upon insects do not discriminate between insects which feed upon vege- 
tables, or have other habits which are injurious, aud those which prey 
upon other insects and may for tlrs reason be highly beneficial. Neither 
do those which feed upon seeds discriminate to any noteworthy extent 
between the seeds of noxious weeds and cultivated grains. 
Insects, themselves, assist to maintain the balance ot life iu the insect 
world much more than birds, and often in a manner very different from 
our preconceived notions. For example, we have noted that the Martin 
devours wasps, which seems a very commendable trait, for this insect is 
noxious and often harmful to man. But if we study the habits of the 
common mud-wasp we find that it fills up the cell in which its egg is laid 
with spiders, which it paralyzes but does not kill, for the food of its un- 
developed young. But the spider, too, is a noxious insect, aud in our par- 
