XXII. NESTS AND NO NESTS.

Strolling across the moor in the sunshine to-day, past the lonely pine where the night-jar sits crooning to his lady-love in the twilight, I came suddenly across his grey mate herself, and saw her flutter up sleepily in dazed surprise from the bare ground where she was sitting. As she flapped her mottled wings and sailed slowly away, like a blinking owl disturbed in the daytime, I noticed that I had lighted unawares upon her nest, or rather, her eggs, for she lays them on the open, without bed of any sort. I left them untouched, for I am no collector. A few minutes later, I came abreast of the low cliff where the sand-martins have established their twittering colony. The soft yellow sandstone that forms the cutting is honey-combed with their tunnels; and as I leaned on my stick and looked, I saw the busy brown birds gliding in and out, with their long curved flight, and carrying back mouthfuls of gnats and mayflies to their fledgelings in the burrows. It was beautiful to watch them swooping in great arcs over the gorse and bracken, and then darting straight, with unerring accuracy, to the mouth of their tunnels. They alight at the very door with all the skill of born pilots, never missing or overshooting the mark by one inch, but steering upon it so truly that they look as though failure or miscalculation were impossible.

These two little episodes coming together set me thinking; ’tis a bad habit one indulges in when one walks too much alone in the open. In towns one doesn’t think, because the shop-windows, and the horses, and the noise, and the people, and the omnibuses distract one; but in the country, one gives way a great deal too readily to what Plato calls the “divine disease” of thinking. I began to philosophize. How curious, I said to myself, that we have but five kinds of bird in England that hawk on the wing after insects in the open; and of all those five, not one builds a proper respectable nest, woven of twigs and straws, like a sparrow or a robin! Every one of them has some peculiar little fancy of his own—goes in for some individual freak of originality. The night-jar, which is the simplest and earliest in type of the group, lays its eggs on the bare ground, and rises superior in its Spartan simplicity to such petty luxuries as beds and bedding. The swift, that ecclesiologically-minded bird, which loves the chief seats in the synagogue, the highest pinnacles of tower or steeple, gums together a soft nest of floating thistle-down and feathers, by means of a sticky secretion from its own mouth, distilled in the last resort from the juices of insects. The swallow and the house-martin, again, make domed mud huts, and line them inside with soft floating material. Finally, the sand-martin excavates with its bill the soft sandstone of cliffs or roadside cuttings, and strews a bed within for its callow young of cotton-grass and dandelion parachutes.

Why this curious variety among themselves, and this equally curious divergence from the common practice of bird-kind in general? Clearly, thought I, it must bear some definite relation to the habits and manners of the birds which exhibit it. Let me think what it means. Aha, aha, eureka! I have found it! The insect-hawking birds are not a natural group; by descent they have nothing at all to do with one another. Closely as the swift resembles the swallow in form, in flight, in shape of bill, in habits and manners, we now know that the swift is a specialized woodpecker, while the swallow and the martins are specialized sparrows. (I use both words, bien entendu, in quite their widest and most Pickwickian evolutionary acceptation.) The swift and the night-jar belong to one great family of birds; the swallow, the house-martin, and the sand-martin to another. The likeness in form and in mode of flight has been brought about by similarity in their style of living. Two different birds of two different types both took, ages since, to hawking after flies and midges in the open air. Each group was thus compelled to acquire long and powerful wings, a light and airy body, a good steering tail, a wide gape of mouth, and a rapid curved flight, so as to swoop down upon and catch its petty prey unsuspected. So, in the long run, the two types which hawk most in the open, the swifts and the swallows, have grown so like that only by minute anatomical differences can we refer the remoter ancestry of one species to the woodpeckers and humming-birds, and the remoter ancestry of the other to the tits and sparrows.

How does their manner of life affect their mode of nesting, however? Indirectly, in this way. Birds that live largely off seeds and fruits and hard-shelled beetles, have hard short beaks to grind their food with, and sit much in thickets, scrub, or hedgerows. But birds that hawk on the wing after small soft flies must have wide soft bills, and a gaping mouth; they can hardly perch at all on trees or bushes, and their feet are too weak to be of much use for walking. Indeed, if a swift once alights on the ground, he can scarcely get up again, so difficult is it for the long wings to work in a narrow space, and so slight a power of jumping have the feeble little legs. Hence it follows that birds of the hedgerow type can readily build nests of twigs and straws, which they gather as they perch, or seek on the ground; and they are enabled to weave them with their hard bills and active feet; while birds of the hawking type cannot pick up sticks or gather straws on the ground, and have beaks quite unadapted for dealing with such intractable materials. The consequence is they have been compelled to find out each some new plan for itself, and to build their nest out of such stray material as their habits permit them.

The night-jar, a stranded nocturnal bird of early type, with very few modern improvements and additions, solves the problem in the easiest and rudest way by simply going without a nest at all, and laying her eggs unprotected in the open. Nocturnal creatures, indeed, are, to a great extent, the losers in the struggle for existence; they always retain many early and uncivilized ways, if I may speak metaphorically. They are the analogues of the street arabs who sleep in Trafalgar Square under shelter of a newspaper. The sand-martin, an earlier type than the swallow or the house-martin, burrows in sandstone cliffs, which are pre-human features, though man’s roads and railways have largely extended his field of enterprise. But the house-martin and the swallow, later and far more civilized developments, have learned to take advantage of our barns and houses; they nest under the eaves; and being largely water-haunters, skimming lightly over the surface of ponds and lakes, they have naturally taken advantage of the mud at the edges as a convenient building material. Last of all, the soaring swift, the most absolutely aërial type of the entire group, unable to alight on the ground at all, has acquired the habit of catching cottony seeds, and thistle-down, and floating feathers in his mouth as he flies, and gumming them together into a mucilaginous nest with his own saliva. The Oriental sea-swifts have no chance of finding even such flying materials among their caves and cliffs, and they have consequently been driven into erecting nests entirely of their own inspissated saliva, without any basis of down or feathers. These are the famous edible birds’-nests of the Chinese; they look like gelatine, and they make excellent soup, somewhat thick and gummy.