F. E. L. Beal

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.

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 wireworms about 1 per cent. Of the beneficial forms ground beetles (3 per cent) and hymenopterous insects, part of which are parasitic (2.5 percent), 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 his 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 To 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, chinquapins, 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 they do 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 their 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 the latter 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.