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bird classification - Bird classification
bird classification - One great advantage of the study of birds is that the amount of facts to be learnt in anatomy is far less than with some other groups. They are wonderfully uniform in structure. There is less difference in structure between an ostrich and a humming-bird than between, say, a lizard and a crocodile. Though this may be gratifying to the student of birds who is content with a broad knowledge of anatomical fact, it has its disadvantages - very distinct disadvantages - to those who want to arrange and classify the species. As there are computed to be over eleven thousand different kinds of birds, it is clear that an arrangement of some kind is wanted; we must have an artificial brain in which to store the characters of each bird in their proper place. But before we can consider this it is necessary to consider first what place birds as a whole occupy in Nature. It used to be thought that warm-blooded birds ought to be put near to the warm-blooded mammals. But it is now the general opinion that, as we have before pointed out in relation to certain details of structure, their proper place is in the neighbourhood of the reptiles. In fact they are regarded as a separate division of an order of vertebrated animals which has received the name of Sauropsida, which signifies 'lizard-like ' animals.

Now, as to these eleven thousand, how are they to be divided? To this simple question innumerable answers have been given - it is hardly an exaggeration to say as many answers as there are ornithologists. Every part of the body has had its turn in affording a base for a classificatory scheme. At first, and with the older generation, it was bill and claw; then came a period of bones; later the muscles were held to be all-important; at present the fashion is in favour of taking all characters into consideration, which is clearly a more reasonable way of looking at the matter. The reason for the divergences of opinion - which implies great difficulty in the subject - is that birds are so modern a race. They are now at their heyday of development. By-and-by, when gaps appear in the now serried ranks, classification will be an easier matter; for classification, after all, is an artificial, unnatural sort of thing, if we believe in a gradual modification of species out of pre-existing species. It is not too much to say that, the more perfect our scheme of classification, the greater our ignorance of the group classified. If the only birds known to science were a Hornbill, a Duck, and a Crow, together with a few of the immediate allies of each, we could easily sort them. But there are so many intermediate forms which absolutely decline to fit accurately into any system. Then the would-be systematist has to distinguish between those characters which imply a deep- seated relationship and those which are only due to similar needs. The aim of classification is, of course, to indicate real relationship, not merely to pigeon-hole in a convenient way. Real relationship is often masked by superficial differences. For instance, the common blindworm of our hedgerows is not, as might be thought, a snake, but a lizard; it appears to be unlike the lizard in having no legs, and to be so far a snake. Indeed, the terror inspired by this peaceful reptile must stand it in good stead with any except human foes. But its whole anatomy is built upon the lizard, and not upon the snake, plan. We disregard, therefore, in a scheme of classification the likeness to a snake, remembering that in Nature, as in morals, appearance are apt to be deceptive. The owls, among birds, are believed by many to offer an instance of the same kind of deception. By all the older systematists, and by many of the more modern, they are placed with the hawks in one group. No doubt the owls bear a certain likeness to the hawks. They have formidable claws and a hooked and powerful beak; they kill their prey; and only differ superficially in that they love the darkness, while the hawks hunt by day. Now, in certain details of anatomy, particularly in the windpipe and the muscles, the owls are much more like that division of birds which includes the goatsuckers. The mention of this latter family brings us face to face with another difficulty. If the superficial likeness of the owls to the hawks is to be distrusted, as merely due to a similar mode of life, and therefore to the development of certain structures which are in direct relation to that mode of life, how about the superficial likeness of the owls to the goatsuckers, which is almost as well marked as to the hawks? In Australia and other parts of the East there are two genera of goatsuckers which have received the names of Podargus and Batrachostomus. These birds are wonderfully like owls. They have the same brown-and-grey and soft plumage; their flight is equally noiseless - and, altogether, anyone who saw the living Cuvier's Podargus recently on view at the Zoological Gardens might well be pardoned for thinking it an owl. The fact is that we must be careful not to be prejudiced in any direction. Superficial similarities may or may not go with real likeness. Speaking generally, one should be disposed to lay greatest stress upon characters which have no obvious relation to mode of life as likely to be of the most use in indicating blood relationship. It is easier, however, to lay down general principles of this kind than to apply them to birds. As has been already mentioned, birds are so uniform in anatomy that in such characters as brain, lungs, and other internal organs which are not so directly under the immediate influence of their surroundings, there is but little difference. Such characters afford no help to the systematist. We are obliged, therefore, to rely upon other and really less important points.

In most books upon ornithology - in this one, for instance - the scheme of classification is set forth in the shape of a list beginning with one particular group and ending with another. This is merely due to the physical properties of sheets of paper. A linear scheme is really an impossibility; to represent classification properly we want a solid diagram, showing how from a root-stock branches arose and pushed their way in every direction. Another defect of the linear scheme is that we must begin somewhere and end somewhere. In this book we begin with the Passeres and end with the Parrots; others start with the Accipitres, in spite of the protest of Michelet against placing the cowardly, fiat-headed, stupid hawks at the summit of bird creation. It doesn't matter where we begin or where we end as long as we carefully bear in mind that a linear classification is only a convenient way of briefly stating certain facts, and that it does not pretend to be a copy of Nature. An alternative method of expressing the facts of structure in space of two dimensions is the Stammbaum, originally made in Germany; but this inevitable tree of life is open to the serious objection of undue dogmatism; and besides, it must be inaccurate, as it is not in three dimensions. A given naturalist may have strong reasons for believing, let us say, that the Struthious birds represent the lowest bird stock, from which arose in a regular series of branches, independently, and alternately from one side or the other, the various groups into which we divide the class in the present book; if so, then the Stammbaum is easily constructed. But the general consensus of opinion is that the inter-relationships of the different groups cannot be expressed with so much simplicity. It is clear that, in any case, the most modified offshoots must occupy the highest branches of the tree, and that we may in a linear scheme conveniently begin or end with them. But it is impossible to arbitrate as to which group is the most specialised. It is, on the whole, agreed that the Ostrich tribe have retained more primitive characters than other birds; but is the elaborate voice-mechanism of the Nightingale, or the almost human intelligence of the Raven or Parrot, to rank first as evidence of high position, i.e. specialisation, remoteness from the original stock? This is a matter about which everybody can legitimately have an opinion; and we cannot at present formulate a creed - for those, that is to say, who are acquainted with the facts.

The scheme that I adopt here is the same as that which Mr. Hudson uses in the pages which follow; it is the plan followed in the B.O.U. list, and approved by most ornithologists in this country as a convenient working outline. I have added to it the fossil groups, and those groups which do not occur in Great Britain. The main scheme is that of Dr. Gadow, used in his valuable account of the anatomy of birds in Bronn's ' Klassen und Ordnungen des Thierreichs.' There is no deep-seated and mysterious reason for my placing Parrots at the end of the Aves Carinatae: it is simply sheer inability to place them anywhere in particular.

Sub-class I. Archaeornithes (contains genus Archaeopteryx only).
Sub-class II. Neornithes.
Division i. Neornithes Ratitae.
  Order i. Ratitae (contains Struthio, Rhea, Dinornis, &c.).
  Order ii. Stereornithes (contains a few fossil genera, Gastomis, Dasornis, &c.).
Division ii. Neornithes Odontolcae.
  Order i. Hesperornithes (the extinct Hesperornis and Enaliornis).
Division iii. Neornithes Carinatse.
  Order i. Ichthyornitnes (fossil Ichthyornis only).
  Order ii. Passeres (thrushes, swallows, flycatchers, tits, &c.).
  Order iii. Picariae (rollers, cuckoos, hornbills, woodpeckers, swifts, colies, trogons, goatsuckers, kingfishers).
  Order iv. Striges (owls).
  Order v. Accipitres (hawks, eagles, American vultures, &c.).
  Order vi. Steganopodes (cormorants, pelicans, solan geese, frigate bird).
  Order vii. Herodiones (herons, storks, ibis, spoonbills).
  Order viii. Odontoglossi (flamingoes).
  Order ix. Anseres (screamers, ducks, geese).
  Order x. Columbse (doves).
  Order xi. Pterocletes (sand-grouse).
  Order xii. Gallinae (curassows, megapodes, pheasants, grouse, Opisthocomus, &c.).
  Order xiii. Tinamidse (tinamous).
  Order xiv. Fulicariae (rails, coots).
  Order xv. Alectorides (cranes, bustards, Cariama, &c.).
  Order xvi. Limicolse (plovers, snipe, knots, &c.).
  Order xvii. Gavise (gulls, skuas).
  Order xviii. Pygopodes (auks, divers, grebes).
  Order xix. Sphenisciformes (penguins).
  Order xx. Tubinares (petrels, albatross).
  Order xxi. Psittaci (parrots).

It will be noticed that, out of these twenty-one groups into which we may divide the Neornithes Carinatse of Gadow, only three are not represented in Great Britain, viz. the Sphenisciformes, Psittaci, and Tinamiformes. So that the student of bird anatomy in this country has plenty of chance of making himself acquainted with the main outlines of structure of the entire class of living birds. Out of the thirty-two minor divisions of these birds, no fewer than twenty-one are to be met with in these islands; and of those that are not, some are quite easy to get hold of - a parrot, for instance.

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