Gambar halaman
PDF
ePub

and eggs

information has been secured concerning the distribution and ravages of the several species.

(3) Bulletin on crows. - Work on this report has been continued; but it is deemed inexpedient to publish the result until additional material has been obtained. It is believed that some disputed points in the history of crows have been settled finally, but others need further study and experiment. The harm done to newly planted corn by crows is counterbalanced in some degree by their services as scavengers, and in the destruction of field mice and insects; moreover, comparatively inexpensive methods of protection have been found for this crop. But when the destruction of chickens, young bir is, and eggs is added to the havoc wrought to grain and fruit during the summer and autumn, the account refuses to balance without additional evidence in favor of the crow. Such evidence may be found in the destruction of harmful insects; but in order to prove or disprove this claim, as well as to determine the extent of injury to the young

of valuable birds, it is necessary to examine the stomachs of numerous crows killed under favorable circumstances during the spring and summer. One thousand stomachs (two thousand would be better) from farming lands in a dozen different States would make it possible to settle with comparative accuracy most of the disputed points, but such stomachs are not easily obtained. In response to an appeal in the Annual Report of 1888, a few offers of assistance were received, and eventually a few stomachs, but in almost every case the volunteer assistants found it much more difficult than anticipated to kill crows in warm weather, and less than one hundred crow stomachs in all have been received. A few of these were empty, and others were taken in cold weather, so that only two or three dozen contain evidence pertinent to the investigation. It is hoped that during the coming season farmers and others interested in the matter will coöperate with the Division in order to secure a suflicient number of stomachs for the completion of this work. Anyone willing to assist will be furnished directions on application to the Division.

The insect remains from the stomachs of fifty crows were submitted to Prof. C. V. Riley, Entomologist of the Department, for examination, and his report on them has been received.

(4) Bulletin on crow blackbirds.-It is intended to make this bulletin as thorough and comprehensive as that on the crow, and the work is being carried out in the same manner. Crow blackbirds are guilty of some of the same crimes as crows, but also have habits peculiar to themselves. As they nest in communities and may be found in flocks at all seasons in some parts of the United States there is less difficulty in collecting them, and the Division now has on hand about five hundred of their stomachs, many of which have been examined.

In connection with the three bird bulletins mentioned above, 1,017 stomachs have been examined since January 1, 1889, while about 250 more, mainly those of bobolinks, meadow-larks, bluebirds, and woodpeckers, have been examined in compliance with special requests for information as to the food of these particular species.

The bobolink stomachs were examined with a view to determining the summer food, and the results showed beyond question that during the breeding season these birds are not only harmless but decidedly beneficial. All the stomachs contained insects in abundance, and many of them larvæ injurious to grass lands.

The investigation of the food of the meadow-lark (Sturnella magna)

was undertaken in response to inquiries concerning its alleged fondness for clover seed; hence stomachs collected in autumn only were examined. These were thirty in number and were collected at various places in North Carolina, New York, Pennsylvania, and Tennessee during the months of October and November. At least 99 per cent of the contents of all these stomachs consisted of insects and only one contained no insects. The remaining 29 contained 25 cat. erpillars, 57 grasshoppers, and more than 80 beetles. About 100 seeds were found, of which 15 were clover, 13 wheat, oats, and corn, and the rest grass and weed seeds. Hence it is evident that the Meadow. lark is one of the birds which the farmer should protect.

In connection with these food investigations the value of the reference collection of seeds has been demonstrated constantly. As yet it contains only about 240 genera of seeds, one third of which were added during the year. It still lacks many common species of the eastern United States on which some of our birds feed.

Since January 1 the collection of stomachs has been increased by 1,096, the total number now on hand being 11,812. During the same time 1,265 stomachs have been examined.

A biological clerk was added to the force of the Division in August and much better progress is now being made in the determination of the food contents of bird stomachs.

COLLECTIONS OF THE DIVISION.

The collection begun by the Division a little more than a year and a half ago has made gratifying progress, now numbering upwards of 4,000 specimens of mainmals, 1,300 birds, and 500 reptiles and batrachians.

IDENTIFICATION OF SPECIMENS.

As stated in previous reports, the Division is prepared to identify and return specimens of mammals and birds received for that purpose. Such specimens may be sent by mail post free in packages to which return penalty envelopes are attached. The number of specimens received for identification from field agents and others during the past year aggregated more than 5,500. Notwithstanding the fact that much labor is involved in the determination of these specimens, and that their numbers are increasing year by year, every effort is made to give the work the attention its importance deserved.

SEED PLANTING BY BIRDS.

By WALTER B. BARROWS, Assistant Ornithologist. For centuries the fact has been recognized that birds are instrumental in distributing the seeds of some plants, and that they are, to use a hackneyed expression, one of the agencies in forest rotation and in resurfacing with vegetation tracts swept bare by wind, water, fire, or the hand of man.

Examples of this kind of work by birds have been cited with some care and detail by a few good naturalists, while sweeping generalizations and extraordinary applications have been made by writers on popular natural history.

It is not for me, at least at the present time, to commend or criticise either class, but with the hope of adding a few grains of solid truth to the common fund of knowledge, and particularly with the desire of awakening interest in facts which almost daily pass unnoticed by farmers, sportsmen, and field naturalists, I have brought together a few of the notes made in connection with the field work and routine examinations of bird stomachs in the U. S. Department of Agriculture.

The smaller land birds of a country, especially those supposed to be beneficial or harmful, are commonly divided into two great groups, insect-eaters and seed-eaters, and this division, though strongly artificial, still has some warrant in fact. When legislators wish to appear extremely exact without specifying each bird by name, they add another category, that of song-birds, and thus many of our State laws aim to protect song and insectivorous birds, while the seedeaters, so-called, are denied any protection, or get what safety they can from alliance with “song-birds."

As a rule, however, the seed-eaters are not the seed-planters; on the contrary, the insectivorous birds more often sow seeds than the true seed-eaters, while the song-birds, particularly the thrushes and their allies, are still busier seed-planters. These statements, at first sight so contradictory, will become intelligible perhaps under the reminder that seeds, as such, are eaten for the kernel or embryo which they contain, and the grinding and digestion of this necessarily destroys the seed. Many fruits and so-called berries on the other hand, are eaten solely for the nourishing matter surrounding or attached to the seeds, and in most such cases the seed escapes destruction and is dropped either by ejection or rejection at a distance from the parent plant. In other words, seeds which simply contain nourishment are eaten and destroyed, while seeds which are contained in nourishment are eaten and survive.

Thus it happens that the armies of sparrows, finches, and similar birds in winter eat and destroy tons of grass seed and weed seed, while the same birds in summer and autumn may eat bushels of blueberries, huckleberries, elderberries, raspberries, strawberries, and similar fruits, and distribute their unharmed seeds over thousands of acres, which otherwise might never support a growth of these species.

But there is every reason to believe that the birds just mentioned do not eat, even at the height of the berry season, one quarter as many berries as some of the so-called insectivorous birds, such for example as the thrushes, catbird, mocking-bird, orioles, wax-wing, vireos, and woodpeckers. As a matter of fact, however, that which is definitely known on this subject is so little in comparison with what easily might be learned, that we can scarcely do more than call attention to our astounding ignorance of the food of some of our common birds.

The few berries already mentioned are such as ripen in summer or early autumn, and without exception disappear before cold weather sets in. Numerous other fruits, however, ripen during autumn and many of them clinging to the twigs throughout a considerable part of the winter afford a food supply for numerous late migrants and winter residents. Among such fruits may be mentioned the berries of the holly (Ilex), cat-briar (Smilar), bitter-sweet (Celastrus), sour-gum (Nyssa), flowering dogwood (Cornus), mountain ash and chokeberry (Pyrus), hackberry (Celtis), bayberry (Wyrica), and the various sumachs and other species of the genus Rhus. Anything like complete lists of the fruits eaten by birds, or of the birds which eat the different fruits would be tedious in the extreme, and moreover it is extremely improbable that any single individual or institution in this country possesses the data for making such lists.

The collection of stomachs in the Ornithological Division of the Department of Agriculture now numbers nearly 12,000, and is daily increasing, yet in this large collection very few species indeed are represented by a fair number of stomach's taken at all seasons of the year. Recently a question arose as to the food of the Upland Plover (Bartramia), and the collection being appealed to showed only a single stomach. A short time ago, after taking about one hundred seeds of five different kinds from less than a dozen stomachs of the Yellow-rumped Warbler (Dendroica coronata), I turned to compare these with the stomach contents of the Palm Warbler (Dendroica palmarum hypochrysca), and was disappointed to find but two stomachs of the latter species taken in autumn. All this is through no fault of the Division of Ornithology, but simply results from the size of the field. Several hundred species of birds are common in one part or another of our great country, and it is not to be expected that any collection can show a dozen stomachs of

a each species for each month of the year.

But although we may not at present list either the seeds that are eaten or the birds that eat them, we may get some useful hints and perhaps draw some conclusions from the facts which have been observed already. It has been stated that many insectivorous birds eat fruit. One of the most noteworthy examples of this kind is seen in the case of swallows, birds usually considered to be strictly insec tivorous. I am free to confess that ten years ago I should have scouted the idea that swallows ate anything but insects, and had the farmers and fishermen along our Atlantic coast asserted then that swallows ate bayberries by the thousand in August, just before leaving for the South, in all probability I should not have given the matter a second thought, although the proof was directly at hand. Nevertheless it is now certain that several species of our swallows, notably the white-bellied, bank, and barn swallows, do feed very largely on the bayberry or waxberry (Myrica cerifera) wherever it is found, and my only regret is that I was so blind years ago as not to see that the swallows hovering by thousands among the bayberry bushes were greedily eating the berries instead of picking up flies as I then supposed. My eyes were first opened to this habit of the swallows by Dr. A. K. Fisher, and to the same person I am indebted for several similar hints, among others for notes relating to the fruit-eating habits of the vireos. Having seen a kingbird (Tyrannus) gorging himself with cultivated cherries about six years ago, my faith in purely insectivorous birds was considerably shaken, and the revelation in regard to swallows and bayberries completed its overthrow.

It may be remembered that the annual report of the Ornithologist of the Department of Agriculture for the year 1888 contained some statements in regard to crows eating seeds of poison ivy, statements for which the present writer was responsible. Among these was the remark that the excrement from a crow roost at Arlington Cemetery contained a large number of seeds of poison Rhus. Mr. Otto Widmann, «f St. Louis, wrote me soon after stating that in his own experience with crows he had always found the seeds in the pellets or castings ejected from the mouth, never in the droppings.

a

This led to further investigations, and although in one or two in. stances seeds were found in the intestines of crows, it was found that the great majority of seeds, with much gravel and other indigestible matter, were ejected by the mouth after the nutritious matter had been digested.

Two living and healthy crows were procured, and were subjected to careful experiment for several months, and it was speedily shown that they were able to disgorge at will anything digestible or indidigestible, or in any way distasteful. As for poison ivy berries one crow swallowed over eighty in a few moments, and within forty minutes ejected the seeds by the mouth, all cleaned, polished, and enveloped in a thick coating of sand. Whenever grain or seeds were fed to these birds they invariably swallowed large quantities of sand after it, scooping it up, a teaspoonful or more at a time, and washing it down with repeated swallows of water.

It seems hardly necessary to say that any bird who treats berries or stone fruits in this way, 'undoubtedly distributes the seeds under such conditions that many are sure to grow. In order to give some idea of the number of seeds thus distributed by crows alone, it was stated in the Annual Report for 1888 that a single pound of dried deposit taken from the Arlington roost contained by actual count 1,041 seeds of poison ivy (Rhus toxicodendron), 341 seeds of poison sumach (Rhus venenata), 3,271 seeds of other sumachs, 95 seeds of Virginia juniper, 10 seeds of flowering dogwood, and 6 seeds of sourgum; a total of 4,764 seeds. The material, which covered about 4 square feet, was taken at random from above the layer of leaves and represented the average deposit on the roost at that time. As the roost covered upwards of 15 acres this would give a total in round numbers of 778 million seeds, or enough to plant more than 1,150 acres as closely as wheat is sown.

By actual experiment it was shown that at least 90 per cent of the poison seeds found at the roost were entirely uninjured, and under favorable conditions would grow. Of course the conditions were not favorable at the roost, and most if not all the seeds would perish, but it should be remembered that on an average the crows are at the roost only about one half the time during the winter, thus spending twelve hours of daylight scattered over the surrounding country, and twelve hours more at the roost. In view of what has been said about the rapidity of digestion in crows, it seems certain that as many seeds would be scattered away from as at the roost and many of these would be sure to grow.

It seemed perfectly natural to conclude that crows did much larm by thus sowing poisonous seeds; but while subsequent investigation does not lessen our estimate of the harm thus done, it appears that if we condemn the crow for this we must also condemn many other birds. How many we do not know, but we have found large numbers of seeds of poison sumach in the stomachs of the bluebird (Sialia sialis), Yellow-rumped Warbler (Dendroica coronata), Flicker (Colaptes auratus), Downy Woodpecker (Dryobates pubescens), Hairy Woodpecker (D. villosus), Pileated Woodpecker (Ceophlaus pileatus), and Bob White (Colinus virginianus), and there is little doubt that they will be found in the stomachs of many other birds when a systematic search is made. At the same time it is unsafe to predict it except in a very few cases.

Although the common crow undoubtedly is very fond of poison Rhus berries, the fish crow (C. ossifragus) appears to avoid them,

« SebelumnyaLanjutkan »