The Indian sand-martin (Cotile sinensis) is, I believe, the smallest of the swallow tribe. So diminutive is he that you could put him in your watch-pocket, were you so minded, without fear of damaging his plumage. His charm lies in his littleness and activity rather than in his colouring, for he belongs not to the dandies. Neat and quiet are the adjectives that describe his attire. The head, shoulders, and back are pale brown tinged with grey. The wing-feathers are dark brown. The under parts are white with a touch of grey on the chin and breast. The sexes dress alike. This description applies equally well to the sand-martin (Cotile riparia) that nests in sand-pits in England, for the only differences between this species, which occurs sparingly in India, and the Indian form are that the former is a little larger and possesses a dark necklace.

The feeding habits of sand-martins are those of the rest of the swallow tribe. They live on minute insects which they catch on the wing, not, after the manner of fly-catchers, by making little aerial sallies from a perch, but by careering speedily through the air during the greater part of the day and seizing every insect that they meet.

The Indian sand-martin is a species especially dear to the ornithologist because it nests in winter, when comparatively few other birds are so occupied. Speaking generally, the cold weather may be said to be the “silly season” of the bird world.

There is one drawback to India from the point of view of the ornithologist, and that is the habit of the great majority of birds of building their nests at the time when the sun shines forth pitilessly from a cloudless sky for twelve hours out of the twenty-four, burning up all vegetation and raising the temperature of the air to furnace heat. Under such conditions the pleasure of watching the birds is tempered by the physical discomfort to which the bird-watcher is put. Very pleasant, then, is it, after months of excessive heat, to awake from sleep one morning to find that the cool weather has come at last, to feel the morning air blow fresh against the cheek, and to look out on an earth enveloped in dense mist. Before one’s horse is saddled, the first rays of the sun dissipate the mist with almost magic suddenness, and then one rides forth over dew-bejewelled plains of grass. If on such a morning one repairs to a sand-pit or a river bank, one is likely there to meet with a colony of sand-martins, for it is early in the cold weather that those birds begin to construct their nests, which are holes bored in sand-banks by the birds themselves.

Like the majority of very small birds, sand-martins show but little fear of human beings. Tits, white-eyes, warblers, sand-martins, etc., will come in search of food quite close up to a motionless human being. Mr. W. H. Hudson relates in his Birds and Man how, when one day he went into his garden and walked under the trees, there was a great commotion among the little birds overhead, who mobbed him in the manner they mob an enemy. He discovered that the reason of this strange behaviour on the part of the small birds that usually paid no attention to him, was that he was wearing a striped cloth cap, which the birds appeared to mistake for a cat. It would almost seem that there is so vast a difference in size between a tiny bird and a human being that the former fails to recognise the latter as a living object provided he keeps still. This does not imply poor eyesight on the part of birds. The minds and eyes of birds are almost invariably directed on small things. Now, a man bears to a small bird much the same relation as a horse three hundred hands high would bear to a man. As regards detail, the eyesight of birds is probably superior to that of men, for each sand-martin seems never to mistake its nest, although the entrance to it is merely one of several score of holes scattered irregularly over the face of the cliff. To the human eye these holes look all very much alike, but each must possess minute peculiarities which loom large in the eye of the sand-martin. Whether or not the above explanation is the true one, the fact remains that a human being can take up a position within a few feet of the cliff without disturbing the martins in their nest-building operations.

Some birds, when busy at their nests, work with feverish haste, as though they were under contract to finish them by a given date. Not so the sand-martins. With them, the spells of work at the nest would seem to be mere interludes between their gambols in the air. Each bird appears to visit its nest every few seconds, but generally it contents itself with hovering in front of the hole for a fraction of a minute and then dashes away. Frequently one sees a martin perch at the aperture for a few seconds without doing any work, and then fly off again. For every visit made with the object of doing work, ten or twelve seem to be made for the mere fun of the thing. Sand-martins appear to derive the greatest pleasure from the contemplation of the growing nursery. If the cliff be examined carefully, its soft sandy surface will be found to be scored in many places by marks made by the sharp little claws of the martins as the birds alight.

A colony of nesting martins presents a very animated appearance. The main body dash through the air to and fro in front of the cliff, uttering their feeble twittering, but a few are always at the nest holes, either resting or working. These latter are constantly reinforced from those on the wing, and vice versa, so that there are two streams of birds, one flying to the cliff and the other leaving it. Suddenly the whole flock, including both the resting and the flying birds, will, as if affected simultaneously by a common influence, fly off en masse and disappear from sight. But they are never absent for long. At the end of two or three minutes all are back again.

The birds utter unceasingly, when on the wing, a twittering note, not so harsh as that of the sparrow, but sufficiently harsh to make it appear that the birds are squabbling. A certain amount of bickering does take place among the sand-martins. Every now and again a bird may be observed chasing its neighbour in a very unneighbourly manner. Occasionally two will attack one another with open beak, and fall interlocked to the ground. A prettier sight is that of a couple of martins resting side by side at the orifice of the nest hole twittering lovingly to one another. The excavation that leads to the nest is a round passage, less than three inches in diameter. After proceeding inwards and slightly upwards for about two feet, it ends in a globular cavity of larger diameter. This is the nesting chamber, and is lined with grass, fine twigs, feathers, and the like. Two or three white eggs are laid. Sand-martins probably bring up more than one brood in the year. Their nests are likely to be found in all the winter months.

Cotile sinensis is a permanent resident in India and is common in all the northern portions of the country, but is not often seen so far south as Madras. It is curious that this species should be abundant in North India and rare in the south, where insect life is so plentiful. There must be something in the climatic conditions of South India that suits neither this nor the other species of sand-martin. Precisely what this is I cannot conjecture. Birds vary greatly in their adaptability to climate. Some, such as the hoopoe, appear absolutely indifferent to heat or cold, moisture or dryness; others, as most wagtails, shun heat. The two common crows of India afford an excellent illustration of the way in which allied species differ in their power of adapting themselves to variation in climate. The grey-necked species (Corvus splendens) is found throughout the length and breadth of the plains of India, but does not ascend the Himalayas to any great height, and is, in consequence, not found in Murree Mussoorie or Naini Tal. The corby (C. macrorhynchus), on the other hand, is found in all parts of the plains save in the Punjab, and ascends the Himalayas up to 10,000 feet or higher, and is the only crow that occurs in most of the Himalayan hill stations. It is thus evident that the black species is far less sensitive to cold than the other, but why does it occur so sparingly in the Punjab? The connection between climate and the distribution of birds is a fascinating subject about which very little is known. Possibly in the varying sensitiveness of birds to climatic conditions lies the secret of some of the phenomena of bird migration.