The laughing gulls and the black skimmers were often found with their nests intermingled, and they hovered over our heads with the same noisy protest against our presence. Although they often—not always—nested so close together, the nests were in no way alike. The gulls' dark-green eggs, heavily blotched with brown, two or three in number, lay on a rude platform of marsh-grass, which was usually partially sheltered by some bush or tuft of reeds, or, if on wet ground, was on a low pile of driftwood. The skimmers' eggs, light whitish green and less heavily marked with brown, were, when the clutch was full, four to six in number. There was no nest at all, nothing but a slight hollow in the sand, or gravel or shell débris. In the gravel or among the shell débris it was at first hard to pick out the eggs; but as our eyes grew accustomed to them we found them without difficulty. Sometimes we found the nests of gull and skimmer within a couple of feet of one another, one often under or in a bush, the other always out on the absolutely bare open. Considering the fact that the gull stood ready, with cannibal cheerfulness, to eat the skimmer's eggs if opportunity offered, I should have thought that to the latter bird such association would have seemed rather grewsome; but, as a matter of fact, there seemed to be no feeling of constraint whatever on either side, and the only fighting I saw, and this of a very mild type, was among the gulls themselves. As we approached their nesting-places all these birds rose, and clamored loudly as they hovered over us, lighting not far off, and returning to their nests as we moved away.
The skimmers are odd, interesting birds, and on the whole were, if anything, rather tamer even than the royal terns and laughing gulls, their constant associates. They came close behind these two in point of abundance. They flew round and round us, and to and fro, continually uttering their loud single note, the bill being held half open as they did so. The lower mandible, so much longer than the upper, gives them a curious look. Ordinarily the bill is held horizontally and closed; but when after the small fish on which they feed the lower mandible is dropped to an angle of forty-five degrees, ploughing lightly the surface of the water and scooping up the prey. They fly easily, with at ordinary times rather deliberate strokes of their long wings, wheeling and circling, and continually crying if roused from their nests. When flying the white of their plumage is very conspicuous, and as they flapped around every detail of form and coloration, of bill and plumage, could be observed.
When sitting they appear almost black, and, in consequence, when on their nests, on the beaches or on the white-shell dikes, they are visible half a mile off, and stand out as distinctly as a crow on a snow-bank.[2] They are perfectly aware of this, and make no attempt to elude observation, any more than the gulls and terns do. The fledglings are concealingly colored, and crouch motionless, so as to escape notice from possible enemies; and the eggs, while they do not in color harmonize with the surroundings to the extent that they might artificially be made to do, yet easily escape the eye when laid on a beach composed of broken sea-shells. But the coloration of the adults is of a strikingly advertising character, under all circumstances, and especially when they are sitting on their nests. Among all the vagaries of the fetichistic school of concealing-colorationists none is more amusing than the belief that the coloration of the adult skimmer is ever, under any conditions, of a concealing quality. Sometimes the brooding skimmer attempted to draw us away from the nest by fluttering off across the sand like a wounded bird. Like the gulls, the skimmers moved about much more freely on the ground than did the terns.
The handsome little laughing gull was found everywhere, and often in numerous colonies, although these colonies were not larger than those of the skimmer, and in no way approached the great breeding assemblages of the royal terns on the two or three islands where the latter especially congregated. They were noisy birds, continually uttering a single loud note, but only occasionally the queer laughter which gives them their name. They looked very trim and handsome, both on the wing and when swimming or walking; and their white breasts and dark heads made them very conspicuous on their nests, no matter whether these were on open ground or partially concealed in a bush or reed cluster. Like the skimmers, although perhaps not quite so markedly, their coloration was strongly advertising at all times, including when on their nests. Their relations with their two constant associates and victims, the skimmer and the royal tern—the three being about the same size—seemed to me very curious. The gull never molested the eggs of either of the other birds if the parents were sitting on them or were close by. But gulls continually broke and devoured eggs, especially terns' eggs, which had been temporarily abandoned. Nor was this all. When a colony of nesting royal terns flew off at our approach, the hesitating advent of the returning parents was always accompanied by the presence of a few gulls. Commonly the birds lit a few yards away from the eggs, on the opposite side from the observer, and then by degrees moved forward among the temporarily forsaken eggs. The gulls were usually among the foremost ranks, and each, as it walked or ran to and fro, would now and then break or carry off an egg; yet I never saw a tern interfere or seem either alarmed or angered. These big terns are swifter and better fliers than the gulls, and the depredations take place all the time before their eyes. Yet they pay no attention that I could discern to the depredation. Compare this with the conduct of king-birds to those other egg-robbers, the crows. Imagine a king-bird, or, for that matter, a mocking-bird or thrasher, submitting with weak good humor to such treatment! If these big terns had even a fraction of the intelligence and spirit of king-birds, no gull would venture within a half-mile of their nesting-grounds.
It is one of the innumerable puzzles of biology that the number of eggs a bird lays seems to have such small influence on the abundance of the species. A royal tern lays one egg, rarely two; a gull three; a skimmer four to six. The gull eats the eggs of the other two, especially of the tern; as far as we know, all have the same foes; yet the abundance of the birds is in inverse ratio to the number of their eggs. Of course, there is an explanation; but we cannot even guess at it as yet. With this, as with so many other scientific questions, all we can say is, with Huxley, that we are not afraid to announce that we do not know.
The beautiful royal terns were common enough, flying in the air and diving boldly after little fish. We listened with interest to their cry, which was a kind of creaking bleat. We admired the silver of their plumage as they flew overhead. But we did not come across vast numbers of them assembled for breeding until the fourth day. Then we found them on an island on which Captain Sprinkle told us he had never before found them, although both skimmers and gulls had always nested on it. The previous fall he had waged war with traps against the coons, which, although there was no fresh water, had begun to be plentiful on the island. He had caught a number, two escaping, one with the loss of a hind foot, and one with the loss of a fore foot. The island was seven miles long, curved, with occasional stretches of salt marsh, and with reaches of scrub, but no trees. Most of it was bare sand. We saw three coon tracks, two being those of the three-footed animals; evidently the damaged leg was now completely healed and was used like the others, punching a round hole in the sand. We saw one coon, at dusk, hunting for oysters at the water's edge.
The gulls and skimmers were nesting on this island in great numbers, but the terns were many times more plentiful. There were thousands upon thousands of them. Their breeding-places were strung in a nearly straight line for a couple of miles along the sand flats. A mile off, from our boat, we were attracted by their myriad forms, glittering in the brilliant sunlight as they rose and fell and crossed and circled over the nesting-places. The day was bright and hot, and the sight was one of real fascination. As we approached a breeding colony the birds would fly up, hover about, and resettle when we drew back a sufficient distance. The eggs, singly, or rarely in pairs, were placed on the bare sand, with no attempt at a nest, the brooding bird being sometimes but a few inches, sometimes two or three feet, from the nearest of its surrounding neighbors. The colonies of breeders were scattered along the shore for a couple of miles, each one being one or two hundred yards, or over, from the next. In one such breeding colony I counted a little over a thousand eggs; there were several of smaller size, and a few that were larger, one having perhaps three times as many. A number of the eggs, perhaps ten per cent, had been destroyed by the gulls; the coons had ravaged some of the gulls' nests, which were in or beside the scrub. The eggs of the terns, being so close together and on the bare sand, were very conspicuous; they were visible to a casual inspection at a distance of two or three hundred yards, and it was quite impossible for any bird or beast to overlook them near by. These gregarious nesters, whose eggs are gathered in a big nursery, cannot profit by any concealing coloration of the eggs. The eggs of the royal and Cabot's terns were perhaps a shade less conspicuous than the darker eggs of the Caspian tern, all of them lying together; but on that sand, and crowded into such a regular nursery, none of them could have escaped the vision of any foe with eyes. As I have said, the eggs of the skimmer, as the clutches were more scattered, were much more difficult to make out, on the shell beaches. Concealing coloration has been a survival factor only as regards a minority, and is responsible for the precise coloration of only a small minority, of adult birds and mammals; how much and what part it plays, and in what percentage of cases, in producing the coloration of eggs, is a subject which is well worth serious study. As regards most of these sea-birds which nest gregariously, their one instinct for safety at nesting time seems to be to choose a lonely island. This is their only, and sufficient, method of outwitting their foes at the crucial period of their lives.
We found only eggs in the nurseries, not young birds. In each nursery there were always a number of terns brooding their eggs, and the air above was filled with a ceaseless flutter and flashing of birds leaving their nests and returning to them—or eggs, rather, for, speaking accurately, there were no nests. The sky above was alive with the graceful, long-winged things. As we approached the nurseries the birds would begin to leave. If we halted before the alarm became universal, those that stayed always served as lures to bring back those that had left. If we came too near, the whole party rose in a tumult of flapping wings; and when all had thus left it was some time before any returned. With patience it was quite possible to get close to the sitting birds; I noticed that in the heat many had their bills open. Those that were on the wing flew round and round us, creaking and bleating, and often so near that every detail of form and color was vivid in our eyes. The immense majority were royal terns, big birds with orange beaks. With them were a very few Caspian terns, still bigger, and with bright-red beaks, and quite a number of Cabot's terns, smaller birds with yellow-tipped black beaks. These were all nesting together, in the same nurseries.
It has been said on excellent authority that terns can always be told from gulls because, whereas the latter carry their beaks horizontally, the terns carry their bills pointing downward, "like a mosquito." My own observations do not agree with this statement. When hovering over water where there are fish, and while watching for their prey, terns point the bill downward, just as pelicans do in similar circumstances; just as gulls often do when they are seeking to spy food below them. But normally, on the great majority of the occasions when I saw them, the terns, like the gulls, carried the bill in the same plane as the body.
On another island we found a small colony of Forster's tern; and we saw sooty terns, and a few of the diminutive least terns. But I was much more surprised to find on, or rather over, one island a party of black terns. As these are inland birds, most of which at this season are breeding around the lakes of our Northwestern country, I was puzzled by their presence. Still more puzzling was it to come across a party of turnstones, with males in full, brightly varied nuptial dress, for turnstones during the breeding season live north of the arctic circle, in the perpetual sunlight of the long polar day. On the other hand, a couple of big oyster-catchers seemed, and were, entirely in place; they are striking birds and attract attention at a great distance. We saw dainty Wilson's plover with their chicks, and also semipalmated sandpipers.