Encyclopædia Britannica, Ninth Edition/Trogon
TROGON, a word apparently first used as English[1] by Shaw (Mus. Leverianum, p. 177) in 1792, and now for many years accepted as the general name of certain birds forming the Family Trogonidæ of modern ornithology, the species Trogon curucui of Linnæus being its type. But, since doubts exist as to whether this is that which was subsequently called by Vieillot T. collaris or the T. melanurus of Swainson, though evidence is in favour of the former (cf. Cabanis, Mus. Heineanum, iv. p. 177, and Finsch, Proc. Zool. Society, 1870, p. 559), several recent writers have dropped the Linnæan specific term.
The Trogons are birds of moderate size: the smallest is hardly bigger than a Thrush and the largest less bulky than a Crow. In most of them the bill is very wide at the gape, which is invariably beset by recurved bristles. They seize most of their food, whether caterpillars or fruits, on the wing, though their alar power is not exceptionally great, their flight being described as short, rapid, and spasmodic. Their feet are weak and of a unique structure, the second toe, which in most birds is the inner anterior one, being reverted, and thus the Trogons stand alone, since in all other birds that have two toes before and two behind it is the outer toe that is turned backward. The plumage is very remarkable and characteristic. There is not a species which has not beauty beyond most birds, and the glory of the group culminates in the Quezal (q.v.). But in others golden green and steely blue, rich crimson[2] and tender pink, yellow varying from primrose to amber, vie with one another in vivid coloration, or contrasted, as happens in many species, with a warm tawny or a sombre slaty grey to say nothing of the delicate freckling of black and white, as minute as the markings of a moth's wing the whole set off by bands of white, producing an effect hardly equalled in any group. It is impossible within brief space to describe its glowing tints; but the plumage is further remarkable for the large size of its contour-feathers, which are extremely soft and so loosely seated as to come off in scores at a touch, and there is no down. The tail is generally a very characteristic feature, the rectrices, though in some cases pointed, being often curiously squared at the tip, and when this is the case they are usually barred ladderlike with white and black.[3] According to Gould, they are larger and more pointed in the young than in the old, and grow squarer and have the white bands narrower at each succeeding moult. He also asserts that in the species which have the wing-coverts freckled, the freckling becomes finer with age. So far as has been observed, the nidification of these birds is in holes of trees, wherein are laid without any bedding two roundish eggs, generally white, but certainly in one species (Quezal) tinted with bluish green.
The Trogons form a very well-marked Family, belonging to the multifarious group treated in the present series of articles as Picarix; but, instead of being (so far as is known) like all the rest of them and, as Prof. Huxley believed, "desmognathous," they have been shown by W. A. Forbes (Proc. Zool. Society, 1881, p. 836) to be "schizognathous " thus demonstrating, in the words of the latter, " that the structure of the palate has not that unique and peculiar significance that has been claimed for it in the classification of birds." Perhaps the explanation of this anomaly may lie in the fact that the Trogons are a very old form. The remains of one, T. gallicus, have been recognized by Prof. A. Milne-Edwards (Ois. foss. de la France, ii. p. 395, pi. 177, figs. 18-22) from the Miocene of the Allier, and it may not be too much to suppose that the schizognathous structure was more ancient than the desmognathous. Again too this fortunate discovery of that eminent palaeontologist seems to account for the remarkable distribution of the Trogons at the present day. While they chiefly abound, and have developed their climax of magnificence, in the tropical parts of the New World, they yet occur in the tropical parts of the Old. The species now inhabiting Africa, forming the group Hapalodcrma, can hardly be separated generically from those of the Neotropical Trogon, and the difference between the Asiatic forms, if somewhat greater, is still comparatively slight. It is plain then that the Trogons are an exceptionally persistent type; indeed in the whole Class few similar instances occur and perhaps none that can be called parallel. The extreme development of the type in the New World just noticed also furnishes another hint. While in some of the American Trogons (Pharomacriis, for instance) the plumage of the females is not very much less beautiful than that of the inales, there are others in which the hen birds retain what may be fairly deemed a more ancient livery, while the cocks flaunt in brilliant attire. Now the plumage of both sexes in all but one[4] of the Asiatic Trogons, Harpactes, resembles rather that of the young and of those females of the American species which are modestly clothed. The inference from this fact would seem to be that the general coloration of the Trogons prior to the establishment, by geographical estrangement, of the two types was a russet similar to that now worn by the adults of both sexes in the Indian region, and by a portion only of the females in the Neotropical. The Ethiopian type, as already said, very closely agrees with the American, and therefore would be likely to have been longer in connexion therewith. Again, while the adults of most of the American Trogons (Pharomacrus and Eiqrtilolis excepted) have the edges of the bill serrated, their young have them smooth or only with a single notch on either side near the tip, and this is observable in the Asiatic Trogons at all ages. At the same time the most distinctive features of the whole group, which are easily taken in at a glance, but are difficult to express briefly in words, are equally possessed by both branches of the Family, showing that they were in all likelihood for the possibility that the peculiarities may have been evolved apart is not to be over looked reached before the geographical sundering of these branches (whereby they are now placed on opposite sides of the globe) was effected.
It remains to say that about sixty species of Trogons are recognized, which Gould in the second edition of his Monograph of the Family (1875) divides into seven genera; but their characters are hardly laid down. Pharomacrus, Eupiilotis, and Trogon inhabit the mainland of tropical America, no species passing to the northward of the Rio Grande nor southward of the forest district of Brazil, while none occur on the west coast of Peru or Chili. Prionotelus and Tmetotroyon, each with one species, are peculiar respectively to Cuba and Hispaniola. The African form Hapaloderma has two species, one found only on the west coast, the other of more general range. The Asiatic Trogons, Harpactes (with eleven species according to the same authority), occur from Nepal to Malacca, in Ceylon, and in Sumatra, Java, and Borneo, while one species is peculiar to some of the Philippine Islands. (a. n.)
- ↑ Trogonem (the oblique case) occurs in Pliny (H. N., x. 16) as the name of a bird of which he knew nothing, save that it was mentioned by Hylas, an augur, whose work is lost; but some would read Trygonem (Turtle-Dove). In 1752 Möhring (Av. Genera, p. 85) applied the name to the "Curucui" (pronounced "Suruquá" fide Bates, Nat. Amazons, i. p. 254) of Marcgrave (Hist. Nat. Brasiliæ, p. 211), who described and figured it in 1648 recognizably. In 1760 Brisson Ornithologie, iv. p. 164) adopted Trogon as a generic term, and, Linnæus having followed his example, it has since been universally accepted.
- ↑ M. Anatole Bogdanoff determined the red pigment of the feathers of Pharomacrus auriceps to be a substance which he called "zooxanthine" (Comptes Rendus, 2d November 1857, xlv. p. 690).
- ↑ In the Trogon of Cuba, Prionotelus, they are most curiously scooped out, as it were, at the extremity, and the lateral pointed ends diverge in a way almost unique among birds.
- ↑ Or two species if H. macloti be more than a local form of H. reinwardti.