6 ECONOMIC VALUE OF BIRDS. 
in devouring small rodents, in destroying the seeds of 
harmful plants, and in acting as scavengers. — 
Leading entomologists estimate that insects cause an 
annual loss of at least two hundred million dollars to the — 
agricultural interests of the United States. The state- 
ment seems incredible, but is based upon reliable sta- 
tistics. This, of course, does not include the damage 
done to ornamental shrubbery, shade and forest trees. 
But if insects are the natural enemies of vegetation, birds 
are the natural enemies of insects. Consider for a mo- 
ment what the birds are doing for us any summer day, 
when insects are so abundant that the hum of their united 
voices becomes an almost inherent part of the atmosphere. 
In the air Swallows and Swifts are coursing rapidly == 
to and fro, ever in pursuit of the insects which constitute 
their sole food. When they retire, the Nighthawks and 
Whip-poor-wills will take up the chase, catching moths 
and other nocturnal insects which would escape day-flying 
birds. The Flycatchers lie in wait, darting from ambush 
at passing prey, and with a suggestive click of the bill 
returning to their post. The Warblers, light, active crea- 
tures, flutter about the terminal foliage, and with almost 
the skill of a Hummingbird pick insects from leaf or 
blossom. The Vireos patiently explore the under sides of 
leaves and odd nooks and corners to see that no skulker 
escapes. The Woodpeckers, Nuthatches, and Creepers 
attend to the tree trunks and limbs, examining carefully 
each inch of bark for insects’ eggs and larvse, or exca- 
vating for the ants and borers they hear at work within. 
On the ground the hunt is continued by the Thrushes, 
Sparrows, and other birds, who feed upon the innumer- 
able forms of terrestrial insects. Few places in which 
insects exist are neglected ; even some species which pass 
their earlier stages or entire lives in the water are preyed 
upon by aquatic birds. 
