100 USEFUL BIRDS. 
are subject to a more or less regular periodical pruning. 
Large quantities of twigs and small branches fell from the 
oaks and other trees in 1896, and it appeared as if the 
oak pruners might do considerable injury to these trees; 
but birds and other natural enemies attacked the insects, 
and the trees were not injured, —very likely in most cases 
they were even benefited by this removal of the twigs from 
the upper branches. Jays, Crows, and Hawks break off 
strong twigs and small branches to use in their nest build- 
ing. Squirrels gnaw off many twigs while gathering nuts 
and acorns, or while building their nests. When branches 
are injured by insects or overshading to such an extent that 
they die, they are removed later (when weakened by decay) 
by the action of the wind, or are broken off in winter by 
ice and snow. Thus the pruning of the trees is effected. 
THE GUARDIANS OF THE TREES. 
Birds guard the Trees the Year round. — We know that 
trees are subject to many injuries by reason of the undue 
multiplication of animals that feed upon them. The foliage 
is devoured by insects and other animals; the fruit and 
seeds by insects, birds, and squirrels; the twigs are killed 
by borers or girdlers ; the bark is eaten by mice, hares, squir- 
rels, or porcupines ; the trunks are attacked by wood borers ; 
the roots have insect enemies ; even the very life blood, the 
sap, is sucked out by aphids. When we consider well the 
fecundity, voracity, and the consequent great possibilities 
for mischief possessed by their enemies, we wonder that 
trees survive at all. Still, trees spring up and grow apace. 
In a wooded country a few years’ neglect of field and pasture 
suffices to clothe them with a growth of bushes and saplings, 
and in time a wood lot succeeds the cleared land. That 
trees are able thus to spring up and grow to maturity with- 
out man’s care is sufficient evidence that they are protected 
by their natural friends from the too injurious inroads of 
their natural enemies. Among these friends birds hold a 
high place. 
It is generally believed that there are few birds in deep 
’ woods. Travellers often have remarked the scarcity of birds 
