Birds that feed on insect-life abound, and include a large pro portion of the smaller species. Vireos, warblers and kinglets search actively for insects among leaves and twigs, picking off their prey at rest or flying out a few inches after some escaping titbit. Flycatchers (Tyrannidae) watch from commanding perches and fly out to snap up passing insects on the wing, or occasionally to pick them from the ground. Nuthatches and creepers search over the bark of trees for insects, spiders or eggs hidden in the crevices, and woodpeckers chisel out coleopterous grubs from their hidden tunnels in wood. Usually these are found in decaying trunks, but occasionally some of the stronger woodpeckers will cut in through 1 in. of hard wood to secure a grub. The flicker (Co/aptes) feeds much on the ground on ants, which it secures by its long tongue as the insects run about their hills. More than 6,000 ants have been taken from the stomach of one flicker. Swifts, swallows and nightjars feed exclusively on the wing, securing flying insects in their capacious mouths. In the stomach of one nighthawk there have been found 5o species of flying insects comprising several thousand individuals. Cuckoos con sume large numbers of hairy caterpillars, from which the stomach becomes so filled with hairs stuck in the lining that its inner surface appears covered with short, stiff fur. Hummingbirds live on the nectar of flowers and tiny flies, Hymenoptera, beetles and spiders that find a home in blossoms or in the bark of trees.
Grebes, divers, herons, mergansers, cormorants and pelicans feed on fish of various kinds, most often on species not especially ,desirable from a human standpoint. Albatrosses and shearwaters take quantities of squid, and the smaller petrels seem to secure the miscellaneous array of smaller marine creatures known col lectively as plankton (q.v.). Hawks and owls feed extensively on small mammals and other birds. Some eat frogs, snakes and large insects, as well as crayfish. Larger owls may capture and consume smaller ones, and partly-grown brown pelicans, when ravenous with hunger, may seize and swallow a small member of the colony, that has just been fed. The flesh of dead animals, even in the form of putrid carrion, is sought by vultures that eat with impunity where death from poison from bacillary action would be the fate of another creature.
Though most birds seek their food day by day and so live an existence that involves continual search for sustenance, a few species form food-stores against a time of scarcity. Most remarkable among these is a group of North American wood peckers (Balanosphyra formicivora), that drill holes in the trunks of trees, in which they fit acorns, and so preserve a part of the acorn harvest for subsequent consumption. The birds work assiduously, as 13,200 acorns have been estimated as the store on one large tree-trunk, with an average density of 6o to the square foot. That the instinct for storage sometimes goes astray is shown when the carefully-drilled holes are filled with pebbles instead of nuts. The red-headed woodpecker (Melanerpes ery
throcephalus) fills cavities with quantities of acorns or other small nuts, over which it piles bits of bark to conceal them. Many shrikes (Lanius), when food is abundant, frequently im pale the bodies of grasshoppers, birds, mice or other prey on thorns, to return to them later if needed.
Hawks and owls swallow their prey entire or in large fragments, digest out all nutritive matter and form the bones, fur, scales, feathers or chitin into pellets, which are subsequently regurgi tated, leaving the stomach empty to receive another meal. Alba trosses eject pellets composed of the beaks of squids, flycatchers masses of insect chitin, and even hummingbirds may throw up tiny pellets made up of the indigestible portions of their insect food. Birds with strong, muscular gizzards, that feed on seeds, swallow sand or gravel that serves as millstones to triturate into digestible starch meal the seeds they have eaten.
The Brahmans maintain towers where food for birds is placed, and where birds may nest. In Japanese temples shelves are built where swallows may erect their homes. Indians in the eastern United States placed hollow gourds on bare stubs of trees to provide nesting cavities for the purple martin (Progne subis), a species of swallow, a practice that was adopted by early colonists from Europe, and that is followed to-day in country districts in the southern States. From these somewhat rude foundations there have developed complicated procedures for the attraction of birds about human homes. The martin-gourd has been trans formed into ornate martin-houses containing many compart ments, each of a size to house a pair of birds, and boxes or houses have been designed for many other hole-nesting birds. Though in use in many places, particularly in Germany, at an earlier date, it is since the beginning of the present century that methods for the attraction of birds have received widespread attention. In the United States and Europe single-compartment houses (nest ing-boxes ) are set up for wrens, bluebirds, tits, woodpeckers and similar birds, and where favourably located are occupied without the slightest hesitation. These bird-houses are of many types, and so many are used that commercial companies have been formed for their manufacture.
Large pieces of suet tied to the trunks or limbs of trees, where birds may feed without fear of capture from cats, draw woodpeckers, nuthatches and titmice. A shelf built on an outside window ledge will draw many birds where they may be seen to the best advantage. Sunflower and canary seed, wheat, chick feed, moderately fine-ground corn, nut meats and crumbs of bread are all relished by feathered neighbours. A mixture of suet and nut meats, preferably peanuts, ground medium fine in a food grinder, is especially relished by titmice and jays. Birds come to such feeding stands throughout the year.