FOOD OF THE BOBOLINK, BLACKBIRDS, AND GRACKLES.

By F. E. L. BEAL, B. S.,

Assistant Biologist, U. S. Department of Agriculture.

INTRODUCTION.

The birds commonly known as bobolinks, meadowlarks, orioles, blackbirds, grackles, and cowbirds are all comprised in a group known as the family Icteridæ, which is represented in the United States by 29 species and subspecies. These differ remarkably in plumage, nesting habits, and methods of obtaining food. The plain black in which many of them are clothed is relieved in the redwing by a touch of brilliant color, and in the bobolink (in spring dress) by white and buff; in the orioles it is usually reduced to a few patches to offset the bright tints; and in the meadowlarks is restricted to a black crescent on the breast. The orioles build their nests in trees, sometimes at a considerable height, and obtain their food among the leaves and branches. The bobolinks and meadowlarks build upon the ground and depend for food upon such insects and seeds as they find on the surface. The other species take an intermediate position, some, such as the crow blackbird, building in trees, and others on low bushes and rushes, but all obtaining the greater part of their food on the ground.

In this bulletin are discussed the food habits of the bobolink, the cowbird, the yellow-headed blackbird, the red-winged blackbird, the California red-winged blackbird, the rusty blackbird, Brewer's blackbird, the crow blackbird, and the boat-tailed grackle. These comprise all the important members of the group with the exception of the meadowlarks and orioles. One or more of these species may be found at some time of the year in every State and Territory. As they are much given to nesting and feeding about farms and stock yards or to visiting outlying grainfields and pastures, the character of their food becomes a question of considerable importance to the cultivator.

1

1A report on the food of the meadowlark and Baltimore oriole was published in the Yearbook of the Department of Agriculture for 1895, pp. 419-430; a preliminary report on the food habits of the crow blackbird appeared in the Yearbook for 1894, pp. 233-248; and the grain-eating habits of most of the blackbirds were discussed under the title 'Birds injurious to grain,' in the Yearbook for 1897, pp. 345-354.

Writers on ornithology give notes on the food of various species of birds, based for the most part on field observation, and in some cases on examination of stomachs, but usually such investigations are neither extensive nor systematic. In the early days, when birds were abundant and grainfields few, blackbirds, or 'maize thieves,' as they were called, were the first species to render themselves objects of notice by their attacks upon the crops of the early settlers, and bounties were offered for their destruction; in fact, they had already acquired a bad reputation with the aborigines by their depredations upon the patches of maize. Their very pronounced taste for grain, and their habit of associating in large flocks, soon attracted the attention of pioneer farmers everywhere; and it did not take these shrewd observers long to decide that the birds were a nuisance and to plan for their extermination. All devices of this kind, however, have (fortunately, perhaps) proved futile. The birds still flourish, though in somewhat reduced numbers, and are still a source of considerable damage in many places.

At the present day direct bounties are not so much in vogue as they were when the country was newer; and State laws protecting birds have become numerous. But the evil repute of the blackbirds has caused them to be omitted from many of these statutes, while in others either blackbirds in general or particular species are specially exempted from protection. Blackbirds in general are specially exempted in Maryland, Michigan, Wisconsin, Minnesota, and Arkansas; the crow blackbird in Vermont, Massachusetts, South Carolina, and Illinois; the ricebird (bobolink) in Georgia; the common blackbird' and the crow blackbird in New York; the crow blackbird in Rhode Island; and the crow blackbird and redwing in New Jersey.

In certain States near the Atlantic seaboard some species, notably the bobolink, are regarded as game, and an open season is provided for shooting them. In New Jersey reedbirds' (bobolinks) may be lawfully killed from August 25 to January 1; in Pennsylvania from September 1 to November 30; in Delaware from September 1 to February 1; and in Maryland between September 1 and November 1. In the District of Columbia the redwing is included with the bobolink, and shooting is permitted on Tuesdays, Thursdays, and Saturdays, between August 21 and February 1.

The investigation of the food of blackbirds by the examination of the contents of their stomachs, while confirming to a certain extent the popular estimate of their grain-eating propensities, has shown also that during the season when grain is not accessible these birds destroy immense quantities of seeds of harmful weeds, and that during the whole of the warmer portion of the year, even when grain is easily obtained, they devour a great number of noxious insects. The vegetable portion of the food usually considerably exceeds the animal.

The latter consists mostly of insects,' with the addition in a few species of some crustaceans and snails and now and then a small vertebrate. The vegetable food comprises chiefly hard seeds, of which any grain may be taken as a sample. Fruit is eaten by a few species, but not to an injurious extent, and various other vegetable substances are occasionally taken, such as bits of fleshy tubers or roots, mast, mushrooms, etc.

If the blackbirds were to be rated in the order of their grain-eating propensities as shown by stomach examinations, putting those that eat least at the head of the list, they would stand about as follows: Bobolink, redwing, cowbird, rusty blackbird, yellowhead, crow blackbird, boat-tailed grackle, Brewer's blackbird, and California redwing. It is a singular fact that the first two are the ones against which the greatest complaint has been made, thus showing that some factors beside the amount of grain actually eaten by the individual must be taken into account in determining the relative harmfulness of the species. In the case of the bobolink, however, it should be explained that the stomachs upon which the record is founded were nearly all taken in the North, and do not exhibit the bird's rice-eating propensities. Still it is probable that if a proportionate number of stomachs from Southern States were included in the examination there would be no great change in the result. The damage from which the complaint arises is due to the fact that all the bobolinks reared in the Eastern States gather in spring and autumn upon a limited area and attack a single crop-rice. But owing to the comparative shortness of the rice-eating period the amount consumed by each bird must constitute but a small percentage of the food of the year.

The redwing probably owes its bad reputation as a grain eater to its superabundance in the great grain-raising regions of the West. Number of individuals, rather than amount of grain consumed by each, is here probably the important factor. The cowbird, well known as a frequenter of roads and barnyards, is not notorious as a grain eater, and it is probable that the greater part of the 16 percent of grain found in its stomach is waste. The rusty blackbird has not been accused of much damage, and in fact is not in this country at harvest time, so that the greater part of the grain it eats is also probably waste. The yellowhead has gained an unenviable reputation in some parts of the West, and in point of harmfulness is reckoned by the farmers with the redwings, with which it associates. This is not surprising, as nearly 40 per cent of its food is grain; if it were as abundant as the redwing, it would probably be a much greater nuisance than that species. The crow blackbird, while eating a consider

1 For convenience, spiders and myriapods (thousand-legs) are classed as insects in this investigation.

able quantity of grain, has not been the cause of so much complaint as the foregoing species, perhaps because of its well-known habit of nesting about farmsteads, where it obtains a large portion of its food from the barnyards and grain cribs. The boat-tailed grackle is so local in its distribution that its food habits are familiar to comparatively few. It confines its grain eating almost exclusively to corn, which it appears to eat at every opportunity. Unlike most of the other species, it also damages fruit. The western Brewer's blackbird, with grain constituting more than 60 percent of its food, would naturally be supposed to be a dangerous neighbor for the grain grower, and where it has come in contact with the grainfield it has fulfilled this expectation. The California redwing is confined to a comparatively small part of the country, and its food habits have not yet received much attention. It seems almost certain that it must become a nuisance, but the record of its food is too meager to justify final conclusions.

The animal food of these nine species of blackbirds must be counted for the most part in their favor, as the insects eaten are generally noxious. Only one species (the crow blackbird) shows any special fondness for the valuable predaceous beetles (Carabidae), and these amount to less than 6 percent of its food. The snout-beetles (Rhynchophora), commonly known as weevils, seem to be specially sought during the early summer. In the five months from April to August, inclusive, 9 percent of the food of the bobolink consists of these harmful beetles, a record which is slightly exceeded by the redwing for the same time. In May they constitute more than one-fourth of the food of Brewer's blackbird. As all the members of this group of beetles are noxious, and as two species that have been identified in great numbers in the birds' stomachs are very harmful to forage crops, the benefit derived from this destruction is obvious. In the consumption of grasshoppers, Brewer's blackbird heads the list, more than 16 percent of its food consisting of these pests; while the redwing (excluding the California bird) stands at the foot, with a little less than 6 percent. In August, Brewer's blackbird takes more than 47 percent of its food in grasshoppers, and the rusty blackbird and cowbird only a little less. Being mainly terrestrial, the blackbirds do not naturally come in contact with caterpillars so frequently as they would if they sought their food upon trees or shrubs; but nevertheless these insects constitute 13 percent of the food of the bobolink, nearly 6 percent of that of the redwing, and but little less of that of several others. The other insects eaten are, with an occasional exception, harmful, and though distributed among several different orders, form a noticeable percentage of the food. The crustaceans and snails may be considered neutral.

In regard to the economic status of the blackbirds, it may be said that the damage done by the redwings and some other species has apparently arisen from the excessive number of individuals rather than from the habits of the species. Thoughtful students of nature have observed that every race or species has a certain high-water mark of abundance, beyond which it can not rise without danger of encroaching upon and injuring other species. This is true of every species, whether at its normal abundance it be beneficial to man or otherwise. The exemplification of this principle is most noticeable in the case of insects, many species of which frequently exceed their ordinary bounds and spread destruction among crops. But the rule is equally applicable to birds; however useful they may be in a general way, it is possible under certain conditions that particular species may become

too numerous.

There is no reasonable doubt that in the Mississippi Valley the redwings and yellowheads, and farther west Brewer's blackbird, are much too abundant for the interests of the grain grower. The facilities for nesting afforded by the prairie sloughs and marshes, where for ages these species have been undisturbed, have given rise to such immense hordes that they can in a few hours destroy hundreds of acres of grain, or at least take so much that the remainder is not worth harvesting. Originally the birds obtained their food from wild plants, but with the advent of civilized man and the planting of grainfields a new source of food was provided. The wild rice (Zizania aquatica), which was one of their favorite foods, does not ripen till September, but wheat and oats are ripe from June to August, and are much more abundant and more easily obtained than any of the wild seeds. What wonder that the birds at once availed themselves of this new supply of food spread before them with such a lavish hand! In the early days of settlement the fight near large marshes to save the grain from redwinged blackbirds was as fierce as is now the struggle in the South to save the rice crop from the bobolinks. As the country has become more thickly settled a greater area of grain is sown and the damage is relatively less and more widely distributed. With the further advance of civilization, and the broadening of the area of cultivation, many of the marshes will be drained and the present nesting places will become arable fields. This will necessarily reduce the numbers of the birds, and it is almost certain that in time they will reach the limit at which they are no longer harmful, as is already the case in the Eastern States.

Perhaps the most peculiar case presented by any of our birds is that of the bobolink. Loved and cherished in the North, and there made the subject of poetry and romance, in the South it is execrated and destroyed and conceded but one redeeming quality-that its body is