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360 ORNITHOLOGY AND OOLOGY. 
noxious insects in their different forms. It is perfectly safe 
to say, that it would destroy a thousand insects in making 
up the amount of food that I mentioned above ; and it is not 
improbable, that, during this month, it actually eats that 
number daily. 
During the first half of May, its labors are undoubtedly 
beneficial; for its food still consists almost entirely of in- 
sects: but after the middle of that month, when the small 
birds have begun to lay their eggs and hatch their young, 
the Crow divides its diet pretty equally between them and the 
insects. Now, it is not apparent, at the first glance, how 
immensely injurious it becomes the moment it begins to 
destroy the eggs and young of our small birds; but we may 
demonstrate it to an approximation. We will allow, that, 
during the latter part of May, half of its food consists of 
injurious insects and other vermin: it is therefore beneficial 
in the whole month about twenty-three units. But it is 
perfectly reasonable to say, that it destroys at least the eggs 
or young of one pair of Sparrows, four in number ; one pair 
of Warblers, four in number; and one pair of Thrushes or 
Starlings, four in number: for I have known one pair of 
Canada Jays to kill and devour the half-grown young of four 
families of Snowbirds (Junco hyemalis), sixteen birds in all, 
in one forenoon; and have seen a pair of crows, in two 
visits to an orchard, within a half-hour’s time, destroy the 
young birds in two robins’ nests. 
Now, let us see what the injury amounts to that it does in 
destroying the four eggs or young of the Sparrows, Warblers, 
and Thrushes. It is a well-known fact, that the young of 
all our small birds, whether insectivorous or graminivorous 
in the adult stage, are fed entirely on insects. Bradley 
says that a pair of Sparrows will destroy 3,360 caterpillars 
for a week’s family supplies. For four weeks, at the lowest 
estimate, the young of our Sparrows are fed on this diet; 
and the family that the crow destroys would, in that time, 
eat at least 13,440 noxious insects; and, as they feed more 
