‘FRIENDS OF OUR FORESTS 79 
cialize on insects, but each individual 
member of the group still further special- 
izes, so as to leave no loophole for the 
escape of the enemy. 
The quantity of animal food required 
to drive the avian engine at full speed is 
so very great that it is no exaggeration 
to say that practically all the waking 
hours of our warblers, from daylight to 
dark, are devoted to food-getting. What 
this never-ceasing industry means when 
translated into tons-weight of insects, it is 
impossible even to guess, but the practical 
result of the work of our warblers and 
other insectivorous birds is that we still 
have our forests, and shall continue to 
have them so long as we encourage and 
protect the birds. 
In the case of orchards and shade trees, 
there are other means at our disposal of 
controlling the insect enemy, notably the 
use of sprays. Sprays are very impor- 
tant, since birds are too few in number 
immediately to control insect outbreaks, 
especially nowadays, when the number of 
destructive native insects has been so 
greatly increased by importations from 
all quarters of the globe. But for the 
preservation of our forests we must rely 
largely upon our birds, since the use of 
sprays or of other agencies over our vast 
woodland tracts would be too expensive, 
even were it not quite impracticable for 
many other reasons. 
MEANS OF INCREASING THE NUMBER OF 
WARBLERS 
Insects are very numerous, and there is 
reason to believe that much benefit would 
result if we could multiply the present 
number of their enemies—the birds. The 
erection of bird boxes and shelters is an 
easy way to increase the number of cer- 
tain species of birds, like swallows and 
chickadees. Unfortunately, with few ex- 
ceptions, our warblers do not build their 
nests in cavities, and hence can not be 
induced to occupy bird boxes. 
Many of them, however, nest in bushes, 
vines, and shrubbery, and by planting 
clumps of these near houses something 
can be done toward increasing the num- 
bers of certain species, as the yellow 
warbler and the redstart. Because our 
warblers are chiefly insectivorous, their 
food habits bar them from the usual bird 
lunch-counter in times of hard storms. 
During migration, warblers are pecu- 
liarly exposed to the danger of prowling 
cats. Many species feed close to or even 
on the ground, and then they are so much 
concerned with their own business that 
any tabby, however old and lazy, is equal 
to catching one or more individuals daily. 
The bird lover can do good service by 
summarily disposing of vagrant cats, 
which, during migration, work havoc in 
the ranks of our small birds. 
They can also restrain the pernicious 
activities of their own pets, for these, 
however well fed, are still subject to the 
predatory instincts of their wild ancestry, 
which impel them to stalk a live bird with 
all the zeal and cunning of their fore- 
bears. 
PLUMAGES OF WARBLERS 
Little difficulty is experienced, even by 
the tyro, in distinguishing watblers from 
other birds, but to recognize the several 
species is not so easy, particularly as the 
adult males and females of many species 
are markedly dissimilar, while the young, 
both in the first and second plumages, 
often differ from the adults. So far as 
possible the various plumages are shown 
in the illustrations of Mr. Fuertes, which 
are so admirable as to do away with the 
need of descriptive text. All are ap- 
proximately one-half life size. 
