toad, as he spreads out his short fat legs and puffs out his warty
skin, and to compare him with the nervous, anxious, little frog,
starting at every danger. And still more curious is it to see him
getting out of his skin, as he does several times a year. For his skin
does not peel off in pieces as it does in the watery frogs, but splits
along his back; then he wriggles about till it lies in folds on his
sides and hips, and, putting one of his hind feet between the front
ones, draws the skin off the leg like a stocking off a foot. With the
other leg he does the same, and then, drawing out his front legs, pulls
the whole skin forward, and stripping it over his head, swallows it;
thus deliberately putting his old coat inside him, and appearing in one
that is glossy, fresh, and new. The toad has many enemies in spite of
his acrid taste, and he shows his wisdom by hiding in walls and under
stones in the daytime, and coming out in the dusk of evening to hunt
the beetles and grubs so often out of reach of the water-loving frog.
[Illustration: Fig. 19.
The Flying Tree-Frog of New Guinea[62] (_Wallace_).]
But the toad is not the only land relation of the frog; there are
others of the group that venture even farther from water; for in most
parts of the world (though not in England), tree-frogs, with sucking
disks at the ends of their toes and fingers, climb the trees and hunt
for insects among the leaves and branches; while in Borneo Mr. Wallace
found one (Fig. 19) with webbed feet, which it spread out, and so flew
down from the trees. There are plenty of the ordinary tree-climbing
frogs to be seen in the south of France, their small green bodies
peeping out from under the dull gray olive-leaves; and to be heard,
too, in an endless chorus all night long when the spring arrives.
But how can these tree-dwellers bring up their little ones in water?
Some of them come down and lay their eggs in the ponds, and even sleep
down in the mud in winter. Others lay their eggs in little puddles of
water in the hollows of the trees, and there the young ones live their
tadpole life; while in one curious tree-frog of Mexico, called the
_Nototrema_, the mother has a pouch in her back, and the father places
the eggs in it for the little tadpoles to live in a moist home till
they leap out as perfect frogs.
Nor is this the only case in which fathers and mothers take care of
their young. In one species of frogs living near Paris, the father[63]
winds the long string of gluey eggs round his thighs, and buries
himself in the ground till the young tadpoles are ready to come out,
and then he leaps into the water. And in one of the tongueless toads,
the Surinam toad,[64] the mother’s soft skin swells up, forming ridges
and hollows, and when her eggs are laid the father clasps them in his
feet, and, leaping on her back, puts an egg into each hollow. Then
the mother goes into the water, and remains there while each tadpole
completes its changes in its own hole, jumping out at last a finished
toad.
Yet, in spite of curious habits such as these, the frogs and their
companions on the whole lead a very monotonous life. They are, it is
true, more intelligent than fish, and have learned to know more of the
world, but in the long ages that have passed since their ancestors
roamed in the coal-forest marshes, other and higher animals have taken
possession of the land, and left room only for a few scattered groups
of _amphibia_. Still, however, they remain hovering between two lives,
and filling such spots as neither the fishes nor the land animals can
occupy; and when we hear them croaking in the quiet night, or see them
leaping on the marshy ground, they remind us that we have still living
in our day, a link between the fish whose world is a world of waters,
and the air-breathing animals which have become masters of the land.
[Illustration: THE REPTILES IN THEIR PALMY DAYS.]
CHAPTER V.
THE COLD-BLOODED AIR-BREATHERS OF THE GLOBE IN TIMES BOTH PAST AND
PRESENT.
And now the transformation is complete, for when we pass on to the next
division of backboned animals, the “Reptiles,” we hear nothing more
of gills, nor air taken from the water, nor fins, nor fishes’ tails.
From this time onward all the animals we shall study live with their
heads in the air, even if their bodies may be in the water; they swim
with their legs or, as in the case of the snakes, with their wriggling
bodies, and they lay their eggs on the land where their young begin
life at once as air-breathers.
Yet they can often remain for a long time both under water and under
ground, for they are still cold-blooded animals, breathing very slowly,
and easily falling into a state of torpor when the air around them is
cold and chill. They are but the first step, as it were, to active
land-animals; yet they have played a great part in the world, and when
we know their history we shall be surprised to find how much Life has
been able to make of her cold-blooded children.
To learn how this has been, however, we must travel away from home and
our own surroundings. The tiny brown lizard which runs over our heaths,
while its legless relation, the slowworm, burrows in the ground,--the
few snakes which glide through the grass of our meadows, and the
stray turtles thrown at rare intervals on our shores,--tell us very
little about true reptile life. It is to Africa, India, South America,
and other warm countries, that we must go to find the formidable
crocodiles, huge tortoises, large monitor-lizards, and dangerous
boa-constrictors, cobras, and rattle-snakes. And even then, strong
and powerful as some of these creatures are, they do not tell us half
the history of the cold-blooded air-breathers. For the day of reptile
greatness, like that of the sharks and enamel-scaled fish, was long
long ago.
Now that we know how frogs pass from water-breathing to air-breathing,
and how axolotls, accustomed to live all their life in the water, can
lose their gills and become land-animals, we can form an idea how in
those ancient days, while still the huge-plated newts were wandering
in the marshes, some creatures which had lost their gills would take
to the land, and their young ones starting at once as air-breathers,
as the black salamanders do now (see p. 80), would in time lose all
traces of the double or _amphibian_ life, and become true air-breathing
reptiles.
At any rate, there we find them appearing soon after the coal-forest
period passed away, at first few and far between, in company with the
large amphibians, but spreading more and more as the ages passed on,
till they in their turn became monarchs of the globe. Already, when the
coal-forests had but just passed away, a lizard,[65] in some points
like the monitors that now wander on the banks of the Nile, was living
among his humbler neighbours; and from that time onwards we find more
and more reptiles, till just before the time when our white chalk was
being formed by the tiny slime-animals at the bottom of the sea, we
should have seen strange sights if we could have been upon the globe.
For the great eft was no longer
“... lord and master of earth.”
All over the world, and even in our own little England, which was then
part of a great continent, cold-blooded reptiles of all sizes, from
lizards a few inches long to monsters measuring fifty or sixty feet
from head to tail, swarmed upon the land, in the water, and in the
air. There were among them a few kinds something like our tortoises,
lizards, and crocodiles; but the greater number were forms which have
quite died out since birds and beasts have spread over the earth, and a
wonderful and powerful set they were.
Some were vegetable-feeders, which browsed upon the trees or fed upon
the water-weeds, as our elephants and giraffes, our hippopotamuses and
sea-cows do now. Others were ferocious animal-eaters, and their large
pointed teeth made havoc among their reptile companions, as lions and
tigers do among beasts. Some swam in the water devouring the fish,
while others, like birds or bats, soared in the air.
In the open ocean were the sea-lizards, some called Fish-Lizards,[66]
like huge porpoises thirty feet long, but really cold-blooded reptiles,
with paddles for legs, and long flattened tails for swimming. Woe to
the heavily-enamel-scaled fish when these monsters came along, their
pointed teeth hanging in their widely-gaping mouths as they raised
their huge heads, with large open eyes, out of the water! Then among
these were others with long swan-like necks and small heads,[67] which
would strike at the fish below them in the water, while other slender,
long-bodied monsters,[68] measuring more than seventy feet from tip to
tail, flapped along the sea-shore with their four large paddles, or
swam out to sea like veritable sea-serpents, devouring all that came
in their way. These were all water-reptiles, while there were also
many smaller land-lizards playing about upon the shore, and among the
trees and bushes. But the strangest of all were perhaps the “Flying
reptiles”[69] of all sizes, from one as small as a sparrow to one which
measured twenty-five feet from tip to tip of its wings. These reptiles
did not fly like birds, for they had no feathers, but only a broad
membrane, stretching from the fifth finger of their front claw to their
body, and with this they must have flown much as bats do now, while
some of them were armed not only with claws, but also with hooked beaks
and sharp teeth, with which they could tear their prey.
And meanwhile upon the land were wandering huge creatures, larger than
any animal now living, which were true reptiles with teeth in their
mouths, yet they walked on their hind legs like birds, probably only
touching the ground with their short front feet from time to time, as
kangaroos do. They had strong feet with claws, the marks of which they
have left in the ground over which they wandered, supporting themselves
by their powerful tails as they went.
Some of them were peaceful vegetarians,[70] browsing on the tree-ferns
and palms, and rearing their huge bodies to tear the leaves from the
tall pine-trees. But others were fierce animal-feeders. Fancy a monster
thirty feet high,[71] with a head four or five feet long, and a mouth
armed with sabre-like teeth, standing upon its hind legs and attacking
other creatures smaller than itself, or preying upon those other
huge reptiles which were feeding peacefully among the trees. Surely
a battle between a lion and an elephant now would count as nothing
compared to the reptile-fights which must have taken place on those
vast American lands of the west, or on the European pasture-grounds,
where now the remains of these monsters are found.
But where are they all gone? We know that they have lived, for we
can put together the huge joints of their backbones, restore their
gigantic limbs, and measure their formidable teeth, but they themselves
have vanished like a dream. As time went on, other and more modern
forms, the ancestors of our tortoises, lizards, crocodiles, and
afterwards snakes, began to take the place of these gigantic types;
while warm-blooded animals, birds and beasts, began to increase upon
the earth. Whether it was that food became scarce for these enormous
reptiles, or whether the birds and beasts drove them from their haunts,
we are not yet able to find out. At any rate they disappeared, as the
ancient enamelled fishes and large newts had disappeared before them,
and soon after the beds of white chalk were formed, which now border
the south of England and north of France, only the four divisions of
tortoises, lizards, crocodiles, and snakes, survived as remnants of the
great army of reptiles which once covered the earth.
* * * * *
Ah! if we could only have a whole book upon reptiles to show how
strangely different these four remaining groups have become during the
long ages that they have been using different means of defence; and
how, even in a single group, they employ so many varied stratagems to
survive in the battle of life! Look at the tortoises with their hard
impregnable shells, the crocodiles with their sharp-pointed teeth and
tough armour-plated skins, and the silently-gliding snakes with their
poisonous fangs or powerful crushing coils. See how the tiny-scaled
lizard darts out upon an insect and is gone in the twinkling of an eye,
and then watch the solemn chamæleon trusting to his dusky colour for
protection, and scarcely putting one foot before another in the space
of a minute.
Each of these has his own special device for escaping the dangers of
life and attacking other animals, and yet we shall find, before we
finish this chapter, that they are all formed on one plan, and that it
is in adapting themselves to their different positions in life that
they have become so unlike each other.
We shall all allow that the Tortoises are the most singular of any, and
it is curious that they are also in many ways the nearest to the frogs
and newts, although they are true reptiles. Slow ponderous creatures,
with hard bony heads (Fig. 20), wide-open expressionless eyes, horny
beaks, and thick clumsy legs, the tortoises seem at first sight to be
only half alive, as they lumber along,
“Moving their feet in a deliberate measure
Over the turf,”
carrying their heavy shell, and eating, when they do eat, in a dull
listless kind of way. They do, in truth, live very feebly, for they
can only fill their lungs with air by taking it in at the nostrils
and swallowing it as frogs do, and then letting it drift out again as
the lungs collapse, for their hard shell prevents them from pumping
it in and out by the movement of their ribs like other reptiles. This
slowness of breathing and the fact that they have only three-chambered
hearts like frogs (see p. 76), so that the good and bad blood mix at
every round, causes them to be very inactive, and they digest their
food very slowly, and have been known to live months and even years
without eating.
[Illustration: Fig. 20.
The Greek Tortoise.]
This sluggishness would, indeed, certainly be their ruin in a bustling
greedy world, if it were not for the strong box in which they live.
Take in your hand one of the small Greek[72] or American[73] tortoises,
so often sold as pets, and you will see how well he can draw back out
of harm’s way, while at the same time you will, I think, be sorely
puzzled to understand how he is made. His head, his four legs, and his
tail, with their thick scaly skin, are intelligible enough. But why do
all these grow on to the inside of his shell, so that when you trace
them up you cannot find the rest of his soft body? You would hardly
guess that his shell _is_ the rest of his body, or at least of his
skeleton. But it is so. The arched dome which covers his back is made
of his backbone and ribs, and the shelly plates arranged over it are
his skin hardened into horny shields, which, in the Hawksbill turtle,
form the tortoise-shell which is peeled off for our use; while the flat
shell under his body is the hardened skin of his belly, and the bones
which belong to it.
[Illustration: Fig. 21.
Carapace of the Tortoise.
_j_, Joints of the backbone grown together; _r_, ribs formed into
a solid cover; _sh_, shoulder bones; _h_, hip bones covered by
carapace, which has grown over them.
]
Let us make this clear, for it is a strange history. If you look at
the skeleton of a lizard (Fig. 23, p. 103), it is all straight-forward
enough. His head fits on to his long-jointed backbone, which is able to
bend in all parts freely, down to the very tip of his tail. His front
legs with their shoulder bones (_s_), and his hind legs with their hip
bones (_h_), are attached in their proper places to his backbone, and
lastly, his ribs (_r_) protect the inside of his body, and by expanding
and contracting pump the air in and out of his lungs, the front ribs
being joined underneath in a breastbone. It is easy to see, therefore,
that the lizard may be active and nimble, twisting his body hither and
thither, and escaping his enemies by his quickness. But the tortoise
is slow and sluggish, and has only managed to baffle the numberless
animals which are looking out for a meal by fabricating a strong box to
live in. But he had to make this out of the same kind of skeleton as
the lizard, with the one difference that he has no breastbone. Let us
see how it has been brought about. The bones of his neck are jointed
and free enough as you can see (Fig. 21), and so are the joints of his
tail, beginning from behind his hip bones (_h_). But with his back it
is different. The backbone can be clearly seen inside the empty shell,
running from head to tail so as to cover the nerve-telegraph, but the
joints (_j_) have all grown together, and on the top they have become
flattened into hard plates,[74] while the ribs (_r_) which are joined
to them have also been flattened out and have grown firmly together so
as to make an arched cover or _carapace_. If now you look at the back
of the young tortoise (Fig. 22), which has been taken out of the egg
before it was full-grown, you will see these plates (_p_) on the side
where the tortoise-shell (_ts_) has been peeled off. They have not yet
widened out enough to be joined together, and the ribs (_r_) are as yet
only united by strong gristle. But what is that row of oblong plates
(_mp_) round the edge? Those are the marginal plates, and they are
mere skin bones, like the bony plates of the crocodile, but they are
all firmly fixed together so as to bind the edges of the ribs, while
plates of the same kind form the shell under the body, and the whole is
covered by the horny skin.
[Illustration: Fig. 22.
Back of a Young Tortoise.--(_From Rathke._)
_ts_, Tortoise-shell covering the whole carapace; this has been
removed on the right side; _mp_, marginal plates binding the edges
of the ribs; _np_, neck-plate; _p_, plates formed of the top of the
backbone joints which have grown together; _r_, ribs which have not
yet spread out so as to form a continuous shell; _lm_, _lm′_, front
and hind leg muscles not yet covered by the carapace.
]
But there still remains another great puzzle. How come the shoulder
bones and hip bones of the tortoise to be inside his ribs instead of
being outside them, as in other animals? But look again at our baby
tortoise, and you will see that the muscles of his front legs (_lm_,
Fig. 22) are not covered by ribs, neither are those of his hind legs
(_lm′_). They stand just like those of other animals, in front between
the ribs and the neck, and behind between the ribs and the tail. But as
the tortoise grows up, the bony plates press forwards and backwards,
and cover up the shoulders and hips, protecting the soft legs and neck,
and giving him the curious appearance of living inside his own backbone
and ribs.
In this way, then, the tortoises have managed to hold their own in the
world. Living slowly, so that they sometimes go on growing up to eighty
years old, wanting but little food, and escaping the cold by sleeping
the winter months away in some sheltered nook, they ask but little from
Life, while they escape the dangers of sluggishness by growing their
skeletons so as to form a citadel which even birds and beasts of prey
can rarely break through. They are, it is true, often eaten when young,
and the jaguar of Brazil knows how to dig the poor American tortoise
out of his shell and eat him; while large birds are formidable enemies
to our Greek tortoise, and are said to drop it down on the rocks,
and break it to pieces. But, on the whole, they escape most of these
dangers, and wander in the woods and dry sandy places of sunny Greece
and Palestine, laying their bullet-shaped eggs in warm spots to hatch,
seldom wandering far from home, and lying down for their winter’s sleep
under heaps of drifted leaves or in holes of the ground.
These are true Land-tortoises,[75] and so are the gigantic tortoises
which used to live in the island of Aldabra, and others still surviving
in the Galapagos and other islands near Madagascar, which weigh at
least 200 pounds, and on whose backs Mr. Darwin rode when he found
them travelling up the island to get water to drink, feeding on the
juicy cactus as they went. Some carapaces in our museums belonging to
these tortoises measure four feet long and three broad; yet they were
timid fellows when alive, drawing back completely within their shells
when danger was near. We even find some smaller land-tortoises[76] in
America, called the Box-tortoises, which have soft joints in their
under shell, so that they can draw it up both in front and behind,
shutting themselves completely in.
Not so the River-tortoises,[77] which are greedy animal-feeders, and
as they live in the water do not need the same protection. Their box
is much flatter and more open at the ends, so as to allow them to
swim freely with their webbed feet; and they are fierce and bold,
the Snapping Turtle[78] of the lakes and rivers of America being a
terrible fellow, tearing the frogs and fishes in the water with his
sharp claws, and even snapping strong sticks in half with his powerful
beak. The Mud-tortoises, too, which swim swiftly with their strong legs
and long neck outstretched, do not need a hard shell, and they have
scarcely any plate below, and only a gristly leathery covering above,
which looks very like the mud in which they hide.
Lastly the Sea-tortoises or Turtles, which swim in the warm parts of
the Atlantic and Pacific Oceans, have only an open flat shell under
which they cannot draw their head and feet, for they strike out boldly
into the open ocean, feeding on seaweed, jelly-fish, and cuttle-fish,
rowing grandly along with their broad paddles which they feather like
oars as they go. They have only one time of weakness--when they come
on islands, such as Ascension and the Bahama Islands, which they
choose probably because they find fewer large animals there. There
the mother turtle arrives at night, looking fearfully around, and if
all is still comes flapping in over the sand, and, clearing a hole
with her flippers, lays about 200 soft round eggs and covers them up
and leaves them. Then in about a month the young turtles come out and
make at once for sea, though many of them fall victims to large birds
of prey on their way. Woe, too, to the mother when she is laying her
eggs, if these large birds are near, for she cannot defend her soft
body; or, worse still, if the natives are on the look-out; for then
the Green Turtle,[79] coming ashore from the Atlantic, is tilted over
on her back and killed for food; and the Hawk’s-bill Turtle[80] from
the Indian or Pacific Oceans is cruelly stripped of its shell for
ornaments. Yet they must run these risks, for their eggs would not
hatch without the warm sun, and we see how great is the gap between the
last water-breathers and the first air-breathers, when we remember that
the frogs go back to lay their eggs in the water, while the tortoises,
even when they live far out at sea, are forced to come in to shore, in
spite of great dangers, to lay their eggs that their little ones may
begin life upon land.
* * * * *
[Illustration: Fig. 23.
Skeleton of a Lizard.
_sp_, Spinous processes, which in the tortoise are flattened into
plates; _r_, ribs; _s_, shoulder bone; _a_, upper arm; _e_, elbow;
_fa_, forearm; _h_, hip bone; _th_, thigh bone; _k_, knee; _l_,
bones of the leg; _q_, quadrate bone between upper and lower jaw.
]
And now, if we leave the tortoises and turn to the Lizards, we find
them meeting life’s difficulties in quite a different way. Here are
no sluggish movements, horny beaks, and strong boxes; but bright-eyed
creatures covered with shining scales, their mouths filled with sharp
teeth, with which even the small lizards can bite fiercely, and having
nimble lissome bodies, which wriggle through the grass or up the
trees in the twinkling of an eye. Yet the lizards, as we have seen,
are formed on the same plan as the tortoise, and their scales are
thickenings in their outer skin, just as his tortoise-shell is, and not
true scales like those of fish. They have learned to hold their own by
sharpness and quickness, and are probably the most intelligent of all
the cold-blooded animals, though even they are only lively in a jerky
way under the influence of warmth. They can breathe more easily than
the tortoise, for their ribs rise and fall, drawing in and driving out
the air they need; but they are still cold-blooded, for their heart has
only three chambers. It is when the bright sun is shining that they
love to dart about, chasing the insects upon which they feed; and the
joints of their backbone move so easily upon each other that they can
twist and turn in all imaginable ways, keeping their heads twisted in a
most comical manner when on the watch for flies. Nay, the very vertebræ
themselves are so loosely made that they can split in half, and if you
seize a lizard by the tail he will most likely leave it in your hand
and grow another.
They can live both in dry sandy places, where larger animals cannot
find food and water, and in thick underwood, and marshy unhealthy
places, where more quickly-breathing animals would be poisoned by the
fetid air; and we find them swarming in hot countries in spite of
enemies, their scales protecting them from the rough surface of the
rocks and trees on which they glide, their feeble legs scarcely ever
lifting their body from the object on which they glide rather than walk.
[Illustration: Fig. 24.
Gecko and Chamæleon.]
The true land-creepers, like our little Scaly Lizard,[81] lurk in
dry woody places, and on heaths and banks, darting out on the unwary
insects. Many of them lay their eggs in the warm sand or earth, but
the Scaly lizard carries them till they are ready to break, so that
the young ones come out lively and active as the eggs are laid. Others
have taken to the water, and among these are the Monitors of Africa
and Australia, which feed on frogs and fish and crocodiles’ eggs, and
are so strong and fierce that they often drag larger animals under the
water. Some are tree and wall climbers, such as the “Geckos,” with
thick tongues and dull mottled skins, and they have sharp claws and
suckers under their toes, so that they can hang or walk upside down,
on ceilings or overhanging rocks, or on the smooth trunks of trees;
and they love to chase the insects in the hot sultry nights, tracking
them to their secret haunts. They are far more active than the large
gentle Iguanas or Tree-Lizards of South America, from a few inches to
five feet long, which may be seen among the branches of the trees of
Mexico, their beautiful scales glistening in the sun as they feed on
the flowers and fruit. They swarm on all sides in those rich forest
regions, scampering over the ground, and then clinging with their claws
to the tree-bark as they gradually mount up into the dense foliage; and
they have many advantages, for not only can they climb to great heights
out of the reach of beasts of prey, but they can also swim well, having
been known to fling themselves from the overhanging branches into the
water below when danger was near. They do not, moreover, descend as
gracefully as the “Flying Lizards” of the East Indies, which have a
fold of skin stretched from the lengthened ends of their hinder ribs,
so that they sail from branch to branch as they chase the butterflies
and other insects.
But the most curious of all tree-lizards is the Chamæleon, with his
soft warty skin, his round skin-encircled eyes, his bird-like feet, and
his clinging tail. He never hurries himself, but putting forward a leg,
at the end of which is a foot whose claws are divided into two bundles,
he very deliberately grasps the branch, as a parrot does, loosens his
tail, draws himself forward, and then fastens on again with tail and
claws; while his eyes, each peering out of a thick covering skin,
roll round quite independently of each other, one looking steadily
to the right, while the other may be making a journey to the left.
What is he looking for? Just ahead of him on a twig sits a fly, but
he cannot reach him yet. So once more a leg comes out, and his body
is drawn gradually forwards. Snap! In a moment his mouth has opened,
his tube-like tongue, with clubbed and sticky tip, has darted out and
struck the fly, and carried it down his throat, while the chamæleon
looks as if he had never moved. It is not difficult to imagine that
such a slow-moving animal, whose natural colour is a brownish green
like the leaves among which he moves, would often escape unseen from
his enemies. And when light falls upon him, his tint changes by the
movement of the colour-cells in his skin, which seem to vary according
to the colour of the objects around, whenever he is awake and can see
them.
So by the waterside, on the land, and among the trees, the lizard tribe
still flourish in spite of higher animals; and just as we found some
legless kinds among the _amphibia_ burrowing in the ground, so here,
too, we find legless lizards, some with small scaly spikes in the
place of hind legs, others, like the glass-snake of America[82] and
our English slowworm[83] (or blindworm), which have no trace of feet
outside the skin, but glide along under grass and leaves, eating slugs
and other small creatures, though they are true lizards with shoulder
bones and breastbones under the skin.
* * * * *
Here, then, we seem to be drifting along the road to snake-life, but we
must halt and travel first in another direction, upwards to a higher
group of animals, which may almost be called gigantic flesh-eating
lizards, though they are far more formidable and highly-organised
creatures. These are the Crocodiles, and no one looking at them can
doubt for a moment that they at least are well armed, so as to have an
easy time of it without much exertion. Huge creatures, often more than
twenty feet long, with enormous heads and wide-opening mouths, holding
more than thirty teeth in each jaw, they look formidable indeed as
they drag their heavy bodies along the muddy banks of the Nile, their
legs not being strong enough to lift them from the ground. Their whole
body is covered with strong horny shields, and under these shields, on
the back, are thick bony plates, which will turn even a bullet aside,
and quite protect the crocodile from the fangs of wild beasts. Their
eyelids are thick and strong, and they have a third skin which they can
draw over the eye sideways like birds; their ears, too, have flaps to
cover them, and their teeth are stronger and more perfect than any we
have yet seen, for they are set in sockets, and new ones grow up inside
the lower part of the old ones as they are broken or worn away.
[Illustration: Fig. 25.
The Nile Crocodile.--(_Tristram._)]
But it is in the water that we see them in their full strength; there
they swim with their webbed feet and strokes of their powerful tail,
and feed upon the fishes and water animals--monarchs of all they
survey. Nor is the crocodile content with mere fish-diet. Often he
will lie with his nostrils just above the water and wait till some
animal--it may be a goat, or a hog, or even a good-sized calf--comes
to drink, then he will come up slowly towards it, seize it in his
formidable jaws, or sometimes strike it with his powerful tail, and
drag it under water to drown. For he himself can shut down his eyelids
and the flaps over his ears, and he has a valve in the back of his
throat which he can close, and prevent the water rushing down his
open mouth; and after a while he rises slowly till his nostrils are
just above the water, and he can breathe freely while his victim is
drowning, because his nose-holes are very far back behind the valve.
Then when it is dead he brings it to shore to tear it to pieces and eat
it.
Thus the crocodiles of the Nile and the Ganges, the Gavials with their
long narrow snouts, and the Alligators of America, with their shorter
and broader heads, feed on fish and beasts, and all dead and putrid
matter, acting as scavengers of the rivers; while they themselves are
almost free from attack, except when tigers fall upon them on land.
But it is the young crocodiles which run the most risks when they come
out of the small chalky eggs which have been hatched in the warm sand
of the shore. True, their mother often watches over them at this time,
and even feeds them from her own mouth; but in spite of her care many
of them are eaten in their youth by the tortoises and fishes which they
would themselves have devoured by-and-by, if they had lived to grow up;
while the monitors, ichneumons, waterfowl, and even monkeys, devour
large numbers of crocodiles’ eggs.
* * * * *
And now, if we were to turn our backs upon the great rivers in which
these animals dwell, and wander into the Indian jungle or the South
American forest, we might meet with enemies far more dangerous and
deadly, although they stand much lower in the reptile world. Who would
think that the huge boa of South America, and the python and poisonous
cobra of India, or even our own little viper, whose bite is often death
to its victim, are creatures of lower structure than the harmless
little lizard or the stupid alligator? Yet so it is. For Snakes have
no breastbone and have lost all vestiges of front legs and shoulder
bones, nor have they any hips or hind legs except among the boas and
rock-snakes; and even these have only small traces of hips, which carry
some crooked bones, ending in horny or fleshy claws, in the place where
hind legs ought to be. They have no eyelids (and by this we may know
them from the legless lizards), but their skin grows right over the
eyes, so that when a snake casts its skin there are no holes where
the eyes have been, but only clear round spaces like watch-glasses, in
the scaly skin. Their ears have no drum, and are quite hidden under
the scales with which their body is so thickly covered that they must
feel very little as they glide along. These scales, like those of the
lizard, are thickened parts of the outer skin, and if you stretch a
piece of snake-skin you can see them lying embedded in it, the clear
skin itself showing between.
[Illustration: Fig. 26.
Skeleton of a Snake.
_sp_, Spinous processes of the joints; _r_, ribs; _q_, quadrate
bones, joining upper and lower jaws; _e_, front of the lower jaw,
where there is an elastic band in the place of bone; _b_, ball end
of joint, facing the tail; _c_, cup end of joint, facing the head.
]
We must not, however, imagine that the snake is at a disadvantage
because he has lost so many parts which other reptiles possess. On
the contrary, he has most probably lost them because he can do better
without them. The transparent tough skin over his eye is a far better
protection in narrow rugged places, and among brakes and brambles,
than a soft movable eyelid; and if he does not see as well as the
crocodile, he has a most delicate organ of touch in his long, narrow,
forked tongue, with which he is constantly feeling as he goes, touching
now on one side, now on the other, each object he comes near, and
drawing the tongue in at every moment to moisten it in a sheath at the
back of his throat. A breast bone, moreover, would have been a decided
hindrance to him, for he wants the free use of all his ribs; and as
to the loss of his legs--in the place of four he has often more than
two hundred. For all along his backbone, except just at the head and
tail, a pair of ribs grow from each vertebra, being joined to it by a
cup-and-ball joint (_c_ and _b_, Fig. 26), and the muscles between them
are so elastic that the ribs can be drawn out so that the body seems to
swell, and then drawn back towards the tail. In doing this they strike
the ground and the snake moves forwards, just as a centipede does on
its hundred legs.
It is worth while to take our harmless Ringed Snake in your hand to
feel this curious movement to and fro of the ribs, and to notice how
the creature forces itself through your grasp. Moreover, you will learn
at the same time one use of the broad single plates under the snake’s
body (see Fig. 27), for they, like all the scales, are loose from the
skin on the side towards the tail; and as they are fastened by muscles
to the ends of the ribs, you will find that at each movement they stand
up a little like tiles on a roof, and their edges coming against your
hand help to drive the snake forward.
Another thing you will learn if the snake does not know you, and that
is how strangely they hiss, often with their mouth closed, while their
whole body seems to quiver. This is very puzzling at first, till you
learn that one of their lungs has shrunk up, and the other is a very
long and narrow bag stretching nearly the whole length of the snake’s
stomach, and the hissing sound is made by drawing in and forcing out
the air from this long bag.
[Illustration: Fig. 27.
Common Ringed Snake.[84]
Where the body is coiled the single under plates are seen.]
Meanwhile, another way in which the snake will escape from your hold
unless you grasp it tightly, is by wriggling in all directions, so that
you do not know where to expect it next; for the whole of the joints
of its backbone are joined by a succession of cups-and-balls, the ball
of one joint fitting into the cup in the one behind it. It is easy to
see how such joints can move almost every way, since the ball can twist
freely in the cup wherever the muscles pull it (except where checked by
the spines on the top of the backbone), and can even turn so much to
one side that the snake can coil itself round or tie itself into a knot.
A creature that can glide along so smoothly, twist about so freely
round trees, through narrow openings and tangled brushwood, and even
swim in the water, has no small advantage in life; and the snake can
also coil itself up under a heap of dead leaves or in a hollow trunk
of a tree for safety, or to watch for its prey when no animal would
suspect it was near. But even the harmless snakes have something
besides this, namely, the power of swallowing animals much broader and
thicker than themselves. You will see on looking at the lizard’s skull
(p. 103) that its bottom jaw is not joined at once to the top one,
but there is a bone (_q_) between, which enables it to open its mouth
wider than if the two jaws touched each other. Now this bone (_q_) in
the snake’s jaw is so loosely hung that it moves very easily, and the
lower jaw also stretches back far behind the upper one, so that when
the snake brings the jaw forward it can open its mouth enormously wide.
Nor is this all; it can actually stretch the bones of its jaws apart,
for they have not their pieces all firmly fixed together. In the front
of the mouth each jaw has elastic gristle in the place of bone, and the
two halves of the jaw can thus be forced apart from each other, making
room for a very large mouthful indeed.
[Illustration: Fig. 28.
The Boa Constrictor in the Forests of South America.]
Now the snake’s teeth are all curved towards the back of his mouth, and
they are never used for chewing or tearing, but only for holding and
packing down its food. So when he seizes a creature too large to be
easily swallowed, he fastens his front teeth into it and then brings
forward _one_ side of his jaws. He then fixes the teeth of this side
into the animal, and holds it fast while he brings forward the jaws on
the _other_ side, fixes these teeth, then loosens and brings forward
the others, and so on. In this way he keeps his mouth stretched over
the prey and gradually forces it down his elastic throat, moistening
it well all the time with slime from two glands, one on each side of
his mouth, and when it is swallowed he lies down and rests while the
stomach digests its heavy load.
We see, then, that even harmless snakes have many advantages. Thus our
ringed snake, feeding on mice and lizards, frogs and fish, wanders
through the grass and bushes of warm sunny banks, feeling this side
and that with his delicate forked tongue, and gliding so fast that the
lizards and mice try in vain to escape; while in the water he seizes
the frogs by their hind legs and jerks them into his mouth. He does not
even always stop to kill his food, for a live frog has been known to
jump out of a snake’s mouth as it yawned after its meal. So he lives
through the summer, changing his skin several times by loosening it
first at the lips, so that two flaps lie back over the head and neck,
and then rubbing himself through moss, bush, or bramble, so that the
skin is drawn off inside out like a glove, and the new skin appears
underneath, fresh, hard, and bright, ready for use. Then in the warm
season the mother lays her ten or twenty soft eggs in a mass of slime,
and leaves them in some sunny spot, or under a heap of warm manure
to hatch, and she herself wanders away, and when winter comes coils
herself up in the trunk of some hollow tree, or under the hedge, to
sleep till spring comes round again. Life does not always, however,
flow so smoothly as this, for the snakes have their enemies; the fox
and the hedgehog love to feed upon them, the buzzard and other birds
of prey swoop down upon them from above, and the weasels attack them
below; and this, perhaps, is partly the reason why the ringed snake
generally keeps near the water, into which it can glide when danger
threatens.
All snakes are not, however, so harmless as our little ringed snake.
The Pythons of India and the Boas of America, though they have no
poison in their teeth, can work terrible mischief with their powerful
joints as they coil round even good-sized animals, such as an antelope
or a wild boar, and crush them in their folds. Then it may be seen what
a terrible weapon this flexible backbone is, as the muscles draw it
tighter and tighter round the unfortunate animal, breaking its bones
in pieces, till, when it is soft enough to be swallowed, the snake
gradually forces it down its capacious mouth, moistening it with saliva
as it goes. These large boas and pythons would, in fact, probably
devastate whole countries if it were not that when they are young they
are devoured by other animals, so that very few live to grow into
dangerous marauders.
Other snakes have taken a still more terrible way of killing their
prey. There may be some chance of escape from a coiling snake, unless
he already holds you with his teeth, but the poisonous Cobra[85] may
strike before you know that you have startled him, and though the
Rattlesnake[86] makes a sharp noise as he shakes the loose horny
plates to call his mate or to alarm an enemy, yet when he means to
strike his prey it is too late when the sound is heard to get out of
reach of his fatal fangs. From the snake’s point of view, however, it
is clearly an advantage to be able with one single stroke to paralyse
its prey, so that it has only to wait for the poison to do its work,
and then its meal is ready. Even our little viper (see p. 121), needs
only to strike a mouse once, and then draws back as the poor victim
springs up and falls and dies, soon to be packed down its destroyer’s
throat.
[Illustration: Fig. 29.
The Cobra di Capello.[87]--(_From Gosse._)
The mouth being closed, the poison fangs cannot be seen. The tongue is
perfectly harmless.]
Yet this terrible poison, which acts so speedily, is no special gift to
the snake. It has only lately been discovered by M. Gautier that we,
and probably all animals, have in our saliva some of the very poison
with which the cobra kills its prey, only with us it is extremely
diluted, and is useful in digesting our food. The cobra, however, has
the poison, which no doubt exists in the slimy saliva of all snakes,
specially concentrated and collected in two glands, one on each side
of its jaw. From each of these glands (_g_) a small canal passes under
the eye to the edge of the jaw (_c_), and opens immediately above a
large curved fang (_f_). This fang is fastened to a bone in the cheek
which moves easily, so that the poison teeth can be shut back and lie
close against the gum when they are not wanted, and when they are
wanted can be brought quickly down again. Though the fang looks round
like ordinary teeth, it is really flattened out like a knife-blade, and
then the edges are curved forwards so as to form a groove or, in some
snakes, a closed tube, down which the poison can run to the point.
[Illustration: Fig. 30.
Jaw of a Rattlesnake.
_ff._ Poison fangs; _g_, gland secreting poison; _c_, canal leading
from gland to base of fang; _t_, harmless tongue; _s_, saliva
glands.
]
Now when the snake wishes to strike its prey it raises its head, brings
down the fangs and drives them into the creature’s flesh, and at the
same time certain muscles press upon the poison gland, so that the
liquid poison is forced into the wounds. If, however, the fang was
fixed to the canal, the snake’s weapon would be gone if the point were
broken, so we find that the canal-opening lies just _above_ the tube of
the tooth, and behind are six small reserve teeth, covered by a tender
sheath skin, ready to grow up and take its place when wanted.
Should we not think that with such weapons as these the poisonous
snakes would conquer every enemy? Yet they, too, only have their fair
chance of life, for besides the destruction of their eggs other dangers
await them. The rapacious birds, with their feathery covering, their
horny and scale-covered legs and feet, and their hard beaks, will offer
battle even to a poisonous snake. The buzzard makes short work of our
common viper or adder, whose fangs, though fatal to small animals, are
not nearly so powerful as those of snakes of hot countries. Seizing the
viper with his claws in the middle of its body, the buzzard takes no
notice of its frantic struggles as, winding itself about his feet, and
striking wildly at his breast, his wings, and his scaly legs, it
“... doth ever seek
Upon its enemy’s heart a mortal wound to wreak.”
Keeping his own head well back out of danger, the bird lets the snake
exhaust itself, waiting only till he can give a fatal blow with his
beak upon its upraised head, and then, soon despatching it, tears it
to pieces for a meal. Nor is even the dreaded Cobra safe from danger,
for he finds his match in the powerful Adjutant birds (see p. 128), and
in the Indian Ichneumon or Mungoos, which attacks the snake boldly,
skilfully dodging the fatal stroke until it has broken the neck of its
enemy; while in Africa the bold Secretary bird is complete master of
the dreaded poisonous snakes of that country. In fact, there is little
doubt that every kind of snake, either in youth or age, falls a victim
to some kind of bird or beast; and even the poisonous sea-snakes,
which swarm in the tropical seas, probably find their masters in the
pugnacious saw-fish and the thick-skinned shark.
[Illustration: Fig. 31.
Common English viper (_Pelias berus_), with poison-fangs showing in
the open mouth, and the soft harmless tongue outstretched to feel.]
We see, then, that it is not without some struggle that these
cold-blooded reptiles have held their own in the world, nor is it
to be wondered at that only these four types--tortoises, lizards,
crocodiles, and snakes--should have managed to find room to live among
the myriads of warm-blooded animals which have filled the earth.
These four groups have made a good fight of it, and many of them even
make use of warm-blooded animals as food. The tortoises, it is true,
feed upon plants, except those that live in the fresh water, and
feed chiefly on fish, snakes, and frogs, while most of the lizards
are insect-feeders. But the crocodile, as he lurks near the river’s
edge, and the snake, when he fastens his glittering eye on a mouse or
bird, are both on the look-out for animals higher in the world than
themselves.
It is, perhaps, natural that we should shrink from cold-blooded
creatures, especially as they _seem_ to show very little affection.
Yet lizards, tortoises, and snakes can all be made to know and care
for those who are kind to them; while, as we have seen, the fierce
crocodile watches over and feeds her young, and the python coils
herself over her eggs, and will take no food till they are hatched.
Moreover, we can scarcely look at the quaint shell-covered tortoise, or
examine the heavily-mailed coat of the alligator, or the poison-fangs
of the snake, without admiring the curious devices by which these
animals have managed to survive in a world which once belonged to their
ancestors, before our present swarm of warm-blooded animals multiplied
and took possession of their kingdom.
[Illustration: THE EARLIEST KNOWN WATERBIRDS]
CHAPTER VI.
THE FEATHERED CONQUERORS OF THE AIR.
PART I.--THEIR WANDERINGS OVER SEA AND MARSH, DESERT AND PLAIN.
It is a warm sunny day in early spring, one of those few bright days
which sometimes burst upon us in April, just after the swallows have
come back to us, searching out their old nooks under the eaves, or
their old corners in the chimneys, to build their new nests. There
they are, clinging with their sharp claws to the edge of the cottage
thatch, while the impudent little sparrow, which has remained hopping
about all the winter long, chirrups at them from a neighbouring
apple-tree. Upon the grass-plot near a blackbird is pecking at a worm,
and from the wood beyond a thrush trills out his clear and mellow
song, accompanied from time to time by the distant cry of the cuckoo
calling to his mate. For it is the love-time of the birds; and as we
watch them flying merrily hither and thither in the bright sunshine,
we ask ourselves whether we must not have made a great leap on leaving
the cold-blooded snakes and tortoises, since now we find ourselves
among such merry, warm-hearted, passionate little beings, with their
beautiful feathery plumage, their light rapid flight, their love for
each other, their skill in nest-building, and their patient care for
their little ones.
And, indeed, we have come into quite a new life, for now we are going
to wander among the conquerors of the air, who have learned to rise far
beyond our solid ground, and to soar, like the lark, into the clouds,
or, like the eagle, to sail over the topmost crags of the mountains,
there to build his solitary eyrie.
Even the little sparrow, which flits about by the roadside, can laugh
at us with his impudent little chirp, as he flies up out of reach to
the topmost branch of a tree. And yet a glance at his skeleton will
show us that he has the same framework as a reptile, only it is altered
to suit his mode of life.
[Illustration: Fig. 32.
The Sparrow.
With wings raised, as in the skeleton on next page.]
True, his breastbone (_b_, Fig. 33) is deep and thin instead of flat,
and those joints of his backbone which lie between his neck and tail
are soldered firmly together, more like those of the tortoise, and he
stands only upon two feet. Yet this last difference is merely apparent,
for if you look at the bones of his wings you will find that they are,
bone for bone, the same as those in the front legs of a lizard, only
they have been drawn backwards and upwards so as to work in the air.
[Illustration: Fig. 33.
Skeleton of a Sparrow (from a specimen).
_q_, Quadrate bone, peculiar to reptiles and birds and some
_amphibia_; _b_, breastbone; _m_, merrythought or collar bone; _c_,
coracoid bone, over which the tendon works to pull up the wing;
_p_, ploughshare bone, on which the tail grows.
Wing bones--_a_, upper arm; _e_, elbow; _fa_, fore arm; _w_, wrist;
_t_, thumb; _ha_, hand.
Leg bones--_th_, thigh bone; _k_, knee; _l_, lower part of leg;
_h_, heel; _f_, foot.
]
There is the upper arm (_a_) answering to the same part of the lizard’s
front limb (p. 103); there is the elbow (_e_); then the two bones of
the fore-arm (_fa_); then the wrist (_w_), and a long hand (_h_), which
has lost almost all trace of separate fingers, except the little thumb
(_t_), which carries some feathers of its own, known as the “bastard”
wing. Now when the sparrow is resting he draws back his elbow, folds
his wrist joint, and brings the whole wing flat to his body. But when
he wishes to fly he stretches his arms out and beats the air with them,
and as his hand moves over most space, it is there that you will find
the longest quill feathers, which stretch right to the tip of his wing;
then next to these follow the feathers of his fore-arm, while those
of the upper arm are short and close to his body, and over all these
are the rows of covering feathers, which make the whole wing thick and
compact.
Here, then, we have the lizard’s front legs turned into a wonderful
flying machine in the bird, and this in _quite a different way_ from
the flying lizards which lived long ago, and which had only a piece of
membrane to flit with, like bats. And now what has happened to the hind
legs, the only ones used as legs by the birds? Look at the sparrow as
he clasps the bough with his toes, and you will, perhaps, be puzzled
why the first joint of his leg turns back like an elbow and not forward
like a knee. Ah! but that joint is his ankle, and the knob behind is
his heel (_h_), for the bones of his foot have grown long and leg-like;
and he always stands upon his toes, the rest of his foot forming a firm
support to hold his body up in the air. Look at the skeleton and you
will find his true knee (_k_) up above; and if you go to the Zoological
Gardens and watch the Adjutant birds, you will often find them resting
their whole foot upon the ground (see Fig. 34), and comical as it
looks, it will help to explain the curious foot and leg of a bird.
[Illustration: Fig. 34.
The Adjutant Bird.
Showing the foot resting from heel to toe upon the ground.]
Already, then, we see that the bird is using the same bones as a
reptile, though he uses them in a different way; and besides these
resemblances between the skeletons of birds and reptiles there are two
special ones easy enough for us to understand. We saw in the snakes
and the lizards that they have a separate bone (9, Figs. 23 and 26)
joining the lower jaw on to the head; now you will find this same bone
in the sparrow and in all birds (see Fig. 33), but in quadrupeds this
bone is not to be found, the part representing it being changed into
one of the bones of the ear. Again, the sparrow’s skull is joined to
his backbone by a single half-moon-shaped knob, which fits into a
groove in the first joint or vertebra. This also we find in reptiles,
while all higher animals have two such knobs, so that although they
can nod the head upon these, they cannot turn it upon them, and
consequently the first joint turns with the skull upon the second
vertebra.
These, then, are some of the reasons why Professor Huxley tells us that
though frogs and reptiles look in many ways so like each other, yet in
truth the frogs must be grouped with the gill-breathing and fish-like
animals;[88] while the cold-blooded reptiles, when we come to look
closely into them, are linked with such different looking creatures as
the bright and merry birds.[89] But we have also another and stronger
reason for thinking that reptiles and birds are distant connections;
for in those far bygone times (see p. 92), when the huge land-lizards
browsed upon the trees, the birds living among them were much more
like them in many ways than they are now. From their skeletons and
feathers which we find, we know that the strange land birds[90] which
then perched on the trees had not a fan-shaped tail made of feathers,
growing on one broad bone as our birds have now (_p_, Fig. 33), but
they had _a long tail of many joints like lizards_, only that each
joint carried a pair of feathers, and like lizards too they had _teeth
in their jaws_, which no living bird has. They must have been poor
flyers at best, these earliest known birds, for their wings were small
and the fingers of their hand were separate more like lizard’s toes,
two of them at least having claws upon them, while their long hanging
tail must have been very awkward compared to the fan-shaped tail they
now wear. For some time they were the only birds we know of, but later
on we come upon the bones of water-birds[91] telling the same story.
For some about the size of small gulls,[92] though they flew with
strong wings and had fan-shaped tails, still had teeth in their horny
jaws, set in sockets like those of the crocodile, while their backbones
had joints like those of fishes rather than birds; and with them were
other and wingless birds[93] rather larger than our swans, but more
like swimming fish-eating ostriches, for their breastbones were flat,
not thin and sharp like the sparrow’s, and they had scarcely any wings,
short tails, long slender necks, and jaws full of teeth, this time set
in grooves like those of lizards and snakes.
In these and many other points the early birds came very near to the
reptiles--not to the flying ones, but to those which walked on the
land. And now, perhaps, you will ask, did reptiles then turn into
birds? No, since they were both living at the same time, and those
reptiles which flew did so like bats, and not in any way like the
birds which were their companions. To explain the facts we must go
much farther back than this. If any one were to ask us whether the
Australian colonists came from the white Americans or the Americans
from the Australians, we should answer, “neither the one nor the other,
and yet they are related, for both have sprung from the English race.”
In the same way, when we see how like the ancient birds and reptiles
were to each other, so that it is very difficult to say which were
bird-like reptiles and which were reptile-like birds, we can only
conclude that they, too, once branched off from some older race which
had that bone between the jaws, that single neck joint, and the other
characters which birds and reptiles have in common.
But long ago they must have gone off each on their own road, the
reptiles filling the world for a time, flying and walking and swimming,
till they found at last that creeping was their most successful way of
life; the birds on the other hand becoming more and more masters of
the air and the water, so that, while keeping the same bones and parts
as the reptiles, they have grown into quite different beings in their
form and habits, giving up the long-jointed tail of the _Archœopteryx_,
or ancient-winged bird, for the compact feathered fan which helps to
balance them in their flight, and the teeth of the water-birds for the
sharp and horny beak, which, together with their claws, is their chief
weapon of attack and defence now that they have employed their front
limbs as wings.
Nor shall we have far to look for the secret of their success in life.
Just as the reptiles have an advantage over the naked frogs and newts
by having strong scaly coverings in their skin, so the birds have an
advantage over the reptiles in that beautiful feathery plumage which
covers their body, and the powerful muscles which work their limbs. For
it is by means of these that they have been able to move quickly and
travel far, and to develop that bright nervous intelligence which has
grown more and more active as they have been carried into fresh scenes
and experiences, overcoming new difficulties and enjoying new pleasures.
Remember for a moment how weak the lizard’s limbs are, so that his
body always drags upon the ground; and then look at the bird’s tight
grasp of the bough and the rod-like legs which raise his body above
it. Watch him as he beats the air with his wings, rising and sinking,
turning and swerving at will, and you will see that he has earned
freedom, strength, and active life, by means of the strong muscles
which move these legs and wings, and the feathers which provide him
with an instrument for beating the air. Feel a sparrow’s fat little
breast, or see how much meat comes off the wing and breast of a pigeon,
and then, if you consider that all this flesh is muscle used for moving
his wings, you will not wonder at his easy flight. For the muscles of a
bird’s breast often weigh more than all his other muscles put together,
and while one enormous mass of muscle in front of the breast works to
pull down the wing, another smaller one, ending in a cord or _tendon_,
passing like a pulley over the top of a bone (_c_, Fig. 33, p. 126),
pulls it up, so that by using these, one after the other, the bird
flies.
But where have the feathers come from,--those wonderful beautiful
appendages, without which he could not fly? They are growths of the
bird’s skin, of the same nature as the scales of reptiles, or those
on the bird’s own feet and legs; and on some low birds such as the
penguins they are so stiff and scale-like that it is often difficult
to say where the scales end and the feathers begin. All feathers, even
the most delicate, are made of horny matter, though it splits up into
so many shreds as it grows that they look like the finest hair, and Dr.
Gadow has reckoned that there must be fifty-four million branches and
threads upon one good-sized eagle’s feather.
When these feathers first begin to grow they are like little grooved
pimples upon the flesh, then soon these pimples sink in till a kind
of cup is formed all round them, and into this cup the soft layer
just under the outer skin sends out fibres, which afterwards form the
pith. Round these fibres rings of horny matter form, and then within
these rings, in the grooves of the soft pimple, the true feather is
fashioned. First the tips of the feathery barbs, then the shaft, and
then the quill appear, as the feather grows from below, fed by an
artery running up into the pimple; till at last, when the whole is
full-grown, the quill is drawn in at the base, and rests in its socket,
complete.
Some of these feathers are weak and soft, with slender shafts and loose
threads growing all round them, and these are the downy feathers which
lie close to the body and keep the bird warm. Others, which cover the
outside and form the wings and tail are flat, with strong quills and
shafts, and a double set of barbs growing upon each shaft; and if you
look at these wing feathers under a strong microscope you will see
that they have a special arrangement for helping them to resist the
air. For not only have all the little featherlets or _barbs_ rows of
other featherlets or _barbules_ growing upon them, but these again are
covered with fine horny threads, often hooked at the tip, which cling
to the next barb, so that the feather is woven together as it were, in
a close web, and if you strike it against the air you will find that it
resists it strongly.
Now in a bird’s wing the feathers are so arranged that they lap one
under the other from the outside of the wing to the body, so that
when the bird strikes downwards they are firmly pressed together, and
the whole wing, which is hollow like the bowl of a spoon, encloses a
wingful of air, and as this is forced out behind, where the tips of the
feathers are yielding and elastic, he is driven upwards and forwards.
When, however, he lifts his wing again, the feathers turn edgeways and
are separated, so that the air passes through them, and he still rises
while preparing for the next stroke. All this goes on so rapidly that
even the heron makes 300 strokes in a minute, and the wild duck 500,
while in most birds they are so rapid that it is impossible to count
them; yet all the while the little creature can direct his flight where
he will, can pause and direct his wings to the breeze so as to soar,
can swoop or hover, wheel or strike, guiding himself by the outspread
tail and a thousand delicate turns of the wing.
All this complicated machinery, however, would not have served the
bird much if his body had been as heavy, and his blood as cold, as
those of the lizard and the crocodile. But here he has made a great
step forward. In the first place, he has a heart with four chambers,
two on the right side and two on the left; and while one of those on
the right side receives the worn-out blood from the body and pumps it
_to_ the lungs to be refreshed, one of those on the left side receives
it _from_ the lungs when it is refreshed, and the other pumps it into
the arteries to feed the body. So here we see for the first time among
our backboned animals a creature whose good and bad blood are never
mixed in the heart (compare pp. 23 and 76), but it gets all the benefit
possible from its breathing, and the blood is kept fresh and pure.
Moreover, a bird’s lungs are large, and are continued into several
large air-sacs, which in their turn open out into tubes which carry
air actually _into the bones_, many of which are hollow instead of
containing marrow like those of other animals.[94]
And now we begin to see how wonderfully these little creatures are
fitted for flying. With all this air within them, not only is their
blood kept hot by constant purifying, but their bodies are much lighter
than if their bones were solid, and they can present a much broader
surface to float upon the air without increasing equally in weight.
Meanwhile, their feathery covering prevents the cold air around from
chilling them, so that they are not only warm-blooded animals, but
actually warmer-blooded even than ourselves.
Thus, then, Life has spread her feathered favourites over the world.
For them there are no limits except the extreme depths of the
water below, and the height beyond the atmosphere above. Wherever
air-breathing creatures can go, there some bird may be found. On the
dizzy ledges of inaccessible cliffs, on the wide bosom of the open
ocean, on the sandy wastes of the desert, in the tops of the highest
trees, on the cloud-capped peaks of the mountains, diving or swimming,
flying or soaring, running, perching, darting, or sailing for miles and
miles without one moment’s rest, they find their way everywhere, and
there is no spot from the icebound countries of the Arctic zone to the
warm bright forests of the tropics where they do not penetrate; while
their sharp eyes, kept free from dust and harm by a third eyelid moving
rapidly sideways,[95] see far into the distance, and thus as they
soar into the sky they have a power, possessed by no other animals,
of overlooking a wide domain. Nor have they been obliged, like the
reptiles, to take up strangely different forms to suit their various
habits, for so wonderfully does their body meet all their wants that
very slight changes, such as a broad body and webbed feet for the
swimmers, long bare legs for the waders, a long hind toe for grasping
in the perchers, and sharp claws and beak for the birds of prey, fit
each one for his work, and are some of the chief distinctions we can
find between them.
Even the heavy running birds, the Ostriches of Africa, the Rheas of
South America, and the Emus and Cassowaries of Australia, still remain
truly bird-like, though their wings are unfit for flight. True, their
breastbones are flat instead of keel-shaped, for they have no need of
strong muscles to move their wings, which now serve only as sails to
catch the wind as they run, and in many other ways they are an older
type than our flying birds; but their wing bones are formed as if
they were used for flying, and their feathers, though loose and downy
because they have no little booklets, are like those of other birds.
[Illustration: Fig. 35.
The Ostrich[96] at full speed.]
Strong powerful creatures they are, even in confinement. Yet how little
can we picture to ourselves, when we see the Ostrich trotting round his
paddock in the Zoological Gardens, with his wings outspread, what he is
when he courses over the free desert!--
“Where the zebra wantonly tosses his mane,
With wild hoof scorning the desolate plain;
And the fleet-footed ostrich over the waste
Speeds like a horseman who travels in haste.”
There the soft pads under the _two toes_ of each foot rebound from
the yielding sand as his well-bent legs straighten with a jerk one
after the other, making his body bound forward at full speed. Then he
raises his wings, sometimes on one side, sometimes on both, to balance
himself, and to serve as sails to help him; and with this help his
stride is sometimes as great as twenty feet, and he dashes along at the
rate of twenty-six miles an hour. He is not so heavy as he looks, for
many, of his bones are hollow, his feathers are downy and soft, and his
wing-bones are small; and it is to his featherless thighs that you must
look for the strong muscles to which he trusts for all his speed, as
with outstretched neck he bounds across the plain.
If we go back to long bygone times, before the lion, the leopard, and
other ferocious animals found their way into Africa, we can imagine
how this great running bird took possession of the land and became too
heavy for flight; while as time rolled on, he gained that strength of
body and leg which now is his great protection as he dashes along, his
four or five wives following in his train. The ostriches can travel
over wide distances from one oasis to another, feeding on seeds and
fruit, beetles, locusts, and small animals, and fighting fiercely with
legs and beak if attacked. And when the springtime comes the wives lay
their eggs in a hole scooped in the sand, or often in some dry patch of
ground surrounded by high grass, till sixteen or twenty are ready; and
then they take their turn (the father among the rest) of sitting upon
them, at least at night, even if they leave them to the heat of the sun
by day. And when six weeks have passed the father grows impatient,
and, pressing the large bare pad in front of his chest against each egg
in turn, breaks it, pulls out the membranous bag with the young bird
in it, shakes him out, and, swallowing the bag, goes on to another. In
this way the whole downy brood are soon set free, and begin picking up
small stones to prepare their gizzard or muscular second stomach for
grinding, while their parents scrape the sand and find and break up
food for them.
So the ostrich lives its life in Africa, from Algeria right down to
Cape Colony; while its smaller and lighter-coloured relations, the
Rheas, with their _three-toed_ feet, course over the plains of Paraguay
and Brazil, on the other side of the Atlantic, often swimming from
island to island, in the bays or across the rivers, but quite unable to
fly with their soft hair-like feathers, though their wings are larger
than those of the ostrich. Then when we turn to the East we find other
running birds; the Cassowary, with its three toes, its horny helmet,
its five long single feathers, and its five naked pointed quills in
the place of a wing, feeding on fruit and vegetables in New Guinea, or
sharing the dreary scrubs of Australia with the almost wingless Emus
wandering in pairs, the only constant married couples among the running
birds.
Nor is New Zealand left without a representative of this family, for
there we have the curious little Apteryx or Kiwi (Fig. 36), with its
thick stumpy legs, its long beak, and its soft downy body, under which
are hidden its aborted wings. Perhaps it is because he is small and
insignificant that the apteryx has lived on till now, crouching under
the bushes by day and creeping about in the twilight, thrusting his
long nose-tipped beak into the damp ground to draw out the worms. For
long ago, though in the memory of man, as we learn from the traditions
of the Maories, other wingless birds called Moas,[97] which were six
or seven feet high, lived in New Zealand, and had fierce fights with
the natives. We find their bones now, often charred from having been
cooked in the native ovens, and when they are put together they give us
skeletons which show that these birds must have been as formidable as
that great bird of Madagascar, the Æpyornis, whose gigantic bones and
eggs, three times the size of ostrich eggs, have been found, though the
bird itself has never been seen.
[Illustration: Fig. 36.
Wingless birds of New Zealand.
The giant Moa (_Palapteryx_) and the tiny Apteryx. The Moa is no longer
to be found alive.]
But these are gone now, and their relations the Emus are fast following
them: for however well these flightless birds may flourish on the
broad plains and deserts, where only their wild companions are around
them, they are sadly at the mercy of man. The proud eagle can fly far
beyond the reach of the hunter’s gun; the little lark, if she be only
wary enough, may trill out her song in the blue vault above and leave
the cruel destroyer far below; but the emu and the cassowary, the rhea
and the ostrich, have lost the power to leave the earth; and if it were
not that we prize the two last for their feathers, they, too, like
their companions, might live to rue the day when they became runners
instead of conquerors of the air.
* * * * *
It is very different, however, with the water-birds, for they have not
only kept the power of flight, but have gained the double advantage
of also floating safely on the water. Look at our common wild duck.
We might have taken him just as well as the sparrow for our type of a
bird, and yet while the sparrow leads a land life in the trees, the
duck’s home is on the water, and many of his relations live cradled on
the open ocean.
See his broad boat-like body which floats without any effort of his;
notice how closely it is covered with short thickly-grown feathers,
which protect him from the chilly water, while he keeps them well-oiled
with his beak, from an oil-gland which all flying birds have at the
base of the tail. Watch how he swims, drawing his webbed foot together
as he brings it forward, and spreading it like a fan to strike the
water as he drives it back. Then, as he feeds, watch him gobbling in
the mud and then shaking his head as he throws his beak up in the air.
For he, like all ducks and geese, has a set of thin horny plates inside
his broad bill, and they sift the mud, while the tender tooth-like
edges of his beak and tongue feel out the suitable morsels.
All this time he is a water animal, but when he rises and flies he is
also master of the air, for his strong wings carry him stoutly, so that
he can migrate from one pool to another; or in winter, when the pools
are frozen, to the open sea. He is by no means the best flyer of his
family, and yet he is spread over Europe and North America, and even as
far east as Japan, while his ocean-loving cousin, the eider-duck, lines
her nest and lays her eggs high up in Arctic latitudes, and dives and
swims in the open ocean. So too his relations, the wild swans and geese
which wander in the lakes and swamps of Lapland, Siberia, and Hudson’s
Bay, feeding on water-weeds, worms, and slugs, build their nests in the
summer in the far north, and then fly thousands of miles southwards to
their winter homes, their strong wings whirring in the air as they go.
Yet these are scarcely as true sea-birds as the divers, the Guillemots
and Puffins, the Auks and Grebes, which swim out all round our coasts,
and dive deep down to feed on the fish below. How clumsy they are on
land and how skilful in the water! You may see numbers of guillemots
and puffins in summer on the high cliffs of the north of Scotland, or
of Puffin Island in the Menai Straits; the guillemots laying their
eggs on the bare ledges, and the puffins in holes which they burrow
in the cliffs face; and they sit so doggedly upon their nests, and
shuffle and hop along so awkwardly, that men climbing up, or let down
by ropes from above, knock them over as they go. But wait till the
eggs are hatched, and the little ones have broken out of their shelly
prison, each one cracking his shell from inside by means of a little
horny knob, which all baby birds have for this purpose at the end
of their beak, and which falls off when they are fairly born. Then
fathers, mothers, and young ones, able to take care of themselves as
soon as hatched, launch out into the open sea in August, and there is a
sight of diving and swimming and fishing grand to behold. The awkward
legs, placed so far back on their body, now serve as powerful oars and
rudders to drive their smooth satiny bodies through the water. Their
thin narrow legs cut through the waves like knives, while their short
stumpy wings, closely laid against their down-covered bodies, keep them
from being chilled, and so do the air-bubbles which are entangled in
their short thick feathers, and which give their backs the appearance
of being covered with quicksilver when they dive[98] after the fish
below.
And then when the winter comes, those which have bred in the north
fly and swim southwards to our coasts, where they are joined by the
true divers and grebes which have come from the rivers and estuaries,
where they have made their nests on some reedy bank or floating upon
the water, and lived till their young ones are strong. This is their
seafaring time; and whether near the shore, or miles out at sea, they
dive and swim and make the ocean their home till spring comes round
again.
[Illustration: Fig. 37.
A Group of Sea-Birds.
1. Cormorant. 2. Black-winged Tern. 3. Gulls. 4. Puffins. 5. Guillemots.]
Still all their roving is done chiefly by swimming, and they leave it
to the Gulls and Petrels, the Terns and the powerful Cormorants and
Gannets, to fly hither and thither over the wide sea. These birds have
indeed reached the climax of a seafaring life, with their powerful
wings, their sharp and often hooked beaks, and their short legs. They,
too, feed upon the water, coming up with a fish in their mouth, but
they do not dive under and swim like the guillemots. On the contrary,
flying is their forte; they swoop down, and scarcely have they gone
a few feet under water than they are up again, skimming on the waves
as they swallow their prey, which may be anything from dead floating
creatures to living fish which have ventured too near the surface. Yet
they swim well too, and though the common gulls rarely go more than
twenty miles from the shore, they are quite at home on the open ocean,
and there is no habitable part of the globe without them. Still more
venturesome are the petrels:--
“Up and down, up and down,
From the base of the wave to the billow’s crown,
And amidst the flashing and feathery foam
The stormy petrel finds a home.”
They are smaller and lighter than the common gulls, and are never so
happy as when darting over the foam of an angry sea, while their more
delicate relations, the Terns or sea-swallows, with their long pointed
wings and forked tails, are taking shelter in the quiet bays.
Lastly, king among all sea-flying birds is the gigantic petrel, the
Albatross. What a grand fellow he is when he is once on the wing,
though he has some difficulty in starting. Flying onward, onward,
without resting day or night, his pure white body near down to the
water, his large head and short thick neck slightly bent, and his
long, narrow, black wings, often measuring ten feet from tip to tip,
widely outspread, he beats a few powerful strokes, and then sails
along, using his head and tail as rudders to turn his wings to the
wind. Often he will follow a ship for days, sailing round and round in
circles, and yet keeping easily ahead, while all the time his bright
eye watches the water to catch every chance of food. Jelly-fish,
cuttle-fish, and real fish of all kinds, together with any dead
creatures he may find afloat,--all is food to him, and his powerful
beak will cut through the toughest morsel. For days and days he will
fly on, never tiring, and feeding as he goes; and if he alights for
a time upon the water he rises with difficulty, unless the waves are
high and bear him up on their crests; and when he comes to rest it is
on some island in mid-ocean, where he seeks a mate, and brings up his
nestlings either on the low ground or on the top of a high mountain, in
a hollow lined with grass and moss. Truly, if we look at the far-flying
albatross we must acknowledge that the wings of a bird have given him
the command of the sea as well as the land.
[Illustration: Fig. 38.
Albatrosses and Penguins.]
He forms a strange contrast to the curious stunted bird form which we
may find in those same islands where the mother albatross lays her
eggs. For there, in the islands of the South Pacific, close by the side
of the albatross nest, are whole groups of strange-looking birds, the
Penguins, with their fat, white, feathered breasts, their dark head
and beak, their curious hind legs set right at the end of their body,
and their small paddle-like wings, covered with short stiff feathers,
quite useless for flight. We have come upon a strange story here, for
our penguin is a low relation, of the guillemots and puffins whom we
left in the north, and, like the great northern auk, which has now been
extinct for many years, he has lost the use of his wings. He has no
dangerous enemies on these rocky inaccessible islands, where he and his
companions form dense penguin rookeries upon the ground, unless it be
the large gulls or skuas which steal the eggs. Nor has he any need for
flying, for the sea is all around him, and even if he wishes to migrate
to warmer waters in winter, he does so by swimming. Therefore we find
that his wings are lost to him for any flying purpose, and nothing
can be more awkward than he looks, shuffling or hopping along with
outstretched arms, like a fat baby, till he comes to the water’s edge.
But when he dives in and swims it is quite a different matter. Then his
easy wavy motion, like that of a seal, shows at once that his stumpy
imperfect wings are excellent fins, while his feet serve him both as
oars and rudders.
Thus we have traced our swimming and web-footed birds to their
extreme types--the strongest flyer in the albatross, and the lowest,
most fish-like bird in the penguin; while, if we were to follow the
pointed-winged frigate-bird in his flight, or see the pouched pelican
in his home, we should find another group of these web-footed birds,
no longer merely standing upon rocks, but perching upon the boughs of
trees, and building their nests by the side of rivers in warm countries
nearly all over the world, or among the mangrove bushes of the tropical
islands.
* * * * *
And now, if we return to our northern shores and pause upon the broad
wet sands at low tide, we may chance to find whole flocks of active
little birds hovering and running and wading in the water, or pecking
on the sands; and the double-noted whistle of the Curlew, or the
musical cry of the Peewit (or Lapwing), tell us at once that they are
“waders,”--birds with bare legs, flat toes, and long beaks, which drop
down on the muddy flats by the sea, seeking their food at the edge
of the water. There they are, Curlews and Dunlins and Sandpipers,
Plovers and Knots, Oystercatchers feeding on mussels and limpets, and
Turnstones tilting up the lumps of mud to find food beneath. One and
all they are running hither and thither, to seize here a shrimp or
sandhopper or a tiny fish, there a worm or a sea-slug; making the most
of their time before the sea comes up and covers their feeding ground.
[Illustration: Fig. 39.
A group of Wading Birds.
1, Stilt; 2, Avocet; 3, Peewit; 4, Dunlins; 5, Curlew Sandpiper;
6, Sanderling; 7, Oystercatcher; 8, Curlew; 9, Turnstone.]
Here we have no webbed feet or legs set far back, but three long, flat,
straight toes, well fitted for walking on marshy ground and treading
lightly on water-plants, and slender bodies well balanced on long thin
legs, which move so quickly as they run that you can scarcely see them;
while, when they fly, their long wings carry them lightly through the
air, with their legs stretched out behind.
[Illustration: Fig. 40.
The Flamingo.
A duck-billed and web-footed bird among the waders.]
What connection can there be between these active light little beings,
and the broad-bodied web-footed swimmers? Go to the Zoological Gardens,
and look at the Flamingo, with his long legs and curious curved
beak. He is of the true swimming type, with his webbed feet and his
sieve-like bill, with its rows of horny strainers like the geese; yet
he feeds by wading in salt-water lakes and pools on the sea-shore,
raking the bottom for food, and showing how a swimmer and a wader may
once have had the same starting-point, before the one went out to sea,
and the other in to shore. And then when we come back to our own little
waders, and learn that they visit the sea, and feed upon the wet sands
from the autumn to the spring, and then fly inland to build their nests
in the damp meadows, feeding on earthworms, slugs, and insects of the
land, we can see what an advantage this double life must be to them.
Notice, too, how shy and timid they have become from living among other
animals, and watching for every danger. Try to get near one, and see
how it will run on, turning its head hither and thither to watch, and
at last will rise and be out of sight in no time. Or go and look for
plover’s eggs on the swampy grounds in our northern counties in the
early summer, when
“... from the shore
The plovers scatter o’er the heath,
And sing their wild notes to the listening waste.”
The mother will no sooner see you than she will crouch down, running
along a rut, and then move slowly away with a drooping wing as if
wounded, hoping to make you follow her and pass by the little earthy
hollow where her precious eggs are lying. The experience of life has
made these little ground-nesting birds very intelligent, since they
have had a land as well as a watery home, and the little moor-hen,
which, like the rails and crakes, has taken entirely to a freshwater
life in ponds, brooks, canals, and rivers, has learned to hide her nest
so skilfully, and to dive and swim so cleverly, that even a trained
water-spaniel often loses her when close upon her home.
And as the swimmers have their large birds in the albatross, so the
waders too have theirs in the Herons, the Storks, and the Cranes.
Who does not know how the storks fly in flocks to the sunny south
in winter, and come back in the spring to build their nests in the
chimneys of the houses of Holland and Germany, feeding on the banks of
rivers, and in the fens on lizards, fish, frogs, and water-snakes; or
how the cranes pass their summer in the stormy north, and their winter
among the old ruins of Egyptian greatness? But the herons remain with
us all the year, feeding on shrimps and crabs on the weed-covered
shores, or more often in ponds and lakes upon frogs, water-rats, and
fish. How patiently you may see a heron stand with his head slightly
bent, still and motionless, till a fish passes by! Then quick as a
flash of lightning, his head darts forward, impaling or seizing the
prey in the strong beak, and he is off to eat it at his leisure. Thus
he lives a solitary life all the year until the springtime, when he
flies off to some group of lofty trees where for generations his family
have built their nests, and, meeting with his fellows, piles up huge
masses of sticks and grass among the tangled boughs.
And there the young herons are hatched and fed in the ancient heronry
till they can perch and fly. For now among the waders we have come
to birds that can perch, as we did among the swimmers (see p. 148).
The heron has no longer the three-toed flat foot of the wader, with
perhaps a slight spur behind, but a large fourth toe, with which he
can grasp the bough; and as he flies across the country, uttering his
strange harsh cry, often rising even higher than the hawks and falcons,
and alighting on the top of some tall tree, few people would think of
classing him among the waders, so like is he to those true land-birds
whose life is spent in the air and whose home is in the trees.
[Illustration: THE FIRST KNOWN LAND BIRD]
CHAPTER VII.
THE FEATHERED CONQUERORS OF THE AIR.
PART II.--FROM RUNNING TO FLYING: FROM MOUND LAYING TO NEST BUILDING:
FROM CRY TO SONG.
So the deserts and plains have their ostriches and cassowaries, the
open ocean its albatrosses and its penguins, the shores their ducks,
gulls, and waders, and the little inland pools and marshes their
water-birds, which come there to build their nests and seek for food.
Yet these are after all not by any means the larger portion of the bird
world. It is in the woods and forests, the moors and pastures, on the
solitary mountain peaks above, and in the snug valleys nestling below,
that we find the myriads of song birds and game birds and birds of
prey; of climbing birds such as the Woodpeckers; swiftly sailing birds
such as the Swifts, cooing Wood-pigeons and cawing Rooks; terrible
Eagles and Hawks, or sweet-singing Nightingales and Thrushes.
All these birds have had a very different education from that of the
far-sailing albatross or the running ostrich. They have grown up in
the midst of innumerable dangers; for enemies of all kinds--beasts and
reptiles and other birds--live all round about them, making food scarce
and destroying their young, so that of the millions born into the world
thousands upon thousands perish every year before they grow up. We
should expect, then, that these land birds would learn many devices for
protecting themselves and their little ones. The guillemot can afford
to lay her egg on the bare rock, for few animals can climb the high
cliffs where she makes her home; and the penguin on her solitary island
may lay hers in the mud on the ground. But the little lark must look
carefully for high grass in which to build her nest, and the rook must
weave a strong basket-work of twigs to make a home for her nestlings in
the top of the high elm.
Moreover, the land birds cannot sleep safely on the ground, where
weasels and stoats, foxes and wild cats, prowl by night in search of
prey; they must take their rest on the boughs of the tall trees and
cling on by their toes even when they are in the deepest slumber. This
they could not do if they had the stumpy cushioned feet of the ostrich,
the webbed feet of the duck, or the flat three-toed feet of the waders.
It is the fourth toe turned backwards, and growing very long in many
of the perching birds, which gives them their grasp; while a special
muscle, beginning behind the thigh (_th_, Fig. 33, p. 126), coming
round over the front of the knee (_k_), and then passing behind the
heel (_h_), and on to the toes, keeps them bent. Picture for a moment
this muscle sending its cords or tendons from behind the leg over the
knee, and then drawn back by the heel, and you will see that the more
heavily the bird sleeps, pressing upon its legs, the more the knees
will be bent forward, the tighter the cord must be stretched, and the
stronger the grasp will be upon the bough.
Again, as to food, the land birds will be more closely pressed than
those which can at all times fish in the sea. There is great scarcity
of land food in the winter, while in summer whole flocks of newly-born
fledgelings are clamouring for their daily bread. So we shall find
that every kind of eatable thing is turned to account, and we have
among land birds seed-eaters, vegetable-feeders, and fruit-eaters;
insect-devourers, and feeders on slugs and worms and snails; and
flesh-eaters which feed on other birds, or on mice, bats, and larger
animals; while large flocks of birds of all kinds visit different
parts of the earth in the various seasons, going north in summer to
build their nests, and south in winter, in search of food. All these
birds live chiefly in the air; while on the ground there are the
scratchers--fowls, partridges, turkeys, and grouse, which rake out
the hidden grains, and rarely rise into the air except when they are
frightened, or to roost on the trees at night. And between these ground
birds and the true tree birds we have the doves and pigeons, some of
which feed on fallen seed and grains, and others on fruit. And each
and all of these birds have some difference in beak and claw, in their
manner of nest building and rearing their young, and in their habits
and ways, which enables them to make the most of their lives.
* * * * *
Even nest building does not come to all land birds by nature, and, as
we shall see, it depends very largely on the habits and the structure
of the builders. Thus the Partridges, and their relations the Pheasants
and Grouse, lay their eggs in the thick grass of the meadows or among
the heather, and at most sometimes scratch together a few dry grass
blades for a bed. In this they remind us much of the ostrich family,
which also scrape a hole in the ground for their eggs and scratch
food for their children; and in fact there is a group of curious
heavily-flying birds, called Tinamous, in South America, which are so
like quails and partridges on the one hand, and ostriches on the other,
that they lead us to wonder whether it was not from the ancestors of
such birds as these in ancient times that the heavy running birds
started on one road, while the lighter and swifter birds took to the
wing.
The wings of all the scratching birds are even now short and round, and
their flight is feeble. Their chief home is on the ground, where they
crouch among the thick herbage when the keen-eyed hawk is hovering
overhead, never taking to their wings till no other chance is left
them. The mother partridge runs many dangers as she sits upon her
dark-coloured eggs in some sheltered spot, for weasels and stoats will
attack her and steal her eggs if she leaves them for a moment, or kill
her herself if they can take her unawares in the dark night. She could
never hope to rear her young ones if they did not come out of the egg
well covered with down, and able to run and pick by her side while she
and the father scratch the ground with their short blunt claws to get
ant-cocoons, and later on worms and insects for them.
Yet so well does scratching answer, in getting at buried food such as
other birds cannot find, that there are a large number of these ground
birds all over the world. The Guinea fowls of Africa, the spurred
Peacocks, Pheasants, and Jungle fowls of India (from which last our
tame fowls probably come), the wild Turkeys of America, the Quails
which live in all parts of the old world from Australia to England,
and the Ptarmigans of our northern countries, which put on their white
plumage in winter--all these show how advantage has been taken of every
nook in which ground birds could find shelter. We find them hiding in
thick jungles and shady woods, or even in open ground among high grass
and corn, scratching mother earth for their daily food; washing not in
water but actually in the dust, by rolling in it, and then shaking it
off; escaping many dangers by wearing a plumage very much the same in
colour as the different grasses and leaves among which they hide; and
feeding on insects, worms, and seeds, and whatever they can find upon
the ground or under it.
[Illustration: Fig. 41.
Brush turkeys[99] and their egg mounds.]
And when we travel far off to Australia, we find ground birds which
do not even sit on their eggs, nor take care of their young, but
leave them as reptiles do to be hatched in the sun. The Brush-turkeys
and Megapodes of Australia and the islands near, and the Maleos of
Celebes--all of them scratching birds--come out of the thick jungle
and lay their brick-red or pale-coloured eggs on the shore, never
taking any more notice of them. The maleos simply scratch a hole in the
sand and bury the eggs, the brush turkeys and megapodes[100] scratch
together all kinds of rubbish and dead leaves, carrying them in their
long curved claws, and adding them to the heap till they have made a
mound sometimes more than seven or eight feet high, and twenty feet
across at the base; an astounding size, when we consider that the
brush turkeys are not nearly as large as a good-sized turkey, and the
megapodes not larger than hens. It is to these mounds that the mothers
come about every ten days, and lay an egg _upright_, till each has laid
eight or nine, and then she comes no more; but after many weeks the
little chicks work their way out fully fledged, and fly away to get
their own living. The probable reason, Mr. Wallace tells us, for this
curious habit of mound-building, is that the eggs are so large that the
mother can only lay one every ten days, so that if she sat upon them
she would be worn out with fatigue and want of proper food before they
were all laid and hatched.
* * * * *
We see then that the scratching birds live nearly all over the world,
yet, no doubt, it is a disadvantage to them that in their ground life
they have become so heavy that they cannot fly so lightly or so far as
their near allies, the pigeons, which, like them, feed on the ground.
For the Pigeons have already made many steps forward in life. Their
wings are strong, so that they can fly for great distances; their
toes are slender and well fitted for perching; and though it is true
that our tame pigeons and the wild rock-pigeons from which they are
descended do not build nests, but lay their eggs in dovecots or church
towers, or, if they are wild, in holes in the rocks, yet the beautiful
blue-gray wood-pigeon, with her pure white collar and soft cooing note,
builds a nest in the trees--
“The stock-dove builds her nest
Where the wild flowers’ odours float;”
though it is but a rough one, made, as well as her weak feet and bill
can do it, of a few stout twigs, laid so loosely that her two little
white eggs may be seen from below, and even sometimes fall through.
[Illustration: Fig. 42.
Wood-pigeon on her nest.]
Yet, though but a beginner in nest building, she is a true tree bird,
and her little ones are born naked and helpless, far out of reach of
the ground, and must be fed and cared for till they can fly. So she
feeds them with infant pap from her own mouth. The “crop” or bag in
which the partridge or hen stores the grain she picks up is large and
single; but the pigeon has two bags, one on each side of the throat,
and when she is feeding her young these bags secrete a large quantity
of milky fluid, which, mixing with the tender shoots she has pecked
off in the spring, or with the oily seeds she has gathered for her
autumn brood, makes a soft food, which she pours into the mouths of her
nestlings till they fly and feed themselves.
In the pigeons, then, we are gradually rising from the ground
birds,--where the father generally has many wives[101] and the young
ones run as soon as they are hatched,--to the tree birds, where father
and mother, taught by the helplessness of their brood, share the cares
of nest building and the pleasures of love. Even the pigeons did not
all at once become tree birds, for we have them in all stages now from
the ground to the air. Many years ago, in the island of Mauritius,
there were heavy flat-breasted pigeons, the Dodos, which lived entirely
on the ground without the power to rise, so that when the Dutch settled
there, bringing rats with them in their ships, the Dodos soon fell
victims to the intruders, and now there is not one left. Again, in New
Guinea now, there are ground pigeons which fly heavily and slowly, and
only go to the trees to roost. Then come our own tame pigeons, the
rock-pigeons, and the stock-dove which builds in boles in the trees;
and then our wood-dove and his relations, with their rude nests and
their mixed food of grain and grass. And among these are the wonderful
long-winged passenger pigeons[102] of America, which fly in flocks of
hundreds of thousands through Ohio, Kentucky, and Indiana, in search of
nuts and seeds, breaking down the boughs of the trees by their weight
where they alight, and then darkening the whole sky as they start off
again in a succession of vast multitudes to another forest where beech
nuts, acorns, and chestnuts are plentiful, or to the rice-grounds of
Carolina, to take their fill.
And, lastly, we come to the beautiful green fruit-eating pigeons of
India and the East--the feeders on nutmegs and palm-fruits and juicy
berries of all kinds. These are true tree birds, difficult even to
find, so like are they to the colour of the leaves; yet they still
build the loose untidy nests of their kind.
Nor need we wonder at this, for fine nest building requires both
strength and delicacy in the bill and feet; and the next group of birds
escapes it altogether by finding or making holes in trees and banks,
and lining them with moss or leaves. This group is the Climbers, which
come, as it were, between the ground birds and birds of active flight,
for they clamber swiftly up the trunks and over the branches of trees
in search of fruits and insects, seldom going down to the ground, but
flitting from tree to tree to find fresh hunting grounds.
[Illustration: Fig. 43.
The great green Woodpecker.[103]]
What is that green object, about as large as a small squirrel, which we
see mounting the trunk of one of the elm trees, as we lie resting on
the moss in some quiet wood? There it goes, dodging now to this side,
now to that, with its head well lifted and its stiff tail bent against
the trunk. It is the green woodpecker at his work. His long large feet,
with toes divided _in pairs_, two in front and two behind, take firm
hold of the tree with their sharp claws; his breast, which is flatter
than that of most birds, lies close against the bark, as he mounts
by a number of rapid jumps, which are made by pressing his strangely
stiff horny tail against the trunk, while he hops forward with both
feet, making a slight rustling noise, and moving so fast that it is
difficult to see how he does it.
Now he pauses; it is to try a suspicious place in the bark, and tapping
it with his beak he finds that it gives a hollow sound. This tells
him at once that it is rotten, and there is an insect within; and
pecking, a hole with rapid blows of his chisel-like bill, he inserts
his narrow bill, and darts a long gluey tongue, with barbed tip, into
the dark passage, bringing out the intruder, which is swallowed in a
moment. A strange tongue this is of the woodpecker, for it has two
long bony branches at its roots, and each one is like a bow bent under
and round the back of the bird’s head, and as these bows are tightened
or slackened by the slender muscles the tongue is drawn in, or thrust
out to an extraordinary length. Moreover, it has at its tip a horny
covering beset with tiny barbs, and every time it goes back to the
mouth these are bathed in gluey slime to catch the next insect it may
meet. Nor is the woodpecker obliged always to drill for his food. The
tiny ants, as they wander up and down the trees, the beetles and bees
settling on the branches--all may fear this gluey weapon, for all alike
disappear within the long thin beak.
And now, perhaps, our friend has flown to another tree, and is some
way up it. Where is he gone? Climb up and look, and you will find a
small round hole, small outside but not inside, for the woodpecker has
hollowed out the soft rotten wood, and within, if it be early summer,
the mother is still sitting upon five or seven pure white eggs, out
of which the naked little ones will soon creep. He is a clever fellow
the woodpecker, but he is by no means the chief or most conspicuous
of the climbers, for in this group we have some of the most gaudy and
remarkable of birds. The brilliantly-coloured Barbets, the gaudy-headed
Toucans, with their clumsy bills and long barbed tongues, and the
gorgeously-tinted Parrots and Parroquets, with their soft fleshy
tongues so well adapted for speech, are all climbers, with toes divided
two and two, and they wander about the trees of South America and the
East, feeding on fruits and seeds.
Where in any other part of the animal kingdom can we find so many
brilliant colours crowded together as in the plumage of birds, and
especially in birds of tropical countries? The large land animals
cannot afford to wear such bright coats lest they should attract their
enemies, nor can even birds often put on gay plumage in our northern
climates, where the trees are bare for half the year. But in warm sunny
latitudes, where the trees are always green and the foliage thick and
heavy, and where brilliant fruits and flowers often peep out among the
leaves, the gaily-coloured birds can wander in comparative safety, and
even the gaudy parrots are not easily detected as they clamber from
bough to bough, using not their _tail_ like the woodpecker, but their
_beak_, as a third foot to hold on by as they climb.
None of these birds build nests; indeed, they could hardly do so with
their clumsy beaks and thick heavy feet; they either, like the ground
parrots, put together a few leaves in hollows of the earth or in ants’
nests; or, like the fruit-eating parrots and toucans, they lay their
eggs in tree-holes, where the bright-coloured mother is safely hidden
till she is set at liberty again. Even the cuckoos which, though they
are climbers, have taken much more to the wing than their associates,
sometimes avoid the trouble of nest building by laying their eggs in
the nests of other birds, as our own spring visitor always does. Some
of them, however, in America and elsewhere, have contracted better
habits, and build very respectable nests of their own.
[Illustration: Fig. 44.
The Kingfisher.[104]]
Indeed, we shall now soon begin to make progress in nest building, for
the next group of birds, which _dart_ at their food with wide-gaping
mouth and seize it on the wing, have among them many clever little
architects. It is true our English kingfisher builds in holes on the
river bank, lining her nest with fishes’ bones, and the Nightjar
(wrongly called the goatsucker), with her wide-gaping mouth, lays her
egg on the ground. But both these are lowly Darters, for the kingfisher
sits on a bough close above the water, and pounces down upon the fish
or water-insects; and the lonely nightjar, with her strange wailing
cry, flits among the bushes in the twilight, or often even creeps after
her prey.
Neither of these birds can compare in flight with the Swifts, as they
dart upon the wing from some high pinnacle to collect a mouthful of
insects, and come back to eat them, nor to the lovely little Humming
Birds of America, which poise themselves so deftly on the wing,
while their slender bill searches the long-tubed flowers for insects
or seizes these as they pass. These living jewels of nature build
beautiful and delicate nests of leaves and grass and spiders’ webs
interwoven like fairy cradles; while the swift makes a far stronger
home of hair and feathers, grass and moss, glueing them together with
saliva[105] from his mouth, and fastening them under the eaves or
on the top of some tall waterspout. It is easy to see why the swift
chooses such lofty spots, for his slender weak toes are ill-fitted for
standing on the ground, and he rises with great difficulty when once
he has alighted there, but from a height he can drop easily on to the
wing, and skim the air for his food.
Now the swift, which visits us only in summer to build his nest, when
insects are plentiful, and spends the rest of his time in Africa, is
a type of a whole army of birds, lovely, bright, and gay, with short
weak feet, long wings, and a gaping mouth surrounded by bristly hairs,
which swarm in hot countries where insects are to be found all the year
round. Among these are the beautiful little Bee-eaters and Rollers of
the East and Africa, which revel in insect food, and sometimes visit
us in the summer, coming over to the south of Spain, or even, in the
case of the rollers, as far north as Sweden; while in South America
the dull-coloured Puff-birds, the brilliant Jacamars with their
metallic-looking feathers, the delicate little Todies, the bright green
Motmots, and the lovely Humming-birds, swarm in countless numbers,
hiding among the dense foliage, or darting in the bright sunshine after
bee or butterfly, or other unwary insects.
* * * * *
But we must not pause too long among these smaller groups of birds, for
the multitude of perching birds, which form nine-tenths of the whole
bird kingdom, await us with their delicate nests and their happy family
life. Ah! now we are really coming to nature’s feathered favourites,
for what can be sweeter than the song of the nightingale, the skylark,
or the thrush? or more touching than the fact that the young ones learn
from their father the loving notes; that they, in their turn, may be
able to woo and win some gentle mate to share their nests and bring up
their young ones? It is for this that they have gained that wonderful
singing instrument which they have deep down in their throat. For
they do not produce their sounds as we do, just below the back of the
mouth, but at the lower end of the windpipe, just where it divides into
two branches, one going to each lung. There, where the rush of the air
is strongest, is found a complicated apparatus, moved by a whole set
of muscles, upon which the little fellow plays, and seems never to be
exhausted, so much air has he in all parts of his body. And as the song
pours through the windpipe there again he can help to give it its soft
mellow tones, for while in hoarse-crying birds, like the sea birds and
the waders, this tube is long and stiff, in the sweet singing birds
it is short, and the bony rings composing it are thin and far apart,
with soft delicate membrane between them, which can be shortened or
lengthened to modulate the tones. And so we hear them in the springtime
pouring forth their full tide of song to tempt a young wife to come
and help them to build a nest; or, in the full pleasure of success,
trilling out their delight in the warm bright sunshine, and calling on
all the world to be as happy as they.
Yet it is not by any means all the perching birds which have this
wonderful gift of song. Even among our own birds, the jay, the crow,
the raven, and others, use their musical instrument for talking in a
way that is no doubt useful to them, but scarcely pleasant to hear;
and in America there is a whole group of songless perching birds--the
bright coloured chatterers, the fly-catching tyrant-birds, the American
ant-thrushes, which have not even developed a true singing instrument
in their throat, and only utter shrill or bell-like cries. Yet they
all build nests and cherish their helpless young ones; and so large and
varied is the group of perching birds, whether in the Old or New World,
that they fill all the stray nooks and corners of bird-life, often
imitating the habits of the other smaller groups so as to get at food
of all kinds. Thus, while the Finches with their delicate matted nests,
the Warblers, and a large number of the smaller birds, lead a true tree
and bush life, feeding on fruits and insects, the Thrushes, Blackbirds,
Crows, Redbreasts, and Larks are _ground-feeders_, which, though they
do not scratch with their feet like the partridges, turn up the ground
with their bills and pick out the worms and grubs.
For this reason the Song-thrushes love to build their nest of twigs and
moss lined with soft wood chips, in some thick hedge near to a meadow
or garden, where they can drop down and pull up the unfortunate worms
before they have gone home underground after their nightly rambles, or
pounce upon unwary snails, and, taking them in their beak, crack the
shell upon a stone, and carry off the dainty morsel to their brood;
while the Lark, with her long hind toe, so well fitted for walking,
hides her nest in a furrow on the ground; and the greedy cunning
Magpie, feeding, as she often does, on young animals, seems to fear
the same fate for her own brood, and builds a large egg-shaped dome of
thorny branches, with the thorns sticking out on all sides, and lined
with mud and soft roots, leaving only a small hole for a door. Lastly,
the sagacious Rooks, though ground-feeders, build strong homes which
last from year to year, in the top of the high elms, and set out in
companies in the early morning to their feeding grounds.
[Illustration: Fig. 45.
Nest of the Common Wren.[106]]
Then, as there are ground-feeders among the perchers, so, too, there
are _climbers_, for the Creepers, the Wryneck, and the Nuthatch, run
up and down the trees, feeding on insects and nuts, which the nuthatch
breaks so cleverly with his beak; and we might almost fancy them to be
first cousins to the woodpeckers, if it were not for their three toes
in front and long claw behind, and their short thick beak and tail.
Even the little Wren, with her cocked-up tail, imitates the climbers
as she creeps through the hedges and underwood, though she is a true
perching bird, and builds one of the most perfect of nests of moss and
grass, woven into the shape of a ball, with a tiny hole for a door.
Then, to match the _darting_ birds, we have the Swallow and the Fly
Catcher which follow insects on the wing, so that the swallow and swift
were long confounded together, though the skeleton of the swallow shows
that it belongs to perching birds. Again, the Shrike imitates the birds
of prey, feeding on small mice, reptiles, and birds, and impaling them
upon a sharp thorn while he tears them to pieces with his beak. Yet he
is a true percher, singing as beautifully as many of the smaller birds,
and he is even said to use his power of song to lure victims within
reach. Lastly, and perhaps most curious of all, the little Dipper or
Water-Ouzel, with his clear loud song, and his structure so like to the
thrushes, has actually taken to the habits of water-birds, and dives
into the depths of the river, running along upon the bottom and feeding
on water-snails and water-insects.
[Illustration: Fig. 46.
Nest of the Tailor-Bird[107] of India or China.]
All these we find among English birds; and if we had space to speak of
other countries, we should find the same history there, for the more we
study bird-life the more we find that these Perchers are its highest
types, and have learned to make the most of their kingdom. It is they
who build the most perfect nests, from the rough strong basket-work
of the crow or the magpie, to the wren’s thickly-woven ball, or the
finches’ matted cups; while in America the Hang-nests weave their
lovely pear-shaped homes, and suspend them like fruit from the tips
of the branches; and in India and China the Tailor-birds actually sew
leaves together with cotton fibre or cobweb threads, which they draw
through with their slender bill and strengthen with saliva.
The smaller the bird and the more delicate its feet and bill, the more
closely woven, as a rule, is its nest. Yet all are built with care; the
mother bird, as a rule, choosing the position and laying the twigs,
while the father helps her to collect the materials. So rapidly do
these little creatures work, that among our smaller English birds the
early morning sees the work begun, and by evening it is ended. Other
birds are longer, according to the amount of material they have to
collect; but all labour industriously till the cradle is finished, and
then begins the laying, the sitting, the tender care of the mother for
her little ones, and of the father for his wife and brood.
* * * * *
And indeed there is much need both of skill in nest building and
of watchfulness for many a long day after, for if the perchers are
the highest, they are not by any means the strongest of birds; and
while they feed on insects and smaller creatures, they have to guard
their little ones with anxious care against the larger birds of prey
which rule as masters in the higher regions of the air. It is on
rocky pinnacles and in the clefts of inaccessible heights among the
mountains that we must look for the nests of the Eagle, the Vulture,
and the Falcon. Strong, powerful, and untiring in flight, they sail
majestically high up in the air, not to sing a joyful song like the
lark, but with piercing eye to search every corner for miles around,
for animals of all sizes, from the dead ox or mule to the tiny living
mouse or bird, which can serve for a meal.
[Illustration: Fig. 47.
The Eagle bringing food to its young.--(_From a coloured lithograph by
Keulemann._)]
It needs only a glance at them to see that they are strong destroyers,
with their powerful wings, their sharp hooked beaks, their long toes
with pointed claws, and their strong muscular thighs; and because
most men admire strength and power, we call such birds _noble_,
though their nobility chiefly consists in loving their little ones,
and asking neither pity nor shelter from others, as they themselves
are pitiless in return. Those which we are apt to like the least, the
carrion-feeding Vultures of hot countries, are really the most useful
and harmless, for they feed chiefly on dead animals and clear the land
of carrion; and for this reason neither their beak nor their claws are
as strong as those of the fighting birds. But though they are grand
in flight they are but repulsive-looking birds when compared with the
lordly eagles. The beautiful Golden Eagle of Europe, with its dark
plumage and the golden sheen on its back and tail, is indeed a splendid
object, as
“He clasps the crag with hooked hands,
Close to the sun in lonely lands,”
or still more, as he sweeps along with steady flight, circling round
and glancing with searching eye over the plain beneath. Suddenly his
attitude changes; he closes his wings, and, head downwards, drops to
earth slantingwise with a rushing noise, seizing in his claws the
startled fawn as it dashes by at full speed, the frolicking rabbit
darting into its hole, or the terrified bird upon whom his choice has
fallen. Then, with a powerful stroke he rises up again, and is lost to
sight as he soars aloft and regains the rocky peak where his eyrie is
built and his children are clamouring for food.
So, too, the dexterous Falcon swoops upon his prey swift as an arrow,
his pointed wings striking the air, and then closing at once upon his
body, while his long rounded tail guides him in his flight. Who would
think that such a powerful and bold robber could have anything in
common with the soft feathered owl which sits blinking its large eyes
in the hollow of the tree till the twilight falls? And yet the Owl,
with very little change in structure, has become as fitted to follow
prey at night as the falcon is by day--
“What time the preying owl, with sleepy wing,
Sweeps o’er the cornfield, studious.”
The soft, round, broad wings, which would serve badly for striking a
quarry from on high, are exactly fitted for gliding in the silence
of the night, as, guided by wide open eye and ear, he skims over the
fields or round the stacks in the yard to pounce noiselessly upon the
unwary mouse or to seize the flying beetles and bats. Then the sharp
claws appear quickly from under the downy feathered feet, and clutch
the smallest prey with needle-like precision; and away the owl flies
to his nest, so quietly that even the other animals close by are not
alarmed, but in ignorant security remain till he comes to strike again.
And as the day and the night by land have their relentless freebooters,
so the sea too has its eagle king; for the Osprey, with its nest on
a high rock, hovers over the open sea, and, dashing into the deep,
returns with a large fish in its claws; and, as it tears the flesh from
under the glittering scales, reminds us that there is no spot on the
earth in which some bird does not seek its prey.
We have now in very brief outline followed the feathery tribe from
the flightless penguin to the boldly-soaring eagle, the king of the
air. Those feathers which in the swimming bird are scarcely more than
finely-divided scales, and in the ostrich mere loose nodding plumes,
have become in the albatross, the vulture, and the soaring falcon,
flying instruments of such power and strength that the earth and the
water are as nothing to them compared with the free ocean of air; while
even the tiny graceful swallow flies for hundreds of miles to its
winter home.
Indeed, we have here one of the great secrets of bird success; for
while most animals must roam within limited districts, and get their
food there as best they can, thousands and tens of thousands of birds
set off, when the colder weather makes food scarce in any one region,
and travel hundreds of miles to more genial climates, where insects
are still to be found, and the trees are still covered with fruit and
leaves. How strange it is to think that while we are making the best
of our winter, the swallow has taken her unerring flight to Africa,
the swans and cranes have long since made their southward journey,
and myriads of small birds have gone in search of food and warmth, to
return next spring as certainly to their old haunts, where they can
breed in cool and comfortable quarters!
If we could only get the birds to tell us how they have learned the
routes they take, and by what rules they are guided! One thing we know,
that each kind of bird makes its nest in the coldest region which it
visits, and where, at the time its young brood are ready, insect and
other life is abundant; so that while the wild duck and goose, the
woodcock, snipe, and field-fare, go to the far north to lay their eggs,
and come to us in the sharper weather to feed when there is nothing
but ice and snow in the home they have left, the swallow, the cuckoo,
the swift, and the wheatear, on the other hand, visit us in the spring
to build, and when autumn comes on take their flight to Africa and the
East; and even many of the song-thrushes and robin-redbreasts which
remain with us in England start off from Germany to warmer climates.
Others, again, such as some of the Reed-warblers, the Stint, and the
Ortolan Bunting, only make our island a house of call between the
arctic regions where they breed in the summer when mosquitoes are
swarming there, and the south where they winter after flying thousands
of miles.
It would take too long to discuss here why and how they go, even if we
knew it with certainty; but it is most probable that their ancestors
first learned the routes now taken when Europe and Africa had not
so wide a sea between them, and we can see that it must be a great
advantage to be able to travel from climate to climate, so as to find a
plentiful table spread at all times of the year; while they may return
to the north to breed, not merely because there is food there, but also
because in still earlier times, when the northern countries were much
warmer than they are now, they doubtless lived there altogether, and,
though now obliged to go south, have never lost the tradition of their
old home.
Thus the birds, with their feathery covering and powerful wings,
have left their early friends, the reptiles, far far behind. Taught
by their many dangers, many experiences, and many joys, they have
become warmhearted, quickwitted, timid or bold, ferocious or cunning,
deliberate as the rook, or passionate as the falcon, according to the
life they have to lead; or, in the sweet tender emotions of the little
song-birds, have learned to fill the world with love and brightness and
song. If mere enjoyment were all that could be desired in life, where
could we expect to find it better than in the light-hearted skylark as
she rises in the early summer morning to trill forth her song of joy,
or in the happy chuckle of the hen as her little ones gather around her.
Yet we cannot but feel that, happy as a bird’s life may be, it still
leaves something to be desired; and that, with their small brain and
their front limbs entirely employed in flying, they cannot make the
highest use of the world. The air they have conquered; and among the
woods and forests, over the wide sea, and above the lofty mountains,
they lead a busy and happy existence, bringing flying creatures to
their highest development, and showing how Life has left no space
unfilled with her children. Yet, after all, it is upon the ground,
where difficulties are many, conditions varied, and where there is
so much to call for contrivance, adaptation, and intelligence, that
we must look for the highest types of life; and while we leave the
joyous birds with regret, we must go back to the lower forms among the
four-footed animals, in order to travel along the line of those that
have conquered the earth and prepared the way for man himself.
[Illustration: HOME OF THE EARLIEST KNOWN MILK GIVERS]
CHAPTER VIII.
THE MAMMALIA OR MILK-GIVERS.
THE SIMPLEST SUCKLING MOTHER, THE ACTIVE POUCH-BEARERS, AND THE
IMPERFECT-TOOTHED ANIMALS.
Our backboned animals have now travelled far along the journey of
life. The _fish_, in many and varied forms, have taken possession of
the seas, lakes, and rivers; the _amphibia_, once large and powerful,
now in small and scattered groups, fill the swamps and the debateable
ground between earth and water; the _reptiles_, no longer masters of
the world, but creepers and skirmishers still holding their own in many
places either by agility, strength, or the use of dangerous weapons,
swarm in the tropics, and even in colder countries glide rapidly
along in the warm sunshine, or hide in nooks and crannies, and sleep
the winter away. And the _birds_,--the merry, active, warmhearted
birds,--live everywhere, making the forests echo with their song,
rising into the heights of the clear atmosphere, till the world lies as
a dim panorama below them, crowd the water’s edge with busy fluttering
life, and even wander for days and weeks over the pathless ocean, where
nothing is to be seen but sky and water.
Yet still the great backboned division is not exhausted; on the
contrary, the most powerful if not the most numerous group is still
to come; that group which contains the kangaroos and opossums, the
dreamy sloths, the night-loving moles and hedgehogs, the gentle lemurs
and the chattering monkeys, the whales, seals, and walruses for the
water; the herds of wild cattle and antelopes, of noble elephants and
fleet horses, for the forests, mountains, and plains; and the ferocious
beasts of prey, which make these gentler animals their food; while
last, but not least, comes man himself, the master and conqueror of all.
Where, then, shall we look for the beginning of this vast multitude
of warm-blooded, hairy, and four-limbed animals? If we turn back to
the past, we get but little help; for though in that early time, when
huge reptiles overran the world and swam in the waters, we find small
animals (see Fig. 48), probably of the marsupial or pouched family,
living in the forests, yet even if these were the earliest of their
race, which is not at all likely, they would tell us very little about
the beginning of the milk-givers, since only their lower jaws remain,
and we can only guess at their relationship by these having that
peculiar inward bend which we still find in all pouched animals.
[Illustration: Fig. 48.
A, Jaw of Dromatherium; B, Tooth of Microlestes; both milk-givers,
probably marsupials, found in beds of the same age as those
containing the ancient swimming lizards.
]