Appletons' Popular Science Monthly, October 1899

A FEATHERED PARASITE

Nothing could more clearly prove that a common law runs through the whole domain of Nature than the fact that in every division of her realm there seems to be a class of parasites. In the vegetable world, as is well known, there are various plants that depend wholly upon other plants for the supply of their vital forces. And in the human sphere there are parasites in a very real and literal sense – men and women who rely upon the toil and thrift of others to sustain them in worthless idleness.

In view of the almost universal character of this law it would be strange if these peculiar forms of dependence did not appear in the avian community. We do find such developments in that department of creation. Across the waters there is one bird which has won an unenviable reputation as a parasite, and that is the European cuckoo, which relies almost wholly on the efforts of its more thrifty neighbors to hatch and rear its young, and thereby perpetuate the species. Strangely enough, our American cuckoos are not given to such slovenly habits, but build their own nests and faithfully perform the duties of nidification, as all respectable feathered folk should. However, this parasitical habit breaks out, quite unexpectedly it must be conceded, in another American family of birds which is entirely distinct from the cuckoo group.

In America the cowbird, often called the cow bunting, is the only member of the avian household that spirits its eggs into the nests of other birds. The theory of evolution can do little toward accounting for the anomaly, and even if it should venture upon some suggestions it would still be just as difficult to explain the cause of the evolution in this special group, while all other avian groups follow the law of thrift and self-reliance.

The cowbird belongs to the family of birds scientifically known as Icteridæ, which includes such familiar species as the bobolinks, orioles, meadow larks, and the various kinds of blackbirds, none of which, I am glad to say, are parasites. The name Molothrus has been given to the genus that includes the cowbirds. They are confined to the American continent, having no analogues in the lands across the seas. The same may be said, indeed, of the whole Icteridæ family. It may be a matter of surprise to many persons that there are twelve species and subspecies of cowbirds in North and South America, for most of us are familiar only with the common cowbird (Molothrus ater) of our temperate regions. Of these twelve species only three are to be found within the limits of the United States, one is a resident of western Mexico and certain parts of Central America, while the rest find habitat exclusively in South America. A fresh field of investigation is open to some enterprising and ambitious naturalist who wishes to study several of these species, as comparatively little is known of their habits, and indeed much still remains to be learned of the whole genus, familiar as one or two of the species are. Their sly, surreptitious manners render them exceedingly difficult to study at close range and with anything like detail.

Are all of them parasites? It is probable they are – at least to a greater or less degree – except one, the bay-winged cowbird of South America, which I shall reserve for notice later on in this article. We might assert that our common cowbird is the parasite par excellence of the family, for, so far as I can learn from reading and observation, they never build their own nests or rear their own young, but shift all the duties of maternity, save the laying of the eggs, upon the shoulders of other innocent birds.

These avian "spongers" have a wide geographical range, inhabiting the greater part of the United States and southern Canada, except the extensive forest regions and some portions of the Southern States. The center of their abundance is the States bordering on the upper Mississippi River and its numerous tributaries. They occur only as stragglers on the Pacific coast west of the Cascade and Sierra Nevada Mountains. The most northern point at which they have been known to breed is the neighborhood of Little Slave Lake in southern Athabasca. In the autumn the majority of these birds migrate to southern Mexico, although a considerable number remain in our Southern States, and a few occasionally tarry for the winter even as far north as New England and southern Michigan.

The male cowbird looks like a well-dressed gentleman – and may have even a slightly clerical air – in his closely fitting suit of glossy black, with its greenish and purplish iridescence, and his cloak of rich metallic brown covering his head, neck, and chest. He makes a poor shift as a musician, but his failure is not due to lack of effort, for during courtship days he does his level best to sing a variety of tunes, expanding and distorting his throat, fluffing up his feathers, spreading out his wings and tail, his purpose evidently being to make himself as fascinating as possible in the eyes of his lady love. One of his calls sounds like the word "spreele," piped in so piercing a key that it seems almost to perforate your brain.

One observer maintains that the cowbirds are not only parasitical in their habits, but are also absolutely devoid of conjugal affection, practicing polyandry, and seldom even mating. This is a serious charge, but it is doubtless true, for even during the season of courtship and breeding these birds live in flocks of six to twelve, the males almost always outnumbering the females. However, if their sexual relations are somewhat irregular, no one can accuse them of engaging in family brawls, as so many other birds do, for both males and females seem to be on the most cordial terms with one another, and are, to all appearances, entirely free from jealousy. Who has ever seen two cowbirds fighting a duel like the orioles, meadow larks, and robins? Their domestic relations seem to be readily adjusted, perhaps all the more so on account of their lax standards of sexual virtue.

In obtruding her eggs into the nests of other birds Madame Cowbird is sly and stealthy. She does not drive the rightful owners from their nests, but simply watches her opportunity to drop her eggs into them when they are unguarded. No doubt she has been on the alert while her industrious neighbors have been constructing their domiciles, and knows where every nest in the vicinity is hidden. Says Major Charles Bendire: "In rare instances only will a fresh cowbird's egg be found among incubated ones of the rightful owners. I have observed this only on a single occasion." From one to seven eggs of the parasite are found in the nests of the dupes. In most cases the number is two, but in the case of ground builders the cowbird seems to have little fear of overdoing her imposition. Major Bendire says that he once found the nest of an ovenbird which contained seven cowbird's eggs and only one of the little owner's.

If parasitism were the only crime of the cowbird one would not feel so much disposed to put her into the avian Newgate Calendar; but she not only inflicts her own eggs upon her innocent victims, but often actually tosses their eggs out of the nests in order to make room for her own. Nor is that all; she will sometimes puncture the eggs of the owners to prevent their hatching, and thus increase the chances of her own offspring. Whether this is done with her beak or her claws is still an open question, Major Bendire inclining to the belief that it is done with the claws.

Her finesse is still further to be seen in the fact that she usually selects some bird for a victim that is smaller than herself, so that when her young hopefuls begin to grow they will be able to crowd or starve out the true heirs of the family. In this way it is thought that many a brood comes to an untimely end, the foster parents having no means of replacing their own little ones when they have been ejected from the nest. However, I am disposed to think that the cowbird's impositions are not usually so destructive as some observers are inclined to believe. I once found a bush sparrow's nest containing one cowbird and four little sparrows, all of which were in a thriving condition. The sparrows were so well fed and active that as soon as I touched the nest they sprang, with loud chirping, over the rim of their cottage and scuttled away through the grass. They were certainly strong and healthy, in spite of the presence of their big foster brother. Before they flitted away I had time to notice how the little family were disposed. The cowbird was squatted in the center of the nest, while his little brothers and sisters were ranged around him, partly covering him and no doubt keeping him snug and warm. They were further advanced than he, for while they scrambled from the nest, he could do nothing but snuggle close to the bottom of the cup, where he was at my mercy.

A wood thrush's nest that I found contained two young thrushes and two buntings. All of them were about half fledged. Being of nearly the same size, the queerly assorted bantlings lived in apparent peace in their narrow quarters. I watched them at frequent intervals, but saw no attempts on the part of the foundlings to crowd out their fellow-nestlings. The cowbirds were the first to leave the roof-tree. Thus it appears that the intrusion of the cowbird's eggs does not always mean disaster to the real offspring of the brooding family, but of course it always prevents the laying of the full complement of eggs by the builders themselves.

Even after the youngsters have left the nest the mother cowbird does not assume the care of them, but still leaves them in charge of the foster parents. It is laughable, almost pathetic, to see a tiny ovenbird or redstart feeding a strapping young cowbird which is several times as large as herself. She looks like a pygmy feeding a giant. In order to thrust a tidbit into his mouth she must often stand on her tiptoes. Why the diminutive caterer does not see through the fraud I can not say. She really seems to be attached to the hulking youngster. By and by, however, when he grows large enough to shift for himself, he deserts his little parents and nurses and seeks companionship among his own blood kindred, who will doubtless bring him up in the way all cowbirds should walk.

It is surprising how many species are imposed on successfully by the cowbird. The number, so far as has been observed, is ninety, with probably more to be added. Among the birds most frequently victimized are the phœbes, the song sparrows, the indigo birds, the bush sparrows, and the yellow-breasted chats. Even the nests of the red-headed woodpecker and the rock wrens are not exempt. Some species, notably the summer warblers, detect the imposture and set about defeating the purposes of the interloper. This they do by building another story to their little cottage, leaving the obtruded eggs in the cellar, where they do not receive enough warmth to develop the embryo.

While it is surprising that acute birds should allow themselves to be imposed on in this way, perhaps, after all, they look upon the cowbird as a kind of blessing in disguise; at least, he may not be an unmixed evil. They may act on the principle of reciprocity – that "one good turn deserves another." What I mean is this: In my rambles I have often found the cowbirds the first to give warning of the approach of a supposed danger. Having no domestic duties of their own, they can well secrete themselves in a tall tree overlooking the entire premises, and thus play the useful rôle of sentinel. This, I am disposed to believe, is one of the compensating uses of this parasite, and may furnish the reason for his being tolerated in birdland. And he is tolerated. Has any one ever seen other birds driving the cowbird away from their breeding precincts, or charging him with desperate courage as they do the blue jays, the hawks, the owls, and other predatory species? He evidently subserves some useful purpose in the avian community, or he would not be treated with so much consideration.

A young cowbird that I purloined from the nest and reared by hand did not prove a very pleasant pet. He was placed in a large cage with several other kinds of young birds. At first he was quite docile, taking his food from my hand and even allowing some of his feathered companions to feed him; but in a few weeks he grew so wild and manifested such a fierce desire for the outdoor world that I was glad to carry him out to the woods and give him his freedom. A young red-winged blackbird and a pair of meadow larks developed a different disposition.

The dwarf cowbird (Molothrus ater obscurus) is similar to his relative just described, except that he is smaller and his geographical range is more restricted. He is a resident of Mexico, southern Texas, southwestern Arizona, and southern California. His habits resemble those of the common cowbird. Another bunting, having almost the same range, although a little more southerly, is the red-eyed cowbird, which is larger and darker than our common cowbird and has the same parasitical habits.

In South America three species have been studied by Mr. W. H. Hudson, who, in collaboration with Mr. P. L. Sclater, has published a most valuable work on Argentine ornithology. One of these is called the Argentine cowbird (Molothrus bonariensis). It is a bona fide, blue-blooded parasite, and has been seen striking its beak into the eggs of other birds and flying away with them. The males, it is said, show little discrimination in pecking the eggs, for they are just as likely to puncture the cowbird eggs as those of other birds. Every egg in a nest is frequently perforated in this way. These buntings lay a large number of eggs, often dropping them on the ground, laying them in abandoned nests, or depositing them in nests in which incubation has already begun, in which cases all of them are lost. However, in spite of this wastefulness the birds thrive, thousands of them being seen in flocks during the season of migration.

And, by the way, a description of their habits by Mr. Hudson has thrown an interesting light on the subject of migration in the southern hemisphere. South of the equator the recurrence of the seasons is the exact reverse of their recurrence north of the equator, and therefore the breeding season of the birds is in the autumn instead of the spring; the flight from winter cold occurs in the spring instead of in the autumn, and is toward the north instead of toward the south. Thus, in February and March the Argentine cowbirds are seen flying in vast battalions in the direction of the equatorial regions – that is, northward – in whose salubrious clime they spend the winter. As our northern autumn draws near and the southern summer approaches these winged migrants take the air line for their breeding haunts in the Argentine Republic and Patagonia. At the same time the migrants of the northern hemisphere are pressing southward before the blustering mien of old Boreas. It all seems wonderful and solemn, this world-wide processional of the seasons and the birds.

Naturally, one would expect to find some other eccentricities in this aberrant family besides that of parasitism, and in this expectation one is not disappointed. There are two other species of cowbirds in the Argentine country – the screaming cowbird (Molothrus rufoaxillaris) and the bay-winged cowbird (Molothrus badius). The latter is only partly a trencher on the rights of other birds – that is, it is only half a parasite. Indeed, it sometimes builds its own nest, which is quite a respectable affair; but, as if to prove that it still has some remnants of cowbird depravity in its nature, it frequently drives other birds from their rightful possessions, appropriates the quarters thus acquired, lays its eggs into them, and proceeds to the performance of its domestic duties like its respectable neighbors. Its virtue is that it never imposes the work of incubation and brood rearing on any of its feathered associates, even though it does sometimes eject them from their premises.

But what is to be said of the screaming cowbird? Instead of inflicting its eggs on its more distant avian relatives it watches its chance and slyly drops them into the domicile of its bay-winged cousins, and actually makes them hatch and rear its offspring! This seems to be carrying imposture to the extreme of refinement, or possibly developing it into a fine art, and reminds one of those human good-for-naughts who "sponge" off their relatives rather than go among strangers. One can scarcely refrain from wondering whether grave questions of pauperism and shiftlessness ever enter into the discussion of "the social problem" in the bird community.

THE COLUMBUS MEETING OF THE AMERICAN ASSOCIATION

The Columbus meeting of the American Association for the Advancement of Science was looked forward to with considerable interest as the first in the new half century of that body. Would the impression and stimulus of the great semicentennial gathering at Boston last year be found to continue, or be followed by a reaction? The meetings west of the Alleghanies are always smaller than the eastern ones, and the brilliancy of the Boston meeting could not be looked for in any interior city. The general expectation was for an "off-year" gathering.

But only in point of attendance was this impression verified. The register of those present showed three hundred and fifty-three names – a good number for an interior meeting, very few of the Western gatherings having exceeded it. In all other respects the general feeling of the members indicates that the meeting was notably successful and enjoyable, and the remarks made by the writer a year ago as to the real value of the smaller and less conspicuous meetings he feels to have been well exemplified. It was a scientific working meeting, with enough of social intercourse and attentions to be delightful, but not distracting. In these aspects the "golden mean" was markedly preserved.

The arrangements of the local committee for the convenience of the members and the success of the meeting in general were remarkable in their completeness. Nothing seems to have been overlooked, and some advances were made upon any previous year. The daily programmes were well printed and on hand early every morning – a most important point, not always heretofore attained. A complete telephone service between the section rooms and the central hall was a feature of special advantage, each section reporting to headquarters every paper as it was taken up. This was then posted on a bulletin, so that any one could know at any time what was going on in each section. A great amount of delay and disappointment, that has often been felt by members anxious to hear certain papers in different sections, was thus entirely obviated. Columbus has set an example in this feature that must be followed in the arrangements for all future meetings. The entire service on these telephones was rendered not by professional operators, but by young lady students of the university, and it was well and gracefully done.

It is fitting also that recognition should be given to some who have been less prominent in the local arrangements, but have had a large share in their preparation. While the public resolutions of thanks have made well-deserved mention of the local committee and its officers, especially Prof. B. F. Thomas, the indefatigable secretary, it is known in Columbus that much of the planning and arranging was the work of Prof. Edward Orton, Jr., the son of the president of the meeting, and that very much is owing to his laborious activity in the perfection of the local adjustments.

The place of meeting was eminently pleasant and suitable – the wide campus and fine buildings of the Ohio State University. To members from the East it was a matter of great interest to see this noble institution, one of the best examples of the great educational enterprises of the central States. In his address of welcome at the opening of the association the president of the university, Dr. William O. Thompson, outlined the history of public education in the West as dating back to provisions in the "Ordinance of 1787," looking to educational advantages for the great "Northwest Territory." The State University of Ohio is one of the youngest of its kind, but now one of the most important, among the States formed from that great region, although Ohio was the first to be organized into Statehood.

Among the numerous fine structures scattered over the broad area of the campus, one of the most interesting is Orton Hall, containing the collections in geology and archæology, which are very extensive, as well as the laboratories, workrooms, and classrooms of the geological department, and at present the University Library. Here the meetings of Section E (Geology and Geography) were held. In the adjacent Botanical Hall, with its greenhouses, etc., Section G held its meetings. But most of the sections met in Townshend Hall, where the telephone service above described connected all the rooms.

The Ohio State University not only welcomed and accommodated the association, but had a strong representation among the officers of the meeting. The venerable president, Dr. Orton, has long been professor of geology in the university, and his collections are displayed in the hall that so appropriately bears his name. Section C (Chemistry) and Section G (Botany) both had secretaries from the university faculty – Professors Weber and Kellerman, respectively – while the arrangements for the meeting have been already spoken of as largely due to Professor Thomas and Professor Orton, Jr.

The ladies' reception committee did everything for the comfort and convenience of the visiting ladies. Their musicale and garden party in the grounds were described as extremely enjoyable, and the provision of private carriages to convey ladies and aged members across the broad spaces of the campus to and from the entrances was a very delicate and highly esteemed convenience, especially on warm days. The association was favored in the weather, which, though somewhat hot out of doors, was not severe, and the rooms were pleasant and airy.

The excursions given to the members were all of them scientific; they were not merely pleasure trips. This point was a marked feature of the Columbus meeting, and one well worthy of future imitation as far as may be. Not every place, however, has such marked facilities in this respect. On Saturday, August 26th, three free excursions were provided to points of geological or archæological interest. They were about equally shared by the members, together with representatives of the local committee. One party left on Friday evening, passing the night at Sandusky, and going by boat thence to the celebrated islands of Lake Erie, there to see the wonderful glacial furrows in the corniferous limestone on Kelley's Island and the recently opened strontia cave on Put-in-Bay Island. These islands are also favorite pleasure resorts for the whole neighborhood, and the trip was one of great interest and enjoyment. Another party, on Saturday morning, went to points of special importance in the coal region of the Hocking Valley, under the direction of Mr. R. M. Haseltine, chief mine inspector of Ohio. At Corning the party went down into Mine No. 8, owned by the Sunday Creek Coal Company, which has recently been equipped with electric power generated by utilizing the waste gas from neighboring gas-wells. This is said to be the first mine in Ohio to improve this natural source of power. At a depth of sixty-five feet the visiting party were taken by mine cars to a point where a remarkably fine exposure has been made of a carboniferous "forest," with upright trunks of Sigillaria and associated forms of coal vegetation finely displayed. At a point somewhat nearer the entrance, but at a lower level, lunch was served by the company, in a chamber lighted by electricity, two hundred feet underground and a mile from daylight! Another mine was visited later, and the machinery and appliances examined; this was No. 16, at Hollister, owned by the Courtright Coal Company.