Fig. 88.–Swift. Cypselus apus. × ⅓. (From Natural History of Selborne.)
C. caffer occurs in South Africa, Abyssinia, and Uganda, and exceptionally on the Congo; C. horus across Tropical Africa; C. andicola in Argentina, Peru, and Bolivia: C. montivagus in the last two countries. C. pacificus of East Asia, with Japan and the Burmese countries, reaches Australia in winter. Some species lay four or five eggs, and C. melanoleucus of western North America utters a peculiar twitter in its nest, placed in clefts of rocks.[[244]] Five species of Tachornis, or Palm-Swift, here included under Cypselus, are found throughout the Ethiopian Region, from India and the Malay countries to China, and in the West Indies; T. (Claudia) squamata occupying Guiana, Brazil, and East Peru. The toes point forward in two pairs, the tail is forked. These birds usually attach their nests of cottony down and feathers to the leaves or spathes of palms with their saliva, but also breed on native huts.
Fossils referred to Cypselus and Collocalia occur in the Lower Miocene of France, while Aegialornis of the Eocene (p. [315]) is placed here by M. Milne-Edwards and re-named Tachyornis.
Fam. XII. The Trochilidae, or Humming-birds, so called from the sound often made by the vibrating wings, are New World forms noted for their grace and beauty. The English name dates back to at least 1632, while one species from Hispaniola is mentioned as "paxaro mosquito" by Oviedo in his Hystoria general de las Indias, as early as 1525. This appellation still remains as the French "Oiseau-mouche," that of Trochilus having been borrowed from Pliny by Barrère, who believed Humming-birds to be allied to the Wren, the Trochilus in part of the Latin author. Τροχίλος, however, was applied by the Greeks to the smaller Plovers (p. [295]), and apparently ὄρχιλος to the Wren, so that Pliny or his copyists originated a chain of errors. From native sources we have the names Guainumbi, Ourissia, and Colibri, from the Spanish "Picaflor" and Tominejo (atom); from Mexico "Chupa-rosa" and "Chupa-myrta" (Rose-sucker and Myrtle-sucker); from the West Indies "Murmures" and "Bourdons."[[245]]
The sternum is enormously developed both in length and depth of keel, thus furnishing a wide base for the attachment of the particularly strong wing-muscles, which support the untiring flight. Herein Humming-birds resemble Swifts, but the head is much more compressed, and the bill is slender and elongated, except in nestlings; they are in fact the longest billed members of the Class Aves in proportion to their size, which in this Family reaches the minimum. Both mandibles may be serrated, and the maxilla is hooked in Androdon and Rhamphodon; but for details of the variable beak, remiges and rectrices, reference must be made to the species described below. The metatarsus, feathered in such genera as Eriocnemis and Loddigesia, is short; the toes being usually diminutive, but sometimes stronger, and the claws either small and rounded, or elongated, curved, and sharp. The ten primaries, of which the outermost is the longest, except in Aithurus–where it is shorter than the next–are frequently rigid; in the male "Sabre-wings" (p. [435]) the shafts of two or three are extraordinarily dilated and curved; while the tenth is occasionally filiform at the tip or narrowed throughout. The secondaries are only six, or rarely seven. The tail of ten feathers may be long or short, but differs profoundly in shape, texture, and colour; being for example cuneate in Phaëthornis and Sphenoproctus, nearly square in Urosticte and Hylocharis, rounded in Adelomyia and Polytmus, deeply forked in Sappho, Lesbia, and the four genera next named, of which Prymnacantha has the outer pair of rectrices very narrow and pointed, Loddigesia, Spathura, and Discura spatulate.
The very characteristic tongue consists of a double tube, tapering and separating into two externally lacerated sheaths at the tip, which contain the extensile portion. The "horns" of the hyoid apparatus are greatly elongated, and pass round and over the back of the head, meeting near the top, and thence stretching in an ample groove to terminate in front of the eyes. This arrangement, analogous to that found in Woodpeckers, allows the tongue to be suddenly protruded to a considerable distance, and withdrawn again in an instant. The furcula is U-shaped; the syrinx has one or two pairs of tracheo-bronchial muscles; the aftershaft is very small; a crop is present; while down is absent from both nestlings and adults.
Except in the "Hermits" (p. [435]), the brilliant coloration almost defies description, the most exquisite metallic[[246]] or jewel-like hues glorifying a background of green, blue, or brown; while crests, ear-tufts, neck-frills, and pendent beards ending in points or forks, add to the effect. Only among the Passerine Sun-birds (Nectariniidae) of the Indian and Ethiopian Regions can a fitting parallel be found; but these, though often erroneously termed Humming-birds, have no connexion with our New World group. Eulampis and Pterophanes are exceptional in not having dusky remiges. The females are usually sombre in comparison, and lack the ornaments of their consorts, which are said to be occasionally smaller. The statement that young males have no distinctive plumage seems incorrect.
These gems of Ornithology extend from the north to the extreme south of America, the habits differing slightly with the climate; Selasphorus rufus of the Western United States reaches Mt. St. Elias in Alaska, Trochilus colubris occurs in the east up to lat. 57° N., Eustephanus galeritus frequents Tierra del Fuego even in snowy weather, while Oreotrochilus chimborazo and O. pichincha brave the storms of the volcanic regions of the Andes of Ecuador, close to the perpetual snow at a height of sixteen thousand feet. The forms found in the furthest north and south are few, and draw towards the equator at the cold time of year; while the successional flowering of insect-attracting plants, and the seasonal alteration of the snow-line, cause latitudinal or altitudinal movements of the same nature. Only eighteen species are recognised as occurring north of Mexico by New World ornithologists, but many more inhabit Central America, which are either peculiar to that region and even its elevated tablelands, or range into South America; none, however, being migrants in the strict sense of the word. The headquarters of the Family lie in Colombia and Guiana, though Venezuela, Peru, Bolivia, and Brazil claim many, and some of the finest, forms: on the other hand, the dry Peruvian plains and the Argentine Pampas lack sufficient insect-food to be favourite residences. With regard to the West Indies the numbers increase from the Bahamas to Trinidad, each island often having its own species; Eustephanus galeritus, E. fernandensis and E. leyboldi occupy the Juan Fernandez group, and the first-named Chili and the Straits of Magellan also. Humming-birds may be roughly divided as alpine, sub-alpine, and lowland, while it may be noticed that comparatively few inhabit the great forest-clad delta of the Amazon, the congenial centre of so much bird-life.
The Trochilidae live almost entirely in the air, and fly powerfully, though seldom to great distances; they will flit from flower to flower for hours, darting off to each new blossom with arrow-like speed, and remaining suspended before it, with the body vertical and the wings in a state of tremulous motion, while probing the inmost recesses. This is commonly accompanied by a vibratory movement of the tail, which in some cases opens and shuts like a fan. The humming sound, produced at each new departure or change of course, and audible for several yards, is due to a pulsation of the wings, so rapid that little can be seen of the bird but an indistinct misty outline. Messrs. A. and E. Newton give the following charming account of Eulampis holosericeus[[247]]:–"One is admiring the clustering stars of a Scarlet Cordia, the snowy cornucopias of a Portlandia, or some other brilliant and beautiful flower, when between the blossom and one's eye suddenly appears a small dark object, suspended as it were between four short black threads meeting each other in a cross. For an instant it shows in front of the flower; an instant more, it steadies itself, and one perceives the space between each pair of threads occupied by a grey film; again another instant, and emitting a momentary flash of emerald and sapphire light it is vanishing, lessening in the distance, as it shoots away, to a speck that the eye cannot take note of,-–and all this so rapidly that the word on one's lips is still unspoken, scarcely the thought in one's mind changed. It was a bold man or an ignorant one who first ventured to depict Humming-birds flying; but it cannot be denied that representations of them in that attitude are often of special use to the ornithologist. The peculiar action of this, and probably many or all other species of the Family, is such, that at times, in flying, it makes the wings almost meet both in front and behind at each vibration. Thus, when a bird chances to enter a room, it will generally go buzzing along the cornice; standing beneath where it is, one will find that the axis of the body is vertical, and each wing is describing a nearly perfect semicircle. As might be expected, the pectoral muscles are very large, indeed the sternum of this bird is a good deal bigger than that of the common Chimney Swallow (Hirundo rustica, L.). But the extraordinary rapidity with which the vibrations are effected seems to be chiefly caused by these powerful muscles acting on the very short wing-bones, which are not half the length of the same parts in the Swallow; and accordingly, great as this alar action is, and in spite of the contrary opinion entertained by Mr. Gosse (Nat. Sojourn in Jamaica, 240), it is yet sometimes wanting in power, owing, doubtless, to the disadvantageous leverage thus obtained; and the old authors must be credited who speak of cobwebs catching Humming-birds."
