horses get up and lie down?
7. For what purposes do the following mammals use their
tails—cows, squirrels, rabbits? What mammals do you know
which are without tails?
8. Observe and describe the differences—apart from
speed—between walking, trotting, and galloping, in the
case of the horse.
9. Describe how you have tamed any wild animal. Why is it
easier to tame a young animal than an old one?
10. Describe cases of mammals showing antipathy to certain
colours. How do you explain the dislike?
11. Which domestic mammals are (_a_) most shy, (_b_) most
inquisitive, (_c_) most gentle, (_d_) most suspicious,
(_e_) most intelligent?
12. Of what shape is the pupil of the eye in a dog, a cat,
and a sheep? Does the shape of the pupil change from time
to time in any of these animals? (1898)
13. Describe the fore-foot of a cat, a dog, and a sheep. The
bones of the foot need not be described in detail. Draw a
footprint of each animal (fore-foot), and show how each
part of the print is produced. (1898)
14. Give a short account of the life of a bat. When and
where does it seek its food? How does it pass the winter?
(1898)
15. Give illustrations (from your own experience if
possible) of the curiosity of dogs and cats. Show that
their curiosity is necessary to their welfare. (1901)
16. Mention animals which are nocturnal (only coming forth
at night), animals which burrow in the ground, animals
which are solitary, and animals which are social. (1901)
17. How are young cats treated by their mother when they are
helpless, when they first run about freely, and when they
are able to get their own food? (1903)
18. Mention some of the peculiarities which serve in most
cases to distinguish the hind limb of a quadruped from the
fore limb. (1905)
19. The habits of an animal can be inferred from its teeth.
To what extent is this statement true of (_a_) the cat,
(_b_) the rabbit? (King’s Scholarship, 1905)
FOOTNOTES:
[13] _The Descent of Man._ Cheap edition, 1s. (Murray).
[14] Gilbert White, _The Natural History of Selborne_.
[15] See Lloyd Morgan’s _Habit and Instinct_ (Arnold), Thompson-Seton’s
_Wild Animals I have known_ (Nutt), and Long’s _School of the Woods_
(Ginn).
CHAPTER XV. THE PIGEON: A TYPICAL BIRD.
51. HABITS AND STRUCTURE OF THE PIGEON.
1. =General observations upon the dovecote pigeon.=—Watch a group of
pigeons. What is the shape of the body? With what is the body covered?
What is the colour of the feathers? Does the bird walk or hop? How many
walking limbs has it? Has it any other means of moving from place to
place, in addition to walking? How many wings has it? Are the wings
anterior or posterior (p. 217) to the legs? Watch a pigeon preening its
feathers; why does it apply its bill so frequently to its tail? Can the
bird bend its neck easily in all directions? On what do pigeons feed?
How do they pick up their food? Do they chew the food? What is the
voice of the pigeon like? At what time of the year do pigeons moult?
How many eggs does the hen-pigeon lay? What is the colour of the eggs?
What are newly-hatched pigeons like? How do the parent birds feed them?
Try to find a wood-pigeon’s nest. What is its shape? What is it made
of? Is the top open or closed-in?
2. =The external characters.=—Closely examine a dead pigeon in respect
of the following features:
(_a_) _Feathers._—In what direction do the free ends of the feathers
point? Where are the longest feathers?
(_b_) _The head._—What is the general shape of the head? Notice the
horny _bill_; is it blunt, pointed, or hooked? Does it bear teeth?
Observe the _cere_, a whitish patch of swollen skin at each side of
the base of the upper beak, and surrounding the _nostril_. Examine
the large _eyes_, and notice the upper and lower eyelids and the
transparent third eyelid. Find the _ear-opening_, a little below and
behind the level of the eye, and hidden by the small feathers of the
neck. Open the mouth and see the pointed _tongue_.
(_c_) _The neck._—In the feathered bird this appears short; it will be
better seen after the removal of the feathers (contour feathers) which
cover it.
(_d_) _The trunk._—What is the apparent shape of the trunk? Where is
its heaviest part?
(_e_) _The wings._—Open out the wings fully and measure the distance
from tip to tip; compare it with the length of the trunk. Which
surface, upper or lower, of the expanded wing is rounded (convex)
and which is hollowed (concave)? Put up an umbrella and, holding it
by the handle, move it quickly (i) away from you, (ii) towards you.
In which direction of motion does the air offer more resistance? Is
it an advantage for the expanded wing to be convex above and concave
below? Why? Feel the wing-bones through the skin, and notice that the
wing-skeleton consists of three parts corresponding to the bones of
your upper-arm, fore-arm, and hand (with the wrist) respectively; and
that they are bent on each other in the form of a Z when the wings
are folded. The large _quill-feathers_ attached to the segment which
corresponds to the hand and wrist are called _primaries_; count them.
Those attached to the fore-arm are called _secondaries_; count them.
Find the tuft of smaller feathers which spring, at the front edge
of the wing, from the thumb; this tuft is called the _thumb-wing_.
The primaries and secondaries collectively may be called the rowing
feathers. Notice the smaller feathers which, on both the upper and
lower surface of the wing, cover the quills of the primaries and
secondaries; these smaller feathers are called the _wing-coverts_.
(_f_) _The legs._—Feel the leg-bones through the skin, and make out
the various segments. Is the whole of the hind-limb feathered? Which
part is devoid of feathers? With what is this part covered? How many
toes are there? Do any point backwards? Stretch out the legs and notice
that the toes open. Bend the ankle-joint and notice that the toes close
automatically. Of what use is this in perching?
(_g_) _The tail._—Examine the tail and notice the large quill-feathers
attached to it; count them. As they are largely used for steering
during flight they are sometimes called the steering feathers.
3. =The feathers.=—Examine the arrangement of the feathers. The short
feathers which clothe the body generally are called _contour feathers_
because they determine the contour of the unplucked bird; remove one
or two and place them aside. The feathers which cover the bases of
the large quills are called _coverts_—wing-coverts or tail-coverts
according to their position. Remove one or two for future examination.
Examine the arrangement of the _quill-feathers_ of the wings, and
notice how the vane or web of one partially overlaps the next. The
vane is supported by a shaft. Are the two sides of the vane of equal
width? Is the narrower side directed forwards or backwards? Pull out a
quill-feather from each wing and compare them. How could you recognise,
if you did not know, whether any particular feather had come from the
right or from the left wing? Pull out a quill-feather from the tail;
are the sides of the vane of equal width?
4. =Examination of various feathers.=—Examine in detail a
_quill-feather_ from the wing. Make out:
(_a_) _The quill._—Is it hollow or solid? Try to bend it and notice its
great strength. Observe the small hole at its base.
(_b_) _The shaft._—This is the prolongation of the quill, and carries
the web or vane. Is the shaft hollow or solid? Notice the small tuft of
down on the inner face of the feather, at the junction of the quill and
shaft.
(_c_) _The vane._—Hold up the feather to the light and examine the
vane with a lens. Notice that the vane consists of a number of laths
which spring from the shaft; these are called _barbs_. Try to separate
the barbs, and observe that they offer considerable resistance to the
pull, as if they were somehow fastened together. Examine a barb with a
strong lens and observe the finer branches, called _barbules_, which
it bears. The barbules on one side of the barb carry little hooks,
while those of the other side bear flanges, on which fit the hooks of
barbules carried by the next barb below. The hooks and flanges cannot
be seen without a microscope.
(_d_) _Other feathers._—Compare the _covert_ and _contour feathers_
with the quill feathers. Observe, in the contour feathers, the less
perfect interlocking of the barbs of those parts which are covered by
other feathers.
Pluck the pigeon, and notice the hair-like structures left in the skin.
They are called _filoplumes_. Pull one out and examine it with a lens;
it bears a few barbs at its upper end, but these do not interlock.
Examine a nestling-pigeon, and notice the _down-feathers_ which clothe
it temporarily. Each is at first covered at the base with a horny
sheath. The barbs do not interlock. The down-feathers are pushed off by
the growth of the permanent feathers.
5. =The plucked pigeon.=—Observe that feathers do not grow on all parts
of the body, but are confined to definite _feather-tracts_, which can
be recognised by the scars left by the quills. Notice especially the
sockets of the large wing-and tail-quills. Make out the _oil-gland_,
a small knob just above the tip of the true tail. It furnishes a
lubricating fluid used in preening the feathers. Examine more closely
the different regions of the body—the neck, the joints of the limbs,
etc., which were disguised by the feathers. The filoplumes have already
been seen. Feel the great _muscles of the breast_, and the edge of the
_sternum_ or breast-bone in the middle line. Just in front of this feel
the soft crop, with the grain which is probably present in it.
Before boiling the bird in order to separate and examine the bones,
open the _crop_ and inspect its contents. Cut away the enormous muscles
of the breast (why are they so large?) and open the body-cavity behind
and remove the internal organs, being careful not to break any bones.
6. =The skeleton.=—Boil the bird until the flesh can be easily removed.
A small nail-brush will be found useful in cleaning the bones. Keep
as many of these in contact as possible, and make out and examine the
following parts:
(_a_) _The skull_, with the rounded brain-case, horny beak, and large
eye-sockets. Notice, at the back of the skull, the _single_ knob, which
fits into a hollow on the first vertebra.
(_b_) _The backbone._—Notice the long neck, the fusion of many of
the vertebrae in the trunk-region, and, at the end of the tail, the
“ploughshare bone.” This last supports the tail-quills.
(_c_) _The breast-bone_, or sternum, produced ventrally into a thin
plate called the _keel_ (to which were attached the great muscles of
the breast), and connected by ribs to the backbone.
(_d_) The position of the _shoulder joint_, and the socket for the bone
of the upper-arm. Notice the =V=-shaped “merrythought.”
(_e_) _The bones of the fore-limb_ (wing).—Make out the parts belonging
to the upper-arm, fore-arm, and wrist and hand, and notice that the
bones of the wrist and hand are firmly fused together to give increased
strength.
(f) _The large hip-bones._—Notice their forward extension and fusion
with the joined vertebrae of this region, and the resulting increased
firmness of this part.
(_g_) The bones of the _hind-limbs_.
7. =Pneumatic bones.=—Examine the bone of the upper-arm of the pigeon
and notice, just below the head of the bone, a small hole which leads
into the interior. Break the bone across; is it hollow or solid? Does
the inside contain marrow? How does it differ from the corresponding
bone of a rabbit?
8. =Different breeds.=—Examine various breeds of domestic pigeons, and
compare them with the common variety, as regards colour, shape, method
of flight, extent of feathering of the hind-limbs, etc.
=Birds.=—It is probable that no class of animals has been more studied
than that of the birds; and the reasons for this are not difficult to
find. The wonderful power of flight—rivalled only by the insects—and
the perfect adaptation of structure to this power; the habits,
always interesting and in many cases showing a curious parallelism
to human institutions; the beautiful voices of song birds; the grace
of movement; the mysteries of migration; and, it may be added, the
remarkable story of the origin of birds which has been revealed by
modern zoology,—form a combination of characters, at once familiar and
elusive, which has greatly stimulated human sympathy and imagination.
It is well to begin the study of birds by first taking one familiar
species and examining it somewhat closely, and afterwards comparing
and contrasting other members of the class. Such a convenient type for
study is found in the dovecote pigeon.
[Illustration: FIG. 178.—Pigeons.]
=The pigeon.=—The body of the common dovecote pigeon (Fig. 178) is
ovoid in shape, tapering gently at the neck and appearing, in the
living animal, to pass insensibly into the head. The fore-limbs are
modified to form a pair of =wings=, which are set on a little above and
in front of the centre of gravity of the body. Except during flight the
weight of the body is entirely supported by the hind-limbs or =legs=,
which are fixed almost exactly below the centre of gravity of the body,
_i.e._ in the best imaginable position. Each foot bears four toes, the
first of which is directed backwards. Each toe is armed with a claw.
The body generally is clothed with =feathers=, remarkable structures
which are as characteristic of birds as hairs are (p. 220) of mammals.
The great majority of the feathers are small, overlapping and
plate-like, with their free ends pointing backwards; and they form
a light, warm, and smooth covering which is admirably adapted to the
animal’s needs. Certain large feathers, carried by the wings and tail,
are used in flight. The legs are feathered to the ankle-joint, but the
feet are covered only with scales. The general colour of the dovecote
pigeon is a slaty blue.
The head is rounded, and terminates in front in a horny =bill=, which
does not bear teeth. At the base of the upper beak there is, on
each side, a whitish patch of swollen skin called the =cere=, which
surrounds the opening of the =nostril=. The =eyes= are large and
round; in addition to upper and lower eyelids, each is provided with
a transparent =third eyelid=, which can be flicked rapidly across the
eyeball. Birds generally have very powerful sight and depend more upon
this sense than upon any other. There are no external ears, but when
the feathers are separated, a little below and behind the eyes, a pair
of apertures leading to the internal =ears= may be seen.
=Habits.=—The pigeon lives upon grain, which it picks up by means of
its horny bill. The length and flexibility of the neck are a great
help in feeding. The food is swallowed immediately and passed into
a large bag called the =crop=, which is really a dilatation of the
lower part of the gullet. Here it is macerated for some time before it
passes onward to the true stomach. The hinder part of the stomach is
called the =gizzard=; it has very thick walls and a hard horny lining.
In the gizzard the food is ground up by the aid of small stones which
the pigeon swallows for the purpose. The stomach is followed by a
much-coiled intestine, in which the process of digestion is completed.
The pigeon differs from many birds in walking instead of hopping.
When perching, it bends its legs at the ankles, an action which
automatically closes the toes in such a manner that the perch is
grasped behind by the first toe and in front by the second, third, and
fourth. The weight of the body is sufficient to maintain a tight clasp
upon the perch, so that the bird is able to sleep comfortably in this
position.
[Illustration: FIG. 179.—A Falcon. The regions of a bird’s body.]
The hen-pigeon lays two white =eggs=, which are sat upon by the
parents for fourteen days and thereby kept at a temperature of about 40
degrees Centigrade. The young birds then break through the shell and
are hatched. As the chicks are at first quite helpless and unable to
feed themselves, the parents supply them with a milky fluid secreted by
their crops. This is sometimes called “pigeon’s milk.” Newly hatched
pigeons are covered with fine feathers called =down=, which are pushed
off by the development of the permanent feathers beneath them. The
nests of wood-pigeons (Fig. 180) are usually built in trees; they are
somewhat rough structures, composed of twigs, and open at the top.
[Illustration: FIG. 180.—Wood-pigeon’s nest.]
=The wings.=—A bird’s wings are full of interest, from whatever point
of view they are considered. Even now, the exact manner in which they
and the tail are used to bring about the many different movements of
flight is not fully understood; but a general idea may be obtained by
an examination of the bones and feathers and the careful observation of
flying birds.
[Illustration: FIG. 181.—The skeleton of the limbs and tail of a
flying-bird. _OA_, bone of upper arm; _OS_, bone of upper leg; _Rd_,
_Ul_, bones of fore-arm; _T_, _Fi_, bones of leg; _HW_, _MH_, bones of
wrist; _F_, _F_, _F_, bones of fingers; _Z_, _Z_, _Z´_, _MP_, bones
of foot; _Scp_, shoulder blade; _Cr_, keel on sternum (_St_); _Pg_,
ploughshare bone.]
The =bones= of the fore-limb and the neighbouring regions show a
remarkable modification of the primitive plan. The bones of the upper
arm _OA_, (Fig. 181) and fore-arm (_Rd._, _Ul._,) are arranged much
like the corresponding bones of the rabbit; but those of the wrist and
hand are unlike anything we have yet examined. The fourth and fifth
fingers have entirely disappeared; and the first (thumb), second, and
third, though they can be still recognised (Figs. 181, _F_, _F_, _F_
and 184_a_), have become consolidated with what remains of the wrist
(_HW_, _MH_) to form a firm mass which is in no danger of “giving”
during the powerful down-stroke of the wing. The head of the bone of
the upper arm fits into a socket (_gl.cv._, Fig. 182) at the junction
of the shoulder-blade (_scp._) and another and stouter bone (_cor._)
which runs back and is attached to the breast-bone or sternum (_st._).
The sternum in its turn is connected by means of ribs with the spinal
column, which is strengthened here by the fusion of some of its bones.
The ventral part of the sternum is produced into a large plate called
the _keel_ (_car._, Fig. 182), which gives attachment to the great
muscles of the breast, used in the movements of the wings. So great is
the development of these muscles in flying birds that in the pigeon
they have a weight equal to one-fifth the total weight of the body. The
three segments of the wing, corresponding to the upper-arm, fore-arm,
and wrist and hand respectively are, in the position of rest, bent
upon each other like the letter =Z=. The large quill =feathers= of the
wing, fixed along the hinder border of the limb, are in two series
(Fig. 179). Those attached to the fore-arm are called _secondaries_;
while those attached to the wrist and hand are known as _primaries_. A
smaller tuft of feathers borne by the thumb is called the bastard-wing
or _thumb-wing_. The smaller feathers covering the bases of the
wing-quills are called _wing-coverts_.
[Illustration: FIG. 182.—Pigeon. The bones of the trunk. _actb_, socket
for bone of upper leg; _car_, keel of sternum; _cd.v_, vertebrae of
tail; _cor_, coracoid; _fur_, merrythought; _gl.cv_, socket for bone of
upper arm; _pyg.st_, ploughshare bone; _scp_, shoulder blade; _s.scr_,
fused vertebrae of hip region; _st_, sternum; _st.r_, _vr.r_, rib;
_th.v.1_, first, and _th.v.5_, last thoracic vertebra. (× ⅓.)]
=The hind-limbs and tail.=—The hind-limbs, or legs, of birds are the
sole support of the body except during flight, and a relatively great
weight is thus thrown upon them. To provide for this, the skeleton of
the hip region is exceptionally strong. Not only are the bones of the
spine here welded together into one solid mass, but the hip-bones
extend forward much further than is the case in quadrupeds, and are
firmly attached to the fused vertebrae. Each hip-bone possesses a
socket (_actb_., Fig. 182) into which fits the head of the bone of the
upper leg. Another fusion of bones is to be noticed at the end of the
tail, resulting in the _ploughshare-bone_ (Fig. 182, _pyg. st._) which
supports the large _steering feathers_ of the tail. The quills of these
feathers are covered at their bases by the _tail-coverts_.
Just above the end of the tail of a plucked pigeon is to be seen a
small conical body, the _oil-gland_, from which the bird obtains a
fluid which it applies to the feathers during the preening process.
=The feathers.=—Feathers do not grow upon all parts of a bird’s body,
but are restricted to certain definite areas or “_feather tracts_”
which, however, differ in arrangement in different species.
[Illustration: FIG. 183.—Pigeon. _A_, portion of a wing feather; _cal_,
quill; _rch_, shaft; _B_, filoplume; _C_, nestling-down.]
One of the large feathers of the wing of the pigeon is illustrated
in Fig. 183, _A_. It consists of a hollow, horny =quill= (_cal._),
prolonged into a solid =shaft= (_rch._) which supports the web or
=vane=. The outer face of the feather is slightly convex and smooth;
while the inner surface is somewhat concave and rough, and carries a
little tuft of down at the junction of quill and shaft. The growing
feather is nourished by a conical projection of the deeper part of the
skin, which fits into a small hole (_inf. umb._) at the base of the
quill. It is easily shown that the vane of the feather is composed,
on each side, of a large number of parallel laths which spring from
the shaft. These laths are called =barbs=. Considerable resistance is
felt when an attempt is made to pull the barbs apart, but the manner
of their connection cannot be clearly seen without the aid of the
microscope. A fairly low magnifying power, however, shows (Fig. 184)
that each barb bears extremely delicate threads—=barbules=—on each
side, arranged on the barb much as the barbs are arranged on the shaft.
The barbules on one side of each barb (the side furthest from the
quill) are seen to carry tiny _hooks_; while the barbules of the other
side of the barb are furnished with _flanges_. The hooked barbules of
one barb cross the flanged barbules of the next and interlock with
them; so that relatively great force is required to pull the barbs
apart and destroy the continuity of the web. The quill-feathers of the
tail, and the coverts, have webs of similar structure.
[Illustration: FIG. 184.—Structure of a Feather. _A_, small portion
of a feather with pieces of two barbs, each having to the left three
hooked barbules, and to the right a number of flanged barbules; _B_,
hooklet of one barbule interlocking with flange of another barbule;
_C_, two adjacent flanged barbules; _D_, a hooked barbule. (After
Pycraft.)]
The =contour-feathers= are used for protection and warmth rather than
for flight, and hence have less-perfectly interlocking barbs. The
hair-like structures seen on the skin of the plucked bird are extremely
simple feathers called =filoplumes= (Fig. 183, _B_). Each consists
of a long, slender axis, bearing at the end a few barbs which do not
interlock.
The =down-feathers= (Fig. 183, _C_), which form the temporary covering
of nestling pigeons, also bear barbs which do not interlock.
At regular intervals, either once or twice a year, birds =moult=, that
is, shed most or all of their feathers and grow new ones. The moulting
usually takes place gradually and symmetrically: a flight feather from
each wing, for example, being dropped at the same time.
=Flight.=—The outstretched wing of a pigeon has a relatively great
area; and is markedly convex on the upper surface and concave on
the lower, resembling in this respect an open umbrella. The great
difference in the resistance which the inside and outside of an open
umbrella respectively oppose to the wind is familiar to everyone, and
illustrates the advantage of the dome-shape of the outstretched wing.
The force which the great breast-muscles put into the down-stroke of
the wing is enormous in comparison with the weight of the body, and
is sufficient to push the bird upwards and forwards in the air. The
gently tapering shape and smooth surface of the feathered bird diminish
the resistance of the air. When the wing is raised again for the next
stroke, the quill-feathers are turned a little edgewise, so that the
air slips between them; just as an oarsman “feathers” his oar to lessen
the resistance to the blade in the return-stroke. The direction of the
wing-stroke can be altered in accordance with the direction of air
currents, and the fan of tail-feathers is capable of being opened or
closed, raised or lowered, and turned at various angles to act as a
rudder.
But the method of flight which perhaps most of all excites the
observer’s admiration is =soaring=, in which the bird seems to remain
almost passive, with outstretched wings and spread tail, and mounts
automatically in a spiral course. Exactly how the soaring is performed,
only the birds themselves know; but it must be similar in essence to
the arrangement of the sails of a yacht so as to select that component
of the force of the breeze which will drive the boat in the required
direction, even though this be almost “in the teeth of the wind.” Such
spiral soaring may be seen to perfection, among common British birds,
in the skylark (p. 316). A breeze is necessary for soaring.
In =hovering=, the motion of the wings is extremely rapid, and the bird
remains poised in one place. The kestrel (p. 330) derives its common
name of “windhover” from its habit of using this method of flight when
looking for food.
=The pigeon’s air supply.=—We know that a man breathes more quickly
when he is taking active exercise than at ordinary times; and we might,
from this and similar observations, expect to find the most perfect
breathing organs in animals which lead the most active lives. Of all
vertebrate animals, birds probably perform the most work in proportion
to their size; and it is not surprising, therefore, to learn that they
have special facilities for quickly replacing fouled air by fresh.
The =lungs= are comparatively small, but they are not the only organs
of respiration (p. 242); for the windpipe opens also into several
=air-sacs=, which supply nearly all parts of the body with air, and
even communicate with the interior of certain bones. The bone of the
pigeon’s upper-arm, for example, is hollow and contains air. By means
of the system of air-sacs, the air in the lungs is _completely_ renewed
at each respiratory act, and thus the waste carbon-dioxide in the blood
can be exchanged for fresh oxygen much more completely than it is in
mammals. One result of this is that the blood of birds is much warmer
than that of mammals. The air-sacs are also an assistance to flight by
rendering the body more buoyant.
=Different breeds of pigeons.=—The various breeds of domestic pigeons
furnish one of the best examples of the changes in structure which
breeders can bring about, after several generations, by careful
crossing. In spite of the great differences between, say, the
=tumbler=, with its habit of turning head-over-heels in the air;
the =pouter=, with its exaggerated crop; the =Jacobin=, with its
neck-feathers reversed; the =fantail=, with its large number of erect
tail-feathers; and others,—there can be no doubt that all these
varieties have been artificially produced from the =rock-pigeon=; and
it is curious to observe occasional reversions to the characters of
the ancestral stock. “The rock-pigeon is of a slaty blue, with white
loins.... The tail has a terminal dark bar, with the outer feathers
externally edged at the base with white. The wings have two black bars.
Some semi-domestic breeds, and some truly wild breeds, have, besides
the two black bars, the wings chequered with black. These several
marks do not occur together in any other species of the whole family.
Now, in every one of the domestic breeds, taking thoroughly well-bred
birds, all the above marks, even to the white edging of the outer
tail-feathers, sometimes concur perfectly developed. Moreover, when two
birds belonging to two or more distinct breeds are crossed, none of
which are blue or have any of the above-specified marks, the mongrel
offspring are very apt suddenly to acquire these characters.”[16] This
is a striking instance of the tendency exhibited by living things to
revert to ancestral characters, even though these latter may have lain
dormant for hundreds of generations.
EXERCISES ON CHAPTER XV.
1. Why does a bird require a long neck, and a keel upon the
breast bone? (1898)
2. Draw the bones of a bird’s wing, and mark the places of
insertion of the largest quills. (1898)
3. What bones carry the primary and secondary quills of a
bird’s wing, and the quills of the tail? Illustrate your
answer by a drawing. (1901)
4. Point out the chief differences between the skulls of a
quadruped and a bird. (1901)
5. Describe one of the large feathers of a bird’s wing. (1898)
6. Draw general plans of the fore-limbs of a mammal and a
bird. Letter the principal bones, so as to show how they
correspond in the two animals. (1901)
7. If the skull of a bird were placed before you, what
features would enable you to recognise it with certainty? (1901)
8. How does the fact that a bird stands on two legs affect
the skeleton of the trunk? (1897)
[Illustration: FIG. 184_a_.—Comparison of Bat and Bird.]
9. Point out the chief differences between the wing of a
bird and that of a bat.
10. Explain how the barbs of a quill feather are attached
to one another. Describe a feather at the time when it is
forcing its way through the skin. (1905)
11. What peculiarities distinguish feathers which aid in
flight from feathers which merely prevent loss of heat? (1906)
12. Describe the wing of a bird, both as to skeleton and as
to external appearance. Compare the skeletal parts with
those of the corresponding structures in a Mammal. (1908)
FOOTNOTE:
[16] Darwin, _The Origin of Species_ (Murray). Cheap edition, 1s.
CHAPTER XVI. THE DEVELOPMENT AND EDUCATION OF THE CHICK.
52. A HEN’S EGG.
Obtain three or four hen’s-eggs, and make the following observations
upon them:
1. =External appearance.=—What is the _colour_ of the egg? What is
its _shape_? How does the shape differ from that of a cricket ball or
other sphere? The shape of an egg is said to be ovoid. [What is the
difference between an ovoid and an oval?] Measure, with a tape, the
length and breadth of the egg, and also its distance round, (i) in the
direction of its greatest length, (ii) in the direction of its greatest
width. What advantages has this shape? Could a hen sit so comfortably
upon her eggs if they had sharp corners? Put an egg upon the table
and roll it gently. Does it roll in a straight line? Does it roll far
before coming to rest? Compare the rolling of a cricket ball or other
sphere. Is it an advantage that an egg is not likely to roll far, or in
a straight line? Why?
2. =The strength of the shell.=—Hold an egg with your thumb at one end
and your first or second finger at the other, and press exactly in the
line of the length of the egg. You cannot break the shell.
3. =Structure.=—(_a_) _The shell._—Tap the egg gently at the middle
of its broad end until the shell cracks. Then carefully remove small
pieces of the shell and notice the _shell-membrane_, a tough skin
which is closely applied to the inside of the shell. Snip through the
membrane in the middle of the broad end; notice the _air-chamber_
which lies beneath it. Observe the inner membrane which separates the
air-chamber from the inside of the egg. Hold a piece of shell up to
the light, and notice the small, almost transparent dots. The shell is
perforated by very small pores, through which the air can pass.
(_b_) _The white of the egg._—Tap the shell so as to crack it all round
at its widest part; raise bits of shell carefully and see the membrane
here. Tear through the membrane and notice that in this region there
is no air-space, but the white lies just beneath the shell-membrane.
Separate the halves of the shell, notice the position and shape of the
yolk, and then let the contents of the egg fall gently into a basin.
Observe the appearance, colour, and transparency of the white, and try
to distinguish two tangled cords of firmer white—the _balancers_ (Fig.
185)—arising close to the yellow yolk.
(_c_) _The yolk._—What is the shape of the yolk as it lies in the
basin? How does it differ from the shape of a yolk suspended naturally
in the white? What is the cause of the change of shape? Notice
carefully a small paler patch in the middle of the upper surface. This
is the lightest part of the yolk, so that the yolk always settles with
this part uppermost after any turning of the egg, and therefore the
pale patch is always more directly exposed to the heat of the hen’s
body (during incubation) than is any other part of the yolk. Prick the
yolk and notice that the yellow, fluid contents flow out. You have
evidently pierced the thin bag which formerly preserved the shape.
(_d_) _A hard-boiled egg._—Boil an egg in water for five minutes,
and then chip round the shell in the direction of the length and,
with a sharp knife, cut the whole egg into halves along this plane.
Make a drawing of the section, indicating the shell, shell-membrane,
air-chamber, white, and yolk in position. Observe that the white is no
longer transparent and fluid, but an opaque, white, and elastic solid.
Try to peel off the white in layers. They will probably break off
short, but you may be able to see that the white is deposited in spiral
sheets around the yolk.
=The hen’s egg.=—A hen’s egg bears a somewhat similar relation to the
adult bird that the maize or bean seed (Chapter I.) bears to the adult
plant; for the egg contains
(1) a speck of living matter which little by little grows and becomes
marked off, by orderly arrangement, to form the various regions and
organs of the adult animal; and
(2) a store of food, which enables the young chick to develop in
security, without being hampered, whilst still weak and helpless, by
the necessity of earning its own living. The changes by which the speck
of living matter becomes the perfect chick will be considered in the
next section. We must now examine the structure of the egg itself, and
see what provision it contains for the nourishment and safety of the
developing bird.
The egg is ovoid in =shape=, one end being distinctly broader than the
other. This shape has the advantage of preventing the egg from rolling
very far when placed upon a slightly inclined surface, and it is worthy
of notice that the eggs of birds which lay on cliffs and other exposed
situations are usually more elongated and pointed than others, so
that when stirred they do not roll away, but simply describe a small
circle and come to rest again. In the case of eggs which are laid
in cup-shaped nests (Fig. 197) the pear-shape lends itself to close
packing, and thus allows the eggs to be more easily kept warm by the
parent bird.
The =shell= (_sh._, Fig. 185) is composed of a chalky material, and is
perforated by small pores, through which the developing chick obtains
fresh oxygen from the air, and gives off its surplus carbon dioxide
(p. 242). A small piece of shell easily snaps, but the shape of the
complete shell so distributes an outside pressure, especially one in
the direction of the long axis, that relatively great force is required
to break it. The shell is lined by a thin, parchment-like =membrane=
(_sh. m._). At the broad end of the egg this membrane is double, and
the two layers enclose an =air-chamber= (_a_).
Inside the shell-membrane are the white or albumin, and the yolk.
The =white= (_alb´._) is a viscous, transparent fluid. Its innermost
part (_alb._), which immediately surrounds the yolk, is of thicker
consistency than the rest, and is prolonged into two twisted cords
called the =balancers= (_ch._), which suspend the yolk in position.
[Illustration: FIG. 185.—Semi-diagrammatic view of a fowl’s egg at the
time of laying. _a_, air-space; _alb_, dense layer of albumin; _alb´_,
more fluid albumin; _bl_, germinal disc; _ch_, balancers; _sh_, shell;
_sh.m_, shell-membrane; _sh.m 1_, _sh.m 2_, its two layers separated to
enclose air-space; _yk_, yolk. (After Marshall.) (× 1.)]
The =yolk= is a golden-yellow fluid enclosed in a thin, elastic
membrane and hence preserving a spherical shape. On its upper surface
(but under the membrane) is a small circular patch (_bl._) of paler
colour. This patch, called the =germinal disc=, is about ⅛” in
diameter; it contains the living matter from which the chick will be
formed; the rest of the yolk, and the white, are simply a store of
inert food which is used up by the growing chick.
=The work of the balancers.=—In order that the small living patch of
pale yolk, the germinal disc, may grow and develop into the chick it
must be kept warm. When eggs are hatched in the natural manner, the
heat is supplied by the body of the sitting hen, and the upper part of
the egg is consequently kept warmer than the rest. It is important that
the living part of the egg shall always lie nearest the hen’s body and
thus be kept warm, and this is secured by an arrangement as effective
as it is simple. The yolk is lightest in the neighbourhood of the
germinal disc, and therefore always lies with this part uppermost. If
the egg is slowly turned over, the yolk remains “right side up.” If it
is turned over quickly, the yolk soon swings round into its original
position. The twisted cords of white, the balancers, not only sling
up the yolk and guard it from being thrown to one side by a sudden
movement, but they also prevent it from rotating too quickly—and so
possibly injuring the delicate body of the young chick—when it rights
itself after the egg has been turned over.
The balancers are rendered necessary by the hen’s habit of turning her
eggs two or three times a day. It is often supposed that the eggs are
turned in order to keep them equally warm on all sides, but this is
unnecessary. Most probably the egg is turned in order to alter slightly
the young chick’s position from time to time, and allow its parts to
grow naturally, unimpeded by the other contents of the egg.
53. THE DEVELOPMENT OF THE CHICK.
1. =A simple incubator.=—Eggs are best incubated in the natural
manner, that is, by the warmth of the hen’s body; but if a sitting
hen cannot be obtained, an ordinary water-oven, such as is used in
chemical laboratories, may be made to answer. It should be heated
by a self-regulating burner, and kept at a temperature of about 40°
C. The eggs should be turned two or three times a day, and the air
of the oven should be kept moist by sprinkling water upon pieces of
cloth, blotting paper, or hay, kept with the eggs. Spring is the most
favourable time of the year for making the observations, as eggs laid
at other seasons are not always in a condition to produce chicks.
2. =How to mark the eggs.=—The most instructive changes take place
during the first five days of incubation. If all the stages of the
first five days are to form the subject of one lesson, an egg should
be marked “5” with pencil, and then put into the incubator or under
the hen five days before the lesson; a day later, an egg numbered
“4” should be put in, and so on. The numbers will then indicate the
length of incubation at the time of the lesson, and the eggs should be
examined in order, from 1 to 5. If one egg is to be examined each day,
five should be put in the incubator at the same time; no numbering will
then be required.
3. =How to examine the eggs.=—Have ready a basin of water, heated
slightly above the temperature of the hand (_i.e._ to about 40° C.),
and dissolve table-salt in it in the proportion of a level teaspoonful
of salt to a pint of water. The young chicks will keep alive longer in
this solution than in ordinary water. Tap the shell in the middle of
its broad end, and open the air-chamber (_a_, Fig. 185) completely.
Then crack the shell in the middle of the length and, keeping the
length of the egg horizontal, cut transversely round the middle of
the shell with scissors in a vertical plane, until the halves are on
the point of coming apart. Then lower the egg into the warm saline
solution, pull the halves of the shell apart, and float out the
contents. Examine the embryo carefully, making out as much as possible,
and then snip round it with a pair of fine scissors to remove it from
the yolk; float it into a watch-glass and cover it with weak alcohol
(equal parts of water and spirits of wine). Examine it with a lens.
After it has remained for a day in weak alcohol, put the embryo into
strong alcohol in a small bottle (writing the age on a label), and
preserve it.
Notice the gradual absorption of the white of the egg as development
proceeds.
4. =Chick after one day’s incubation.=—Notice that the embryo is now to
be distinguished as a streak crossing the germinal disc in a direction
at right angles to the long axis of the egg. Notice a rounded swelling
at one end of the embryo; this is the _head_. Place the egg before
you with the broad end to your left, and observe that the head of the
embryo points away from you.
5. =Chick after two days’ incubation.=—Observe the increase in size of
the embryo; make a note of its length. The head and neck of the embryo
are now almost covered by a very thin transparent bag which has grown
over it from the sides. This bag is called the _amnion_; it is filled
with fluid, and protects the embryo from jars. Remove the amnion and
notice the large _head_; it is now twisted so that its left side lies
against the yolk, while the rest of the embryo still lies “face-down.”
Observe the large _eye_ on the right side of the head; the left eye
cannot be seen without turning the head over. Notice the _heart_, a
small red dot which by help of a lens can be seen to beat rapidly.
Surrounding the embryo is a circular network of _blood-vessels_ which
bring food from the yolk to the heart, to be distributed to the various
parts of the body. How large is the circular area of blood-vessels?
6. =Chick after three days’ incubation.=—The white of the egg is
distinctly shrunken, and the network of blood-vessels is much larger
than before. Remove the amnion and notice the marked increase in size
of the embryo, especially of the _head_. The right side of the head and
neck are still turned towards the shell. They are now quite free from
the yolk, but the body of the embryo communicates with the yolk by a
short, wide tube, the _yolk-stalk_. Try to see a small pit, a little
above and behind the large _eye_. This is the beginning of the right
_ear_. Measure the embryo and the width of the surrounding network of
blood-vessels. Watch, through a lens, the beating of the _heart_.
7. =Chick after four days’ incubation.=—Carefully cut open the amnion
to see the embryo better. Observe that the young chick is still more
completely folded off from the yolk, and that the _yolk-stalk_ is
consequently narrower than before. The head is so strongly bent upon
itself that the snout almost touches the tail. The body also has now
turned over so as to lie with its left side on the yolk. Observe the
two pairs of small buds which are the _rudiments of the limbs_.
8. =Chick after five days’ incubation.=—Cut open the _amnion_, and
notice the great increase in size of the embryo, and especially the
enormous development of the _head_. The _limbs_ now show signs of
division into segments. Observe, under the hinder end of the body, a
small, bladder-like outgrowth, the _allantois_, which in the later
stages grows rapidly and spreads all round the inside of the shell. It
is the breathing organ of the chick.
9. =Effect of varnishing an egg.=—Varnish an egg, and leave it under
the hen with unvarnished eggs for the whole period of incubation (21
days). The varnished egg does not develop, because the varnish closes
the pores of the shell and prevents the embryo from breathing.
[Illustration: FIG. 186.—Hen’s Egg after 1 day’s incubation. _a_,
air-chamber; _hd_, head of embryo; _v.a._, area in which yolk
blood-vessels will appear later; _yk_, yolk. (× 1.)]
=The early development of the chick.=—When the hen’s egg is exposed to
a temperature of about 40°C., the =germinal disc=—the circular patch of
living matter which lies, somewhat like a small inverted watch-glass,
upon the upper surface of the yolk—grows larger, and its parts are
gradually modified to form the various regions of the chick’s body. The
white and yolk of the egg are used up during the process, and by the
time they are absorbed, the young bird is in a condition to break the
shell and take up the activities of an independent life. To watch the
orderly appearance and gradual development of the different systems of
organs is most fascinating, and fortunately the observation of the main
features presents no great difficulty if the foregoing instructions are
followed.
The first signs of the chick are to be seen (Fig. 186), towards the
end of the =first day= of incubation, in a streak which crosses the
germinal disc in a direction at right angles to the long axis of the
egg. One end of the streak is distinctly rounded, and this is the
=head= end (_hd._). In almost all cases, if the egg be placed so that
its broad end is to the observer’s left, the head of the embryo will be
directed away from him.
=A day later=, the embryo is markedly larger, and is partly covered
by a double membrane called the =amnion=.[17] Surrounding the embryo
is now (Fig. 188) a network of fine blood-vessels which ramify over
the yolk and carry small particles of yolk to feed the growing organs.
At the end of the second day the network could be about covered by a
sixpenny piece. On each side, its veins join to form a single small
tube running to the =heart= (_ht._), a tiny red dot which is situated
behind the head and can be seen, by the help of a lens, to be beating
rapidly. The head has grown more than the rest of the embryo, owing to
the rapid development of the primitive brain, and is bent forwards.
The head has turned over a little, so that its right side is directed
towards the egg-shell; the rest of the embryo still lies “face-down.”
The right =eye= (_e._) can easily be seen as a dark spot on the side of
the head.
[Illustration: FIG. 188.—Hen’s Egg after 2 days’ incubation. The amnion
has been removed. _a_, air-chamber; _au_, beginning of right ear; _e_,
right eye; _ht_, heart; _v.a._, network of yolk blood-vessels; _yk_,
yolk. (× 1.)]
By the end of the =third day= (Fig. 189) the head and neck are raised
distinctly above the yolk, and the tail is also more plainly marked
off, so that the body is connected with the yolk only by a short wide
tube, the =yolk-stalk= (_yk.st._, Fig. 187, _B_). The neck as well
as the head has now turned so as to lie with the right side directed
towards the shell. The commencement of the =ear= is to be seen on each
side as a small pit (_au._) a little above and behind the large eye.
[Illustration: FIG. 189.—Hen’s Egg after 3 days’ incubation. The amnion
has been removed. References as in Fig. 188. (× 1.)]
[Illustration: FIG. 190.—Chick Embryo after 4 days’ incubation. The
amnion has been removed. _all_, allantois; _am_, cut edge of amnion;
_f.l._, fore-limb; _h.l._, hind-limb; _ht_, heart; _t_, tail. (After
Duval.) (× 2.)]
On the =fourth day= the embryo turns to lie entirely on its left side.
It becomes more completely folded off from the yolk, and the connecting
yolk-stalk is a narrower tube than before. The previously formed organs
increase in size and complexity. The disproportionate size of the head,
owing to the great development of the brain, is still more marked than
before, and the head is so strongly bent upon itself that the snout
almost touches the tail. One of the most noteworthy features of the
fourth day is the appearance of the =limbs=. As yet these are merely
a pair of small buds (_fl._, _hl._, Fig. 190), and no joints can be
detected in them.
[Illustration: FIG. 191.—Hen’s Egg after 5 days’ incubation. _a_,
air-chamber; _all_, allantois; _am_, amnion; _ar. vasc._, area of yolk
blood-vessels; _emb_, embryo; _yk_, yolk. (After Duval.) (× 1.)]
[Illustration: FIG. 192.—Diagrams illustrating the method of
development of the allantois. _al_, allantois; _am_, amnion fold;
_am.c._, amniotic cavity; _em_, embryo; _yk_, yolk. (After Foster and
Balfour.)]
By the end of the =fifth day= (Fig. 191) the head is enormous, and the
limbs now show signs of being divided into definite segments. A thin
bladder-like structure—the =allantois= (_all._), which appeared on the
fourth day—has grown out from the lower part of the body, behind the
yolk-stalk. Its mode of origin is well shown in Fig. 192. It rapidly
increases in size, and soon extends over the embryo (Figs. 192 _B_,
and 191) and becomes closely applied to the shell-membrane. Air passes
through the pores of the shell, and its oxygen is taken up by the blood
which circulates in the vessels of the allantois. At the same time,
waste carbon dioxide is able to escape from the blood to the outer
air. The allantois is therefore the =breathing organ= of the developing
chick. If the egg is varnished and the shell thus rendered air-tight,
the embryo dies of suffocation at an early stage.
[Illustration: FIG. 193.—Chick after 9 days’ incubation. (After Duval.)
(× 1.)]
The chief organs of the bird are now established, and the later
development may be sketched more briefly. By the end of the =ninth day=
(Fig. 193) the white of the egg is almost used up; the yolk, however,
is still large, and is connected with the chick’s body by the narrow
yolk-stalk. It thus appears that the white is not directly absorbed
by the chick, but is first taken up by the yolk and afterwards passed
on by the yolk blood-vessels which run to the heart. By this time,
too, the allantois has spread at least halfway round the inside of the
shell, that a supply of oxygen adequate to the increased needs of the
animal may be obtained from the air. The chick has now a characteristic
bird-like appearance; the beak has appeared; feathers have begun to
sprout; the neck is long and slender; and the segments of the limbs,
including the fingers and toes, are well defined.
About the =fourteenth day= the chick turns so as to lie lengthwise in
the shell, with its head near the broad end. The yolk-sac dwindles
in size, and at last, about the twentieth day, it is drawn into the
interior of the body. Now the chick becomes restless, and—usually
on the =twenty-first day=—thrusts its beak through the inner
shell-membrane into the air-chamber at the broad end of the egg.
For the first time it draws refreshing air into its lungs, and is
stimulated to break the shell by a knob on its beak, and to creep out
into the world.
54. THE EDUCATION AND LATER GROWTH OF THE CHICK.[18]
1. =Hatching.=—On the 20th or 21st day of incubation remove three or
four eggs from the clutch under the hen, and keep them in a warm cosy
place so that you may watch the process of hatching. Can you hear the
chick tapping the inside of the shell? Could it have been _taught_ to
tap? Which part of the shell cracks first? When the shell has cracked,
can you hear the chick chirping? Could it have been taught to chirp?
Imitate the chirp and listen for a response. Keep the newly-hatched
chicks in a warm, soft place. How soon do they recover from the
exhaustion of hatching? Do the chicks show a liking for warm corners?
Are they afraid of being touched gently?
2. =Locomotion.=—How soon do the chicks begin to run about? Do they
stumble upon obstacles, or do they avoid or leap over them? Do they use
their wings in running, or in jumping down a small step? Put a chick
into a basket, and lower the basket quickly through the air, being
careful not to let the chick fall out. Does it move its wings? How?
3. =Feeding and drinking.=—Lay a few grains of soaked wheat upon the
ground before a chick which has not yet been fed. Does it peck at
them instinctively? Tap a grain with the point of a pencil; does the
chick now peck at it? Does it hit the grain at the first try? Does it
ever strike at a grain which is out of reach? Watch a hen with her
chicks; does she teach them to peck at food? How? Do the chicks know
instinctively the difference between food and grains of sand, or have
they to learn? Try if a chick can distinguish between a small worm and
a bit of red worsted. Are young chicks afraid of large insects?
Take a chick, which has not yet drunk, to a small pool (a few drops) of
water. Does it seem to know the use of the water? Induce it to peck at
the water; does it now drink? How?
4. =The crouching-instinct.=—Clap your hands suddenly and loudly near
young chicks. How do the chicks behave? Does this behaviour render them
less conspicuous?
5. =Non-recognition of hen.=—Having made the above observations on
chicks hatched apart from the hen, put the chicks among their brothers
and sisters with the parent hen. Do the new-comers respond, as readily
as the others, to the clucking, etc., of the hen?
6. =Maternal training and protection.=—How many different meanings can
you recognise in the different sounds of the hen’s voice? How does she
call and protect the chicks when any danger threatens them?
7. =The voice of the chick.=—Notice the different sounds by which a
chick expresses pleasure, alarm, distress, etc.
8. =Preening and scratching.=—At what age do chickens begin to preen
their feathers, and to scratch the ground? Try to discover if these are
instinctive activities, or whether they have to be learnt from the hen.
9. =Change in plumage.=—At what age are the down feathers replaced by
the true plumage? At what age is it possible to distinguish the young
cocks from the young hens?
10. =External characters, etc., of adults.=—Notice the flowing
tail-feathers, hackles (the long feathers on the neck and loins), comb,
and spurs of the cock-birds, and their absence or small size in the
hens. What differences are there as regards voice? How does the hen
announce that she has laid an egg? Which sex is the more pugnacious?
=The recently hatched chick.=—The newly-hatched chick is clothed with
fine down-feathers (pp. 273 and 277). It is generally exhausted by
its struggles to escape from the shell, but it soon recovers, and is
able to run about freely on the second day after hatching. Young birds
which, like the chick, are active immediately after hatching, are said
to be =precocious=.
=Instinct and education.=—From the first, the chick performs certain
movements which are obviously =instinctive=, that is, which have not
been acquired by any process of imitation or instruction. Even in
the egg, it may be heard chirping soon after it has taken its first
breath of air; and the complex activities of walking, running, jumping
over obstacles, and, later, preening the feathers and scratching
the ground—each of which involves the nicest adjustment of several
muscles—are also instinctive. Certain other powers have to be learnt;
the hen, for example, lifts and drops before the chick a particle of
food which she wishes it to seize, and it soon learns to peck. At
first its pecks generally fall a little short of the objects, but
presently it becomes very adroit at catching food. “A chick a day or
so old will catch a running fly at from the seventh to the twelfth
shot.”[19] There does not appear to be much instinctive recognition of
the difference between objects which are valuable as food and those
which are the reverse. Such discrimination comes only by experience,
and to a very young chick a piece of red worsted and a small worm are
equally attractive before being seized. In the same way, the nature of
water has to be learnt. Chicks peck at drops of water, but do not seem
to know the use of water until their beaks are wetted, when they drink
instinctively in the usual manner.
The use of the wings is also a matter of instinct, but it is acquired
somewhat late, and is assisted by parental encouragement and example
even in birds which are noted for their powers of flight. Fowls do
not fly much, but chicks may be observed to use their wings as an aid
in running or jumping. Prof. Lloyd Morgan[20] quotes an interesting
experiment which shows well how deeply the reliance on flight is
stamped in bird-nature. “If a chick a day or two old be placed in a
basket, held firmly in the hand, and then lowered rapidly through
the air, the fledgling will stretch out his little immature wings in
such an attitude as would make them break the fall were they fully
developed; or will, if he be a little older, flap them with flight-like
action, in either case showing an instinctive response.”
=Hens and chickens.=—Chickens which have been hatched in the natural
manner are, from the first, under the control of the hen (Fig. 194),
and her anxious care for their welfare has always been considered one
of the most beautiful examples of the maternal instinct. In their
defence her courage is unbounded; should she discover a succulent
worm or other dainty morsel, her ordinary complacent cluck changes
to a note of invitation, to which the brood at once responds; and at
her danger-signal the chickens run to take refuge under her wings, or
crouch motionless against the ground. The chirp of a chick also is
capable of expressing several states of feeling, such as contentment,
pleasure, alarm, and distress. These different notes are not only
perfectly intelligible to the hen, but are familiar to anyone who has
had experience of poultry.
[Illustration: FIG. 194.—Hen and Chickens.]
In the face of these well-known instances of the perfect understanding
between the hen and her chickens, it is somewhat surprising to find
that chickens, hatched apart from the hen and then placed with the
rest of the brood after a few days, at first pay very little attention
to the hen, except for their instinctive tendency to nestle into warm
places, and do not seem to understand her clucks.
=Adult fowls.=—The down-feathers are soon shed and replaced by the
true plumage, and the chicken gradually takes on the appearance of
the adult. A marked difference is generally to be seen between the
cocks and hens (Fig. 195) of any breed of poultry. The cock is usually
provided with flowing tail-feathers, hackles (elongated feathers on
the neck and loins), a prominent comb, and “spurs”—features which are
either absent or much less perfectly developed in the hens. As great
differences exist between the voices of the two sexes, the crow by
which the pugnacious male challenges his rivals, and the cackle of the
hen when she has laid an egg, being familiar examples.
[Illustration: FIG. 195.—Cock and Hens.]
EXERCISES ON CHAPTER XVI.
1. Point out the differences in appearance and position
between the white and yolk of a fowl’s egg. What becomes
of each during the development of the egg?
2. When does the heart of a chick begin to beat? Describe
its appearance at this time, and explain what must be done
to expose it to view.
3. Explain exactly where the chick is to be found in a
fertile egg which has been incubated for three days. How
big is a chick of that age? Of what colour is it? Does it
give any signs of life? (1898)
4. What is the amnion? Where, in a developing chick, is it
to be found, what is its appearance, when and how is it
formed, and what is its use?
5. Explain the nature and use of the “balancers” of an egg.
6. Explain how a developing chick breathes.
7. What new organs are first seen distinctly on the fourth
and fifth days respectively of incubation of a hen’s egg?
Explain exactly how you would expose them to view, and
describe their appearance.
8. What is the period of incubation of a duck’s egg? Observe
and describe exactly how the hatching duckling breaks open
the shell and escapes from it.
9. Observe and describe a duckling’s first attempt to swim.
Is the action instinctive or not?
10. Make other observations upon ducklings, comparing them
in as many respects as possible with chicks, and write
careful accounts of the results you obtain.
11. How does a fowl’s egg which has been hatched for four
days differ from a fresh-laid egg? Describe the new
structures which have formed in it, so far as they can be
made out by the unaided eye. (1904)
12. Where does the chick begin to form in the egg? Explain
the arrangement which brings it as near as possible to the
body of the sitting hen. (1905)
13. What is the use of the cloudy masses attached to
opposite sides of the yolk of a fowl’s egg? (1906)
FOOTNOTES:
[17] The amnion originates, early in the second day, as a double fold
of the yolk-surface in front of the embryo. Similar folds arise round
the sides and tail, forming a low wall (Fig. 187, _A_); the folds
gradually grow over the embryo (Fig. 187, _B_) until, during the
fourth day, they meet (Fig. 187, _C_) and enclose it in a protective
transparent bag, containing a watery fluid.
[Illustration: FIG. 187.—Diagrams to illustrate the method of
development of the amnion. The embryo and the rest of the yolk are
supposed to be seen in median longitudinal section; the head end is to
the right. For convenience, the yolk-membrane (_yk.m._) is represented
at some distance from its contents. _am_, folds of amnion; _am.c._,
amniotic cavity; _em_, embryo; _yk_, yolk; _yk.st._, yolk-stalk. (After
Foster and Balfour.)]
[18] I desire to acknowledge my indebtedness, in drawing up this
section, to Prof. Lloyd Morgan’s _Habit and Instinct_ (Arnold).
[19] Lloyd Morgan’s _Habit and Instinct_ (Edward Arnold).
[20] Lloyd Morgan’s _Habit and Instinct_ (Edward Arnold).
CHAPTER XVII. SOME FAMILIAR BRITISH BIRDS.
55. THE THRUSH FAMILY.
1. =The song-thrush, mavis, or throstle.=—Throstles are to be seen
throughout the year. Take every opportunity of observing their habits,
and make careful notes of these at the time. Especially attend to the
following characters:
(_a_) _General appearance._—What is the average size of the bird? What
is the length of the tail? At what angle is the tail held? Does the
bird move it in any special manner? What is the prevailing colour of
the body? Notice the light-coloured and spotted breast. Compare the
male and female as regards size, colouration, etc.
(_b_) _Habits._—What situations do throstles chiefly inhabit? Do they
keep near the edge of the wood, or have you often seen them inside
thick woods? Does the bird hop, or walk, when on the ground? Upon what
does it feed? Have you ever seen it cracking the shell of a snail?
If you find a heap of snail-shells near a stone, watch, at a little
distance, for the throstle coming to crack snail-shells on the stone.
Does it also eat worms, or fruit? Describe a throstle’s beak. How would
you describe the flight—as high or low, swift or slow, straight, in
wide curves, or undulating? Does the bird perch on trees? How does it
use its toes in perching?
(_c_) _Song._—In what months does the throstle sing? Does it sing late
at night and early in the morning? How does it compare with other
birds in this respect? In what positions have you seen the bird
singing—when flying, perching, or on the ground? Try to write down the
syllables which seem to you most like the throstle’s song, and notice
how the phrases are repeated. Notice that throstles sing less during
August than in autumn. Listen, in September or October, for young
thrushes learning to sing, and contrast their efforts with the song of
the adult birds.
(_d_) _The nest._—At what time of the year do throstles pair and build
their nests? In what situations have you found the nests? Write a
description of the shape, size, and materials of the first throstle’s
nest you find. Visit it frequently, try not to disturb the birds, and
note the dates of laying of the eggs. How many eggs are laid? What
are their size and colour? How are they arranged in the nest? Do the
broad or the narrow ends point inwards? What are the advantages of this
arrangement (i) for purposes of packing, (ii) when the eggs hatch? Do
both birds sit on the eggs? If only one, which? What is the time of
incubation?
(_e_) _The young._—Are the young birds naked and helpless, or
feathered, at hatching? How do the parent-birds feed them? What is the
appearance of the fledglings? In what respect do they (i) resemble,
(ii) differ from, the parents? How long do the birds remain in the nest
after hatching? Write an account of any education you have observed
them to receive from the parents.
{Make similar observations and notes on other birds, in addition to
the special observations mentioned below, and learn to recognise their
appearance, flight, song, nest, and eggs. A field-glass will be found
of great assistance.}
2. =The missel-thrush, or storm-cock.=—Compare the missel-thrush with
the song-thrush. Notice its larger size, the brighter colour of its
spotted breast, and its somewhat less musical song. Listen for its song
during, or immediately after, a storm, even in winter. In the nesting
season observe the marked courage and pugnacity of the bird.
3. =The blackbird.=—Compare the blackbird with the thrushes in
respect of appearance, food, habits, and song. Notice the difference
in the colouration of the male and female blackbird. Observe that
the young bird has a spotted breast like that of a thrush, but that
old blackbirds are not spotted. Have you noticed a blackbird show a
preference for singing in any particular place? What observations
would lead you to suppose that the blackbird is a near relative of the
thrushes?
4. =Fieldfares.=—Distinguish these birds from thrushes. Notice that
they arrive about October, and frequent fields in large parties.
=The thrush family.=—For many reasons the thrush family forms a
convenient starting point in the study of the habits of common British
birds. It includes some of our very finest songsters and therefore most
popular birds; many of its members are abundant in most parts of the
country, so that nearly every student has the opportunity of observing
them at first hand; the birds are not specially shy; and, lastly, the
family affords excellent material for the method of comparison and
contrast, which, be it repeated, is the essence of all sound work in
nature-study.
The =song-thrush=, which is also known as the =throstle= and =mavis=,
is a shapely bird, easily recognisable by its grey, spotted breast
(Fig. 196), which may be seen all the year round in wooded parts of
the country. The male and female are very similar in appearance, and
of almost equal size, measuring 8 or 9 inches from head to tail. The
thrush generally feeds on the ground, hopping along on a pair of sturdy
legs and feet, seizing and pulling out worms which incautiously show
themselves at the mouths of their burrows, and catching insects and
snails. A thrush usually has a favourite stone on which it cracks the
shells of snails, and it is not uncommon to find, near the stone, a
little heap of broken snail-shells—the remains of many a feast. In
winter, when the summer diet can no longer be obtained, the thrush
subsists largely upon the fruit of hawthorn, mistletoe, etc. Its beak,
as is usual with birds, is distinctly adapted to the capture of its
food, being, in this case, narrow, round, and fairly long. The thrush
is a strong and rather rapid flier.
[Illustration: FIG. 196.—Song-Thrush. (× ⅙).]
Thrushes begin to sing at the first signs of spring, pairing and
commencing the work of nest-building in February or early March.
The throstle’s song is surpassed by very few birds; and many people
consider it equal, if not superior, to the nightingale’s. The song
begins before sunrise, and may be heard when almost all other birds
have retired to rest. The thrush has a curious habit of repeating
each strain two or three times, “lest,” as Browning says, “you should
think he never could recapture the first fine careless rapture.”
Many attempts have been made to imitate the song by words; Mr. R.
Kearton[21] quotes with approval the following rendering by the famous
Scottish naturalist Macgillivray:
“Qui qui qui kweeu quip,
Tiurru tiurru chipiwi,
Too-tee, too-tee, chiu choo,
Chirri chirri chooee
Quiu qui qui.”
But, as Mr. Kearton remarks, “no human words can ever represent,
especially in cold type, the passionate vehemence, the sprightliness,
or the tender pleading of a thrush’s song.”
[Illustration: FIG. 197.—Nest of Song-Thrush. (× ⅓).]
The nest of the thrush (Fig. 197) is a massive structure, deep and
cup-shaped, and open at the top. It is built of small twigs and grass,
and is plastered with mud or cow-dung until the inside is smooth and
hard. It is usually placed in an evergreen bush or tree, but may
also be found in cavities in tree-trunks or in holes in walls, or
even in sheltered places on the ground. The eggs number from 4 to 6;
they are about an inch long, are sky-blue in colour, and marked with
black spots, which are most numerous near the thick end. The eggs are
arranged with their pointed ends inwards; this method not only allows
them to be packed more closely together and therefore to be more
easily covered by the sitting bird, but is also of convenience at the
time of hatching, as the young birds usually emerge (p. 294) at the
thick end. The eggs hatch after a fortnight’s incubation. The young
thrushes are at first blind, almost naked, and are quite helpless. They
make rapid progress, however, and are sufficiently fledged to leave the
nest in about a fortnight after hatching. The fledgling throstle (Fig.
198) is lighter in colour than the adult, and much more distinctly
spotted. In October the young birds may be heard learning to sing;
their first efforts are hesitating and uncertain, but by tireless
practice and careful imitation of the old birds they presently come
into full possession of their delightful powers.
[Illustration: FIG. 198.—Young Song-Thrushes in Nest.]
The =missel=, or =mistletoe=, =thrush= (Fig. 199) much resembles the
song-thrush in appearance and manner of life, but is distinctly larger,
measuring about 10½ inches from head to tail. It has a very pleasing
song, which may be heard, even in the depth of winter, when all other
song-birds are mute. The missel thrush’s habit of singing vigorously
during storms has led to its alternative name of “=storm-cock=.” The
bird is noted for its pugnacity in the breeding season, and for the
courage with which it defends its nest and young; any other birds
approaching the nest are promptly attacked and driven to a distance.
The nest is generally built in a tree, where a branch springs from the
trunk. It is made of dried grass, moss, and wool, and the hen lays from
4 to 6 pale-green eggs, which are speckled with brown.
[Illustration: FIG. 199.—Mistletoe-Thrush. (× ⅙.)]
[Illustration: FIG. 200.—Blackbird (Hen). (× ⅙.)]
The =blackbird= (Fig. 200) may easily be distinguished from the
thrush by its colour—the male being black, with a yellow beak, and
the female blackish brown, slightly mottled below. The blackbird is
slightly larger than the thrush, but in shape and habits the two
birds are very similar; they haunt the same woods, live upon similar
food (_i.e._ worms, insects, snails and, in winter, fruit) and
build their nests in similar situations. The blackbird’s song is,
however, quite distinctive, and consists of mellow, flute like notes,
without the repetition which is so characteristic of the throstle and
missel-thrush. The blackbird is fond of perching, when singing, upon a
bare branch which commands a good view of the surroundings. The nest
(Fig. 201) is much like that of the song thrush, but the inside has a
soft lining of fine grass instead of being hardened with mud. The 4, 5,
or occasionally 6 eggs are bluish-green in colour, and are marked with
_blurred_ brown spots.
[Illustration: FIG. 201.—Blackbird’s Nest.]
Curiously enough, young blackbirds, like young thrushes, are very
distinctly spotted. There can be no doubt that blackbirds and thrushes
are descended from the same stock, and that their ancestors had spotted
breasts. For some reason, the blackbird has lost its family colours,
although, as is so often the case among animals, it is still compelled
to bear the marks of its ancestry during its infancy. Young blackbirds
also receive a musical education from their parents, and may often be
heard practising their song in September or October.
The =fieldfare=, another near relative of the thrush, arrives in
this country about the beginning of October, and stays with us for
the winter, returning in spring to its nesting places among the
pines and firs of Norway. The general colour of the bird is grey,
with reddish-brown on the wings, and its breast is speckled in the
thrush-manner. Fieldfares frequent fields in large parties, especially
in the evenings, but are readily alarmed.
=Other birds of the thrush family.=—The redwing, wheat-ear, whin-chat,
stone-chat, redstart, robin, nightingale, and hedge-sparrow are other
members of the thrush family which can here be only referred to. They
have many points of resemblance, one of the most interesting of which
is that the young birds are invariably spotted. The bill is usually
rather long, stout, and straight, the staple food being insects,
worms, etc., though fruit is also eaten, especially in winter. The
nests are typically cup-shaped, and the eggs greenish or blue, with
or without spots. The young birds are quite helpless and almost naked
when hatched, and can only open their mouths to be fed by the parents.
Even after they have left the nest they need careful and continuous
teaching by the parents before they can be made to understand that
in future they will have to obtain their own food. Birds of this
family, on account of the variable character of their food, are
not so markedly migratory as many others, although they generally
move further southward in winter, as the supply of insects becomes
scarce—their place being taken by birds which have spent the summer
in more northerly regions. This habit is very obvious in the case of
the fieldfare and redwing, which visit us for the winter and return to
Norway and Sweden for the summer. The nightingale, on the other hand,
arrives here from the south in April to build its nest and rear its
young.
56. THE SWALLOW FAMILY, THE SKYLARK, AND CROWS.
1. =The swallow.=—(_a_) _General appearance._—Notice, first of all, the
bird’s colouration, as this readily distinguishes the swallow from the
martins. The whole of the upper surface is steel-blue; the only white
is on the ventral surface. A black band stretches across the breast;
the throat and forehead are pink. Observe the long, deeply forked tail,
and the broad, short bill.
(_b_) _Habits._—What are the earliest and latest dates on which you
have seen swallows? Do the birds seem to prefer the neighbourhood of
water? Have you ever seen them (i) perching on trees, (ii) on the
ground? Why do swallows occasionally alight on the ground? Do they seem
comfortable on the ground? Observe the small and weak feet; are these
adapted to a terrestrial life? Do swallows feed on the ground? What do
they eat? How are the insects caught? What is the advantage of the very
wide gape? How would you describe the flight of the swallow?
(_c_) _Voice._—Does the swallow sing? Describe its voice. Have you
heard it when the bird was on the wing, or only when it was at rest?
What kind of sound is uttered by the swallow when it is alarmed or
angry?
(_d_) _Nest._—In what situations have you found swallows’ nests? (Do
not confuse the nest with that of the house-martin, which lays white,
unspotted eggs.) How soon after their arrival do the birds begin to
build? What is the shape of the nest? Of what materials is it composed?
How many eggs does it contain? What is their colour?
(_e_) _Young._—Look for the newly-hatched young about the last week in
June, and describe their appearance. How soon after hatching do they
leave the nest? Do they at once feed themselves, or are they fed by the
parents? Keep the nest under observation after the young birds have
left it, and notice whether the old birds rear another brood the same
summer.
In September look for the annual congregation of swallows which
precedes their departure for Africa.
2. =The house-martin.=—Distinguish the house-martin from the swallow
by the patch of white on the upper tail-coverts (Fig. 179), and by the
feathered toes. Make notes of the dates of arrival and departure of the
birds. Do house-martins occupy old nests or build fresh ones? What are
the position, material, shape, and size of the nest? How does it differ
from the swallow’s nest? Is the martin of sociable or solitary habits?
Watch the birds building new nests or repairing old ones, and describe
the process. Examine and count the pure-white eggs. What are the
newly-hatched young like? How many broods have you known one pair of
martins to rear in one season? Have you ever known martins to be turned
out of their nests by sparrows? Watch for the autumn congregation.
3. =The sand-martin.=—Notice the small size of the bird, the
mouse-colour of the upper parts, and the black feathers of the wings
and tail. Note the dates of arrival and departure. Is the bird often
seen near houses? Look for the nesting-holes in cliffs, banks, etc.
Examine the holes, and notice that they lead into tunnels which slope
slightly upwards. What is the use of the slope? If possible examine the
nest at the end of the tunnel, and compare it and the eggs with those
of the swallow and house-martin. Observe the peculiar jerky flight.
Does the bird sing? Describe its voice.
4. =The skylark.=—Does the skylark frequent woods or open ground?
Describe the appearance, size, and colouration of the bird, and try to
see the long toes. Especially notice the long claw of the hind-toe.
Have you ever seen the bird perching on trees or bushes? Are the feet
well adapted for perching? Does the skylark run or hop? In what month
does it begin to sing? In March look for larks’ nests in hollows and
ruts of fields. What are the materials of the nest? Describe the number
and appearance of the eggs. Listen to the song, and try to say in
what respects it differs from that of other birds. Does the bird sing
only when flying, or also when on the ground? Describe the skylark’s
flight, and study its method of soaring (p. 278). Observe that the
birds collect into flocks in autumn. Do they leave the country for
the winter? How do they spend the winter? Do they sing in winter? If
possible examine the beak; for what kind of food do you think it best
adapted?
5. =The rook.=—Notice the size, shape, and colouration of the bird. Do
rooks live merely in pairs or in large communities? Do they build on
the ground or in trees? Are the trees high or low? What is the largest
number of rooks’ nests you have seen in one tree? Watch the birds
repairing and building nests in February and March. Of what are the
nests composed? Have you ever seen rooks stealing sticks from other
rooks’ nests? Are the birds quarrelsome? Where do they feed? Do they
hop or walk? Do they keep together when feeding? Do all the birds of
one rookery feed at the same time, or do some remain in the trees? Why?
What is the shape of the beak? How is this associated with the food of
the bird? Do the farmers in your neighbourhood consider rooks useful
or the reverse? Why? What is the voice of the rook like? How does it
vary to express warning, anger, etc. Describe any observations which
lead you to suppose that a colony of rooks has a code of laws. Describe
the flight of the rook; what other birds fly in a somewhat similar
manner? In spring, look beneath the trees for the broken shells of eggs
which may have fallen from the nests. What is their colour? Describe
the appearance and habits of the young birds. Where do rooks spend the
winter? Have you ever seen them visiting and inspecting their nests in
winter?
6. =Other birds of the crow family.=—With the rook compare and contrast
the crow, raven, jackdaw, magpie, and jay.
=The swallow family.=—Swallows and martins are popular with all lovers
of birds, for many reasons. Their arrival is welcomed as visible
evidence of the approach of summer; their graceful and rapid flight
delights the eye; their obvious liking for the neighbourhood of human
dwellings wins our sympathy; and, lastly, they claim our gratitude by
their incalculable services in keeping down insect pests.
The =swallow= (Fig. 202) may readily be distinguished from the martins
by the absence of white from its upper parts, which are glossy and
of a steel-blue colour. The forehead, chin, and throat are of a pink
or chestnut colour; the ventral surface is white, with a black band
crossing the neck. The tail is long, and very deeply forked. The bill
is short and broad, and the gape stretches nearly to the eyes—a great
advantage to a bird living on insects which are caught flying. The feet
are very small and weak, but as the swallow spends most of its time in
the air, and rarely alights on the ground except to collect materials
for its nest, it does not need very sturdy hind-limbs, and the feet are
chiefly used for perching.
[Illustration: FIG. 202.—The Swallow. (× ¼.)]
Swallows arrive in this country about the middle of April, and about a
month later proceed to build their nests in the chimneys of houses and
on the rafters of barns and outhouses. The nest is basin-shaped and
open at the top; it is chiefly composed of mud, which the birds collect
on the ground, place in position, and allow to dry. Short straws are
used to bind the mud together, and the nest is lined with soft grass
and feathers. The hen lays from 4 to 7 eggs, which are a translucent
white, with reddish-brown or grey markings. The first brood of young is
usually hatched about the end of June, but a second or even a third
brood may be raised before the parents depart for the south. Gilbert
White[22] gives the following charming account of the training of young
swallows: “For a day or two they are fed on the chimney-top, and then
are conducted to the dead, leafless bough of some tree, where, sitting
in a row, they are attended with great assiduity, and may then be
called _perchers_. In a day or two more they become _flyers_, but are
still unable to take their own food; therefore they play about near
the place where the dams are hawking for flies; and, when a mouthful
is collected, at a certain signal given, the dam and the nestling
advance, rising towards each other, and meeting at an angle; the young
one all the while uttering such a little quick note of gratitude and
complacency, that a person must have paid very little regard to the
wonders of Nature that has not often remarked this feat.” When the
young bird has learnt to feed itself “it at once associates with the
first brood of house-martins; and with them congregates, clustering on
sunny roofs, towers, and trees.... All the summer long is the swallow a
most instructive pattern of unwearied industry and affection; for from
morning to night, while there is a family to be supported, she spends
the whole day in skimming close to the ground, and executing the most
sudden turns and quick evolutions.... When a fly is taken a smart snap
from her bill is heard, resembling the noise at the shutting of a watch
case; but the motion of the mandibles is too quick for the eye.”
The swallow drinks whilst flying, sipping the water from the surface
of pools. Its song is a delicate and pleasing warble, which is uttered
both at rest and during flight. The voice becomes a squeak when the
bird is alarmed or angry. Just before the autumn migration, swallows
perch in crowds on roofs, hedges, and the branches of trees. They leave
for Africa about the beginning of October.
The =house-martin= may be distinguished from the swallow by the patch
of white upon the upper tail-coverts, and by its feathered toes. Like
the swallow, it arrives in this country about the middle of April. The
birds soon begin to repair their old nests and to construct new ones
under the eaves of houses. The nest is largely composed of clay or
mud, which the birds collect from damp places in the road, etc., place
in position against the wall, and allowed to harden. The completed
nest is somewhat bag-shaped, having only a small hole at the top; it
is lined with soft grass. The eggs are white, without spots. It is
worthy of notice when a wild bird lays white eggs, they are hidden
from sight by the shape or position of the nest, as in the case of
the martins, or the nest is built in an inaccessible place. Exposed
eggs are usually made more or less inconspicuous by being coloured
or spotted. House-sparrows (Fig. 208) have often been known to expel
the defenceless martins from their nests, and to lay their own eggs
therein. The eggs of the sparrow may be recognised by their grey
colour, and by the brown blotches with which they are marked.
The structure of the martin, like that of the swallow, is admirably
adapted to a life in the air, and to a diet of flying insects—the bird
having powerful wings, small and weak feet, and a soft and short but
widely-opening beak. House-martins leave us about the beginning of
October.
The =sand-martin= is distinctly smaller than either the swallow or
house-martin, and it may be further distinguished from them by the
“mouse-colour” of its upper parts. It usually arrives in this country
about a fortnight in advance of its two relatives, and also departs
before them, leaving in August or September. These birds live in
colonies in tunnels which they excavate in banks or friable cliffs
(Fig. 203)—generally in the near vicinity of water. The excavation may
be three feet in length; it slopes slightly upwards to the nest (which
is placed at the end of the tunnel), in order that rain water may not
collect in it. The eggs are pure white, and five or six in number. The
birds are exclusively insectivorous; they do not sing, but utter a
little twitter. The flight is very characteristic, consisting of “odd
jerks and vacillations, not unlike the motions of a butterfly.”
[Illustration: FIG. 203.—Sand Martins’ Nesting Holes.]
[Illustration: FIG. 204.—The Skylark. (× ⅓.)]
=The skylark.=—At the first glance, it is obvious that the skylark
(Fig. 204) is adapted for a life spent largely upon the ground. The
large toes lie flat on the earth, and the long claw of the hind toe
is plainly not very suitable for grasping the twigs of trees in the
act of perching. In fact, the skylark only occasionally perches,
on low bushes. Walking or running on the ground, it lives upon
grubs, caterpillars, flies, worms, etc., and also upon seeds, which
its strong beak enables it to extract from the husks. The body is
brown, the wings being streaked with black, and the dull-white throat
and breast being marked with brown spots—a colouration which is a
considerable protection. The nest is built in March, in a hollow or
rut on the ground; it is lined with dry grass. The four or five eggs
are greenish-grey, and spotted with brown. Whilst the hen sits upon
her eggs (Fig. 205) the cock-bird either hunts for food or sings his
delightful song as he soars in the air. The wonderful powers of soaring
of this bird have already (p. 278) been referred to. When the lark
drops to the ground he alights at a little distance from the nest,
and then runs up to it through the grass. By this device he avoids
revealing the position of his mate and young.
[Illustration: FIG. 205.—Skylark at Home.]
Skylarks rarely sing in the depth of winter; in autumn they form
large flocks which patrol the fields until spring in search for
food—rendering incalculable services to mankind by the destruction of
insect-larvae. During the coldest weather of winter the birds crouch
under banks and hedges.
=The rook.=—The rook (Fig. 206)—often called the crow—is a rather
large bird, measuring about 17 inches from head to tail. Its plumage
is black, but as it becomes adult the feathers covering the face and
nostrils are shed, leaving the skin of these parts bare. The bird
has long and pointed wings, and is a strong flier. The bill is stout
and almost straight. Rooks are no songsters, their harsh “caw” being
destitute of musical qualities. When heard at a distance, however, the
cry “becomes a confused noise or chiding; or rather a pleasing murmur,
very engaging to the imagination, and not unlike the cry of a pack of
hounds in hollow, echoing woods, or the rushing of the wind in tall
trees, or the tumbling of the tide upon a pebbly shore.”[23]
[Illustration: FIG. 206.—The Rook. (× ¹/₁₀.)]
One of the most interesting features of rook-ways is the habit of
living in organised communities.[24] It is true that a primitive form
of social life is found among swallows, martins, and (in winter) larks,
reminding us of the gregarious habits of the rabbit (Chapter XII.)
among mammals; but a rook-society is rather to be compared with the
pack-life of the wild dogs (p. 252), which depends for its integrity
upon the observance of certain rules of conduct by its members.
Naturalists have long known that such a code of laws is in force in
every rookery, but what these laws are we do not fully understand. Here
is a profitable and interesting field of observation for the student.
It has sometimes been observed that certain birds are prevented by the
rest from building until the nests already commenced are finished, and
cases have been known of birds being expelled from the rookery, or even
put to death, after a consultation or “trial,” presumably for some
breach of law. On the other hand, it must be admitted that rooks are
generally arrant thieves, not scrupling to rob their neighbours’ nests
of building-materials to save themselves trouble. They are also very
quarrelsome.
[Illustration: FIG. 207.—Rooks’ Nests in Trees.]
The nests are built on high trees (Fig. 207); they are composed of
sticks and turf, and are lined with moss and soft grass. As each of
several adjacent trees often contains a large number of nests, a sort
of rook-town called a “rookery” is formed. This is added to from year
to year, as the number of the birds increases. During the summer the
rookery forms the headquarters of the community, but about August or
September, before the leaves are shed, the birds leave their nests, to
spend the winter in thicker or evergreen woods, often at some distance.
At intervals during the winter they revisit their spring nests. They
come back to the rookery in February or March, and at once set about
repairing old nests or building new ones. The male bird begins to feed
the female even before the bluish-green eggs are laid, and is a pattern
of domestic virtue throughout the period of incubation. For some time
after hatching, the young birds are fed by the parents. Rooks feed on
the ground in flocks, a few birds remaining behind in the trees as
sentinels to give the alarm when danger threatens. The food consists
very largely of the larvae of injurious insects, especially the grubs
of the cockchafer beetle, and although the birds undoubtedly eat corn
and other young crops, they do far more good than harm.
=Other birds of the crow family.=—The crow, raven, jackdaw, magpie, and
jay are so similar in many respects to the rook and to each other that
naturalists include them all in one group, which they call the crow
family.
=The passerine order.=—The _families_ of the birds hitherto considered
in this chapter, with the flycatchers, wrens, chats, tits, finches,
linnets, starlings, etc., are further grouped together to form what is
called an _order_. The order which consists of these families derives
its name =passerine= from the sparrow[25] (Fig. 208), perhaps the
commonest of the birds included in it. It is probably in this order
that bird structure attains its most perfect development. Again, the
birds of the crow family are generally considered to stand at the
head of the order; if this view is correct, rooks must be regarded as
occupying, among birds, a position which roughly corresponds to man’s
place in the class of mammals.
Passerine birds are nearly all singers, and their toes are generally
adapted for perching. They feed upon insects, seeds (especially the
seeds of grasses), and soft fruit. Their beaks vary in form according
to the nature of the food upon which they most depend, as is well shown
by the soft, widely opening bills of the swallows, the strong but
slender beaks of the thrushes, larks, and crows, and the short, hard
beaks of such seed-eaters as the canary, sparrow, and other finches.
Birds which are exclusively, or almost exclusively, insectivorous are
compelled to migrate to warmer countries to obtain food during the
winter. The eggs of passerine birds are usually coloured or spotted,
and the young birds are hatched in a helpless and almost naked
condition, being carefully tended and fed by both parents until they
are able to fend for themselves. A few familiar birds of other orders
will now be briefly considered.
[Illustration: FIG. 208.—House Sparrows. (× ⅕.)]
[Illustration: FIG. 209.—The Swift. (× ⅙.)]
57. THE SWIFT AND THE CUCKOO.
1. =The swift.=—Distinguish the swift from the swallow by its larger
size, its sooty black colour (except for the dull white of the throat),
and its long, bowed wings. In what respect does the swift resemble the
swallow? Watch for the appearance of swifts about the end of April. Do
the birds arrive singly, in pairs, or in flocks? Notice the rapid turns
and twists of the flying bird. Does it as a rule fly near the ground,
or at somewhat great heights? Have you ever noticed the bird perching,
or settling on the ground? Have you seen it clinging to walls with its
feet? Were these the walls of houses or barns, or of high towers? What
actions would lead you to suppose that the nests are built in high
towers? Are more swifts to be seen in the evening, or during the day?
Can you explain this? Watch during the first half of August, and make a
note of the day on which swifts were last seen.
2. =The cuckoo.=—What is the earliest date on which you have heard the
cuckoo? Imitate the cry by putting your hollowed hands together and
blowing between the thumbs. With practice you will be able to deceive
the bird into thinking that another cuckoo is present, and it will
approach near enough to be seen distinctly. Estimate the size of the
bird, and write down a careful description of its form, colouration,
and method of flight. Try to see that two of its toes point forwards
and two backwards. Have you ever seen cuckoos mobbed by small birds?
Carefully examine as many nests of small birds as possible, and try to
find one containing an egg slightly larger than the rest and perhaps
differently coloured. This will probably be a cuckoo’s egg. Visit the
nest at frequent intervals, both before and after the hatching of the
eggs, and write descriptions of the eggs, the appearance and size of
the young birds, what becomes of each, and the behaviour of the old
birds. What is the latest date on which you have heard the cuckoo?
=The swift.=—Though the swift bears a strong general resemblance to
the swallow, the two birds are not at all closely related, but belong
to different orders. The swallow, like all other passerine birds (p.
320), has 12 tail-feathers, and its first toe is separately movable
and directed backwards. The swift, on the other hand, has only 10
tail-quills, and all its toes point forwards. There are, however, more
obvious differences, which readily enable one bird to be distinguished
from the other, even at a distance. The swift is, with the exception
of a dull-white patch on the throat, of a sooty black hue over all the
body, and in flight its long and powerful wings take the form of a bent
bow (Fig. 209). The swallow flies in bold, sweeping curves, while the
more rapid swift turns sharply in the air, in pursuit of the flying
insects upon which it feeds, in a manner suggestive of the flight of a
bat. While, again, the swallow flies much near the ground, the swift
is usually seen at greater heights. The harsh scream of the swift is,
moreover, in marked contrast with the swallow’s pleasing song.
Swifts do not willingly alight on the ground, even to collect materials
for their nests, nor do they perch on trees or roofs, the arrangement
of their toes being quite unsuitable for either action, and the length
of the wings being such that, even with toes of the normal type,
walking would be almost impossible. The nest, a somewhat rude structure
of grass and feathers, is generally built in high towers or other tall
buildings. The eggs are two in number; they are more conical in shape
than those of the swallow, and, as the position of the nest renders
them independent of protective colouration, are white. The hen-bird
sits on them during the day, but generally leaves the nest and flies
abroad in the evening to hunt for insects. Only one brood is reared,
and the birds take their departure early in August, to spend the winter
in South Africa or Madagascar.
=The cuckoo.=—The cuckoo is placed by naturalists, not among the
passerine birds, but in the order to which the swift belongs. The
reasons for this cannot be fully considered here, but it may be
mentioned that the cuckoo has only 10 tail-feathers, and that it
differs from all passerine birds in having its fourth toe, as well as
the first, directed backwards, the second and third pointing forwards
(Fig. 210).
The cuckoo has a total length of about 14 inches. The upper surface
of the body, and the throat, are grey; the rest of the lower surface
is white, crossed with black bars. The wings are large and powerful,
and the thighs are covered with long feathers. In general appearance,
as well as in manner of flight, the cuckoo bears a great resemblance
to a hawk, which may perhaps be the reason why small birds so often
join forces and attack it. A keen-eyed observer will, however, at once
distinguish the birds by the head and the bill, both of which are
markedly longer in the cuckoo than in the hawk. Cuckoos arrive here
in April, the males usually appearing first. The well-known call, to
which the bird owes its name, is uttered by the male only; the voice of
the female is quite different, and is often compared to the sound of
bubbling water. The cuckoo feeds entirely upon insects; it is believed
to be the only bird which eats the hairy caterpillar of the tiger-moth
(p. 369).
[Illustration: FIG. 210.—The Cuckoo, (× ¹/₇.)]
Of all bird-habits, probably none has excited more interest than the
manner of life of the young cuckoo. Its parents build no nest, but
depend entirely upon other birds for rearing their offspring. The
female cuckoo lays her egg upon the ground and then carries it in her
bill to a nest which contains similarly coloured eggs, if such a nest
is to be found. If not, another convenient nest is selected. It is said
that the male sometimes renders assistance by distracting the attention
of the rightful owners in the meantime. In most cases the owners of
the nest, apparently unaware of the trick, sit upon the strange egg
with the rest, and in due course the young birds are hatched. The young
cuckoo, whilst still blind and naked, wriggles itself under its foster
brothers and hoists them over the edge of the nest. Far from resenting
the crime, the duped parents now devote their energies to feeding the
murderer, and continue their attentions until after it is fully fledged
(about a fortnight after hatching) and perhaps several times their
combined size.
[Illustration: FIG. 211.—Cuckoo’s Egg in Greenfinch’s Nest (Cuckoo’s
Egg on the right).]
The small size of the cuckoo’s egg—about one-fourth of what might be
expected from so large a bird—and its general similarity in colour to
their own eggs, both aid in deceiving the victimised birds in the first
instance, and the disproportionate size of their supposed offspring
shortly after hatching apparently does not arouse their suspicions. It
is believed that any particular female cuckoo lays only eggs of one
type and deposits them, as far as possible, in nests of the mimicked
species—the species, probably, by which she herself was reared.
During the summer, therefore, she visits one such nest after another,
until she has disposed of all her eggs. Further, it is supposed that
her offspring inherit her tendency to lay eggs of the particular
colour, and therefore to prey in their turn upon the species of their
foster-parents. In this country, the meadow pipit, pied wagtail,
robin, and reed-warbler are perhaps the most usual victims of the
cuckoo’s parasitism, but the nests of other species (Fig. 211) are not
uncommonly selected.
The old cuckoos depart about the end of July, apparently leaving the
young ones to find their way south alone.
58. THE DUCK.
1. =Tame ducks.=—Closely observe ducks, both on land and when they are
swimming. Where is the heaviest part of the body? Are the legs attached
in front of, directly below, or behind the centre of gravity? Is the
position of the legs an advantage or a disadvantage (i) in walking,
(ii) in swimming? How does the foot differ from the feet of the birds
previously mentioned? Between which toes is the web stretched? How
are the toes held when the bird lifts its foot in walking? Does it
walk gracefully? How does it swim? Are the legs moved together or
alternately in swimming? Notice how the web folds up when the foot is
moved forwards, and spreads out for the back-stroke. What does the duck
eat? How is the food obtained? Why are a duck’s feathers so little
wetted by the water? Watch, and describe exactly, how the bird preens
its feathers.
How can you distinguish the male (drake) from the female duck, (i) by
appearance, (ii) by the voice? Do the colours of the drake’s plumage
differ at different periods of the year? What relation have the changes
of plumage to the moulting-season? What differences can you observe in
the methods of moulting of ducks and fowls? Is there any time of the
year when (i) ducks, (ii) fowls are unable to fly? Why? When and where
do ducks lay their eggs? Describe the appearance of the eggs. Are young
ducks helpless or precocious (p. 296), naked or clothed, at hatching?
Can they feed themselves? Can they swim?
Examine a dead duck. Notice the thick covering of down-feathers next
the skin. What is its use? Examine and draw a foot, and see how the web
folds between the toes. Observe the soft, sensitive skin on the outside
of the beak; what do you suppose is its use? Notice the shape of the
beak. Open it to see the horny plates fringing its inner edge, and
notice how these, with other plates on the thick, fleshy tongue, form a
strainer.
=The duck.=—The birds of the duck order—which includes also the geese
and swans—differ in many important respects from all our previous
types, and it is interesting to observe how perfectly these differences
are adapted to the manner of life. On land, the ungainly waddle, which
is entailed by the insertion of the hind limbs so far back on the
body (Fig. 212), shows that the duck is not in an entirely congenial
element; in the water the bird is a model of graceful movement,
perfectly balanced, progressing smoothly by alternate strokes of its
webbed feet, and altering its course to any desired direction with the
utmost ease. The duck feeds largely upon the small animals which abound
in the water of ponds, and in the mud of the sides, and the beak is
beautifully fitted for the duties it has to perform. It is covered
on the outside by a soft and highly sensitive skin, which enables the
bird to detect with certainty the presence of its prey in the mud;
the inner edge of the beak is provided with horny plates which, with
similar plates situated on the edge of the thick, fleshy tongue, form a
very efficient strainer, by means of which the useless water and thin
mud can be forced out at the sides of the mouth and separated from the
worms, etc., which were taken into the mouth at the same time. A thick
coat of down-feathers, which lies next the skin and contains a great
deal of entangled air, forms a non-conducting layer which prevents the
undue escape of the heat of the body, and saves the bird from becoming
chilled when in the water. Ducks are, moreover, careful to keep their
feathers well oiled, and may often be seen preening themselves—applying
the bill alternately to the oil-gland on the tail and to the feathers.
The completeness with which water flows off a duck’s back is proverbial.
[Illustration: FIG. 212.—Ducks.]
During the greater part of the year the brilliant plumage of the drake
forms a striking contrast to the sober brown and grey feathers of the
female. Another point of difference is that in the male the four middle
tail-feathers are curled upwards. From July to October, however, before
the moult takes place, the two sexes are very similar in appearance.
Birds of the duck order moult in a somewhat different manner from most
other birds, in that all the quill-feathers are shed at once, instead
of in pairs. Until the new feathers develop, flight is of course out
of the question, and the birds remain as secluded as possible in the
meantime.
The eggs are white and greasy-looking; they are laid in a rough,
open-topped nest, lined with down, which is placed on the ground.
The wild duck covers up the eggs when she leaves the nest. The young
are active immediately after hatching. It has been noticed that the
eggs of precocious birds are generally larger, in proportion to the
size of the parent, than those of birds which are naked and helpless
at hatching—the larger store of egg-food allowing a more complete
development of the young bird in the shell. Further, the nests of
precocious birds are, as a rule, less elaborately constructed.
59. TWO COMMON HAWKS.
1. =The sparrow-hawk.=—Watch for sparrow-hawks near farms. Notice the
general resemblance of the bird to the cuckoo, but distinguish them
by the short head and beak of the hawk. Observe the _bluish-grey_
colouration of the upper parts. Describe the flight of the hawk and, if
possible, its method of catching its prey.
2. =The kestrel or windhover.=—Distinguish the kestrel from the
sparrow-hawk (i) by the _reddish_ colour of its upper parts, and (ii)
by its habit of hovering in mid-air. Have you ever known the kestrel to
prey upon small birds? Upon what does it feed?
=The sparrow hawk and kestrel.=—These two birds are the only British
hawks which the average nature-student is likely to see during
a country walk; and as one of them is given to preying on young
game-birds, chickens, etc., while the other as generally confines
itself to animals which are universally regarded as vermin, it is
important to be able to distinguish them at sight.
[Illustration: FIG. 213.—The Nest of the Sparrow Hawk.]
The =sparrow-hawk= (Fig. 213) attains a length of 13 inches; the female
is slightly larger than the male. The upper parts of the body are
_bluish-grey_ in colour; the lower parts are buffish white, and crossed
with brown bars. The head is short and round; the bill is hooked and
sharp, as in birds of prey generally, and the toes are armed with sharp
claws. The bird is often to be seen near farms, lurking behind hedges
and waiting for an opportunity of dashing upon chickens or other small
birds and carrying them off.
The =kestrel=, which in size and shape much resembles the sparrow-hawk,
is really a species of falcon (Fig. 179). It is unrivalled among common
British birds in its power of remaining poised in one position in
mid-air by that rapid motion of the wings which is called hovering, a
power which has earned for it the name of “windhover.” The kestrel,
though in reality one of the farmer’s best friends, from its wholesale
destruction of field-mice, voles, and many injurious insects, is often
ignorantly confused with the sparrow-hawk. The _reddish_ hue of the
plumage of the kestrel’s upper parts, together with the hovering habit,
ought to render such a mistake impossible to observant eyes, and to
secure the bird from a persecution which may reasonably be directed
against the sparrow-hawk.
EXERCISES ON CHAPTER XVII.
1. Extend the foregoing methods of study to the following
passerine birds:—Starling, finches, wagtails, pipits,
nuthatch, tits, warblers, wrens, and flycatchers, and make
notes of the observations.
2. Try to discover reasons for grouping (_a_) woodpeckers,
nightjars, and kingfishers with swifts and cuckoos; (_b_)
pheasants and grouse with fowls.
3. Compare geese and swans with ducks, and make notes of as
many points of resemblance and difference as possible.
4. Compare and contrast owls with hawks.
5. Arrange the above birds in lists according to (_a_)
food, and the characters of the beak; (_b_) characters of
feet and arrangement of toes; (_c_) nests (open-topped,
covered, built in holes or tunnels); (_d_) colour and
number of eggs; (_e_) condition of young at time of
hatching.
6. How many birds do you know which (_a_) spend only the
summer, (_b_) spend only the winter, (_c_) stay all the
year, in this country? State, in each instance, upon what
food the bird most depends.
FOOTNOTES:
[21] _Our Bird Friends_ (Cassell).
[22] _The Natural History of Selborne._
[23] _The Natural History of Selborne._
[24] A delightful account is given in the story of “Silverspot”
(Thompson-Seton’s _Wild Animals I Have Known_).
[25] Latin, _passer_, a sparrow.
CHAPTER XVIII. FROGS AND TADPOLES.
60. THE LIFE OF THE FROG.
1. =Manner of life.=—Where have you found frogs? Are they commonest in
dry or in damp situations? At what time of the year have you seen them
actually in water? How do frogs move about? Do they walk or hop? Chase
a frog, and notice that its hops become shorter as it is pursued. Upon
what does the frog feed? Have you ever seen frogs abroad in the depth
of winter? Are insects common in winter? How do you suppose frogs spend
the winter? What are the principal enemies of frogs?
2. =External characters.=—Catch a frog; is its body dry or moist? Does
it feel cold or warm? How does it behave when caught? Does it soon
become tame if well treated? Put a frog under an inverted pickle-bottle
and observe it carefully. What is its _size_? What was the size of the
smallest frog you have seen? At what time of the year can the smallest
frogs be seen? What is the _colour_ of the frog? Put one frog with
dark-coloured leaves and soil, and another with light-coloured leaves,
and try to find out if the skin of the first becomes lighter and that
of the second darker in colour. Is it an advantage to the frog to be
able to change slightly in colour? Why? What is the position of the
frog when at rest? Notice the shortness of the body, the hump on the
back, the relative lengths of the limbs, the 4 unwebbed fingers, the 5
webbed toes, and the absence of a tail. What is the advantage of the
long hind-limbs? Mention other leaping animals whose hind-limbs are
longer than the fore-limbs. Is a short-bodied animal (_i.e._ one with
its four limbs pretty close together) less likely to be injured by
the fall, after a leap, than a long-bodied animal? Why? Put the frog
into water, and watch it swim. What is the use of the webs between the
toes? Examine the _head_. Notice the very wide stretch of the mouth,
the small openings of the nostrils, the large prominent eyes, and the
ear-drum—a dark-coloured disc on each side, a little below and behind
the eye.
3. =Breathing.=—Watch the up-and-down movements of the floor of the
mouth, by which the animal pumps air, through its nostrils, in and out
of its mouth-cavity.
4. =Method of feeding.=—Put live insects, small worms, etc., under the
upturned bottle enclosing the frog, and watch the animal’s method of
feeding. Try to see how it uses its tongue. What is the advantage of
the wide gape of the mouth? Can you get the frog to accept dead insects?