ORDER: PASSERIFORMES
Order XIV. PASSERIFORMES.
This Order contains about five thousand five hundred species, being more than half the birds yet known. Their classification is attended with much difficulty, and the anatomy of many more forms must be investigated before anything approaching a satisfactory–not to say final–scheme can be proposed. The earlier taxonomers often based their systems largely on European genera, and were therefore obliged to interpose others, or even to recognise new Families, as their knowledge extended, among the many new discoveries, to various American and Australian forms.
The foundation of recent arrangements of the group, depending on the number or position of the song-muscles, was laid between 1845 and 1847 by Johannes Müller, who divided the then generally accepted Order Insessores into three tribes: (1) Oscines or Polymyodi [Song-birds, or those with many (usually five or seven) pairs of song-muscles]; (2) Tracheophones [where the bronchi take no part in the formation of the voice-organ]; and (3) Picarii [corresponding in the main to Nitzsch's Picariae]; the two former of which included most of the Passerine forms. Simultaneously with Müller, Cabanis proposed a system grounded on similar principles; while in 1867 Huxley recognised of his group Coracomorphae the divisions Polymyodae, Tracheophonae, and Oligomyodae [birds with few song-muscles]. About ten years later Garrod, who was followed between 1880 and 1882 by W. A. Forbes, divided the Passeres into Desmodactyli, with a band joining the muscles of the hallux to the front toes, and Eleutherodactyli, where the hind toe is free. The former contained only the Eurylaemidae; the latter the Mesomyodi (where the syringeal muscles join the bronchial semi-rings in their middle or lateral portion), and the Acromyodi (where they are attached to the extremities). The subdivisions need not be discussed here; but it should be noticed that, as opposed to Müller, the attachment, and not the number, of muscles was the point relied upon. Want of space forbids an account of the subsequent labours of Mr. Sclater,[[264]] Professors Newton[[265]] and Fürbringer,[[266]] and others; but the last-named no doubt influenced considerably the views of Dr. Gadow, mainly accepted below. This author[[267]] takes into consideration not only the attachment, but also the disposition of the muscles of the syrinx, and distinguishes his Passeriformes as (1) Passeres anisomyodae, where the syringeal muscles are unequally inserted, either in the middle, or upon the dorsal or ventral end only, of the bronchial semi-rings; (2) Passeres diacromyodae, where some of the muscles are attached to the dorsal, and some to the ventral ends. The former of these groups may be subdivided into A. Subclamatores and B. Clamatores; the latter into C. Suboscines and D. Oscines. Even the groups (1) and (2) are expressly stated not to rise to the rank of Sub-Orders, while the Oscines and other equivalent divisions are of hardly more than Family value.
The great number of species in the Order Passeriformes makes it necessary to treat the various sections less fully than has been the case in the foregoing portion of the work, while the Families are not, of course, on the same level here as elsewhere.
1. Passeres anisomyodae.
A. Subclamatores.
Fam. Eurylaemidae.–The Broad-bills, a curious Old World group, have been by various authors regarded as allied to the Rollers or to the Flycatchers. They are distinguished from all other Passerine forms by the fact that the hallux is connected with the front toes by a vinculum or band joining the deep plantar tendons, and is thus incapable of independent motion. The beak is very broad, while it is comparatively small in Calyptomena; Corydon, and to a less extent Eurylaemus and Sarcophanops, have a decided terminal hook to the maxilla. The metatarsus is scutellated in front and smooth behind (laminiplantar); the hallux is weak; the third and fourth toes are distinctly united, the claws are very short. The moderate wings have ten primaries in Calyptomena, eleven elsewhere, Eurylaemus having the eleventh very small; the secondaries are nine or ten; the tail of twelve rectrices is usually long and rounded, but is graduated in Psarisomus, short and square in Calyptomena. The adults have no aftershaft or down, the tongue is sagittate, and Sarcophanops has naked orbits. The plumage in Calyptomena viridis of the Indo-Malay countries is bright green, with a large black post-auricular and a yellow pre-ocular spot, three black bars on the wing-coverts, and blackish wing- and tail-quills. The duller female has no black spots or bars. The dense frontal feathers project forward over the beak. C. whiteheadi of Borneo has a black throat. These somewhat inactive birds inhabit thin jungles, utter soft whistles, and feed on fruit; the rest of the Family eat little but insects, though Cymborhynchus macrorhynchus, the Rain-bird of the Malays, enjoys berries.
Fig. 98.–Broad-bill. Calyptomena viridis. × 7⁄16.