SOME COMMON BIRDS USEFUL TO THE FARMER
by F. E. L. Beal, Farmers’ Bulletin 630, USDA, February 1915
Whether a bird is beneficial or injurious depends almost entirely upon what it eats. In the case of species which are very abundant, or which feed to some extent on the crops of the farmer, the question of their average diet becomes one of supreme importance, and only by stomach examinations can it be satisfactorily solved. Field observations are at best but fragmentary and inconclusive and lead to no final results. Birds are often accused of eating this or that product of cultivation, when an examination of the stomachs shows the accusation to be unfounded. Accordingly, the Biological Survey has conducted for some years past a systematic investigation of the food of those species which are most common about the farm and garden.
Within certain limits birds eat the kind of food that is most accessible, especially when their natural food is scarce or wanting. Thus they sometimes injure the crops of the farmer who has unintentionally destroyed their natural food in his improvement of swamp or pasture. Most of the damage done by birds and complained of by farmers and fruit growers arises from this very cause. The berry-bearing shrubs and seed-bearing weeds have been cleared away, and the birds have no recourse but to attack the cultivated grain or fruit which has replaced their natural food supply. The great majority of land birds subsist upon insects during the period of nesting and molting, and also feed their young upon them during the first few weeks. Many species live almost entirely upon insects, taking vegetable food only when other subsistence fails. It is thus evident that in the course of a year birds destroy an incalculable number of insects, and it is difficult to overestimate the value of their services in restraining the great tide of insect life.
In winter, in the northern part of the country, insects become scarce or entirely disappear. Many species of birds, however, remain during the cold season and are able to maintain life by eating vegetable food, as the seeds of weeds. Here again is another useful function of birds in destroying these weed seeds and thereby lessening the growth of the next year.
In the following pages are discussed the food habits of more than 50 birds belonging to 12 families. [We are featuring four of the 50 in this issue, ed.] Many are eastern forms which are represented in the West by slightly different species or sub-species, but unless the food habits differ they are not separately described. In some cases specific percentages of food are given, but for the most part the statements are made without direct reference to the data on which they are based.
The eastern bluebird (Sialia sialis shown in Fig. 1), one of the most familiar and welcome of our feathered visitors, is a common inhabitant of all the States east of the Rocky Mountains from the Gulf of Mexico to southern Canada. In the Mississippi Valley it winters as far north as southern Illinois, and in the East as far as Pennsylvania. It is one of the earliest northern migrants, and everywhere is hailed as a harbinger of spring. Very domestic in habits, it frequents orchards and gardens, and builds its nests in cavities of trees, crannies in farm buildings, or boxes provided for its use.
The bluebird has not been accused, so far as known, of stealing fruit or of preying upon crops. An examination of 855 stomachs showed that 68 per cent of the food consists of insects and their allies, while the other 32 per cent is made up of various vegetable substances, found mostly in stomachs taken in winter. Beetles constitute 21 per cent of the whole food, grasshoppers 22, caterpillars 10, and various other insects 9, while a number of spiders and myriapods, about 6 per cent, comprise the remainder of the animal diet. All these are more or less harmful, except a few predacious beetles, which amount to 9 per cent. In view of the large consumption of grasshoppers and caterpillars we may at least condone this offense, if such it may be called. The destruction of grasshoppers is very noticeable in August and September, when these insects make up about 53 per cent of the diet.
It is evident that in the selection of its food the bluebird is governed more by abundance than by choice. Predacious beetles are eaten in spring, as they are among the first insects to appear; but in early summer caterpillars form an important part of the diet, and these are later replaced by grasshoppers. Beetles are eaten at all times, except when grasshoppers are more easily obtained.
So far as its vegetable food is concerned the bluebird is positively harmless. The only trace of any useful product in the stomachs consisted of a few blackberry seeds, and even these probably belonged to wild rather than cultivated varieties. Following is a list of the various seeds which were found: Blackberry, chokeberry, juniperberry, pokeberry, partridgeberry, greenbrier, Virginia creeper, bittersweet, holly, strawberry bush, false spikenard, wild sarsaparilla, sumac (several species), rose haws, sorrel, ragweed, grass, and asparagus. This list shows how little the bluebird depends upon the farm or garden to supply its needs and how easily by encouraging the growth of some of these plants, many of which are highly ornamental, the bird may be induced to make its home on the premises.
Two species of bluebirds inhabit the Western States—the mountain bluebird (Sialia currucoides) and the western bluebird (Sialia mexicana subspecies). In their food habits they are even more to be commended than their eastern relative. Their insect food is obtainable at all times of the year, and the general diet varies only in the fall, when some fruit, principally elderberries, is eaten, though an occasional blackberry or grape is also relished. In an examination of 217 stomachs of the western bluebird, animal matter (insects and spiders) was found to the extent of 82 per cent and vegetable matter to the extent of 18 per cent. The bulk of the former consists of bugs, grasshoppers, and caterpillars. Grasshoppers, when they can be obtained, are eaten freely during the whole season. Caterpillars also are a favorite food and are eaten during every month of the year; March is the month of greatest consumption, with 50 per cent, and the average for the year is 20 per cent. Two stomachs taken in January contained 64 and 50 per cent, respectively, of caterpillars, Beetles also are eaten and comprise mostly harmful species.
The vegetable matter consists of weed seeds and small fruits. In December a few grapes are eaten, but elderberries are the favorites whenever they can be found. It is only when these are in their greatest abundance that vegetable exceeds animal food.
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.
In the eastern part of the country the barn swallow (Hirundo erythrogastra shown in Fig. 2) now builds exclusively under roofs, having entirely abandoned the rock caves and cliffs in which it formerly nested. More recently the cliff swallow (Petrochelidon lunifrons) 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 (Progne subis) and the white-bellied, or tree, swallow (Iridoprocne bicolor) nest either in houses supplied for the purpose, in abandoned nests of woodpeckers, or in natural crannies in rocks. The northern violet-green swallow, (Tachycineta thalassina), the rough-winged swallow, (Stelgidopteryx serripennis), and the bank swallow (Riparia riparia) still live in practically such places as their ancestors chose.
Field observation convinces an ordinarily attentive person that the food of swallows much 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 mosquitoes and their allies, 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.
Unlike many other groups of birds, the six species of swallows found in the Eastern States extend in a practically unchanged form across the continent, where they are reinforced by the northern, or Pacific-coast, violet-green swallow.
It is a mistake to tear down from the eaves of a barn the nests of a colony of cliff swallows, for so far from disfiguring a building they make a picturesque addition to it, and the presence of swallows should be encouraged by every device. It is said that cliff and barn swallows may be induced to build their nests in a particular locality, otherwise suitable, by providing a quantity of mud to be used by them as mortar. Barn swallows may also be encouraged by cutting a small hole in the gable of the barn, while martins and white-bellied swallows will be grateful for boxes like those for the bluebird, but placed in a higher situation.
The eastern meadowlark (Sturnella magna shown in Fig. 3) is a common and well-known bird occurring from the Atlantic coast to the Great Plains, where it gives way to the closely related western species, (Sturnella neglecta) which extends thence westward to the Pacific. It winters from our southern border as far north as the District of Columbia, southern Illinois, and occasionally Iowa. The western form winters somewhat farther north. Although it is a bird of the plains, and finds its most congenial haunts in the prairies of the West, it is at home wherever there is level or undulating land covered with grass or weeds, with plenty of water at hand.
In the 1,514 stomachs examined, animal food (practically all insects) constituted 74 per cent of the contents and vegetable matter 26 per cent. As would naturally be supposed, the insects were ground species, as beetles, bugs, grasshoppers, and caterpillars, with a few flies, wasps, and spiders. A number of the stomachs were collected when the ground was covered with snow, but even these contained a large percentage of insects, showing the bird’s skill in finding proper food under adverse circumstances.
Of the various insects eaten, crickets and grasshoppers are the most important, constituting 26 per cent of the food of the year and 72 per cent of the food in August. It is scarcely necessary to mention the beneficial effect of a number of these birds on a field of grass in the height of the grasshopper season. Of the 1,514 stomachs collected at all seasons of the year, 778, or more than half, contained remains of grasshoppers, and one was filled with fragments of 37 of these insects. This seems to show conclusively that grasshoppers are preferred, and are eaten whenever they can be found. Especially notable is the great number taken in August, the month when grasshoppers reach their maximum abundance; stomach examination shows that large numbers of birds resort at this time to this diet, no matter what may be the food during the rest of the year.
Next to grasshoppers, beetles make up the most important item of the meadowlark’s food, amounting to 25 per cent, about one-half of which are predacious ground beetles. The others are all harmful species.
Forty-two individuals of different kinds of May beetles were found in the stomachs of meadowlarks, and there were probably many more which were past recognition. To this form and several closely allied ones belong the numerous white grubs, which are among the worst enemies to many cultivated crops, notably grasses and grains, and to a less extent strawberries and garden vegetables. In the larval stage they eat the roots of these plants, and being large, one individual may destroy several plants. In the adult stage they feed upon the foliage of trees and other plants, and in this way add to the damage which they began in the earlier form. As these enemies of husbandry are not easily destroyed by man, it is obviously wise to encourage their natural foes.
Among the weevils found in the stomachs the most important economically are the cotton-boll weevil and the recently introduced alfalfa weevil of Utah. Several hundred meadowlarks were taken in the cotton-growing region, and the boll weevil was found in 25 stomachs of the eastern meadowlark and in 16 of the western species. Of the former, one stomach contained 27 individuals. Of 25 stomachs of western meadowlarks taken in alfalfa fields of Utah, 15 contained the alfalfa weevil. In one stomach 23 adults were found, in another 32 adults and 70 larvae, still another had 10 adults and 40 larvae, while a fourth had 4 adults and 100 larvae.
Caterpillars form a very constant element of the food, and in May constitute over 24 per cent of the whole. May is the month when the dreaded cutworm begins its deadly career, and then the lark does some of its best work. Most of these caterpillars are ground feeders, and are overlooked by birds which habitually frequent trees, but the meadowlark finds and devours them by thousands. The remainder of the insect food is made up of ants, wasps, and spiders, with some bugs, including chinch bugs, and a few scales.
The vegetable food consists of grain and weed and other hard seeds. Grain in general amounts to 11 per cent and weed and other seeds to 7 per cent. Grain, principally corn, is eaten mostly in winter and early spring and consists, therefore, of waste kernels; only a trifle is consumed in summer and autumn, when it is most plentiful. No trace of sprouting grain was discovered. Clover seed was found in only six stomachs, and but little in each. Seeds of weeds, principally ragweed, barnyard grass, and smartweed, are eaten from November to April, inclusive, but during the rest of the year are replaced by insects.
Briefly stated, more than half of the meadowlark’s food consists of harmful insects; its vegetable food is composed either of noxious weeds or waste grain, and the remainder is made up of useful beetles or neutral insects and spiders.
A strong point in the bird’s favor is that, although naturally an insect eater, it is able to subsist on vegetable food, and consequently is not forced to migrate in cold weather farther than is necessary to find ground free from snow.
Among the early spring arrivals to their northern homes none is more welcome than the phoebe (Fig. 4). The common phoebe (Sayornis phoebe) breeds throughout the United States east of the Great Plains, and winters from the South Atlantic and Gulf States southward. Its western relative, the black phoebe, (Sayornis nigricans) is found from Texas west to the Pacific coast, which it occupies as far north as Washington, replacing through most of this region the common or eastern form.
Though naturally building its nest under an overhanging cliff of rock or earth, or in the mouth of a cave, the preference of the eastern species for the vicinity of farm buildings is so marked that in the more thickly settled parts of the country the bird is seldom seen at any great distance from a farmhouse, except where a bridge spanning a stream affords a secure spot for a nest. Its confiding disposition renders it a great favorite, and consequently it is seldom disturbed.
The phoebe subsists almost exclusively upon insects, most of which are caught upon the wing. An examination of 370 stomachs showed that over 89 per cent of the year’s food consists of insects and spiders, while wild fruit constitutes the remainder. The insects belong chiefly to noxious species, and include many click beetles, May beetles, and weevils. Other beetles, belonging to 21 families that were identified, make up 10.65 per cent. They appear to be eaten very regularly in every month, but the most are taken in spring and early summer. May is the month of maximum consumption, with 20.43 per cent. Beetles altogether amount to 15.3 per cent, which places them second in rank of the items of animal food. The notorious cotton-boll weevil was found in six stomachs taken in the cotton fields of Texas and Louisiana, and five individuals of the strawberry weevil were taken from one collected in Texas. Many other beetles contained in the stomachs are equally harmful, but are not so widely known. Such are the corn leaf-beetle, which feeds upon corn; the 12-spotted cucumber beetle and the striped cucumber beetle, both of which seriously injure and sometimes destroy cucumber and squash vines; and the locust leaf miner, which is sometimes so numerous that all the locust trees over large areas are blasted as by fire.
In the phoebe’s diet hymenopterous insects stand at the head, as in the case with most of the flycatchers. They are eaten with great regularity and are the largest item in nearly every month. A few are useful parasitic species, but these are offset by a number of sawfly larvae, which are very harmful insects. Ants were found in 24 stomachs. No honeybees were identified. In their season grasshoppers are much relished, while wasps of various forms, many flies of species that annoy cattle, and a few bugs and spiders are also eaten regularly. It is evident that a pair of phoebes must materially reduce the number of insects near a garden or field, as the birds often, if not always, raise two broods a year, and each brood numbers from four to six young.
There is hardly a more useful species about the farm than the phoebe, and it should receive every encouragement. To furnish nesting boxes is helpful, but not necessary, as it usually prefers a more open situation, like a shed or a nook under the eaves, but it should be protected from cats and other marauders.
The black phoebe has the same habits as its eastern relative, both as to selection of food and nesting sites, preferring for the latter purpose some structure of man, as a shed or, better still, a bridge over a stream of water, and the preference of the black phoebe for the vicinity of water is very pronounced. One may always be found at a stream or pool and often at a watering trough by the roadside.
Careful study of the habits of the bird shows that it obtains a large portion of its food about wet places. While camping beside a stream in California the writer took some pains to observe the habits of the black phoebe. The nesting season was over, and the birds had nothing to do but eat. This they appeared to be doing all the time. When first observed in the morning, at the first glimmer of daylight, a phoebe was always found flitting from rock to rock, although it was so dusky that the bird could hardly be seen. This activity was kept up all day. Even in the evening, when it was so dark that notes were written by the aid of the camp fire, the phoebe was still engaged in its work of collecting, though it was difficult to understand how it could catch insects when there was scarcely light enough to see the bird. Exploration of the stream showed that every portion of it was patrolled by a phoebe, that each one apparently did not range over more than 12 or 13 rods of water, and that sometimes two or three were in close proximity.
The number of insects destroyed in a year by the black phoebe is enormous. Fortunately, the examination of stomachs has supplemented observation in the field, and we are enabled to give precise details. Of the 333 stomachs examined, every one contained insets as the great bulk of the food. Only 15 contained any vegetable food at all, and in no case was it a considerable part of the contents of the stomach. The insects eaten were mostly wasps, bugs, and flies, but many beetles also were destroyed.
Useful beetles belonging to three families amount to 2.8 per cent of the food. Other beetles of harmful or neutral species reach 10.5 per cent. Wasps, the largest item of the food, were found in 252 stomachs and were the whole contents of 15. The average for the year is 35 per cent. Parasitic species were noted, but they were very few. Ants were found in 48 stomachs, and for a short time in midsummer they constitute a notable part of the food. Various wild bees and wasps make up the bulk of this item. No honeybees were found.
Bugs in various forms constitute 10.56 per cent and are eaten in every month but May. Stinkbugs appear to be the favorites, as they were contained in 10 stomachs. Plant lice were found in one stomach. Flies, forming the second largest item, were found in 97 stomachs and completely filled 3. They constitute the most regular article in the black phoebe’s diet. The maximum consumption occurs in April, 64.3 per cent. The black phoebe well merits its title of flycatcher.
Moths and caterpillars amount to 8.2 per cent of the food. They were found in 72 stomachs, of which 51 contained the adult moths and 28 the larvae or caterpillars. One stomach was entirely filled with adults. This is one of the few birds studied by the writer that eats more moths than caterpillars, for as a rule the caterpillars are largely in excess. Flycatchers, taking their food upon the wing, would naturally prove exceptions to the rule. Crickets are evidently not a favorite food of the black phoebe, as they amount to only 2.45 per cent. They were found in 39 stomachs, but usually the amount in each was small, though one stomach was entirely filled with them. Grasshoppers did not appear. Dragon flies were eaten to some extent, and these illustrate the fondness of the species for the neighborhood of water.
The vegetable matter eaten consisted chiefly of small wild fruits of no economic importance.
Another phoebe inhabiting the Western States and breeding as far north as Alaska is the Say’s phoebe (Sayornis sayus). Investigation of its food was based on the examination of 86 stomachs, and while none were available for the months when insects are most numerous, the bird proved to be one of the most exclusively insectivorous of the family. That it takes a few useful insects can not be denied, but these are far outnumbered by the harmful ones it destroys, and the balance is clearly in favor of the bird. Its vegetable food amounts to only 2 per cent and is made up of a little wild fruit, seeds, and rubbish.