Cobb's Island
The Atlantic coast, from New Jersey to North Carolina, is bordered by an outlying chain of islets. Many of them are mere sand bars, more or less grown with coarse grasses, and, on their western sides, fringed by marshes which reach out into the bays separating them from the mainland.
Useless for agricultural purposes, these islands have a high commercial value only when they have become the sites of summer resorts; but when they have not suffered from an irruption of hotels and cottages they are, as a rule, tenanted only by an occasional fisherman or the crews of lifesaving stations, whose presence does not materially alter their primeval conditions.
Lacking the natural foes of birds which exist on the mainland, these barren islets make ideal breeding-grounds for birds, which find on them the isolation their peculiar nesting habits require, while the surrounding waters furnish them an abundant supply of food.
In all this chain of bird homes, probably none has been better known to ornithologists than Cobb's Island, on the Virginia coast, north of Cape Charles. Seven miles long, it has been occupied by man only at the extreme southern end; a small sportsman's club-house and a life-saving station being now its only dwellings.
Twenty years ago, Willet, and Least Terns, in large numbers, and Royal Terns bred on Cobb's Island, but today the former is rare while the two later are unknown, and there are left as breeding birds, Common, Forster's, and Gull-billed Terns, Laughing Gulls, Skimmers, Oyster-catcher, Wilson's Plovers, Clapper Rails and Seaside Finches. Willet have disappeared before spring shooting, in what was actually their nesting season. The Least Terns fell vic- tims to the milliners, who greatly decreased the other species of Terns nesting on the island. The former captain of the life-saving station told me of 1,400 Least Terns being killed in one day; while the captain of the station and Mr. E. B. Cobb, owner of the island, informed me that when Terns were first killed for millinery purposes they, with another man, killed 2,800 birds in three days on and near Cobb's Island. The birds were packed in cracked ice and shipped to New York for skinning; ten cents being paid for each one.
In July, 1902 (23-25), I visited Cobb's Island to secure data, photographs and specimens with which to represent its summer bird-life in a Habitat Group. At the same time, it was proposed to study the Black Skimmer. Marvelously graceful in the air, the Skimmer is so conspicuously ugly when at rest, that not even the milliners consider it available for alleged hat decoration; consequently it was spared while its more beautiful neighbors, the Terns, were slaughtered, and it is numerous in favorable localities on the coast from Virginia to Texas.
But in spite of the Skimmer's abundance, its conservatism in the matter of habitat removes it from the field of observation of most ornithologists, and, at the time of which I write, accounts of its habits could be found only in the works of Wilson and Audubon. Neither of these remarkably keen and sympathetic students of bird-life appears, however, to have had an extended experience with the Skimmer during the nesting season. Both state, for instance, that it lays only three eggs; whereas the full complement is four; and, Wilson writes that the "female sits on them only during the night and in wet and stormy weather." As I desired especially to secure photographs of the sitting bird, this question of the day or night incubation was of importance. I made inquiry, therefore, of ornithologists who had been among skimmers, but not one had ever seen a Skimmer on its nest. Hence the life history of the Skimmer appeared to be an unusually attractive subject of investigation. Unique in structure, he was known to be correspondingly unique in feeding habit; while there was something pleasingly mysterious in the birds' supposed habit of coming home only after dark.
Skimmers arrive on the Virginia coast early in May, and begin to lay about June 15; but their nests are so persistently robbed by fishermen that few young are hatched before July 20. The latter part of this month or early August is, therefore, the best season in which to study the domestic economy of the Skimmer household.
It is a memorable moment in the life of the naturalist when the animal of books or museums, or even zoological gardens, is first seen by him, a wild, free creature in its haunts; and when the animal is as singularly formed as the Skimmer, one's desire is intensified by a curiosity to see it use its peculiar and characteristic organs. Imagine, then the joy of an ornithologist who, for the first time, finds himself in a breeding colony of thousands of Skimmers, where the air is filled with a yelping mob of birds whose eggs and young are so numerous on the broad shell-strewn beach, that one cannot walk without danger of stepping on them.
It was not difficult to find a spot in which to begin a study of the birds. Some minutes before reaching the boundary of the territory they inhabited, a band of birds arose in the air and, with more or less extended front, flew toward me only to swing to one side, wheel and fly back again; all uttering a trumpet-like note which is effectively emphasized by violent bill action, the bright red and black mandibles opening widely with each note. When the nests were reached, the uproar increased and with it the excitement and boldness of the particular birds near whose eggs or nests I chanced to be standing. Starting a hundred or more feet away, one after the other charged toward me with such speed and apparent fearlessness, that one could well be pardoned an involuntary dodge ere the birds, when only a few feet away, swerved and passed over one's head.
The nests are hollows in the sand, often only a few feet apart and with absolutely no lining, the Skimmer's bill being evidently not adapted to gathering nesting material or constructing a nest. The four creamy white eggs are conspicuously marked with black, and are more by no means difficult to see; but the downy young so closely harmonize with their surroundings in color, that they are far less easy to discover than the young of any beach-nesting bird with which I am familiar. Their partial invisibility, it should be observed, is not due to their resemblance in form to their surroundings, or to the necessity of distinguishing them from pebbles or shells, as is often the case with young Terns. It is a purely a matter of color and disposition of color which makes them fade into the bare sand about them. Like most young birds, they instinctively know that safety lies only in unquestioning obedience to the parental command, which warns them of threatening danger, and bids them squat close to the sand with neck stretched out and eyes half closed. I could scarcely believe, for a moment, that the first one seen in this attitude was a living bird, but behold ! When
I stooped to pick him up at the touch of my finger tips, he evaded my grasp and scudded over the beach so fast I scarce could catch him.
It was easier to discover the nests of the Skimmers than a vantage point from which one might study the habits of their owners. As yet I had not learned whether they incubated by day or night, and this could be done only by concealing myself and waiting until peace and quiet in Skimmerland came, with the assurance that their enemy had departed. The blind was therefore erected in a depression or on a sand dune within one hundred and fifty feet of twenty or more nests. The whole affair was then covered with beach grass, and into it I crept.
For a time, the birds threatened this unfamiliar object, darting at it with loud screams; but within one hour and a half, it ceased to annoy them and, to my great satisfaction, bird after bird returned to its nest, some alighting directly on the little hollow in the sand, others dropping near-by and
with waddling step, walking to the nest and settling themselves on their eggs or newly hatched young with a low, brooding, churring note reserved for this occasion, and evidently indicative of extreme contentment. This answered the question of day or night incubation; but it would be well to illustrate this fact in the bird's history, and cameras bound about with grasses, where placed near several nests, a thread run from them to the blind, and numerous pictures were thus made of the Skimmer at home.
I passed two days in my blind, enjoying to the full the isolation of the Skimmer's retreat, and the privilege of seeing, unseen, a wild creature in its haunts. Within this short time, some additions were made to our knowledge of the Skimmer's habits. Thus I learned that the hollow where the eggs are laid is not a chance depression, but is made by the bird -- the female, so far as was observed, -- which, squatting close, turns round and round, actually boring out a shallow cavity in the easily yielding sand.
Apparently only the female incubates, but the much larger male often comes and stands by her side while she sits on the eggs, a pleasant picture in bird life suggestive of domestic harmony. In all the pictures made of the sitting bird from the front, one or two of the eggs can be seen through the breast feathers, as though the bird had a larger "clutch" than she could cover. The period of incubation I had no means of determining, but certain it is that once the chick announces his coming by a chicken-like peep, the transformation of a pipped egg into a bright-eyed downy Skimmer, endowed with all the instincts of its kind, is a matter of only two and one-half or three hours.
As soon as the nestling emerges from the egg, the shell is taken by the parent, and, so far as was observed, carried out of sight; a singular custom, common to most birds. The habit is doubtless of importance to a tree-nesting bird, where the egg-shell below might advertise the young bird above; but why, with a beach-nesting species an egg-shell should be considered more conspicuous than an egg it is
hard to say; but there can be no doubt that once it has released its contents, it must be disposed of as quickly as possible.
The chicks seem to appear on successive days, and to leave the nest when a day or two old. They are fed on small fish and doubtless other forms of aquatic life, which, at first, may be partially digested by the parent bird. Whether or not each parent finds its own chicks when the beach becomes alive with hungry youngsters, cannot be confirmed definitely, though there is evidence to show not only that the old birds recognize their offspring, but, that the latter know their parents.
So singular in form is the bill of the adult Skimmer, that Buffon described it as an "awkward and defective instrument" a somewhat surprising conclusion to proceed from so learned a naturalist, and one which Wilson pronounced an "impiety." With the lower mandible averaging half an inch longer than the upper, and with both so thin and flexible
that they can be bent as readily as a table knife, one might be pardoned for believing the Simmer's bill a deformity; but the belief is quickly dispelled when once the bird is seen feeding. Flying low, with bill opened wide, the lower mandible cuts the water like a knife edge, as the birds actually skim the surface for fish and small forms of aquatic life.
In the newly hatched bird, it is of exceeding interest to observe that the mandibles are of virtually equal length, and the lower mandible does not become pronouncedly longer than the upper until the bird takes wing. This may be considered as evidence that this highly specialized character has been developed late in the history of the species; or the development of the bill may be a correlation in growth which defers the perfection of an organ until it can be successfully employed. Certainly without the power of flight, a Skimmer could not "skim." Until, therefore, the bird can fly, it supplements the supply of food brought by the parents by picking up a living along the beach.
Skimmers were frequently seen feeding during the day, particularly along the meeting line of sand and sea, where
they gleaned from the burden of the waves; but it was at dusk that they became really active. Then they followed the course of the streams winding through the marsh, now skimming for a short distance, again rising slightly and uttering a sharp yap, yap, like a pack of hounds on the trail.
In addition to the Skimmers, the breeding birds on Cobb's Island at the time of my visit, were several hundred Common Terns, a small number of Forester's terns, about eight pairs of Gull-billed Terns, a pair each of Oyster-catchers, Willet, and Wilson's Plovers, several hundred Laughing Gulls, and many Clapper Rail. The young Rails furnished the principal fare of several cats which Mr. Cobb had brought to the island to kill the meadow mice which destroyed the sails and rigging of his boats.
Two pairs of Gull-billed Terns were nesting in the Skimmer colony to which I devoted my attention, where, aside from the difference in their eggs, the Terns' nests were at
once distinguishable from the Skimmers' by the large number of shells which had obviously been arranged about them. The Terns' light, thin, somewhat reedy tee-tee-tee, which sometimes suggested a weak-voiced katy-did, was a readily identifiable note.
From my blind among the Skimmers, I could look out over the marsh where the Laughing Gulls nested and in the morning the breasts of the birds facing the east looked like great white flowers with which the marsh was dotted. No attempt was made to study these birds, but they were photographed without difficulty by erecting bundles of grass on tripods near the nests, one evening, and replacing them with grass-covered cameras, the following morning. Exposures were made with a thread run to the blind, (which was made to resemble a musk-rat's nest), a hundred and fifty feet away. Some nests contained newly hatched birds, and comparison of their black and umber down, so like, in general tone the color of the nest, with the gray down of the young Skimmer, which might be described as sand rendered in feathers, shows how perfectly each helpless chick matches its own background.