44G 
ECONOMIC RELATIONS OF OUR BIRDS. 
our birds, even from that of the Swamp Sparrow, a bird which rarely pursues 
its prey upon the wing and which is counted among the seed-eating forms. 
The nocturnal habits, which so many insects possess, do not offer such absolute 
protection against birds as some appear to think. Lepidopterous insects, so 
many of which deposit their eggs under the cover of night, feed in the larval 
state, with some exceptions, during the day, and this is the longest and so the 
most dangerous period of their existence, as it is the most destructive. But 
even when hidden during the day, insects ai’e not secure; birds have learned 
their hiding places and search them out, and some of them make this the busi¬ 
ness of their lives. The Woodpeckers, Nuthatches and Creepers capture those 
that have hidden beneath the bark and in the crevices on the trunks and 
branches of trees; Warblers, Vireos and Flycatchers destroy those that betake 
themselves to the undersides of leaves; and the Thrushes, Finches and Star¬ 
lings pick up those that seek security upon the ground and among the grass. 
“ Mimicry,” though protective, doubtless, to some extent, does not lessen the 
service which birds render. It simply tends to throw the heaviest attacks upon 
the more conspicuous forms. But protective colors, forms and surfaces can 
hardly be as effectual against birds as against predaceous insects, for they sur¬ 
vey their field from a more advantageous point of view, and they discriminate 
well objects both remote and close at hand. Besides, birds, and predaceous in¬ 
sects as well, learn to see as collectors learn to collect. They become experts in 
their business, and this is of as great an advantage to them as “ mimicry” can 
be to other forms. 
While many of our troublesome insects spend their larval states in the stems 
^of plants, in various fruits or beneath the ground, feeding upon the roots of 
plants beyond the reach of most birds, yet even these, while searching for places 
in which to undergo their transformations, and in the winged state, are de¬ 
stroyed by birds in large numbers. If birds do not exterminate noxious insects, 
they nevertheless perform a serviceable mission by holding them within certain 
limits. 
That an approximate estimate may be made of the amount of work which 
birds do in destroying insects, the table given below has been prepared. The 
first four columns are compiled from notes taken in Jefferson county, between 
July 31st and August 7, 1878; those in the last four columns are from notes 
taken in the vicinity of Ithaca, N. Y., in June of 1878. In each column, opposite 
the name of the species, is given the number of individuals which were observed 
in traveling the distance that is given near the foot of each column. The item, 
‘‘ Birds seen or heard, but not named,” includes those individuals which were 
known to exist in the territory passed over, but which, for various reasons, 
could not be identified with certainty. The two series of observations are taken 
for the purpose of comparison in discussing another point. As will be seen 
further on, the different routes were chosen with reference to certain topo¬ 
graphical features, in order that the combined results might include the pecul¬ 
iarities due to them. By referring to the table it will be seen that the average 
number of individuals observed per mile on the four trips in the two localities 
bear a remarkable closeness to one another, that for Jefferson being about 33 
per mile, and that for the vicinity of Ithaca nearly 57 per mile. Since these 
results are so close to one another, they may be fairly assumed to represent a 
definite factor, for the respective localities, at the time the observations were 
taken. 
