Cassell's book of birds; vol. 1

by Alfred Edmund Brehm

a, the Lower Mandible; c, the Tongue; h, m, interior of the Gullet; i, the Upper Larynx.

In the preceding examples the length of the tongue never exceeds that of the bill; but in the case of the woodpeckers it is protrusible to a wonderful extent. On opening the bill of a woodpecker immediately after it has been killed, the tongue seems of ordinary length, or indeed rather short, and shaped somewhat like the spears used by the Caffres in South Africa, called assagais, pointed at the end and furnished with numerous barbs. (See Fig. 10.) This, however, is only the tip of a very remarkable instrument. If the barbed portion be drawn out of the mouth, a person unacquainted with its nature would think that he had got hold of a very long earthworm that the bird had incautiously tried to swallow, but which had stuck in its throat; hence a tongue of this description is called vermiform. The point in its usual position reposes in the ordinary manner between the mandibles; the rest is concealed, but is susceptible of extension, at the pleasure of the bird, to four or five times the length of the bill. The act of protrusion is effected by the remarkable structure of the root of the tongue, or more properly of the os hyoides, or bony apparatus whereby it is attached. The posterior prolongations derived from the os hyoides are compactly curved around the back of the skull; and occasionally they are prolonged forwards to such an extent as actually to reach the nostrils. By means of this somewhat complex arrangement the woodpecker, having broken away the bark of a tree by the powerful strokes of its bill, and thus laid open the retreat of the insects beneath, suddenly darts out its tongue, spears its prey, and instantly brings the transfixed insect into its mouth.

The SENSE OF TOUCH must be of very limited utility; indeed, there seems to be no part of the body of a bird so constructed as to be capable of tactile impressions. The wings, the representatives of hands and arms, are obviously entirely unfit for the exercise of such a function; neither do the legs and feet seem to be better suited to this purpose. The only organ of touch about which there can be no doubt is the bill, yet even this is generally covered with a hard sheath of horn. Nevertheless, in some races the extremity of the bill is soft and largely supplied with nerves. In snipes and wood-cocks, for example, the sensitive extremity of the beak materially assists in procuring their food.

For the systematic arrangement of the class of birds, the conformation of their feet has been found to afford characters of great importance to the ornithologist, inasmuch as the organisation of these members must obviously be in strict relation with the localities they inhabit. To account for the distribution of the feathered tribes, and to explain the relationships that exist between them and other animals, a great variety of ingenious theories have been broached, all of them more or less fanciful. The different families, sub-families, and minor groups into which they have been divided have been again and again sorted, like a pack of cards, frequently more in accordance with the whim of the player than with the established rules of the game. And yet a little reflection will show that the great principles of zoological classification are so simple, and at the same time so immutable, that we sometimes cannot but admire the ingenuity displayed in going wrong.

Fig. 10.—TONGUE OF THE WOODPECKER, SHOWING THE MECHANISM EMPLOYED FOR ITS PROTRUSION.

a, harpoon-like Tip of the Tongue; d, e, f, g, h, Framework of the Throat; i, k, Glands furnishing adhesive secretion.

Few things are more manifest to the student of nature than that, in the distribution of the animal creation, it has been ordained that every locality shall be peopled by forms of life pre-eminently adapted for its occupation. If, therefore, we are asked whether birds ought to be arranged in circles or in squares, in hexagons or in pentagons, in groups of five or in groups of seven, our simple reply would be by inquiring how many localities could be pointed out as requiring appropriate occupants, and to this question it is not difficult to find a satisfactory answer.

The earth, the water, and the air, throughout their broad domains, must each of them be provided with inhabitants peculiarly constructed to live in their diversified regions. Upon the earth, we find the level ground, the mountain, and the glen; we find the pathless forests, and the solitary trees and shrubs, and bushy underwood. We cast our eyes upon the waters, and we see the world of ocean covering two-third parts of this great globe, stretching from pole to pole, rolling its mighty waves through every zone; we see the creeks and shallow bays that margin it all round, and watch the waves as they approach the shore and lay them down to sleep upon the beach. There are the rivers, too, and lakes, and swamps and marshes which are neither land nor water, sometimes overspread with floating vegetation, sometimes a broad expanse of ooze and rushes far too soft to bear the weight of creatures that might try to walk upon the treacherous surface. We look into the air, and there we find between the earth and sky abundant room for birds of every wing. If, therefore, with this little map of the world before us, we reply to the question propounded above, we should be tempted to say that there must necessarily be as many different types of organisation as there are districts therein enumerated; and doubtless a reference to any system of ornithology, however much the classification may be confused by preconceived theories, will convince us that such is essentially the foundation of any natural arrangement.

In taking, therefore, a brief survey of the principal groups, or Orders, under which the feathered races have been distributed, we will begin with those appointed to live on trees, inasmuch as these are regarded by the author of the following pages as being entitled to the highest rank in the class to which they belong, rivalling in intelligence, as some of them do, the apes and monkeys of which they are in general the inseparable companions.