The stomachs of 645 catbirds were examined and found to contain 44 per cent of animal (insect) and 56 per cent of vegetable food. Ants, beetles, caterpillars, and grasshoppers constitute three-fourths of the animal food, the remainder being made up of bugs, miscellaneous insects, and spiders. One-third of the vegetable food consists of cultivated fruits, or those which may be cultivated, as strawberries, raspberries, and blackberries; but while we debit the bird with the whole of this, it is probable--and in the eastern and well-wooded part of the country almost certain--that a large part is obtained from wild vines. The rest of the vegetable matter is mostly wild fruit, as cherries, dogwood, sour gum, elderberries, greenbrier, spiceberries, black alder, sumac, and poison ivy. Although the catbird sometimes does considerable harm by destroying small fruit, it can not on the whole be considered injurious. On the contrary, in most parts of the country it does far more good than harm.
Seven common species of swallows are found within the limits of the United States, four of which have abandoned to some extent their primitive nesting habits and have attached themselves to the abodes of man.
[Illustration: Fig. 7.--Barn swallow. Length, about 7 inches.]
In the eastern part of the country the barn swallow[16] (fig. 7) now builds exclusively under roofs, having entirely abandoned the rock caves and cliffs in which it formerly nested. More recently the cliff swallow[17] has found a better nesting site under the eaves of buildings than was afforded by the overhanging cliffs of earth or stone which it once used and to which it still resorts occasionally in the East and habitually in the unsettled West. The martin[18] and the white-bellied, or tree, swallow[19] nest either in houses supplied for the purpose, in abandoned nests of woodpeckers, or in natural crannies in rocks. The northern violet-green swallow,[20] the rough-winged swallow,[21] and the bank swallow[22] still live in practically such places as their ancestors chose.
Field observation convinces an ordinarily attentive person that the food of swallows must consist of the smaller insects captured in mid-air or picked from the tops of tall grass or weeds. This observation is borne out by an examination of stomachs, which shows that the food is made up of many small species of beetles which are much on the wing; many species of flies, together with large quantities of flying ants; and a few insects of similar kinds. Most of these are either injurious or annoying, and the numbers destroyed by swallows are not only beyond calculation but almost beyond imagination.