III. The Sea Swallow, or White-Fronted Tern.

The Terns of the northern Porangahau beach during the season of 1910 were congregated in two great separate establishments—about two or three thousand in the larger, in the lesser rather fewer than quarter of that number. There was a third narrow line of a few score incubating birds on the southern beach. A bird colony has a twofold interest: each member has its own idiosyncrasy, and may be studied as an individual citizen; there is also the opportunity of watching its habits and customs as one of a gregarious multitude.

The contours of these Porangahau Terneries were approximately deltoid or lanceolate or oblong, dependent, I suppose, on shelter provided either directly, or indirectly and invisibly, by eddies consequent on conflicting currents of air. Unlike the Caspian Tern, the Sea Swallow is particular page 16 in regard to the ruffling of its plumage by wind. Each individual in the Ternery sits facing the breeze. Throughout my visits the hope was constant in my mind that even whilst I watched, the wind might change, and that I might witness the company rise as one bird and face about as in some measure of a stately dance. The larger colonies breeding on the northern beach appeared at first impression to be sitting in two great homogeneous companies. Closer inspection, however, showed that each of them was composed of many smaller companies, and that the effect of uniformity was produced by the sitting members of each sept dovetailing into that of another. Each nest is a shallow pit containing a single egg.¹ Upon it sits the Tern, its breast a bulwark to the racing grit.

Few sights are more elegant than such a colony in repose, the beautiful birds in hundreds facing one direction, settled into the sand as if floating on water, each with the same pure greys below, the same black cap above, the same dark bill, the same long pinions crossed above the back like the forked tails of a great Brazilian butterfly, each bird sheltering the same long tapering delta of bright, clean, shining sand. To and from the fishing ground during incubation there is a continuous page break

Kittiwake And Sea Swallow.

page break page 17 stream of movement, two separate currents flowing, the “clk, clk, clk” of the busy birds continuing hour after hour. Few bird calls can be translated with any exactitude or accuracy, but the call of the flying Tern, I think, does closely resemble the “clk, clk” given in encouragement to a lazy horse. When approached too suddenly the whole vast congregation will rise, the “clk, clk, clk” momentarily ceasing altogether in sudden consternation, then the sudden silence changing immediately into a loud universal chorus of disapprobation, “kek, kek, kek.” On such occasions only a very few of the most steadfast—among the faithless, faithful only they to their eggs—continue to sit. These panics are, however, easily allayed. Almost as fast as they have arisen the reassured birds will again cuddle into their sand-pits. Male and female, I believe, sit alternately. It is the latter who sits the more assiduously, and who takes an especial care of the eggs just before chipping. During this critical time she is fed by her partner with a small shining silver-scaled fish.

Even during the rare intervals of calm weather, when not a grain of sand stirs, the first care of a Tern reoccupying its nest is the ejection of imaginary grit. On these occasions the bird will also breast the sand forward, gently pressing it out. Often, too, after settling on the egg a bird page 18 will, as a final touch, gather little billfuls of sand, and with jerking movements cast them to right and left. In watching the busy life of a great Ternery I have often wondered if even under normal conditions each pair of birds always succeeds in rearing its own chick. It is at any rate no infrequent sight to witness a Tern settle on a nest apparently its own, driven off that nest by another Tern, the first bird therefore really an interloper, or else a genuine owner dispossessed by force. Sometimes I have been inclined to favour the former supposition on account of the small amount of resistance made—anger at the disturbance of a comfortable position rather than rage at dispossession of a treasured egg. On the other hand, I may have been but judging by appearances, for had the sitting bird been, let us say, of a particularly fierce disposition, its resistance would have been successful, and I should then have believed it to be the original owner. Often the judgment of Solomon in regard to the babe claimed by the rival mothers seems to be the principle that decides ownership. The Tern that most dearly loves the egg, imagined rightly or wrongly to be its property, gets it.

Under conditions of storm and stress there are yet stronger reasons for doubting whether each pair of Sea Swallows rear to maturity their own page break

Kittiwake And Sea Swallow Flying.

page break page 19 chick. During rough weather confusion worse confounded reigns. It becomes chaos in the wake of such gales as have been witnessed by me on two occasions on the Porangahau beach. The first was one of those violent dry southers that rush up after sultry weather. In a few moments the whole Ternery—the whole beach indeed—was grey with wagging wisps of drift pouring over shore-line hummocks, racing over wet sea sand like dry thin star snow on keen ice.

At any time there is much vociferation amongst a multitude of birds breeding together; at any time there is difficulty when nests lie close together for the returning birds to alight without disturbance to their neighbours. Now every individual was doubly noisy and more fiercely on the defensive. Each to its utmost was using voice and bill to fend off neighbours attempting to alight, whilst now and again sudden stronger blasts would dash hovering birds against others, compelling those attempting to stand sentinel, again to use their wings, and thus further to increase the confusion. A Tern in the air is as much at home as a fish in water, but under the stress of the varying gusts of the gale, manœuvring into a desired berth becomes to a returning bird as delicate and particular an operation as is the docking of a liner. Exactitude was in fact no longer possible. The ground, erstwhile page 20 in sunshine, dappled with the shade of sentinel stationary birds, erstwhile in calm, dimpled with nest-cups, had become almost at once a shadowless smooth slope. Most of the chicks had hatched, but were tiny creatures who lay as minute hummocks, the sand grit uninterruptedly racing over their small bodies. More, slightly older, missing the hollow of their nests, were hustled before the gale. Too desperate for discrimination, they rushed to the shelter of every Tern that alighted in their vicinity. In the babel of sound and confusion of skirmishing, all personal interest was lost in special parents. Even amongst old birds only the smallest minority seemed to attempt to particularise. I have seen chicks compelled to quit a stance, sometimes even castigated with the old bird's bill. I remember one youngster, particularly obdurate and determined not to vacate its coign of vantage, fairly picked up, lifted a couple of feet above the din, and dropped a yard away. The largest crouching chicks could sometimes and in some degree breast the storm; rising to seek shelter they were at once rolled over. The actual site indeed of the Ternery must have been moved some feet or yards northward, and noting the confusion and turmoil, listening to the ceaseless screeching and screaming, and witnessing the indiscriminate celerity with which the homeless chicks sought shelter, it was impossible to believe page break

Sea Swallow.

page break page 21 that many parents remained in possession of their proper offspring.

There are other occasions, too, greater catastrophes by far, which must entail amongst the old birds the keenest of competition for surviving nestlings. In these disasters, too, parentage is probably settled by Solomon's law. They are consequent on conditions to which littoral species are increasingly subject. Almost everywhere sea-fowl breeding about river estuaries have been ousted by progress of settlement from naturally secure sites. In the one particular instance about which I write, the harm was done in little more than an hour. Although calm and fine locally, a gale evidently had been blowing outside. A heavy sea began late one afternoon to thunder and pound on the beach, and to force an immense weight of water into the lagoon. With the flow of the tide it was a miserable sight to watch the Ternery. With the advancing flood the lowest nests were soon engulfed. As the water still continued to rise, first dozens of sitting birds and then hundreds were flooded off their nests, the egg-pits filled, and the eggs rolled about and floated away. In some cases the birds sat until actually raised by the water, whilst eggs and drowning chicks were everywhere adrift. It was a bit of mere good fortune, a sudden lucky lull that, together with the turn of the tide, saved page 22 the majority of the nests; the sea happened to go down as rapidly as it had risen. Five hundred eggs or tiny chicks had nevertheless perished. Another hour would have seen the last of at least fifteen hundred more, two thousand that is, out of twenty-five hundred eggs and chicks in the particular Ternery affected.

The Sea Swallow tribe well exemplify the general truth that amongst creatures below man in the scale of creation there is that lack of adaptability, that powerlessness to deal with any sudden new situation, which marks the limit of instinctive action. The simplest of experiments with a sitting Tern showed the bird nonplussed by conditions outside the range of experience, outside that hard-set knowledge of the ages, primarily in the bird's frame, but reinforced and corroborated in each successive generation. I found that the removal of the egg three inches away from the egg-pit left the poor owner helpless before a vast insoluble other-world conundrum, a conundrum as of Mars or the moon. As it lay smooth and alluring on the warm sand she did not attempt to sit on it, to touch it, to scoop the sand from beneath it and thus create a new nest, or to roll it into its proper hollow. Watching it always as if fascinated, she merely ran up and down, circling about its vicinity in an agitated manner. I then replaced the egg, its owner being allowed to incubate the page break

Sea Swallow.

page break page 23 miraculously restored treasure until it was thoroughly warmed again. My next experiment was similar to the first, except in this, that the egg was placed on the sand surface within one inch only of the nest. As before, the Tern displayed anxiety, but made no attempt to deal with the problem, only as before running in perturbation about the neighbourhood of the bewitched bedevilled egg. It was then again replaced, and the bird once more allowed to proceed with its incubation. Upon the third removal of the egg it was balanced on the very rim of the nest-pit, poised so delicately that by the least touch the sand upon which it lay would begin to run and presently bear it into the nest. For the third time my Sea Swallow ran round its egg in puzzlement and perplexity, until, as I had foreseen, its fortuitous perambulations stirred the sand about the rim of the nest, and the grit continuing to flow like the sand of an hour-glass, the egg slid on to the side of the pit. In this attitude, unfamiliar as it may have been, the Sea Swallow became for the first time able to deal with the situation. Three inches from the nest on hard sand, no line of action had suggested itself; one inch from the nest, no line of action had suggested itself, but the bird was not so totally devoid of ability to deal with a foreign experience as to be unable to cope with an egg now actually in the nest, page 24 albeit in a strange unwonted position. She moved into the sandpit nest, and once within it the act of scraping was suggested by the feel of loose sand about her belly and legs. She scraped, the egg slid more and more into proper position, and her mental pertubations were over. In their very narrow but very perfect plane the beasts and birds of the earth live simply wise and simply happy, with the happiness that comes of the unopened mind.