The blue jay[45] (fig. 17) is a conspicuous member of our bird population
east of the Plains, especially in autumn when his brilliant plumage
contrasts vividly with the brown> foliage. Even in winter he stays with
us, though at this time he is less common along our northern border. In
spring and summer, while by no means uncommon, the blue jay is not so
often noticed, as the retiring disposition which he assumes during the
breeding season assists in protecting him from enemies. This also allows
him to carry on with considerable impunity that inglorious practice of
nest robbing of which, in a measure, he has been rightfully accused.
[45] _Cyanocitta cristata_.
[Illustration: Fig. 17.--Blue Jay. Length, about 11½ inches.]
Examination of 530 stomachs collected at all times of the year in 30
of our Eastern States and Canada shows that insects comprise about 22
per cent of the yearly sustenance. About three-fourths of these are
injurious, the remainder being neutral or beneficial. Of the injurious
insects, grasshoppers form the largest portion; in August nearly a fifth
of the food. Caterpillars are conspicuous in July and August and at this
time average about a tenth of the stomach contents. Both laboratory
investigations and field observations have established the fact that in
winter the eggs of the tent caterpillar and the hibernating larvæ of the
brown-tail moth in New England are eagerly sought Scarabæid beetles form
about 4 per cent of the yearly food, and click beetles and wire-worms
about 1 per cent. Of the beneficial forms, ground beetles (3 per cent)
and hymenopterous insects, part of which are parasitic (2.5 per cent),
are taken most frequently. A few other invertebrates, as spiders,
millipedes, mollusks, and crustaceans, also are eaten throughout the year.
In the consideration of the vertebrate food of the blue jay we are
confronted with the problem of the destruction of wild birds and their
eggs. Special search was made for every possible trace of such material
in the stomachs, and in 6 of the 530 were found the remains of wild birds
or their eggs. In February two jays had killed a small bird apiece; in
May one had robbed a nest of eggs; in June two had taken a small bird and
a clutch of eggs, respectively; and in August another had robbed a nest
As this trait of the jay appears to be most pronounced during its own
breeding season, it is quite possible for many birds which have suffered
from its boldness early in the season to raise another brood unmolested.
Thirty-nine of the 530 jays examined had fed on hen's eggs. Much of this
food, however, was picked up about rubbish heaps, to which the jay, like
other members of the crow family, is partial. While the result of stomach
analysis would appear to belittle this fault of the blue jay, it is
doubtless quite characteristic of the bird under favorable conditions.
Complaint that the jay is the source of considerable damage to corn in
the fall has been verified to a certain degree by stomach examination.
This grain is taken in every month of the year, but in greater
quantities during winter and early spring, when much of it is necessarily
waste, and it forms about 18 per cent of the yearly food. Cultivated
fruits of various kinds are eaten from June to the end of the year, and
the 15 per cent taken in July apparently justifies complaints against
the bird on this score. The favorite vegetable food of the blue jay is
mast of various kinds, acorns predominating, but beechnuts, chestnuts,
chinquaquins, and hazelnuts also are relished. This food is important in
every month but July and August, the yearly average being over 43 per
cent, and from October to March it constitutes about two-thirds of the
diet. Occasionally harm is done by feeding also on cultivated nuts, as
pecans. Wild fruits are eaten during the summer and fall and constitute
about 7 per cent of the yearly sustenance.
The blue jay probably renders its best services to man in destroying
grasshoppers late in the season and in feeding on hibernating insects and
their eggs, as it does in the case of the tent caterpillar and brown-tail
moth. Such forest insects as buprestid beetles and weevils of various
kinds also fall as its prey.
The blue jay's vegetable food, with the exception of some cultivated
fruit and corn in the fall, is largely neutral. The severest criticism
against the species is the destruction of other birds and their eggs.
Where we wish to attract birds in large numbers about our dooryards, in
our parks, and in game preserves, it will be well not to allow the jays
to become too abundant.