the skin is removed, the bones are seen to be covered by a mass of this
flesh, which is of a red colour, darker in some birds than in others.
For instance, in a Duck the colour is a dark red; in a Pigeon, quite a
pale brown. The flesh is not, however, merely a thick sheet covering
the bones: it can be separated into layers which are themselves made
up of a number of separate pieces of muscle. These individual muscles
are very commonly of a spindle-like shape, being thickest in the
middle and dwindling towards both ends, where they often end in a
tough substance called the tendon, which has a glistening and very
characteristic appearance. All muscles are not of this form--sometimes
they are strap-shaped; and not all of them end in tendons. As the most
important act of the bird’s life that depends upon its muscles is
flying, it is not surprising to find that the muscle which effects the
downward stroke of the wing is the largest. This muscle is known as the
great pectoral, and it is said to be almost as large as all the other
muscles of the body put together. The way in which a muscle effects
the movements of the bones to which it is attached is by contracting.
All muscles are able to contract; they shorten, and, accordingly, the
ends, with whatever they happen to be attached to are brought closer
together. The contraction is governed by the nerves, and it has been
discovered that the nerves actually end in communication with the
fibres of which the muscle is composed. This pectoral muscle lies on
the breast-bone, and nearly completely covers it; indeed, only the
edge of the keel appears, and a very little tract at the sides. When
this muscle is dissected away another muscle, not nearly so large,
comes into view underneath it; this is called the pectoralis secundus,
or the second pectoral. Its action is precisely the reverse of that
of the great pectoral: it pulls the wing up instead of down. Between
them, these two muscles do most of the work in flying. Naturally, in
the ostrich tribe, which do not fly, they are much reduced in bulk.
But they are never absent altogether, even in the Apteryx, which is,
perhaps, further removed from the possibilities of flight than any
other bird.
A very curious muscle runs into the patagium of the wing, which is
that fold of skin which lies between the shoulder and the hand. This
muscle is called the patagial muscle. It starts from the shoulder as a
fleshy band, but soon ends in two long tendons: one of these follows
the upper margin of the patagium, and finally ends in the wrist; the
other passes down over the patagium, and ends below in connection
with some of the muscles of the arm, and also by being attached in
a fan-shaped way to the skin itself. The function of this muscle is
to assist in the folding up of the wing when it is, so to speak, put
away after use. The tendons in which the latter part of this muscle
ends often show a most complicated branching in the patagium; they
frequently offer characteristic differences in different birds, and
are made some use of by the systematist. The bird has got a biceps to
its arm just as we have. It sometimes happens that this biceps gives
off a muscular slip, which runs into the patagium and becomes attached
to the upper of the two tendons of the patagial muscle. A good deal
of stress is laid by certain ornithologists as to whether this biceps
slip is absent or present. Several of the common British birds will
afford material to the beginner to ascertain for himself some of the
chief variations in these and the other muscles of the body. It will
be a good exercise to get a few birds, and to carefully dissect two
of them, belonging to as widely different kinds as possible, side by
side. You might select, for instance, a Crow and a Pigeon, which are
fairly extreme types. To revert to our account of the muscular anatomy
of a bird, it will be impossible to attempt any comprehensive account
of this branch of the subject, because the facts are so appallingly
numerous. We shall content ourselves, therefore, with the mention of
a highly characteristic bird muscle which occurs in the leg. This
muscle is known as the ambiens. This muscle is thin and ribbon-like.
It takes its origin from a little process of the pubic bone usually
called the prepubic process. From this point it runs along the inside
of the thigh until it reaches the knee; it then bends over the knee
and comes out on the other side, where it runs down the leg to join
the deep flexor muscle of the foot. When this ambiens muscle contracts
it pulls upon the flexor muscle, already referred to; the effect of
this is that the toes are brought together by the tendons in which the
last-mentioned muscle ends. The ambiens is far from being universally
present among birds. It is notably absent from the passerine birds
(the Sparrows, Crows, Rooks, and small perching birds generally), and
from the Hornbills, Toucans, Woodpeckers, and that varied assemblage
known as picarian birds. On the other hand, the Storks, Hawks, and
most of the larger birds, have the muscle. But among some of these
it is absent; thus, the Owls on the one hand, and the Herons on the
other, have no ambiens; but from their general resemblance in other
particulars to birds which have an ambiens, it was thought by Professor
Garrod that the loss in them was a recent event, and that they might
be fairly placed in one great group of birds with an ambiens which he
termed, somewhat lengthily, the ‘homalogonatæ,’ or normal-kneed birds,
reserving the name ‘anomalogonatæ,’ or abnormal-kneed birds, for the
passerines, &c., without an ambiens.
_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, appearances 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,
flat-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
Carinatæ: it is simply sheer inability to place them anywhere in
particular.
CLASS. AVES.
SUB-CLASS I. Archæornithes (contains genus Archæopteryx only).
SUB-CLASS II. Neornithes.
Division i. Neornithes Ratitæ.
Order i. Ratitæ (contains Struthio, Rhea, Dinornis, &c.).
Order ii. Stereornithes (contains a few fossil genera,
Gastornis, Dasornis, &c.).
Division ii. Neornithes Odontolcæ.
Order i. Hesperornithes (the extinct Hesperornis and
Enaliornis).
Division iii. Neornithes Carinatæ.
Order i. Ichthyornithes (fossil Ichthyornis only).
Order ii. Passeres (thrushes, swallows, flycatchers, tits,
&c.).
Order iii. Picariæ (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. Columbæ (doves).
Order xi. Pterocletes (sand-grouse).
Order xii. Gallinæ (curassows, megapodes, pheasants,
grouse, Opisthocomus, &c.).
Order xiii. Tinamidæ (tinamous).
Order xiv. Fulicariæ (rails, coots).
Order xv. Alectorides (cranes, bustards, Cariama, &c.).
Order xvi. Limicolæ (plovers, snipe, knots, &c.).
Order xvii. Gaviæ (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 Carinatæ 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.
[Illustration: FIELDFARES. MISSEL-THRUSH. BLACKBIRD.]
Missel-Thrush, or Stormcock.
Turdus viscivorus.
Upper parts ash-brown; under parts white, faintly tinged with yellow,
marked with numerous black spots; under wing-coverts white; three
lateral tail feathers tipped with greyish white. Length, eleven inches.
* * * * *
There are six British thrushes. Of these the missel-thrush and
blackbird are residents throughout the year; the song-thrush is also
found with us at all seasons, and is a winter songster, but many birds
migrate; the ring-ouzel is a summer visitor; the redwing and fieldfare
are winter visitors.
The missel or mistletoe thrush, or stormcock, is the largest, exceeding
the fieldfare, which comes next in size, by at least an inch in
length and two inches in spread of wings. This species possesses
in a marked degree all the characters that everywhere distinguish
the true thrushes, which are world-wide in their range. Theirs is a
modest colouring:--olive-brown above, paler and spotted below; a loud
and varied song, and harsh cry; a statuesque figure; rapid, startled
movements on the ground, with motionless intervals, when the bird
stands with head and beak much raised, in an attitude denoting intense
attention; and, finally, a free, strong, undulating flight.
The missel-thrush inhabits almost the whole of the British Islands,
and is most abundant in Ireland. Throughout England and Wales he is
fairly common, less common in Scotland, and becoming rarer the farther
north we go. He is found in all woods and plantations, but is most
partial to wooded parks, orchards, and gardens, which afford him food
and shelter throughout the year. He is the hardiest of our vocalists,
and is better known as a winter than a summer songster. His song may
be heard in the autumn, but from midwinter until spring his music is
most noteworthy. Its loudness and wild character give it a wonderful
impressiveness at that season of the year. He is not of the winter
singers that wait for a gleam of spring-like sunshine to inspirit
them, but is loudest in wet and rough weather; and it is this habit
and something in the wild and defiant character of the song, heard
above the tumult of nature, which have won for him the proud name of
stormcock.
This thrush is an early breeder, and pairs about the beginning of
February. The birds, after mating, are exceedingly pugnacious,
and attack all others, large or small, that approach the chosen
nesting-site. The nest is not often made in evergreens, to which
blackbirds and song-thrushes are so partial; as a rule, a deciduous
tree--oak, elm, or beech--is made choice of, and the nest may be at any
height, from a few feet above the ground to the highest part of a tall
tree; and as it is built so early in the year, when trees are leafless,
it forms a most conspicuous object. Furthermore, the missel-thrush,
a shy and wary bird at other times, becomes strangely trustful, and
even careless, when nesting, and often builds in the neighbourhood of
a house, or in an isolated tree at the roadside. When building and
breeding the birds are silent, except when the nest is threatened with
an attack, when they become clamorous and bold beyond most species in
defence of their eggs or nestlings.
The nest is large and well made, outwardly of dry grass, moss, and
other materials, woven together; it is plastered with mud inside, and
thickly lined with fine dry grass. The four eggs vary in ground-colour
from bluish white to pale reddish brown, and are spotted, blotched,
and clouded, with various shades of purple, brown, and greyish
under-markings. Two or three broods are reared in the season.
At the end of June the missel-thrushes begin to unite in small parties
numbering a dozen to twenty birds, and to range over the open country,
seeking their food in the pastures and turnip-fields, and on moors
and commons. Where the birds are abundant much larger congregations
are seen. In Ireland I have seen them in August in flocks of about
a hundred birds. They do not keep close together, as is the manner
of starlings and finches, but fly widely scattered, and alight at
a distance apart, a flock of fifty to a hundred birds sometimes
occupying half an acre or more ground. They then look very large
and conspicuous, scattered over the green grass, standing erect and
motionless, or hopping about in their wild, startled manner. These
flocks diminish in number as the season progresses, and finally break
up about midwinter.
In autumn the missel-thrushes devour the yew-berries, and the fruit
of the rowan and service trees; later in the year they feed on the
glutinous berries of the mistletoe, on haws and ivy-berries, and other
wild fruits; but their food for the most part consists of earthworms,
snails, grubs, and insects of all kinds.
Throstle, or Song-Thrush.
Turdus musicus.
FIG. 18.--SONG-THRUSH. ¼ natural size.
Upper parts olive-brown, throat white in the middle; sides of neck and
under parts ochreous yellow spotted with dark brown; under wing-coverts
pale orange-yellow. Length, nine inches.
* * * * *
The protest and recommendation implied by the use of the first name
at the head of this article may be futile; but it is impossible not
to feel and to express regret that so good and distinctive and old a
name for this familiar bird should have been replaced by a name which
is none of these things. Song-thrush is an unsuitable name, for the
very good reason that we have several thrushes, all of them songsters.
By most persons the bird is simply called ‘thrush,’ which is neither
better nor worse than ‘song-thrush.’
The throstle is one of the smaller members of the genus, being about
a third less in size than the noble stormcock. In form, colouring,
motions, language, and habits, he is a very thrush. It cannot be said
that his music is the best--that, for instance, it is finer than that
of the blackbird. The two songs differ in character; both are good of
their kind, neither perfect. The throstle is, nevertheless, in the very
first rank of British melodists, and it is often said of him that he
comes next to the nightingale. The same thing has been said of other
species, tastes differing in this as in other matters. It is worth
remarking that most persons would agree in regarding the nightingale,
song-thrush, blackbird, blackcap, and skylark, as our five finest
songsters, and that these all differ so widely from each other in the
character of their strains that no comparison between them is possible,
and there is no rivalry.
The only species which may be called the rival of the song-thrush is
the missel-thrush, as their music has a strong resemblance. That of the
stormcock has a wonderful charm in the early days of the year, when
it is a jubilant cry, a herald’s song and prophecy, sounding amidst
wintry gloom and tempest. Heard in calm and genial weather in spring,
the throstle is by far the finer songster. His chief merit is his
infinite variety. His loudest notes may be heard half a mile away on
a still morning; his lowest sounds are scarcely audible at a distance
of twenty yards. His purest sounds, which are very pure and bright,
are contrasted with various squealing and squeaking noises that seem
not to come from the same bird. Listening to him, you never know what
to expect, for his notes are delivered in no settled order, as in some
species. He has many notes and phrases, but has never made of them one
completed melody. They are snatches and portions of a melody, and he
sings in a scrappy way--a note or two, a phrase or two, then a pause,
as if the singer paused to try and think of something to follow; but
when it comes it has no connection with what has gone before. His
treasures are many, but they exist jumbled together, and he takes them
as they come. As a rule, when he has produced a beautiful note, he will
repeat it twice or thrice; on this account Browning has called him a
‘wise bird,’ because he can
recapture
The first fine careless rapture.