The Tree Swifts differ almost entirely in their mode of life from any other members of their family. Extensive woods and dense forests are their favourite resorts, such being preferred as are in lowland districts; according to Jerdon, the Indian Klecho constantly builds in these localities, flying from thence over the streams or lakes in the vicinity in search of insects on which it subsists. Whilst resting from its labours it usually selects a withered tree for its perch, and amuses itself by expanding and playing with the beautiful crest upon its head. Its flight is excellent, but it climbs awkwardly among the branches. When upon the wing it utters almost incessantly a loud parrot-like scream; when perched its voice is not quite so harsh. We learn from Bernstein that, unlike all other Swifts, the Klecho usually builds at the summit of a tree, upon a branch of about an inch in thickness. Its strange nest, the walls of which are scarcely thicker than parchment, is constructed of bits of bark, feathers, and other similar materials, woven together, and cemented with saliva. The great peculiarity of the nest consists in the fact that it is only just big enough to contain the one large egg laid by the female, and that the walls are far too delicate to bear the weight of the brooding mother; the bird is, therefore, compelled to perch and support herself upon the branch, and merely allow her breast to cover and warm her offspring. The female lays twice in the season; the egg is perfectly oval and of a blueish tint.
The SALANGANES (Collocalia) are a group of Swifts whose edible nests have been famous from time immemorial, but as to whose life and habits little information has been acquired. These birds are distinguished by their small size, long wings, in which the second quill exceeds the rest in length, their forked or slightly incised tail, small but powerful beak, and delicate feet, the exterior toe of which is directed backwards. In all the members of this group the salivary glands are much developed.
THE SALANGANE PROPER.
The SALANGANE PROPER (Collocalia nidifica), as we will call the species most extensively met with, is from four to five inches long, and twelve inches broad. Its wing measures about four inches and a half, and its tail two and a quarter. The plumage is of a greyish brown, paler upon the under surface; the quills and tail are blackish, and the vicinity of the eyes marked with white. The feathers of the adult have a slight metallic lustre that is not perceptible in the young. It was formerly supposed that these remarkable birds were only found upon the Sunda Islands, but modern observation has proved that they also inhabit the mountains of Assam, the Neilgherries, Sikkim, and Ceylon. Most contradictory tales have been told by travellers as to the materials of which their famous edible nests are composed.
The earliest account of these nests is met with in Bontius, who tells us that "Large flocks of very small birds of the Swallow kind come down during the breeding season, and settle upon the Chinese coasts, where they swarm over the cliffs that overhang the sea. In these situations they build their strange nests, forming them of fish spawn, which they collect from the shore. These nests are much valued by the natives, who will often pay very large sums of money for them, in order to make them into soup, which is considered a dainty." More modern investigators have been equally inaccurate in their surmises, some pronouncing them to be constructed of the flesh of a kind of snail or worm, or a peculiar species of sea-weed, gathered from the shore. Recent observations upon this interesting point have, however, proved that all these explanations are incorrect, and we learn that these luxuries, in which the Chinese so much delight, are formed of a secretion resembling saliva, drawn from under the bird's own tongue. After a great variety of experiments as to its component parts, Marsden pronounces that the material resembles a mixture of gelatine and white of egg, an opinion in which Bernstein, who is a trustworthy authority on this disputed question, entirely coincides; we will, however, describe the nest of the Salangane before we give our readers the real secret of its construction, as vouched for and described by the last-mentioned naturalist. The Salangane usually builds in such deep and dark cavities that the observation of its proceedings as it fastens its small, thin, gelatinous nest to the rock, is attended with great difficulty. This structure is in shape like the quarter of an egg-shell, divided longitudinally along its entire length. Some of these nests are white, some of a brown colour, and opinion differs considerably as to the reason of this variety; we ourselves believe it to depend on the age of the structure, as we have never seen a brown nest occupied, but other authorities pronounce them to be the work of two distinct species. In the markets the white nests command a very high price, while such as are dark are but little esteemed. The two white eggs laid by the Salangane are deposited at the bottom of this remarkable gelatinous receptacle, without any further preparation for their warmth or comfort.
THE KUSAPPI.
THE WHITE-THROATED PRICKLY-TAILED SWIFT (Acanthylis caudacuta).