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Structure-Colours and Ornaments-Display of Ornaments by the Male-
Descriptive Names---The Motions and Habits of fumming-birds-Food -Vests -- Geographical Distribution and Variation- Humming-birds of Juan Fernandez as illustrating Variation and Natural Selection--The relations and affinities of Humming-birds- How to determine doubtful allinities -- Resemblances of Swifts and Humming-birds---Differences between Sun-birils and Humming-birds-Conclusion.
THERE are now about ten thousand different kinds of birds known to naturalists, and these are classed in one hundred and thirty families which vary greatly in extent, some containing a single species only, while others comprise many hundreds. The two largest families are those of the warblers, with more than six hundred, and the finches with more than five hundred species, spread over the whole globe ; the hawks and the pigeons, also spread over the whole globe, number about three hundred and thirty, and three hundred and sixty species respectively; while the diminutive humming-birds, confined to one hemisphere, consist of about four hundred different species. They are thus, as regards the number of distinct kinds collected in a limited area,
the most remarkable of all the families of birds. It may, however, very reasonably be asked, whether the four hundred species of humming-birds above alluded to are really all distinct-as distinct on the average as the ten thousand species of birds are from each other. We reply that they certainly are perfectly distinct species which never intermingle; and their differences do not consist in colour only, but in peculiarities of form, of structure, and of habits; so that they have to be classed in more than a hundred distinct genera or systematic groups of species, these genera being really as unlike each other as stonechats and nightingales, or as partridges and blackcocks. The figures we have quoted, as showing the proportion of birds in general to humming-birds, thus represent real facts; and they teach 115 that these small and in some respects insignificant Linds, constitute an important item in the animal life of the globe.
Humming-birds are, in many respects, unusually interesting and instructive. They are highly peculiar in form, in structure, and in babits, and are quite unrivalled as regards variety and beauty. Though the name is familiar to every one, few but naturalists are acquainted with the many curious facts in their history, or know how much material they afford for admiration and study. It is proposeid, therefore, to give a brief and popular account of the form, structure, habits, distribution, and affinities, of this remarkalile family of birds, as illustrative of the teeming luxuriance of tropical nature, and as throwing light on some of the most interesting problems of natural history.
Structure.-- The humming-birds form one compact
family named Trochilidæ. They are all small birds, the largest known being about the size of a swallow, while the smallest are minute creatures whose bodies are hardly larger than a humble-bee. Their distinguishing features are excessively short legs and fort, very long and pointeil wings, a long and slender bill, and it long extensible tubular tongue; and these characters are found combineil in no other birls. The feet are exceedingly small and delicate, often beautifully tufted with down, and so short as to be hardly visible beyond the plumage. The toes are placed as in most birls, three in front and one behind, and have very strong and sharply curveil claws; and the feet serve probably to cling to il perch rather than to give any movement to the boily. The wings are long and narrow, but strongly formed ; and the first quill is the longest, a peculiarity found in hardly any other birls but a few of the swifts. The bill varies greatly in length, but is always long, slender, and pointed, the upper mandible being the widest and lapping over the lower at each sidle, thus afloriling complete protection to the delicate tongue the perfect action of which is essential to the birl's existence. The humming-bird's tongue is very long, and is capable of being greatly extended beyond the beak and rapidly drawn back, by means of muscles which are attached to the hyoid or tongue-bones, and bend round over the back and top of the head to the very forehead, just as in the woolpeckers. The two Wailes or lamina, of which the tongnies of birds usually seem to be formed, are here greatly lengthened, broadeneil out, and each rolled up; so as to form a complete double tube commerted down the miilille, and with the outer rilges in contact but not
united. The extremities of the tubes are, however, flat and fibrous. This tubular and retractile tongue cnables the bird to such up honey from the nectaries of flowers, and also to capture small insects; but whether the latter pass down tlie tubes, or are entangled in the fibrous tips and thus draw back into the gullet, is not known. The only other birds with a similar tubular tongue are the sunlirils of the East, which however, as we shall presently explain, hava no affinity whatever with the hummingbirds.
Colours und Orncements. The colours of these small Jords are exceeilingly varied and exquisitely beautiful. The basis of the colouring may be said to be green, as in parrots; but whereas in the latter it is a silky greeu, in humming-birds it is always metallic. The majority of the species have some green about them, especially on the back; but in a considerabile number rich blues, purples, and various shacles of red are the prevailing tints. The greater part of the plumage has more or less of a metallic gloss, but there is almost always some part which has an intense lustre, as if actually formed of scales of burnished metal. A gorget, covering the greater part of the neck and breast, most commonly displays this viviil colour ; but it also frequently occurs on the head, on the back, on the tail-coverts above or below, on the upper surface of the tail, on the shoulders or even the quills. The hue of every precious stone and the lustre of very metal is here represented ; and such terms as topaz, amethyst, beryl, emerald, garnet, ruby, sapphire ; gollen, golden-green, coppery, fiery, glowing, iridescent, refulgent, celestial, glittering, shining, are constantly used to name or describe the different species.
No less remarkable than the colours are the varied developments of plumage with which these birds are adorned. The heail is often crested in a variety of ways; either a simple flat crest, or with radliating feathers, or diverging into two horns, or spreading laterally like wings, or erect and busly, or recurved amil pointel like that of a plover. The throat and breast are usually adorned with broad scale-like feathers, or these liverge into a tippet, or send out pointed collars, or clegint frills of long and narrow plumes tipped with metallic spots of various colours. But the tail is even a more varied and beautiful ornament, cither short and rounded, but pure white or some other strongly contrasted tint; or with short pointed feathers forming a star; or with the three outer feathers on each side long and tapering to a point ; or larger, and either square, or round, or deeply forked, or acutely pointed ; or with the two middle feathers excessively long and narrow; or with the tail very long and deeply forked, with broad and richly-coloured feathers; or with the two outer feathers wire-like and having broad spoon-shaped tips. All these ornaments, whether of the heail, neck, breast or tail, are invariably coloured in some effective or brilliant manner, and often contrast strikingly with the rest of the plumage. Again, these colours often vary in tint according to the direction in which they are seen. In some species they must be looked at from above, in others from below ; in some from the front, in others from behind, in order to catch the full glow of the metallic lustre ; hence, when the birds are seen in their native haunts, the colours come and go and change with their motions, so as to produce it startling and beautiful effect.