Flanks or sides of body are the parts approximately covered by the closed wing.
Axillaries are the lengthened feathers springing from the axilla or region beneath the base of the wing.
Supplementary bristles or hairs are those springing from the side of the forehead in front of the rictal bristles.
Nasal bristles or hairs are those springing from the front of the forehead and covering the nostrils.
The measurements in this work are invariably in millimetres, and are taken thus :—
Length.— The distance from the tip of the bill to the tip of the longest tail-feather, unless otherwise stated.
Tail.— The distance from the root of the tail, generally indicated both in the fresh and dried state by the presence of a piece of flesh on the underside, to the tip of the longest feather.
Wing.— The greatest distance from the bend of the wing to the tip of the longest primary, measured straight. When the wing is curved, it is flattened out for the purpose of measurement.
Tarsus.— The distance from the centre of articulation of the tarsus with the tibia to the base of the middle toe.
Culmen.— The distance in a straight line from the feathering of the forehead to the extreme tip of the beak.
BIRDS are distinguished from all other vertebrates by their covering of feathers. Though related to the Reptiles, they differ in being warm-blooded—a feature which is correlated with a four-chambered heart, in which the chambers are completely separated, thus preventing the intermixture of arterial and venous blood which obtains among the lower vertebrates. Of the right and left aortic arches present in the Reptiles, only the right persists in Birds and the left in Mammals. The skull, which presents no sutures in the adult, possesses but a single occipital condyle and the jaws are produced into a beak ensheathed in horn, whilst in more primitive, extinct species, they were armed with teeth. The lower jaw is a complex of several bones, but the right and left rami are never separable as in Reptiles and many Mammals. Proximally the mandible articulates with the skull, after the reptilian fashion, by means of a quadrate bone- The fore-limb has become transformed into a "wing," and the sternum, in accordance with the requirements of flight, has taken on the form of a broad, oblong plate, usually provided with a median keel for the attachment of the pectoral muscles, which have become excessively developed. In the hip-girdle the three elements of the pelvis have become fused. The ilium has become greatly elongated, and is closely applied to the vertebral column, preventing all move-ment between the vertebrae within its grip. As a consequence, these vertebrae, which include more or fewer of the lumbar, the sacral and a variable number of post-sacrals, have become welded together to form a synsacrum. In the hind-limb the proximal row of tarsals have become fused with the shaft of the tibia to form a " tibio-tarsus," while the distal row have fused with the metatarsals to form a tarso-metatarsus. On this account the ankle-joint is "intertarsal" as in many reptiles. Three of the four surviving metatarsals have fused to form a solid, cylindrical shaft or "cannon-bone" as in Dinosaurs, while the fourth has become reduced to a mere nodule of bone supporting the hallux. In many species the hallux has become reduced to a mere vestige, and, in some, it has disappeared altogether, whilst in the Ostrich (Struthio) but two toes remain. With the reptiles on the one hand, and the primitive mammals Echidna and Ornithorhynchus on the other, birds agree in being oviparous.
Hitherto most systems of classification have been founded on living birds only, and have therefore to some extent failed in their purpose. Birds have been commonly divided into two great groups or sub-classes, Ratitae and Carinatae, according to the presence or absence of a median keel to the sternum. But these groups, though accepted by Blanford and Oates, are very un¬satisfactory, since in some "flightless Carinatae the sternum has become reduced to the Ratite condition.
Taking into consideration birds both living and extinct, we have two well-defined sub-classes, the Archaeornithes and Neornithes.
The first is reserved for the Archaeopteryx with an elongated raptilian chain of caudal vertebrae, each bearing a pair of rectrices and having the jaws armed with teeth. The sub-class Neornithes includes all living birds in which the vertebrae supporting the rectrices have become so abbreviated that the tail-feathers have to be arranged fan-wise on either side of a fused mass of bones known as the " pygostyle."
As regards the Neornithes, the palate affords a much more satisfactory basis of division than the sternum. According to this, living birds are divisible into two further groups, the Palaeognathae and Neognathae, the former in substitution for the Ratitae and the latter for the Carinatae.
In the Palaeognathae the vomer is large, and articulates by squamous suture with the pterygoid, while the palatine is applied to the outer margin of the vomero-pterygoid articulation.
In the Neognathae the palatines have shifted inwards, under the vomero-pterygoid articulation, to meet one another in the median line. The pterygoids, in early post-embryonic life, undergo a striking process of segmentation, inasmuch as that portion of their shafts which rests upon the proximal end of the palatine snaps off, as it were from the main shaft, and fuses with the palatine. Later, at the point of fracture a cup-and-ball joint is formed, affording the strongest possible contrast with the squamous suture found in the Palaeognathae.
Where the vomer still retains some semblance of its former size, its proximal bifurcated end may just reach the extreme tip of the anterior end of the pterygoid, but it now depends for its support not upon the pterygoid, but upon the palatine, as, for example, in the Penguins. But among the Neognathae the vomer displays a striking series of stages in degeneration, becoming more and more divorced from the pterygoid, until it finally assumes the form of a minute nodule of bone, and at last, in the Gallinae, it becomes a mere spicule of bone held by a few tendinous fibres to the anterior border of the expanded ends of the palatines, and in some, as in the Falconidae for example, vanishes altogether. If nothing were known of the early post-embryonic developmental stages of the Neognathine vomer, it would have been impossible to divine that the Neognathine was a direct derivative from the Palaeognathine palate.
These two orders, the Palaeognathae and Neognathae, must be divided further, for the Class Aves, in the course of its evolution, has split up into a vast number of different forms. The genetic relation of these forms or types to one another, and the precise affinities of the individual members of the various groups, should as far as possible find expression in any system of classification. These divisions may be known as Orders, which are again divided into Sub-Orders, Families, Genera and Species.
Order I. PASSERES.
This edition of the Fauna follows its predecessor in beginning with the Passeres. The classification and further division of this Group presents more difficulties than all the rest put together.
Briefly, the Passeres may be defined as follows :—Skull aegithognathous (vomer truncated in front). Sternum with a large spina externa, and no spina interna. Clavicle with expanded free ends. Hypotarsus complex.
Wing lacking the biceps and expansor secondariorum muscles. Thigh muscles having no accessory femorocaudal or abiens muscles present.
Only one carotid—the left—is present. Caeca are vestigial. Oil-gland nude. Wing eutaxic.
The arrangement of the Sub-Orders adopted here is that of Gadow (Bronn's Thier-reichs, Bd. vi., ii. Syst. Theil, 1893). But the subdivision of the Anisomyodi is based on that of Pycraft (P. Z. S. 1905-0-7), his Oligamyodi answering in part to that of Huxley (P. Z. S. 1867).
Having regard to the fact that the main divisions of the Passeres are based on the structure of the syrinx, a brief summary of the essential features of this organ, in so far as they concern the systematist, may be welcome.
The syrinx is the term applied to the lower end of the windpipe and the adjacent ends of the bronchi in birds, wherein these portions have become variously modified to form the organ of voice, which, in Mammals, is formed by the larynx—the upper end of the windpipe. "But while in the Mammals the larynx is a comparatively stable structure, in the birds the syrinx presents a very remarkable range of differences both in regard to its fundamental structural characters, as well as of musculature.
For the present it must suffice to give a brief survey of the essential features of the syrinx in the Passeres and, for systematic purposes, the musculature is the dominant factor.
The syrinx, then, in this Group presents wide contrasts, even among Genera of the same Family, but nevertheless it conforms in its essential characters with that of the Aves as a whole. That is to say, it is formed of a number of bony or cartilaginous rings and semi-rings—some of which may be com¬pletely or partially welded—held together by thin membranes which serve not merely to support the framework, but also in the production of the " voice."
In the Anisomyodi the syringeal muscles are inserted either in the middle or on to the dorsal or ventral ends of the semi-rings.
In the Diacromyodi these muscles are inserted into both ends of the semi-rings. They may be limited always to one pair as in Clamatores, to two as in Oligomyodi and some Tracheophonae or there may be as many as seven pairs as in the Oscines. But the structure of the syrinx itself, as apart from its musculature, has been, and still is, a feature of importance in the classification of the Passeres—as witness the Tracheophonae. Briefly three types of syrinx are recognized—the Tracheobronchial, the Tracheal and the Bronchial, the last two being derivatives of the first. The tracheo-bronchial is the type found in the Oscines and Sub-Oscines. Herein the lower end of the trachea has the last four or five rings welded to form a little dice-shaped box communicating below with the bronchi. The bronchial rings I and II are closely attached to this box, while III forms a strong arcuate bar supporting a delicate sheet of membrane stretched between rings I and II on the one hand and IV on the other. The bronchial rings are incomplete on their inner aspects, their free ends supporting a " tympanic membrane," which plays an important part in voice production. At the junction of the bronchi with the trachea is a bony bar—the " pessulus." This supports a thin fold of mem¬brane whose free edge cuts across the bottom of the dice-shaped box of the tracheal tube. By its vibrations it acts like the " free reed" of an organ-pipe. Muscular lips extending from the inner surfaces of bronchial semi-ring III narrow the aperture on either side of the "reed" during the production of the " voice" or song, and thus complete the mechanism of voice production. In the Tracheal syrinx a variable number of the lower tracheal rings are reduced in thickness, leaving wide spaces filled by mem¬brane. The range of sounds produced by this modification is much more limited than in the Tracheo-bronchial syrinx.
In the Bronchial syrinx the voice is produced by modification of the bronchi. But as this type does not occur among the Passeres, its description may be deferred.
It is not the purpose of this survey to pass in review all the anatomical characters which have been used as aids to the classification of this difficult Group, but rather to afford a concise summary of such as are regarded to-day as of importance.
After the syrinx, systematists seem to have relied most upon the plantar tendons of the foot. Sometimes, indeed, too much reliance seems to have been placed upon these ; that is to say, a too arbitrary use has been made of the evidence they afford.
Of these tendons two only are specially recognized in this connexion. These are the Flexor profundus digitorum and the Flexor longus hallucis. The first named arises from the greater part of the hinder face of the fibula and .tibia, beneath all the other flexors, and at the intertarsal joint passes into a tendon, which, running through a perforation in the metatarsal tubercle, divides just above the distal end of the tarso-metatarsus, sending a slip to each front toe. The Flexor longus hallucis arises from the outer condyle of the femur and from the intercondylar region. It accompanies, and is closely associated with, the Fl. profundus throughout its whole length. Passing also into the tendinous condition at the intertarsal joint, it crosses the Fl. profundus tendon near its middle, from behind and from without inwards to be inserted on the terminal phalanx of the hind toe. This, at least, is what obtains in all the Passeres save the Eurylaemidae, where the hallucis tendon anchors itself to the profundus tendon at the point where the two tendons Gross, by a number of tendinous fibres, to form what is known as a "vinculum." No less than eight different modes of anchorage between these two tendons are recognized. The typical Passeriform type is No. VII. of this series"; that of the Eurylaemidae is No. 1.
Nitzsch, in laying the foundations of the study of the pterylosis, opened up a field of great promise, which, so far, has only very partially been explored by systematists. The attempt to use the number of the remiges as a factor in the subdivision of the Passeres has only resulted in the formulation of a test which is based on error. Thus, in the previous edition of this work an attempt was made to form two Groups of Passeres, the one displaying 9, the other 10 primaries. This was unfortunate, since all the so-called " 9-primaried" Passeres possess 10 remiges, while many of the so-called " 10-primaried" Passeres possess 11 remiges. The error has arisen from a failure to distinguish vestigial quills and their coverts. In the " 9-primaried " Passeres the 10th may be reduced to the vanishing point. Where the 10th primary is conspicuously long, as in the Corvidae, the 11th will be found as a " remicle," 1 cm. or more in length. Bearing these facts in mind, there can be no objection, for the sake of convenience, to the continued use of the division into 9-primaried and 10-primaried wings, the remicle being in both cases a negligible quantity.
So far, unfortunately, Ornithologists have made no more use of pterylosis than this numbering of the wing and tail-feathers. A vast amount of work has yet to be done, in investigating the pterylosis of the trunk, for the sake of the evidence it will unquestionably furnish as to the relationship of forms whose affinities can at the present be no more than guessed at. The Paridae, Ampelidae, Oriolidae afford cases in point. True, we cannot discover this evidence by a study of the pterylosis alone— the osteology and myology of these puzzles must also be taken into account—but we shall have made great strides when this pteryological work has been thoroughly done. It is to be hoped that those who use these volumes will endeavour to take up this much neglected work.
The juvenile or "nestling" plumage of the Passeres affords very valuable data to the systematise In the last edition of this work it was pointed out that the juvenile plumage of the " 10-primaried " Passeres seemed to consist of five types. " In the first the nestling resembles the adult female; in the second the nestling resembles the adult female but is more brightly coloured and generally suffused with yellow; in the third the nestling is cross-barred; in the fourth it is streaked; in the fifth and last mottled or squamated."
These divisions of the Passeres seem to be of great importance and have been adopted in this edition with but very minor modifications.
The whole system of classification here accepted is merely provisional and does not, and cannot, pretend to be final, but it is hoped that it will provide a sound basis upon which future Ornithologists can work. No classification will be found upon which there is universal agreement. Many Ornithologists hold that, whilst it is sound science to split species ad infinitum, it is equally unscientific to use the same arguments for splitting genera and families. I have considered classification purely as a means to an end—i. e. to enable the student to recognize any bird whose name and position he desires to ascertain. If "lumping " will assist him in this, I have amalgamated genera and families; but if lumping, by creating huge, unwieldy families, will lead to his confusion, I have split them so as to render his work easier and quicker. Each Order will be dealt with in turn as it is reached in the succeeding volumes.
Scheme of Indian Passerine Families.
A. (DIACROMYODI.) Syringial muscles of the syrinx inserted on the ends of the bronchial semi-rings.
a. The edges of the mandibles never serrated though sometimes notched.
a1. Tongue non-tubular and not bifid or tufted.
a2. The hinder part of the tarsus longitudinally laminated.
a3. Wing with ten primaries, the 11th too minute to be seen.
a4. Nostrils clear of the line of the forehead and nearer the commissure than the culmen.
a5. Plumage of the nestling like that of the adult female, but duller and sometimes darker. a6. Nostrils completely hidden by feathers or bristles.
a7. First primary exceeding half the second in length; plumage
glossy and firm . Corvidae.
b7. First primary less than half
c7. First primary exceeding half
second; plumage lax and soft. Paradoxornithidae.
b8. Nostrils bare or merely overhung by hairs or plumelets.
d7. Rictal bristles always present.
a8. Inner and hind toe very un-equal Sittidae.
B8. Inner and hind toe equal. a9 Wing rounded, tarsus long
and strong Timaliidae.
b9 Wing more pointed, tarsus less strong and long .... Pycnonotidae.
e7. Rictal bristles absent.
c8. Tail-feathers stilf' and pointed……………………… Certhiidae.
d8. Tail-feathers soft and rounded. ……………………..Troglodytidae.
b5 Plumage of nestling mottled or squamated.
c6. Nostrils not covered by any hairs.
f7. .Rictal bristles absent Cinclidae.
g7. Rictal bristles present Turdidae.
d6. Nostrils more or less covered by
c5. Plumage of nestling cross-barred.
e6. Folded wings not reaching beyond middle of tail.
h7. Shafts of rump-feathers soft .. Laniidae.
i7. Shafts of rump-feathers spinous. Campephagidae.
f6. Folded wings reaching to tip of
d5. Plumage of nestling spotted with
e3 Plumage of nestling like the adults,
but brighter Sylviidae.
f5. Plumage of nestling like the adults,
but piler Regulidae.
g3. Plumage of nestling streaked.
g8. Rictal bristles present.
j7. Nostrils covered with hairs……………….. .. Irenidae.
k7. Nostrils quite exposed.
e8. First primary at least half
length of second Oriolidae.
f8. First primary less than half
second ; Eulabetidae.
h6. Without rictal bristles Sturnidae.
b4. Nostrils pierced, partly within line of forehead and nearer culmen than
b3. Wing with nine primaries, the 10th obsolete.
c4 Bill conical, pointed and entire, the longest secondaries reaching to a point midway between the middle and top of wing……….. Fringillidae.
d4. Bill long, slender and notched, the
longest secondaries reaching almost
to tip of wing Motacillidae.
e4. Bill flat, broad and notched,the longest secondaries reaching to the middle
of wing Hirundinidae.
b2. The hinder part of the tarsus transversely
b1 Tongue tubular Nectariniidae.
c1. Tongue bifid, with small brushes at tip.
c2. Plumage not metallic Zosteropidae.
d2. Plumage more or less metallic Chalcopariidae.
b. The edges of the mandibles finely serrated on
the terminal third of their edges Dicaeidae.
B. (ANISOMYODI.) Syringial muscles inserted either in the middle, or on the dorsal or ventral ends of the bronchial semi-rings.
c. Flexor longus hallucis and Flexor profundus
digitorum not united with a vinculum Pittidae.
d. Flexor longus hallucis and Flexor profundus
digitorum joined near the centre with a vin- culum Eurylaemidae.