Popular Science Monthly/Volume 47/September 1895/Variation in the Habits of Animals
|VARIATION IN THE HABITS OF ANIMALS.|
IN the introduction to his Animal Life as Affected by the Natural Conditions of Existence, Carl Semper wrote, in 1879: "It appears to me that of all the properties of the animal organism, Variability is that which may first and most easily be traced by exact investigation to its efficient causes; and, as it is beyond a doubt the subject around which at the present moment the strife of opinion is most violent, it is that which will be most likely to repay the trouble of closer research."
Among other sorts of variability discussed by Semper, that which concerns the change of food habits of animals receives consideration, and several examples illustrating such changes—polyphagy—are cited. For instance, on page 62 the story of the New Zealand parrot (Nestor mirabilis) is told. This parrot, which formerly fed upon the juices of plants and flowers, has acquired the habit of sipping the blood of newly slaughtered sheep, and thereby has come to develop such a love for the taste of blood that it will now alight upon living sheep and peck at the "most minute wounds." Another case is told of two horses in Chili which had developed the habit of eating young pigeons and chickens.
A great many other interesting cases of variability in food habits might be collected by a little observation and by compilation. Two such cases at least have come under my own observation. On a farm in Coffey County, Kansas, a few years ago, there were several horses and mules which greedily devoured the eggs laid in their mangers by improvident hens. I believe that this habit is not uncommon. At any rate, I have been told of several instances in which this same practice has been acquired by other horses. Also upon this farm, during the winter of 1887, a milch cow and a fully grown pig were shut up together in the same lot. This cow, which had been furnishing milk bountifully, suddenly, about a month after her confinement in the lot with the pig, ceased to supply milk at all. At first she was accused of "stubbornly holding her milk," but after several days it was decided that some one was stealing her milk. A careful watch was then kept, and the thief proved to be the pig.
Another kind of variability which is displayed by wild birds has received not a little attention from ornithologists—namely, that which they exhibit in their nesting habits. From the observations of Coues, Ridgway, and Allen, we learn that not only in regard to the place, but also in regard to the manner of building their nests, do birds display considerable variation. Also we know that among wild birds the male aids much more in the rearing of broods than do the males of our various domestic fowls. The wild male often takes turns with the female in sitting on the incubating eggs, and in some instances the male assumes the entire responsibility of rearing a hatched brood while his mate builds a new nest and lays another set of eggs. Domestication seems to have obliterated much of this parental instinct in our male fowls. When, perhaps by reversion, we find such instinct to be developed in our domestic male fowls, we are at once impressed by the unusualness of the occurrence. I know of no instance recorded in which parental instinct seemed to be so fully developed in the male of any of our domestic fowls as in the following case. In the poultry yard upon a farm in La Salle County, Illinois, there was but one pair of turkeys. The hen, one spring, stole away, made her a nest in some hiding place, and in due time began to incubate her eggs. After her disappearance the male became exceedingly lonely. Sometimes he would follow her in her tortuous retreat to the nest after a visit to the house for food; but he returned later, more disconsolate than ever. He strove to make friends with the other fowls, but found none which seemed to realize his loneliness and give him sympathy or affection. After ten days or so of this dreary neglect he gave up in despair and began to sit upon a deserted nest of hen's eggs which he discovered under some shrubbery in a corner of the lawn. From that time on he seemed as contented, important, and preoccupied as any sitting hen. He would not leave the nest until driven by absolute need of food and water. Then he would run to the feeding-pans, greedily swallow a few grains of corn and a gulp of water, and dive again for his nest. As soon as his owners felt convinced that he wished to rear a brood of his own, he was supplied with fresh hen's eggs. He continued thus to persist in his conduct for more than two weeks. Then the turkey hen appeared in the poultry yard with her brood. During that day the male turkey was observed to take food frequently. His visits to the poultry yard became more and more prolonged, while the intervals spent upon the eggs grew shorter and shorter, until finally, after the elapse of two or possibly three days, the nest of hen's eggs was abandoned altogether. From that time on he shared with the turkey hen the care of the brood of his own kind. The abandoned eggs were placed under a hen and hatched in a few days. This instance is not without interest as it stands, but it is much to be regretted that the eggs did not hatch while the male turkey sat upon them. Would he have abandoned his livingbrood with the same or with more reluctance than he showed in deserting the eggs, or would he have reared his adopted offspring?
One other most remarkable instance of a change of habit came under my observation also in Coffey County, Kansas. The individuals which showed a change of habit in this instance were birds in the wild state—namely, blue jays (Cyanocitta cristata). I say individuals, for a score or even scores of blue jays were concerned. These all adopted the same peculiar practice in their warfare with the so-called English sparrow (Passer domesticus), and, moreover, have preserved this habit for at least three successive years.
Since the arrival of the aggressive English sparrow much apprehension has been felt by bird-loving Americans regarding the fate of native American birds. As the area of distribution of the English sparrow rapidly widened, just so rapidly our native birds seemed to be brought into violent conflict with the garrulous stranger, or else they were driven to abandon to the newcomer their nesting sites and retire into the forests or prairies. The question arose as to whether the English sparrow itself on account of numbers would be driven from the cities and towns to take up nesting sites about country barns and farmhouses. The Report of the United States Department of Agriculture for the year 1889 on The English Sparrow (Passer domesticus) in North America, especially in its Relation to Agriculture, contains communications from many parts of the country testifying, not only to the destruction wrought by this sparrow in gardens and upon ripening grain fields, but also to the fact that few American birds seem to be able to resist the aggressions of this sparrow, and many therefore are compelled to abandon their nests to the intruders, even after their eggs have been deposited or are in process of incubation. But the relations of our native birds to the English sparrow seem now to be undergoing a change. F. H. Kirncoll (Auk, vol. vi, July, 1894, p. 261) has stated that in many localities in Illinois the English sparrow and native birds are now found nesting side by side, where only a few years ago the English sparrow occupied all the desirable nesting sites, and assumed so aggressive an attitude toward native birds that one rarely saw a native bird nesting in the regions inhabited by the English sparrow. "Either," he writes, "our native birds have unexpectedly developed powers of resistance at first unsuspected, or the pugnacity of the English sparrow has diminished, for certainly our own songsters have not been driven away, but, on the contrary, seem as numerous as they were twenty years ago. For the past two or three years, since my attention was first called to the matter, I have seen but little if any persecution of our native birds by the foreign sparrows; on the contrary, our own birds are now often the aggressors, and if they do not indulge in persecution themselves are adepts at defense. Very commonly a jay, robin, or catbird will from pure mischief hustle a flock of sparrows into desperate flight."
I find, on referring to the Government report of 1889, that the English sparrow has been present in the town of Burlington, Kansas, for ten or twelve years. My own attention was not attracted particularly to these birds until after they had been there for several years. Upon returning to Burlington in 1889, I began to look about upon the lawn for my old bird friends, and found none of them. Upon inquiry, I was told that they had all been driven away by the English sparrow. The wren house was occupied by sparrows. The martins, robins, bluebirds, and catbirds had all resisted according to their various strengths, and had been worsted in the conflict. The lawn under consideration is one peculiarly attractive to birds on account of its bountiful supply of shade trees. There is a long walk upon it completely shaded by apple and pear trees, of which the ripening fruit proves attractive to insects all summer long, while the fruit itself is no less enticing to bird than insect. On one side of the lawn there are cherry trees with their tempting fruit, and on the adjoining lots a large kitchen garden with its ripening seeds, berries, and freshly turned loam. Altogether this place furnishes a paradise for parent birds. The house itself was covered with vines of the Virginia and trumpet creepers. Within these vines the English sparrow took up its abode and soon so increased in numbers as to be able to mob any other bird that ventured on the premises. (July one pair of blue jays stubbornly clung to their nest in an apple tree. With this pair was throughout the summer waged one long and bitter warfare.
Upon my return the following summer the number of jays had increased and the conflict was much less one-sided. In June, 1891, early the first morning after my return again to Burlington, I heard on the lawn the screeching of a hen hawk. The English sparrows shot in terror into the verandas and among the vines upon the house. Upon inquiry, I was told that the hawks had been chasing the sparrows all spring, and was assured by our colored cook that "dis country am coram' to 'struction sub, when de hawks come to town." I had never known of an instance where hawks had entered a town several miles in area, and supposed that they were made so bold on account of the attraction such an abundance of sparrow food afforded. The cry of the hawk, however, seemed shriller and more satanic than any hawk cry I had ever heard before. Indeed, there was a suggestion of a mocking laugh in these hawk screams. I wondered if this change in tone was due to the new environment of the hawk, to the fact that it was dealing with such helpless prey, or whether the cry came from a hawk new to me.
With these questions in mind I watched carefully for days, without even catching a glimpse of the hawks, although they screamed at intervals all day long among the trees. Each time the demonic scream began the sparrows seemed almost paralyzed with terror, and the hens would hustle their broods into the barn or under the shrubbery. One day, while lying in a hammock watching some sparrows devour a fallen apple, I was startled by the screams of a hawk in the tree just above me. Upon looking upward I discovered that my elusive bird was no other than a blue jay. The fallen apple was abandoned by the sparrows in their fright and the jay sought its nest in a tree near by. For several weeks longer the blue jays always concealed themselves in the trees before they gave their adopted yell, but later in the summer they did not even take the precaution of alighting in the trees before screaming, but sat boldly in view upon the fence, screamed while in flight, and even followed the sparrows into their retreat among the vines. In a few instances they destroyed the sparrows' eggs or young.
For a time the ability thus to imitate the hawk seemed to be confined to the blue jays nesting upon this one lawn. Ofttimes these blue jays would rush to the rescue of other blue jays on neighboring lawns. Eventually, however, other blue jays learned the cry, and in the following summer I heard it on the other side of the town some two miles or more away. The second summer after this imitation of the hawk began, other native birds returned in small numbers. The blue jays often made themselves champions of these returned exiles. The other birds, however, soon learned to resist the English sparrow on their own account.
About a year ago the vines were almost entirely torn away from the house, and in consequence the English sparrow, having no place of refuge from the blue jays, has deserted this lawn. The blue jays now seem to take greater pleasure in routing a venturesome sparrow by means of their own natural call, and have recourse to the imitation of the hawk only as a last resort.
The catbird and robin seem to have learned from the blue jay the efficacy of a vigorous, angry call, and now fight successfully their own battles. Last summer a bluebird nested and sang freely in the trees. Even the wrens ventured to build on a beam in the carriage shed, although they seemed very shy and were rarely heard to sing.
In Ornithological Notes from the West, by J. A. Allen (American Naturalist, vol. vi, p. 18), I find the following references to the blue jays which were observed by him at Leavenworth, Kansas: "The blue jay (Cyanura cristatus) was equally at home and as vivacious and even more gayly colored than at the north. While he seemed to have forgotten none of the droll notes and fantastic ways one always expects from him, he has here added to his manners the familiarity that usually characterizes him in the more newly settled parts of the country, and anon surprised us with some new expression of his feelings or sentiments—some unexpected eccentricity in his varied notes, perhaps developed by his southern surroundings."
Robert Ridgway, in Volume VIII of The American Naturalist, refers to the above instance and others cited by Mr. Allen. "Mr. Allen," he writes, "has called attention to the variation in the notes of different birds at remote localities; and in this I am able to corroborate him, though I think that cases of such variation are very rare, and do not occur in more than perhaps five per cent of the species. I have only detected it in two or three species after the most careful observation, and in very many cases noticed that there was not in the minutest particular any difference between individuals of one species on opposite sides of the continent. Such is undoubtedly the case in a very great majority of the species, any seeming variation that may be observed being more probably the peculiarity of an individual rather than the manifestation of any regional impress."
The conduct of the blue jays instanced above may be used in confirmation of the three quotations made in this article, for the blue jay has certainly in this instance "developed powers of resistance at first unsuspected," which certainly aid it in its warfare with the English sparrow. Moreover, it would confirm Mr. Allen's observation in regard to the variability of the jay's note—his "unexpected eccentricity" in Kansas—if indeed Mr. Allen's observations needed other confirmation than that afforded by Ridgway for certain other birds in southern Illinois and by Dr. Elliott Coues. The latter has observed that the note of Nuttall's whip-poor-will differs from that of the eastern whip-poor-will in that the western species "does not cry 'Whip-poor-will' like" the eastern species, but "drops a syllable, saying 'Whip-poor' or 'Poor-will' as the fancy of the hearer may interpret." Moreover, the practice of mocking the hawk is, at present at least, confined, so far as I know, to the individuals of such a limited area—this one town—that with Mr. Ridgway we must believe this peculiarity exhibited by the blue jay to be scarcely the "manifestation of a regional impress."