454 
ECONOMIC RELATIONS OF OUR BIRDS. 
Tlie assertion,^ “Birds are only united in troops more or less considerable at 
the times of migrations of autumn and spring, that is when insects are infinitely 
less numerous than during the summer however true the impression which 
it conveys may be for Europe, is wholly untrue for the United States both in 
reference to summer residents and to birds of passage. During an average of 
two weeks in the spring and for the same length of time in the fall, the birds of 
passage are j)robably double the number per square mile of our summer resi¬ 
dents. They are ^vith us then nearly one-fifth as long and in double the abun¬ 
dance, consequently they should do, if we leave out of the account the rearing of 
young, nearly two-fifths as much work. We should expect them to eat more, 
relatively, for they are working harder. Many of them have been flying all 
night and not quietly sleeping among the branches as resident birds do. 
Because the insects are infinitely less numerous during the seasons when birds 
are migTating, does not signify that the actual number of insects destroyed is 
necessarily so much less. Tlie hungry and exhausted birds must be fed before 
they can resume their journey, and if they do not find food in abundance they 
only search the more diligently and scrutinize the more closely until their 
wants are supplied. Although most of the insects upon which they feed in the 
fall have nearly or quite passed through the period of their destructiveness, yet 
many of them are the ones which are to hibernate in one state or another, and 
from which the next season’s ravages are to come. Tliose which are consumed 
during the spring are the forms which have suiwived the severities of winter, 
and from which far more of destruction than is actually realized would come if 
they were left to multix^ly during the coming summer. It can hardly be said, 
then, that in the insects which they do destroy, they render a less service than 
do other birds. They sui^plement the woi'k of our summer residents, as it were, 
at both extremities, and they do it well. Let us see to it that they are properly 
protected. 
Some of our birds of passage are quite destructive to some crops in the fall. 
The Tennessee Warbler, called, by some, with us, the Grape-sucker, occasionally 
does serious injury to vineyards by probing with its sharp bill the ripe grapes, 
apparently to obtain the juice. It might be inferred that as this bird is with us 
so short a time, its services in destroying insects can hardly compensate for the 
injury which it may do to vineyards, and, consequently, that it is a fit subject 
for extermination. The very fact, however, that it is with us so short a time 
should make us all the more careful in regard to what steps are taken in respect 
to it. For, if ours is the only injuiy it does, and so far as is now known it is, it 
must lead a long life of usefulness in other places where it may do what other 
birds are not able to accomplish. It is, indeed, one of those small active species 
which feeds quite extensively upon plant-lice and other very small insects which 
are said to be overlooked by most birds. From the stomachs of four specimens 
examined collectively, thirty plant-lice, and thirty small heteropterous insects, 
nine-hundredths of an inch long, were taken. 
(6) The place in ivhich the bird nests. Wherever a hir’d builds its nest 
(except the forms whose young run about as soon as hatched), there or in the 
immediate vicinity, as a rule, its labors are confined until after the young are 
able to feed themselves. In consequence of this, those birds which breed in 
cultivated grounds and in the Adcinity of dwellings are generally the most 
valuable. It should be observed, however, that cultivated gi’ounds are not the 
only places where the insects rvhich ravage them are bi'ed. The army-Avorm 
» Nature's Means of Limiting the Nrmrber of Insects. Am, Nat., Yol. VIII, p. 270. 
