either in the islands or on the continent, and number in all not far from four hundred species, distributed into various subdivisions and genera, but all possessing, to a very large degree, the same common peculiarities, of which the well-known Ruby-throat of eastern North America may be taken as eminently typical. The habits and peculiarities of this numerous family have been closely studied, and many valuable facts in relation to them have been contributed by various naturalists; by none, perhaps, with more intelligent attention than by the eminent Swiss naturalist, M. H. de Saussure, in his visit to the West India Islands and Mexico, to whose observations we are largely indebted.
On the first visit of this naturalist to a savanna in the island of Jamaica, he at once noticed what he at first took to be a brilliant green insect, of rapid flight, approaching him by successive alternations of movements and pauses, and rapidly gliding among and over the network of interlacing shrubs. He was surprised by the extraordinary dexterity with which it avoided the movements of his net, and yet more astonished to find, when he had captured it, that he had taken a bird, and not an insect.
He soon satisfied himself that this entire family not only have the form and aspect of insects, but that they have also the same movements, the same habits, and the same manner of living, with certain insects. Their flight is exactly like that of an insect, and in this respect they form a remarkably exceptional group among birds. When we notice their long wings in our cabinet specimens, we naturally suppose that they use these instruments of flight in the same manner with the Swallow or the Swift. Yet investigation shows that, so very far from this, these wings, comparatively so very long, vibrate even more rapidly than do those of birds with proportionately the smallest wings, such as the Grebe, the Loon, and the Penguin, and that, more than this, they vibrate with an intensity so vastly superior, that they become wholly invisible in the wonderful rapidity of their movements.
The altogether exceptional character of their flight is a subject for never-ceasing astonishment. Until we actually witness it, we should never conceive it to be possible for a bird to vibrate its wings with so great a rapidity, and by them to support itself in the air in the same manner with the Anthraces and other aerial insects. This feat is rendered all the more surprising by the extreme narrowness of the wing and the comparative weight of the body, which is quite considerable, on account of the compactness of the flesh and bones, and the small size of the birds themselves, whose wings displace but a small quantity of air. The resistance of the air to the stroke of the wing of a bird should be, not in proportion to the surface of that wing, but to its square, or even to its cube, if the movement is very rapid. Hence it follows that a due proportion being required as between the weight of the body and the surface of this organ, a small bird cannot keep itself poised in the air except by means of vibrations more rapid than those of a larger kind. This is, without doubt, one explanation of the fact that Humming-Birds, in
their flight, are so insect-like. They pass from bush to bush as if suspended in the air, and pause over each flower, vibrating their wings, in precisely the same manner with the Sphinxes, and with the same humming sounds.
The flight of the Humming-Bird is of two kinds. One of these is used for a horizontal movement, and is so rapid that one can hardly follow it with the eye. This is accompanied by a kind of hissing sound. The other seems to keep the body in the air immovable, in one spot. For the latter purpose the bird assumes a position nearly vertical, and beats its wings with great intensity. These organs must vibrate all the more rapidly, because the immobility of the body requires a shorter stroke, and therefore the more frequently repeated. The equilibrium of the body is preserved by the alternate up and down strokes of the wings, no inconsiderable force being required to keep its immobility, besides that requisite for neutralizing the weight of the body.
The Humming-Bird is entirely aerial. They pass with the rapidity of an arrow, stop, rest for a few seconds on some small branch, and then suddenly depart with so much rapidity that we cannot trace its flight. They disappear as if by enchantment. Their life is one of feverish excitement. They seem to live more intensely than any other being on our globe. From morning to night they traverse the air in quest of honeyed flowers. They come like a flash of light, assume a vertical position without any support, throw their tail forward, expanding it like a fan, vibrating their wings with such rapidity that they become absolutely invisible, plunging, at the same time, their thread-like tongues to the bottom of some long corolla, and then they have gone as suddenly as they came. They are never known to rest on a branch in order more at their leisure to plunge their tongue into the flower. Their life is too short for this delay; they are in too great haste; they can only stop long enough to beat their wings before each flower for a few seconds, but long enough to reach its bottom and to devour its inhabitants. When we take into consideration how entirely aerial is their life, and the prodigious relative force requisite to enable them to keep suspended in the air during the entire day, almost incessantly, either in rapid motion or accomplishing the most violent vibrations, we can but be amazed at the extraordinary powers of flight and endurance they manifest.
The Humming-Bird enjoys even the most tropical heat, avoids shade, and is easily overcome by cold. Though some travellers speak of having met with these birds in the depths of forests, Saussure discredits their statements, having never found any in such situations. They prefer open flowery fields, meadows, gardens, and shrubbery, delighting to glitter in the sun’s rays, and to mingle with the swarm of resplendent insects with which tropical regions abound, and with the habits of which their own so well accord. Nearly all live in the open sun, only a very few are more or less crepuscular and never to be seen except very early in the morning or in the evening twilight.
Mr. Salvin is of the opinion that Humming-Birds do not remain long on the wing at once, but rest frequently, choosing for that purpose a small dead or leafless twig at the top, or just within the branches of the tree. While in this position they trim their feathers and clean their bill, all the time keeping up an incessant jerking of their wings and tail.
In Mexico, where these birds are very abundant, they are attracted by the blossoms of the Agave americana, and swarm around them like so many beetles. As they fly, they skim over the fields, rifle the flowers, mingling with the bees and the butterflies, and during the seasons of bloom, at certain hours of the day, the fields appear perfectly alive with them. The ear receives unceasingly the whistling sounds of their flight, and their shrill cries, resembling in their sharp accent the clash of weapons. Although the Humming-Bird always migrates at the approach of cold weather, yet it is often to be found at very considerable elevations. The traveller Bourcier met with them on the crater of Pichincha, and M. Saussure obtained specimens of Calothorax lucifer in the Sierra de Cuernavaca, at the height of more than 9,500 feet.