Part 16

The study of isolated colonies of birds, particularly of those situated on islands, throws much light on several as yet little-understood problems of bird migration.

With mainland birds of general distribution—the Robin, for example—the individual is, except when nesting, lost in the species, and unless the bird be peculiarly marked who can say whether the Robins which nest with us one year are the same as those of the preceding season—where our summer Robins winter, or our winter Robins summer? and who can tell whether the first Robins to come in the spring are our summer resident birds, or early migrants en route to more northern nesting grounds?

In the case of certain island-inhabiting birds, however, some of these questions may be answered with a fair degree of certainty. Thus Ipswich Sparrows are known to nest only on Sable Island, off the Nova Scotia coast, and we are warranted in believing that the same birds, fate permitting, return to their sandy home year after year. Gannets (Sula bassana) nest in the western hemisphere only on three islets in the Gulf of St. Lawrence, and it is probable that the surviving individuals return each year to their former breeding grounds. The Terns of Muskeget and Penikese, forming the only two large colonies of these birds remaining on the Atlantic coast, return to their island retreats every spring; and actuated by this same love of home, the Brown Pelicans of the Indian River region of eastern Florida annually repair to a certain small island for the purpose of rearing their young. Many similar cases might be cited in confirmation of the belief—supported also by isolated observations on the mainland—that birds nest in the same locality throughout their lives, and, on occasion, may even occupy their previous season’s nest.

As regards the manner in which these island-inhabiting birds arrive at the nesting grounds, as far as our recorded information goes, it seems that without relation to latitude they appear each spring with remarkable regularity, not straggling back a few at a time, but sending on an advance guard, which usually remains only a short time and is followed, a few days later, by apparently the entire colony.

Thus, Mackay writes of the Terns of Penikese: “In 1893 the Terns arrived on May 10th, in the night, an advance guard of several hundred being noted early the following morning at daylight; these all left before noon of the 11th, and on the morning of the 12th, before daylight, immense numbers had again arrived.... In 1896 the Terns commenced to arrive during the night of May 9th; they were in evidence at daylight on the 10th, and continued to arrive all day, and on the morning of the 11th the usual colony had taken possession of the island.” (Auk, xiv, 1897, p. 284.)

The migration of the island-nesting Terns in the tropics is apparently no less regular. Scott states that the Noddy arrived in the Tortugas “on April 20th in large numbers, but remained only two days; after inspecting their breeding grounds, all departed to return about a week later in greatly increased numbers, when breeding was almost at once commenced.” (Auk, vii, 1890, p. 306.)

These insular colonies, however, not only throw much light on certain existing phases of bird migration, but they also furnish us with a clew to the origin of migration itself. This is especially true of those species whose lives are passed in the tropics or subtropics, and which we are accustomed to class as nonmigratory or as “permanent residents,” but which are as regularly migratory, in the real meaning of the word, as if they summered within the arctic circle and wintered south of the equator.

Their movements are apparently in no way influenced by climate nor, at this season, are they governed by the food supply, but prompted solely by the annually recurring physiological change which fits both sexes for reproduction, they repair to a certain islet, perhaps in the heart of their range, with the one object of finding a suitable nesting site in which their eggs may be laid and young reared in safety; and this object accomplished, they desert the locality, where they may be unknown until the following spring.

Divested, therefore, of the complications which ensue when in studying the migration of birds the questions of food and climate must be considered, we have here the problem reduced to its simplest terms; and in the desire for seclusion during the breeding season which induces birds to conceal their nests, if possible perhaps near by, but if necessary after a journey of varying length undertaken especially for the purpose, we have a good and sufficient cause for the origin of bird migration.

An attempt to explain the present manifestation of the migratory movement involves a study of the climatic changes to which our globe has been subjected. No doubt many birds controlled by “heredity of habit” make semiannual journeys which at one time were necessary, but under existing circumstances are no longer required. Why, for example, should the Bobolink winter south of the Amazon, while its ally, the Red-winged Blackbird (Agelaius phœniceus), does not leave the eastern United States? I have, however, no intention of writing an essay on bird migration, and these thoughts are presented merely as preliminary to a study of the life of Pelican Island, of a visit to which they are in part the outcome.

Pelican Island is situated midway between the northern and southern extremities of Indian River, near the eastern shore of a key which here makes the river about three miles wide. It is triangular in shape and contains about three acres of ground, on which grow a few black mangroves, a cabbage palm or two, and great patches of grass; but at least one fourth of its surface is bare ground.

On one of the islands of the near-by Narrows a few pairs of Brown Pelicans are said to have nested, but, with this exception, Pelican Island doubtless forms the nesting ground of all the Pelicans of Indian River.

The question why the birds should select this particular island in preference to the scores of others which, to the human eye, appear to be equally well suited to their needs, is a difficult one to answer. Perhaps no true selection is shown by the existing birds, which, as with many other island-inhabiting species, may be the survivors of a once more widely distributed species, who have been preserved by the protection afforded by their island home. Such a colony might owe its beginning to a pair of birds who were the true selectors of the site of the future colony. The preserving influences of the situation were potent from the beginning. The first brood reached maturity without mishap, and in response to the instinct which prompts a bird to return to the region of its birth, they, with successive generations, came back and eventually established the prevailing conditions.

The attachment of these Pelicans for their home affords a remarkable illustration of the power of habit. Ever since the Indian River region has been subject to annual invasion by tourists, among whom the man with the gun is conspicuous both by numbers and actions, the inhabitants of Pelican Island have been wantonly and, on occasions, brutally persecuted. Scarcely a day passes during February and March that one or more boat loads of tourists, perhaps from the mainland or a passing yacht, do not land on Pelican Island and thoughtlessly cause the death of many young birds by driving them from the vicinity of their nests; or, by frightening the brooding birds, they expose the newly hatched and naked nestlings to the roasting rays of the sun. The harm caused by these visitors, however, is not to be compared to that wrought by so-called “sportsmen,” who, in defiance of every law of manhood, have gone to Pelican Island and killed thousands of the birds simply because they afforded a ready mark for their guns. They had not even the excuse of a demand upon their skill, and must indeed have been very near the level of the brute to have found pleasure in killing birds which the merest novice with a gun would find it difficult to miss.

Perhaps even worse than this exhibition of pure savagery are the raids of the self-styled “oölogists,” who, in the name of science—save the mark!—have journeyed to Pelican Island with the express purpose of taking every egg they could lay their insatiable fingers upon, afterward to boast, in some journal devoted to reporting similar crimes, of the hundreds they had collected in so many hours.

So persistently have the Pelicans been molested that at times they have been foiled to desert their beloved island; but they have exhibited their attachment for it by establishing themselves on the nearest available islet, and on the first opportunity have returned to their native land.

It was in March, 1898, that my best assistant and I boarded the little sloop which was to take us to Pelican Island. Fortunately the birds were now in possession of their ancestral domain, and, as we approached, files of Pelicans were seen returning from fishing expeditions, platoons were resting on the sandy points, some were bathing, others sailing in broad circles high overhead. Soon we could hear the sound of many voices—a medley of strange cries in an unknown tongue. Arriving and departing on wings, the inhabitants of Pelican Island have little need of deep water harbors, and we were obliged to anchor our sloop about a hundred yards from the island and go ashore in a small boat.

No traveler ever entered the gates of a foreign city with greater expectancy than I felt as I stepped from my boat on the muddy edge of this City of the Pelicans. The old birds, without a word of protest, deserted their homes, leaving their eggs and young at my mercy. But the young were as abusive and threatening as their parents were silent and unresisting. Some were on the ground, others in the bushy mangroves, some were coming from the egg, others were learning to fly; but one and all—in a chorus of croaks, barks, and screams, which rings in my ears whenever I think of the experience—united in demanding that I leave the town. If I approached too near, their cries were doubled in violence and accompanied by vicious lunges with their bills, which were snapped together with a pistol-like report.^{102} As I walked from tree to tree, examining the noisy young birds that were climbing about the branches, I seemed to be passing from cage to cage in a zoölogical garden; and as I entered that part of the island where the nests were on the ground,^{101} every bird that could walk left its home, and soon I was driving a great flock of young Pelicans, all screaming at the tops of their voices.

The old birds, in the meantime, were resting on the water. They might have been unpleasant foes, but in their stately, dignified way they accepted the situation, and waited in silence for us to retire. Then they at once returned to their nests, and in a short time comparative quiet was restored on the island.

This is a sketch of life in the Pelicans’ metropolis as one sees it during a brief visit, and all the accounts of the island I have seen were based on just such an experience. Consequently, I shall relate here what was learned of the Pelicans and their home during four days passed with them.

During no hour of the twenty-four did silence reign on Pelican Island; if I went on deck at midnight, the notes of some complaining or pugnacious young Pelicans, who in their sleep had come into too close quarters, were sure to be heard. But the Pelicans’ day began at early dawn, when I could distinguish the diagonal files of from two to a dozen birds solemnly and silently starting out for the fishing grounds. One might think that, like a boat’s crew, their strokes were controlled by a coxswain, as in perfect unison they all flapped their broad wings for about ten beats, and then spread them and sailed for as many seconds.

Generally they headed for the ocean, there to follow the line of the beach, sometimes high in the air, at others low over the curling surf, as their progress was aided or retarded by the wind. How far they went I can not say, but at a point ten miles north of Pelican Island many have been seen still winging their way to the northward, doubtless to some point where fish were abundant. Not once during the four days passed off Pelican Island did I see a Pelican fishing over the surrounding waters. It was not because they were lacking in fish, for they contained a plentiful supply of food; and I could explain the unexpected abstinence of the birds only on the supposition that the fish in the immediate vicinity of the nesting ground were left for the early efforts of the young birds before they were strong enough of wing to accompany their parents to distant fishing grounds.

Brown Pelicans fish at a height of from twenty to thirty feet above the water, not hovering, but flying slowly about, and without a moment’s pause plunging on their prey with a force which would produce serious results if the bird’s breast were not well padded with cellular tissue between the skin and the flesh.

I observed that when the young birds struck at me the movement was accompanied by a widening or bowing out of the sides of the lower mandible, and it is doubtless the same muscular effort which turns the pouch of the diving Pelican into a scoop net, as it were, with an elliptical ring.^{105}

By sunrise most of the fishers appeared to have departed, and at this time, whether because of the absence of so many of the adults or because it was their breakfast hour, a swarm of Fish Crows came from the mainland, apparently from both sides of the river, seeking what they might devour in the way of eggs or young Pelicans, and departing after several hours’ feasting.

About eight o’clock the fishers began to appear, coming, as they went, in dignified lines, which broke up as they reached the island, each bird going to its young. Then the outcry began, and the ensuing two hours were the noisiest of the day.

Pelicans are so well able to supply the wants of their families that, unlike smaller birds who bring to their ever-hungry broods only a mouthful at a time, they are not forced to feed their young at short intervals throughout the day, but the morning meal concluded, they do not again have to provide for their nestlings until afternoon. Immediately after breakfast, therefore, the parent birds went out into the bay to bathe, and the flapping of their wings as they dashed the water over themselves could be heard at a great distance. The bath concluded, the birds gathered in rows on the sand bars jutting out from the island, to vigorously preen their feathers, and doze in the sun; and then, at irregular intervals, bird after bird, prompted apparently purely by a love of exercise, or tempted by a possible resulting exhilaration, mounted slowly into the air until they had attained a great height, when, spreading their wings, they sailed majestically about on broad circles for hours at a time. I was at first inclined to connect this habit with the season of courtship, but observing several birds of the year, who had but recently learned to fly, join their elders, I came to the conclusion that the habit had no sexual significance, and was indulged in solely because the birds enjoyed it.

In the afternoon the fishing parties again started out, and after the resulting catch had been delivered to the clamoring young, the Pelican’s day’s work was concluded, and he betook himself to his favorite roost for the night. At dark a few Cormorants returned to the branches of a dead tree, a single Frigate, after carefully and repeatedly reconnoitering the situation, decided to take lodgings on a neighboring stub, and a Pelican Island day was ended.