Descent of Man [1871]

Charles Darwin

 

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Chapter XIII - Secondary Sexual Characters of Birds


  SECONDARY sexual characters are more diversified and conspicuous
in birds, though not perhaps entailing more important changes of
structure, than in any other class of animals. I shall, therefore,
treat the subject at considerable length. Male birds sometimes, though
rarely, possess special weapons for fighting with each other. They
charm the female by vocal or instrumental music of the most varied
kinds. They are ornamented by all sorts of combs, wattles,
protuberances, horns, air-distended sacks, top-knots, naked shafts,
plumes and lengthened feathers gracefully springing from all parts
of the body. The beak and naked skin about the head, and the feathers,
are often gorgeously coloured. The males sometimes pay their court
by dancing, or by fantastic antics performed either on the ground or
in the air. In one instance, at least, the male emits a musky odour,
which we may suppose serves to charm or excite the female; for that
excellent observer, Mr. Ramsay,* says of the Australian musk-duck
(Biziura lobata) that "the smell which the male emits during the
summer months is confined to that sex, and in some individuals is
retained throughout the year; I have never, even in the
breeding-season, shot a female which had any smell of musk." So
powerful is this odour during the pairing-season, that it can be
detected long before the bird can be seen.*(2) On the whole, birds
appear to be the most aesthetic of all animals, excepting of course
man, and they have nearly the same taste for the beautiful as we have.
This is shown by our enjoyment of the singing of birds, and by our
women, both civilised and savage, decking their heads with borrowed
plumes, and using gems which are hardly more brilliantly coloured than
the naked skin and wattles of certain birds. In man, however, when
cultivated, the sense of beauty is manifestly a far more complex
feeling, and is associated with various intellectual ideas.

  * Ibis., vol. iii. (new series), 1867, p. 414.
  *(2) Gould, Handbook of the Birds of Australia, 1865, vol. ii., p.
383.

  Before treating of the sexual characters with which we are here more
particularly concerned, I may just allude to certain differences
between the sexes which apparently depend on differences in their
habits of life; for such cases, though common in the lower, are rare
in the higher classes. Two humming-birds belonging to the genus
Eustephanus, which inhabit the island of Juan Fernandez, were long
thought to be specifically distinct, but are now known, as Mr. Gould
informs me, to be the male and female of the same species, and they
differ slightly in the form of the beak. In another genus of
humming-birds (Grypus), the beak of the male is serrated along the
margin and hooked at the extremity, thus differing much from that of
the female. In the Neomorpha of New Zealand, there is, as we have
seen, a still wider difference in the form of the beak in relation
to the manner of feeding of the two sexes. Something of the same
kind has been observed with the goldfinch (Carduelis elegans), for I
am assured by Mr. J. Jenner Weir that the bird-catchers can
distinguish the males by their slightly longer beaks. The flocks of
males are often found feeding on the seeds of the teazle (Dipsacus),
which they can reach with their elongated beaks, whilst the females
more commonly feed on the seeds of the betony or Scrophularia. With
a slight difference of this kind as a foundation, we can see how the
beaks of the two sexes might be made to differ greatly through natural
selection. In some of the above cases, however, it is possible that
the beaks of the males may have been first modified in relation to
their contests with other males; and that this afterwards led to
slightly changed habits of life.

  Law of Battle.- Almost all male birds are extremely pugnacious,
using their beaks, wings, and legs for fighting together. We see
this every spring with our robins and sparrows. The smallest of all
birds, namely the humming-bird, is one of the most quarrelsome. Mr.
Gosse* describes a battle in which a pair seized hold of each
other's beaks, and whirled round and round, till they almost fell to
the ground; and M. Montes de Oca, in speaking or another genus of
humming-bird, says that two males rarely meet without a fierce
aerial encounter: when kept in cages "their fighting has mostly
ended in the splitting of the tongue of one of the two, which then
surely dies from being unable to feed."*(2) With waders, the males
of the common water-hen (Gallinula chloropus) "when pairing, fight
violently for the females: they stand nearly upright in the water
and strike with their feet." Two were seen to be thus engaged for half
an hour, until one got hold of the head of the other, which would have
been killed had not the observer interfered; the female all the time
looking on as a quiet spectator.*(3) Mr. Blyth informs me that the
males of an allied bird (Gallicrex cristatus) are a third larger
than the females, and are so pugnacious during the breeding- season
that they are kept by the natives of eastern Bengal for the sake of
fighting. Various other birds are kept in India for the same
purpose, for instance, the bulbuls (Pycnonotus hoemorrhous) which
"fight with great spirit."*(4)

  * Quoted by Mr. Gould, Introduction to the Trochilidae, 1861, page
29.
  *(2) Gould, ibid., p. 52.
  *(3) W. Thompson, Natural History of Ireland: Birds, vol. ii., 1850,
p. 327.
  *(4) Jerdon, Birds of India, 1863, vol. ii., p. 96.

  The polygamous ruff (see Machetes pugnax, fig. 37) is notorious
for his extreme pugnacity; and in the spring, the males, which are
considerably larger than the females, congregate day after day at a
particular spot, where the females propose to lay their eggs. The
fowlers discover these spots by the turf being trampled somewhat bare.
Here they fight very much like game-cocks, seizing each other with
their beaks and striking with their wings. The great ruff of
feathers round the neck is then erected, and according to Col. Montagu
"sweeps the ground as a shield to defend the more tender parts"; and
this is the only instance known to me in the case of birds of any
structure serving as a shield. The ruff of feathers, however, from its
varied and rich colours probably serves in chief part as an
ornament. Like most pugnacious birds, they seem always ready to fight,
and when closely confined, often kill each other; but Montagu observed
that their pugnacity becomes greater during the spring, when the
long feathers on their necks are fully developed; and at this period
the least movement by any one bird provokes a general battle.* Of
the pugnacity of web-footed birds, two instances will suffice: in
Guiana "bloody fights occur during the breeding-season between the
males of the wild musk-duck (Cairina moschata); and where these fights
have occurred the river is covered for some distance with
feathers."*(2) Birds which seem ill-adapted for fighting engage in
fierce conflicts; thus the stronger males of the pelican drive away
the weaker ones, snapping with their huge beaks and giving heavy blows
with their wings. Male snipe fight together, "tugging and pushing each
other with their bills in the most curious manner imaginable." Some
few birds are believed never to fight; this is the case, according
to Audubon, with one of the woodpeckers of the United States (Picu
sauratus), although "the hens are followed by even half a dozen of
their gay suitors."*(3)

  * Macgillivray, History of British Birds, vol. iv., 1852, pp.
177-181.
  *(2) Sir R. Schomburgk, in Journal of Royal Geographic Society, vol.
xiii., 1843, p. 31.
  *(3) Ornithological Biography, vol. i., p. 191. For pelicans and
snipes, see vol. iii., pp. 138, 477.

  The males of many birds are larger than the females, and this no
doubt is the result of the advantage gained by the larger and stronger
males over their rivals during many generations. The difference in
size between the two sexes is carried to an extreme point in several
Australian species; thus the male musk-duck (Biziura), and the male
Cincloramphus cruralis (allied to our pipits) are by measurement
actually twice as large as their respective females.* With many
other birds the females are larger than the males; and, as formerly
remarked, the explanation often given, namely, that the females have
most of the work in feeding their young, will not suffice. In some few
cases, as we shall hereafter see, the females apparently have acquired
their greater size and strength for the sake of conquering other
females and obtaining possession of the males.

  * Gould, Handbook of Birds of Australia, vol. i., p. 395; vol.
ii., p. 383.

  The males of many gallinaceous birds, especially of the polygamous
kinds, are furnished with special weapons for fighting with their
rivals, namely spurs, which can be used with fearful effect. It has
been recorded by a trustworthy writer* that in Derbyshire a kite
struck at a game-hen accompanied by her chickens, when the cock rushed
to the rescue, and drove his spur right through the eye and skull of
the aggressor. The spur was with difficulty drawn from the skull,
and as the kite, though dead, retained his grasp, the two birds were
firmly locked together; but the cock when disentangled was very little
injured. The invincible courage of the game-cock is notorious: a
gentleman who long ago witnessed the brutal scene, told me that a bird
had both its legs broken by some accident in the cockpit, and the
owner laid a wager that if the legs could be spliced so that the
bird could stand upright, he would continue fighting. This was
effected on the spot, and the bird fought with undaunted courage until
he received his death-stroke. In Ceylon a closely allied, wild
species, the Gallus stanleyi, is known to fight desperately "in
defence of his seraglio," so that one of the combatants is
frequently found dead.*(2) An Indian partridge (Ortygornis gularis),
the male of which is furnished with strong and sharp spurs, is so
quarrelsome "that the scars of former fights disfigure the breast of
almost every bird you kill."*(3)

  * Mr. Hewitt, in the Poultry Book, by Tegetmeier, 1866, p. 137.
  *(2) Layard, Annals and Magazine of Natural History, vol. xiv.,
1854, p. 63.
  *(3) Jerdon, Birds of India, vol. iii., p. 574.

  The males of almost all gallinaceous birds, even those which are not
furnished with spurs, engage during the breeding- season in fierce
conflicts. The capercailzie and black-cock (Tetrao urogallus and T.
tetrix), which are both polygamists, have regular appointed places,
where during many weeks they congregate in numbers to fight together
and to display their charms before the females. Dr. W. Kovalevsky
informs me that in Russia he has seen the snow all bloody on the
arenas where the capercailzie have fought; and the black-cocks "make
the feathers fly in every direction," when several "engage in a battle
royal." The elder Brehm gives a curious account of the balz, as the
love-dances and love songs of the black-cock are called in Germany.
The bird utters almost continuously the strangest noises: "he holds
his tail up and spreads it out like a fan, he lifts up his head and
neck with all the feathers erect, and stretches his wings from the
body. Then he takes a few jumps in different directions sometimes in a
circle, and presses the under part of his beak so hard against the
ground that the chin feathers are rubbed off. During these movements
he beats his wings and turns round and round. The more ardent he grows
the more lively he becomes, until at last the bird appears like a
frantic creature." At such times the black-cocks are so absorbed
that they become almost blind and deaf, but less so than the
capercailzie: hence bird after bird may be shot on the same spot, or
even caught by the hand. After performing these antics the males begin
to fight: and the same black-cock, in order to prove his strength over
several antagonists, will visit in the course of one morning several
balz places, which remain the same during successive years.*

  * Brehm, Illust. Thierleben, 1867, B. iv., s. 351. Some of the
foregoing statements are taken from L. Lloyd, Game Birds of Sweden,
&c., 1867, p. 79.

  The peacock with his long train appears more like a dandy than a
warrior, but he sometimes engages in fierce contests: the Rev. W.
Darwin Fox informs me that at some little distance from Chester two
peacocks became so excited whilst fighting, that they flew over the
whole city, still engaged, until they alighted on the top of St.
John's tower.
  The spur, in those gallinaceous birds which are thus provided, is
generally single; but Polyplectron (see fig. 51) has two or more on
each leg; and one of the blood-pheasants (Ithaginis cruentus) has been
seen with five spurs. The spurs are generally confined to the male,
being represented by mere knobs or rudiments in the female; but the
females of the Java peacock (Pavo muticus) and, as I am informed by
Mr. Blyth, of the small fire-backed pheasant (Euplocamus
erythropthalmus) possess spurs. In Galloperdix it is usual for the
males to have two spurs, and for the females to have only one on
each leg.* Hence spurs may be considered as a masculine structure,
which has been occasionally more or less transferred to the females.
Like most other secondary sexual characters, the spurs are highly
variable, both in number and development, in the same species.

  * Jerdon, Birds of India: on Ithaginis, vol. iii., p. 523; on
Galloperdix, p. 541.

  Various birds have spurs on their wings. But the Egyptian goose
(Chenalopex aegyptiacus) has only "bare obtuse knobs," and these
probably shew us the first steps by which true spurs have been
developed in other species. In the spur-winged goose, Plectropterus
gambensis, the males have much larger spurs than the females; and they
use them, as I am informed by Mr. Bartlett, in fighting together, so
that, in this case, the wing-spurs serve as sexual weapons; but
according to Livingstone, they are chiefly used in the defence of
the young. The Palamedea (see fig. 38) is armed with a pair of spurs
on each wing; and these are such formidable weapons that a single blow
has been known to drive a dog howling away. But it does not appear
that the spurs in this case, or in that of some of the spur-winged
rails, are larger in the male than in the female.* In certain plovers,
however, the wing-spurs must be considered as a sexual character. Thus
in the male of our common peewit (Vanellus cristatus) the tubercle
on the shoulder of the wing becomes more prominent during the
breeding-season, and the males fight together. In some species of
Lobivanellus a similar tubercle becomes developed during the
breeding-season "into a short horny spur." In the Australian L.
lobatus both sexes have spurs, but these are much larger in the
males than in the females. In an allied bird, the Hoplopterus armatus,
the spurs do not increase in size during the breeding-season; but
these birds have been seen in Egypt to fight together, in the same
manner as our peewits, by turning suddenly in the air and striking
sideways at each other, sometimes with fatal results. Thus also they
drive away other enemies.*(2)

  * For the Egyptian goose, see Macgillivray, British Birds, vol. iv.,
p. 639. For Plectropterus, Livingstone's Travels, p. 254. For
Palamedea, Brehm's Illustriertes Thierleben, B. iv., s. 740. See
also on this bird Azara, Voyages dans l'Amerique merid., tom. iv.,
1809, pp. 179, 253.
  *(2) See, on our peewit, Mr. R. Carr in Land and Water, Aug. 8,
1868, p. 46. In regard to Lobivanellus, see Jerdon's Birds of India,
vol. iii., p. 647, and Gould's Handbook of Birds of Australia, vol.
ii., p. 220. For the Hoplopterus, see Mr. Allen in the Ibis., vol. v.,
1863, p. 156.

  The season of love is that of battle; but the males of some birds,
as of the game-fowl and ruff, and even the young males of the wild
turkey and grouse,* are ready to fight whenever they meet. The
presence of the female is the teterrima belli causa. The Bengali
baboos make the pretty little males of the amadavat (Estrelda
amandava) fight together by placing three small cages in a row, with a
female in the middle; after a little time the two males are turned
loose, and immediately a desperate battle ensues.*(2) When many
males congregate at the same appointed spot and fight together, as
in the case of grouse and various other birds, they are generally
attended by the females,*(3) which afterwards pair with the victorious
combatants. But in some cases the pairing precedes instead of
succeeding the combat: thus according to Audubon,*(4) several males of
the Virginian goat-sucker (Caprimulgus virgianus) "court, in a
highly entertaining manner the female, and no sooner has she made
her choice, than her approved gives chase to all intruders and
drives them beyond his dominions." Generally the males try to drive
away or kill their rivals before they pair. It does not, however,
appear that the females invariably prefer the victorious males. I have
indeed been assured by Dr. W. Kovalevsky that the female
capercailzie sometimes steals away with a young male who has not dared
to enter the arena with the older cocks, in the same manner as
occasionally happens with the does of the red-deer in Scotland. When
two males contend in presence of a single female, the victor, no
doubt, commonly gains his desire; but some of these battles are caused
by wandering males trying to distract the peace of an already mated
pair.*(5)

  * Audubon, Ornithological Biography, vol. ii., p. 492; vol. i.,
pp. 4-13.
  *(2) Mr. Blyth, Land and Water, 1867, p. 212.
  *(3) Richardson on Tetrao umbellus, Fauna Bor. Amer.: Birds, 1831,
p. 343. L. Lloyd, Game Birds of Sweden, 1867, pp. 22, 79, on the
capercailzie and black-cock. Brehm, however, asserts (Thierleben, B.
iv., s. 352) that in Germany the grey-hens do not generally attend the
Balzen of the black-cocks, but this is an exception to the common
rule; possibly the hens may lie hidden in the surrounding bushes, as
is known to be the case with the grey-hens in Scandinavia, and with
other species in N. America.
  *(4) Ornithological Biography, vol. ii., p. 275.
  *(5) Brehm, Thierleben, &c., B. iv., 1867, p. 990. Audubon,
Ornithological Biography, vol. ii., p. 492.

  Even with the most pugnacious species it is probable that the
pairing does not depend exclusively on the mere strength and courage
of the male; for such males are generally decorated with various
ornaments, which often become more brilliant during the
breeding-season, and which are sedulously displayed before the
females. The males also endeavour to charm or excite their mates by
love-notes, songs, and antics; and the courtship is, in many
instances, a prolonged affair. Hence it is not probable that the
females are indifferent to the charms of the opposite sex, or that
they are invariably compelled to yield to the victorious males. It
is more probable that the females are excited, either before or
after the conflict, by certain males, and thus unconsciously prefer
them. In the case of Tetrao umbellus, a good observer* goes so far
as to believe that the battles of the male "are all a sham,
performed to show themselves to the greatest advantage before the
admiring females who assemble around; for I have never been able to
find a maimed hero, and seldom more than a broken feather." I shall
have to recur to this subject, but I may here add that with the Tetrao
cupido of the United States, about a score of males assemble at a
particular spot, and, strutting about, make the whole air resound with
their extraordinary noises. At the first answer from a female the
males begin to fight furiously, and the weaker give way; but then,
according to Audubon, both the victors and vanquished search for the
female, so that the females must either then exert a choice, or the
battle must be renewed. So, again, with one of the field-starlings
of the United States (Sturnella ludoviciana) the males engage in
fierce conflicts, "but at the sight of a female they all fly after her
as if mad."*(2)

  * Land and Water, July 25, 1868, p. 14.
  *(2) Audubon's Ornithological Biography; on Tetrao cupido, vol. ii.,
p. 492; on the Sturnus, vol. ii., p. 219.

  Vocal and instrumental music.- With birds the voice serves to
express various emotions, such as distress, fear, anger, triumph, or
mere happiness. It is apparently sometimes used to excite terror, as
in the case of the hissing noise made by some nestling-birds.
Audubon*, relates that a night-heron (Ardea nycticorax, Linn.),
which he kept tame, used to hide itself when a cat approached, and
then "suddenly start up uttering one of the most frightful cries,
apparently enjoying the cat's alarm and flight." The common domestic
cock clucks to the hen, and the hen to her chickens, when a dainty
morsel is found. The hen, when she has laid an egg, "repeats the
same note very often, and concludes with the sixth above, which she
holds for a longer time";*(2) and thus she expresses her joy. Some
social birds apparently call to each other for aid; and as they flit
from tree to tree, the flock is kept together by chirp answering
chirp. During the nocturnal migrations of geese and other
water-fowl, sonorous clangs from the van may be heard in the
darkness overhead, answered by clangs in the rear. Certain cries serve
as danger signals, which, as the sportsman knows to his cost, are
understood by the same species and by others. The domestic cock crows,
and the humming-bird chirps, in triumph over a defeated rival. The
true song, however, of most birds and various strange cries are
chiefly uttered during the breeding-season, and serve as a charm, or
merely as a call-note, to the other sex.

  * Ornithological Biography, vol. v., p. 601.
  *(2) The Hon. Daines Barrington, Philosophical Transactions, 1773,
p. 252.

  Naturalists are much divided with respect to the object of the
singing of birds. Few more careful observers ever lived than
Montagu, and he maintained that the "males of songbirds and of many
others do not in general search for the female, but, on the
contrary, their business in the spring is to perch on some conspicuous
spot, breathing out their full and armorous notes, which, by instinct,
the female knows, and repairs to the spot to choose her mate."* Mr.
Jenner Weir informs me that this is certainly the case with the
nightingale. Bechstein, who kept birds during his whole life, asserts,
"that the female canary always chooses the best singer, and that in
a state of nature the female finch selects that male out of a
hundred whose notes please her most."*(2) There can be no doubt that
birds closely attend to each other's song. Mr. Weir has told me of the
case of a bullfinch which had been taught to pipe a German waltz,
and who was so good a performer that he cost ten guineas; when this
bird was first introduced into a room where other birds were kept
and he began to sing, all the others, consisting of about twenty
linnets and canaries, ranged themselves on the nearest side of their
cages, and listened with the greatest interest to the new performer.
Many naturalists believe that the singing of birds is almost
exclusively "the effect of rivalry and emulation," and not for the
sake of charming their mates. This was the opinion of Daines
Barrington and White of Selborne, who both especially attended to this
subject.*(3) Barrington, however, admits that "superiority in song
gives to birds an amazing ascendancy over others, as is well known
to bird-catchers."

  * Ornithological Dictionary, 1833, p. 475.
  *(2) Naturgeschichte der Stubenvogel, 1840, s. 4. Mr. Harrison
Weir likewise writes to me; "I am informed that the best singing males
generally get a mate first, when they are bred in the same room,"
  *(3) Philosophical Transactions, 1773, p. 263. White's Natural
History of Selborne, 1825, vol. i., p. 246.

  It is certain that there is an intense degree of rivalry between the
males in their singing. Bird-fanciers match their birds to see which
will sing longest; and I was told by Mr. Yarrell that a first-rate
bird will sometimes sing till he drops down almost dead, or
according to Bechstein,* quite dead from rupturing a vessel in the
lungs. Whatever the cause may be, male birds, as I hear from Mr. Weir,
often die suddenly during the season of song. That the habit of
singing is sometimes quite independent of love is clear, for a
sterile, hybrid canary-bird has been described*(2) as singing whilst
viewing itself in a mirror, and then dashing at its own image; it
likewise attacked with fury a female canary, when put into the same
cage. The jealousy excited by the act of singing is constantly taken
advantage of by bird-catchers; a male in good song, is hidden and
protected, whilst a stuffed bird, surrounded by limed twigs, is
exposed to view. In this manner, as Mr. Weir informs me, a man has
in the course of a single day caught fifty, and in one instance,
seventy, male chaffinches. The power and inclination to sing differ so
greatly with birds that although the price of an ordinary male
chaffinch is only sixpence, Mr. Weir saw one bird for which the
bird-catcher asked three pounds; the test of a really good singer
being that it will continue to sing whilst the cage is swung round the
owner's head.

  * Naturgesch. der Stubenvogel, 1840, s. 252.
  *(2) Mr. Bold, Zoologist, 1843-44, p. 659.

  That male birds should sing from emulation as well as for charming
the female, is not at all incompatible; and it might have been
expected that these two habits would have concurred, like those of
display and pugnacity. Some authors, however, argue that the song of
the male cannot serve to charm the female, because the females of some
few species, such as of the canary, robin, lark, and bullfinch,
especially when in a state of widowhood, as Bechstein remarks, pour
forth fairly melodious strains. In some of these cases the habit of
singing may be in part attributed to the females having been highly
fed and confined,* for this disturbs all the functions connected
with the reproduction of the species. Many instances have already been
given of the partial transference of secondary masculine characters to
the female, so that it is not at all surprising that the females of
some species should possess the power of song. It has also been
argued, that the song of the male cannot serve as a charm, because the
males of certain species, for instance of the robin, sing during the
autumn.*(2) But nothing is more common than for animals to take
pleasure in practising whatever instinct they follow at other times
for some real good. How often do we see birds which fly easily,
gliding and sailing through the air obviously for pleasure? The cat
plays with the captured mouse, and the cormorant with the captured
fish. The weaver-bird (Ploceus), when confined in a cage, amuses
itself by neatly weaving blades of grass between the wires of its
cage. Birds which habitually fight during the breeding-season are
generally ready to fight at all times; and the males of the
capercailzie sometimes hold their Balzen or leks at the usual place of
assemblage during the autumn.*(3) Hence it is not at all surprising
that male birds should continue singing for their own amusement
after the season for courtship is over.

  * D. Barrington, Philosophical Transactions, 1773, p. 262.
Bechstein, Stubenvogel, 1840, s. 4.
  *(2) This is likewise the case with the water-ouzel; see Mr. Hepburn
in the Zoologist, 1845-46, p. 1068.
  *(3) L. Lloyd, Game Birds of Sweden, 1867, p. 25.

  As shewn in a previous chapter, singing is to a certain extent an
art, and is much improved by practice. Birds can be taught various
tunes, and even the unmelodious sparrow has learnt to sing like a
linnet. They acquire the song of their foster parents,* and
sometimes that of their neighbours.*(2) All the common songsters
belong to the Order of Insessores, and their vocal organs are much
more complex than those of most other birds; yet it is a singular fact
that some of the Insessores, such as ravens, crows, and magpies,
possess the proper apparatus,*(3) though they never sing, and do not
naturally modulate their voices to any great extent. Hunter
asserts*(4) that with the true songsters the muscles of the larynx are
stronger in the males than in the females; but with this slight
exception there is no difference in the vocal organs of the two sexes,
although the males of most species sing so much better and more
continuously than the females.

  * Barrington, ibid., p. 264, Bechstein, ibid., s. 5.
  *(2) Dureau de la Malle gives a curious instance (Annales des Sc.
Nat., 3rd series, Zoolog., tom. x., p. 118) of some wild blackbirds in
his garden in Paris, which naturally learnt a republican air from a
caged bird.
  *(3) Bishop, in Todd's Cyclopaedia of Anatomy and Physiology, vol.
iv., p. 1496.
  *(4) As stated by Barrington in Philosophical Transactions, 1773, p.
262.

  It is remarkable that only small birds properly sing. The Australian
genus Menura, however, must be excepted; for the Menura alberti, which
is about the size of a half-grown turkey, not only mocks other
birds, but "its own whistle is exceedingly beautiful and varied."
The males congregate and form "corroborying places," where they
sing, raising and spreading their tails like peacocks, and drooping
their wings.* It is also remarkable that birds which sing well are
rarely decorated with brilliant colours or other ornaments. Of our
British birds, excepting the bullfinch and goldfinch, the best
songsters are plain-coloured. The kingfisher, bee-eater, roller,
hoopoe, wood-peckers, &c., utter harsh cries; and the brilliant
birds of the tropics are hardly ever songsters.*(2) Hence bright
colours and the power of song seem to replace each other. We can
perceive that if the plumage did not vary in brightness, or if
bright colours were dangerous to the species, other means would be
employed to charm the females; and melody of voice offers one such
means.

  * Gould, Handbook of the Birds of Australia, vol. i., 1865, pp.
308-310. See also Mr. T. W. Wood in the Student, April, 1870, p. 125.
  *(2) See remarks to this effect in Gould's Introduction to the
Trochilidae,, 1861, p. 22.

  In some birds the vocal organs differ greatly in the two sexes. In
the Tetrao cupido (see fig. 39) the male has two bare, orange-coloured
sacks, one on each side of the neck; and these are largely inflated
when the male, during the breeding-season, makes his curious hollow
sound, audible at a great distance. Audubon proved that the sound
was intimately connected with this apparatus (which reminds us of
the air-sacks on each side of the mouth of certain male frogs), for he
found that the sound was much diminished when one of the sacks of a
tame bird was pricked, and when both were pricked it was altogether
stopped. The female has "a somewhat similar, though smaller naked
space of skin on the neck; but this is not capable of inflation."* The
male of another kind of grouse (Tetrao urophasianus), whilst
courting the female, has his "bare yellow oesophagus inflated to a
prodigious size, fully half as large as the body"; and he then
utters various grating, deep, hollow tones. With his neck-feathers
erect, his wings lowered, and buzzing on the ground, and his long
pointed tail spread out like a fan, he displays a variety of grotesque
attitudes. The oesophagus of the female is not in any way
remarkable.*(2)

  * The Sportsman and Naturalist in Canada, by Major W. Ross King,
1866, pp. 144-146. Mr. T. W. Wood gives in the Student (April, 1870,
p. 116) an excellent account of the attitude and habits of this bird
during its courtship. He states that the ear-tufts or neck-plumes
are erected, so that they meet over the crown of the head. See his
drawing, fig. 39.
  *(2) Richardson, Fauna Bor. Americana: Birds, 1831, p. 359. Audubon,
ibid., vol. iv., p. 507.

  It seems now well made out that the great throat pouch of the
European male bustard (Otis tarda), and of at least four other
species, does not, as was formerly supposed, serve to hold water,
but is connected with the utterance during the breeding-season of a
peculiar sound resembling "oak."* A crow-like bird inhabiting South
America (see Cephalopterus ornatus, fig. 40) is called the
umbrella-bird, from its immense top knot, formed of bare white
quills surmounted by dark-blue plumes, which it can elevate into a
great dome no less than five inches in diameter, covering the whole
head. This bird has on its neck a long, thin, cylindrical fleshy
appendage, which is thickly clothed with scale-like blue feathers.
It probably serves in part as an ornament, but likewise as a
resounding apparatus; for Mr. Bates found that it is connected "with
an unusual development of the trachea and vocal organs." It is dilated
when the bird utters its singularly deep, loud and long sustained
fluty note. The head-crest and neck-appendage are rudimentary in the
female.*(2)

  * The following papers have been lately written on this subject:
Prof. A. Newton, in the Ibis, 1862, p. 107; Dr. Cullen, ibid., 1865,
p. 145; Mr. Flower, in Proc. Zool. Soc., 1865, p. 747; and Dr.
Murie, in Proc. Zool. Soc., 1868, p. 471. In this latter paper an
excellent figure is given of the male Australian bustard in full
display with the sack distended. It is a singular fact that the sack
is not developed in all the males of the same species.
  *(2) Bates, The Naturalist on the Amazons, 1863, vol. ii., p. 284;
Wallace, in Proceedings, Zoological Society, 1850, p. 206. A new
species, with a still larger neck-appendage (C. penduliger), has
lately been discovered, see Ibis, vol. i., p. 457.

  The vocal organs of various web-footed and wading birds are
extraordinarily complex, and differ to a certain extent in the two
sexes. In some cases the trachea is convoluted, like a French horn,
and is deeply embedded in the sternum. In the wild swan (Cygnus ferus)
it is more deeply embedded in the adult male than in the adult
female or young male. In the male Merganser the enlarged portion of
the trachea is furnished with an additional pair of muscles.* In one
of the ducks, however, namely Anas punctata, the bony enlargement is
only a little more developed in the male than in the female.*(2) But
the meaning of these differences in the trachea of the two sexes of
the Anatidae is not understood; for the male is not always the more
vociferous; thus with the common duck, the male hisses, whilst the
female utters a loud quack.*(3) In both sexes of one of the cranes
(Grus virgo) the trachea penetrates the sternum, but presents "certain
sexual modifications." In the male of the black stork there is also
a well-marked sexual difference in the length and curvature of the
bronchi.*(4) Highly important structures have, therefore, in these
cases been modified according to sex.

  * Bishop, in Todd's Cyclopaedia of Anatomy and Physiology, vol. iv.,
p. 1499.
  *(2) Prof. Newton, Proc. Zoolog. Soc., 1871, p. 651.
  *(3) The spoonbill (Platalea) has its trachea convoluted into a
figure of eight, and yet this bird (Jerdon, Birds of India, vol. iii.,
p. 763) is mute but Mr. Blyth informs me that the convolutions are not
constantly present, so that perhaps they are now tending towards
abortion.
  *(4) Elements of Comparative Anatomy, by R. Wagner, Eng.
translat., 1845, p. 111. With respect to the swan as given above,
Yarrell's History of British Birds, 2nd edition, 1845, vol. iii., p.
193.

  It is often difficult to conjecture whether the many strange cries
and notes uttered by male birds during the breeding-season serve as
a charm or merely as a call to the female. The soft cooing of the
turtle-dove and of many pigeons, it may be presumed, pleases the
female. When the female of the wild turkey utters her call in the
morning, the male answers by a note which differs from the gobling
noise made, when with erected feathers, rustling wings and distended
wattles, he puffs and struts before her.* The spel of the black-cock
certainly serves as a call to the female, for it has been known to
bring four or five females from a distance to a male under
confinement; but as the black-cock continues his spel for hours during
successive days, and in the case of the capercailzie "with an agony of
passion," we are led to suppose that the females which are present are
thus charmed.*(2) The voice of the common rook is known to alter
during the breeding-season, and is therefore in some way sexual.*(3)
But what shall we say about the harsh screams of, for instance, some
kinds of macaws; have these birds as bad taste for musical sounds as
they apparently have for colour, judging by the inharmonious
contrast of their bright yellow and blue plumage? It is indeed
possible that without any advantage being thus gained, the loud voices
of many male birds may be the result of the inherited effects of the
continued use of their vocal organs when excited by the strong
passions of love, jealousy and rage; but to this point we shall
recur when we treat of quadrupeds.

  * C. L. Bonaparte, quoted in the Naturalist Library: Birds, vol.
xiv., p. 126.
  *(2) L. Lloyd, The Game Birds of Sweden, &c., 1867, pp. 22, 81.
  *(3) Jenner, Philosophical Transactions, 1824, p. 20.

  We have as yet spoken only of the voice, but the males of various
birds practise, during their courtship, what may be called
instrumental music. Peacocks and birds of paradise rattle their quills
together. Turkey-cocks scrape their wings against the ground, and some
kinds of grouse thus produce a buzzing sound. Another North American
grouse, the Tetrao umbellus, when with his tail erect, his ruffs
displayed, "he shows off his finery to the females, who lie hid in the
neighbourhood," drums by rapidly striking his wings together above his
back, according to Mr. R. Haymond, and not, as Audubon thought, by
striking them against his sides. The sound thus produced is compared
by some to distant thunder, and by others to the quick roll of a drum.
The female never drums, "but flies directly to the place where the
male is thus engaged." The male of the Kalij-pheasant, in the
Himalayas, often makes a singular drumming noise with his wings, not
unlike the sound produced by shaking a stiff piece of cloth." On the
west coast of Africa the little black-weavers (Ploceus?) congregate in
a small party on the bushes round a small open space, and sing and
glide through the air with quivering wings, "which make a rapid
whirring sound like a child's rattle." One bird after another thus
performs for hours together, but only during the courting-season. At
this season, and at no other time, the males of certain night-jars
(Caprimulgus) make a strange booming noise with their wings. The
various species of woodpeckers strike a sonorous branch with their
beaks, with so rapid a vibratory movement that "the head appears to be
in two places at once." The sound thus produced is audible at a
considerable distance but cannot be described; and I feel sure that
its source would never be conjectured by any one hearing it for the
first time. As this jarring sound is made chiefly during the
breeding-season, it has been considered as a love-song; but it is
perhaps more strictly a love-call. The female, when driven from her
nest, has been observed thus to call her mate, who answered in the
same manner and soon appeared. Lastly, the male hoopoe (Upupa epops)
combines vocal and instrumental music; for during the
breeding-season this bird, as Mr. Swinhoe observed, first draws in
air, and then taps the end of its beak perpendicularly down against
a stone or the trunk of a tree, "when the breath being forced down the
tubular bill produces the correct sound." If the beak is not thus
struck against some object, the sound is quite different. Air is at
the same time swallowed, and the oesophagus thus becomes much swollen;
and this probably acts as a resonator, not only with the hoopoe, but
with pigeons and other birds.*

  * For the foregoing facts see, on birds of paradise, Brehm,
Thierleben, B. iii., s. 325. On grouse, Richardson, Fauna Bor.
Americ.: Birds, pp. 343 and 359; Major W. Ross King, The Sportsman
in Canada, 1866, p. 156; Mr. Haymond, in Prof. Cox's Geol. Survey of
Indiana, p. 227; Audubon, American Ornitholog. Biograph., vol. i.,
p. 216. On the Kalij-pheasant, Jerdon, Birds of India, vol. iii., p.
533. On the weavers, Livingstone's Expedition to the Zambesi, 1865, p.
425. On woodpeckers, Macgillivray, Hist. of British Birds, vol.
iii., 1840, pp. 84, 88, 89, and 95. On the hoopoe, Mr. Swinhoe, in
Proc. Zoolog. Soc., June 23, 1863 and 1871, p. 348. On the
night-jar, Audubon, ibid., vol. ii., p. 255, and American
Naturalist, 1873, p. 672. The English night-jar likewise makes in
the spring a curious noise during its rapid flight.

  In the foregoing cases sounds are made by the aid of structures
already present and otherwise necessary; but in the following cases
certain feathers have been specially modified for the express
purpose of producing sounds. The drumming, bleating, neighing, or
thundering noise (as expressed by different observers) made by the
common snipe (Scolopax gallinago) must have surprised every one who
has ever heard it. This bird, during the pairing-season, flies to
"perhaps a thousand feet in height," and after zig-zagging about for a
time descends to the earth in a curved line, with outspread tail and
quivering pinions, and surprising velocity. The sound is emitted
only during this rapid descent. No one was able to explain the cause
until M. Meves observed that on each side of the tail the outer
feathers are peculiarly formed (see fig. 41), having a stiff
sabre-shaped shaft with the oblique barbs of unusual length, the outer
webs being strongly bound together. He found that by blowing on
these feathers, or by fastening them to a long thin stick and waving
them rapidly through the air, he could reproduce the drumming noise
made by the living bird. Both sexes are furnished with these feathers,
but they are generally larger in the male than in the female, and emit
a deeper note. In some species, as in S. frenata (see fig. 42), four
feathers, and in S. javensis (see fig. 43), no less than eight on each
side of the tail are greatly modified. Different tones are emitted
by the feathers of the different species when waved through the air;
and the Scolopax wilsonii of the United States makes a switching noise
whilst descending rapidly to the earth.*

  * See M. Meves' interesting paper in Proc. Zool. Soc., 1858, p. 199.
For the habits of the snipe, Macgillivray, History of British Birds,
vol. iv., p. 371. For the American snipe, Capt. Blakiston, Ibis,
vol. v., 1863, p. 131.

  In the male of the Chamaepetes unicolor (a large gallinaceous bird
of America), the first primary wing-feather is arched towards the
tip and is much more attenuated than in the female. In an allied bird,
the Penelope nigra, Mr. Salvin observed a male, which, whilst it
flew downwards "with outstretched wings, gave forth a kind of crashing
rushing noise," like the falling of a tree.* The male alone of one
of the Indian bustards (Sypheotides auritus) has its primary
wing-feathers greatly acuminated; and the male of an allied species is
known to make a humming noise whilst courting the female.*(2) In a
widely different group of birds, namely humming-birds, the males alone
of certain kinds have either the shafts of their primary wing-feathers
broadly dilated, or the webs abruptly excised towards the extremity.
The male, for instance, of Selasphorus platycercus, when adult, has
the first primary wing-feather (see fig. 44), thus excised. Whilst
flying from flower to flower he makes "a shrill, almost whistling
noise";*(3) but it did not appear to Mr. Salvin that the noise was
intentionally made.

  * Mr. Salvin, in Proceedings, Zoological Society, 1867, p. 160. I am
much indebted to this distinguished ornithologist for sketches of
the feathers of the Chamaepetes, and for other information.
  *(2) Jerdon, Birds of India, vol. iii., pp. 618, 621.
  *(3) Gould, Introduction to the Trochilidae, 1861, p. 49. Salvin,
Proceedings, Zoological Society, 1867, p. 160.

  Lastly, in several species of a sub-genus of Pipra or manakin, or
manakin, the males, as described by Mr. Sclater, have their
secondary wing-feathers modified in a still more remarkable manner. In
the brilliantly-coloured P. deliciosa the first three secondaries
are thick-stemmed and curved towards the body; in the fourth and fifth
(see fig. 45, a) the change is greater; and in the sixth and seventh
(b, c) the shaft "is thickened to an extraordinary degree, forming a
solid horny lump." The barbs also are greatly changed in shape, in
comparison with the corresponding feathers (d, e, f) in the female.
Even the bones of the wing, which support these singular feathers in
the male, are said by Mr. Fraser to be much thickened. These little
birds make an extraordinary noise, the first "sharp note being not
unlike the crack of a whip."*

  * Sclater, in Proceedings, Zoological Society, 1860, p. 90, and in
Ibis, vol. iv., 1862, p. 175. Also Salvin, in Ibis, 1860, p. 37.

  The diversity of the sounds, both vocal and instrumental, made by
the males of many birds during the breeding-season, and the
diversity of the means for producing such sounds, are highly
remarkable. We thus gain a high idea of their importance for sexual
purposes, and are reminded of the conclusion arrived at as to insects.
It is not difficult to imagine the steps by which the notes of a bird,
primarily used as a mere call or for some other purpose, might have
been improved into a melodious love song. In the case of the
modified feathers, by which the drumming, whistling, or roaring noises
are produced, we know that some birds during their courtship
flutter, shake, or rattle their unmodified feathers together; and if
the females were led to select the best performers, the males which
possessed the strongest or thickest, or most attenuated feathers,
situated on any part of the body, would be the most successful; and
thus by slow degrees the feathers might be modified to almost any
extent. The females, of course, would not notice each slight
successive alteration in shape, but only the sounds thus produced.
It is a curious fact that in the same class of animals, sounds so
different as the drumming of the snipe's tail, the tapping of the
woodpecker's beak, the harsh trumpet-like cry of certain water-fowl,
the cooing of the turtle-dove, and the song of the nightingale, should
all be pleasing to the females of the several species. But we must not
judge of the tastes of distinct species by a uniform standard; nor
must we judge by the standard of man's taste. Even with man, we should
remember what discordant noises, the beating of tom-toms and the
shrill notes of reeds, please the ears of savages. Sir S. Baker
remarks,* that "as the stomach of the Arab prefers the raw meat and
reeking liver taken hot from the animal, so does his ear prefer his
equally coarse and discordant music to all other."

  * The Nile Tributaries of Abyssinia, 1867, p. 203.

  Love Antics and Dances.- The curious love gestures of some birds
have already been incidentally noticed; so that little need here be
added. In Northern America large numbers of a grouse, the Tetrao
phasianellus, meet every morning during the breeding-season on a
selected level spot, and here they run round and round in a circle
of about fifteen or twenty feet in diameter, so that the ground is
worn quite bare, like a fairy-ring. In these partridge-dances, as they
are called by the hunters, the birds assume the strangest attitudes,
and run round, some to the left and some to the right. Audubon
describes the males of a heron (Ardea herodias) as walking about on
their long legs with great dignity before the females, bidding
defiance to their rivals. With one of the disgusting
carrion-vultures (Cathartes jota) the same naturalist states that "the
gesticulations and parade of the males at the beginning of the
love-season are extremely ludicrous." Certain birds perform their
love-antics on the wing, as we have seen with the black African
weaver, instead of on the ground. During the spring our little
white-throat (Sylvia cinerea) often rises a few feet or yards in the
air above some bush, and "flutters with a fitful and fantastic motion,
singing all the while, and then drops to its perch." The great English
bustard throws himself into indescribably odd attitudes whilst
courting the female, as has been figured by Wolf. An allied Indian
bustard (Otis bengalensis) at such times "rises perpendicularly into
the air with a hurried flapping of his wings, raising his crest and
puffing out the feathers of his neck and breast, and then drops to the
ground"; he repeats this manoeuvre several times, at the same time
humming in a peculiar tone. Such females as happen to be near "obey
this saltatory summons," and when they approach he trails his wings
and spreads his tail like a turkey-cock.*

  * For Tetrao phasianellus, see Richardson, Fauna, Bor. Americana, p.
361, and for further particulars, Capt. Blakiston, Ibis, 1863, p. 125.
For the Cathartes and Ardea, Audubon, Ornithological Biography, vol.
ii., p. 51, and vol. iii., p. 89. On the white-throat, Macgillivray,
History of British Birds, vol. ii., p. 354. On the Indian bustard,
Jerdon, Birds of India, vol. iii., p. 618.

  But the most curious case is afforded by three allied genera of
Australian birds, the famous bower-birds,- no doubt the co-descendants
of some ancient species which first acquired the strange instinct of
constructing bowers for performing their love-antics. The bowers
(see fig. 46), which, as we shall hereafter see, are decorated with
feathers, shells, bones, and leaves, are built on the ground for the
sole purpose of courtship, for their nests are formed in trees. Both
sexes assist in the erection of the bowers, but the male is the
principal workman. So strong is this instinct that it is practised
under confinement, and Mr. Strange has described* the habits of some
satin bower-birds which he kept in an aviary in New South Wales. "At
times the male will chase the female all over the aviary, then go to
the bower, pick up a gay feather or a large leaf, utter a curious kind
of note, set all his feathers erect, run round the bower and become so
excited that his eyes appear ready to start from his bead; he
continues opening first one wing then the other, uttering a low,
whistling note, and, like the domestic cock, seems to be picking up
something from the ground, until at last the female goes gently
towards him." Captain Stokes has described the habits and
"play-houses" of another species, the great bower-bird, which was seen
"amusing itself by flying backwards and forwards, taking a shell
alternately from each side, and carrying it through the archway in its
mouth." These curious creations, formed solely as halls of assemblage,
where both sexes amuse themselves and pay their court, must cost the
birds much labor. The bower, for instance, of the fawn-breasted
species, is nearly four feet in length, eighteen inches in height, and
is raised on a thick platform of sticks.

  * Gould, Handbook to the Birds of Australia, vol. i., pp. 444,
449, 455. The bower of the satin bower-bird may be seen in the
Zoological Society's Gardens, Regent's Park.

  Decoration.- I will first discuss the cases in which the males are
ornamented either exclusively or in a much higher degree than the
females, and in a succeeding chapter those in which both sexes are
equally ornamented, and finally the rare cases in which the female
is somewhat more brightly-coloured than the male. As with the
artificial ornaments used by savage and civilised men, so with the
natural ornaments of birds, the head is the chief seat of decoration.*
The ornaments, as mentioned at the commencement of this chapter, are
wonderfully diversified. The plumes on the front or back of the head
consist of variously-shaped feathers, sometimes capable of erection or
expansion, by which their beautiful colours are fully displayed.
Elegant ear-tufts (see fig. 39, ante) are occasionally present. The
head is sometimes covered with velvety down, as with the pheasant;
or is naked and vividly coloured. The throat, also, is sometimes
ornamented with a beard, wattles, or caruncles. Such appendages are
generally brightly-coloured, and no doubt serve as ornaments, though
not always ornamental in our eyes; for whilst the male is in the act
of courting the female, they often swell and assume vivid tints, as in
the male turkey. At such times the fleshy appendages about the head of
the male tragopan pheasant (Ceriornis temminckii) swell into a large
lappet on the throat and into two horns, one on each side of the
splendid topknot; and these are then coloured of the most intense blue
which I have ever beheld.*(2) The African hornbill (Bucorax
abyssinicus) inflates the scarlet bladder-like wattle on its neck, and
with its wings drooping and tail expanded "makes quite a grand
appearance."*(3) Even the iris of the eye is sometimes more
brightly-coloured in the male than in the female; and this is
frequently the case with the beak, for instance, in our common
blackbird. In Buceros corrugatus, the whole beak and immense casque
are coloured more conspicuously in the male than in the female; and
"the oblique grooves upon the sides of the lower mandible are peculiar
to the male sex."*(4)

  * See remarks to this effect, on the "Feeling of Beauty among
Animals," by Mr. J. Shaw, in the Athenaeum, Nov. 24, 1866, p. 681.
  *(2) See Dr. Murie's account with coloured figures in Proceedings,
Zoological Society, 1872, p. 730.
  *(3) Mr. Monteiro, Ibis, vol. iv., 1862, p. 339.
  *(4) Land and Water, 1868, p. 217.

  The head, again, often supports fleshy appendages, filaments, and
solid protuberances. These, if not common to both sexes, are always
confined to the males. The solid protuberances have been described
in detail by Dr. W. Marshall,* who shews that they are formed either
of cancellated bone coated with skin, or of dermal and other
tissues. With mammals true horns are always supported on the frontal
bones, but with birds various bones have been modified for this
purpose; and in species of the same group the protuberances may have
cores of bone, or be quite destitute of them, with intermediate
gradations connecting these two extremes. Hence, as Dr. Marshall
justly remarks, variations of the most different kinds have served for
the development through sexual selection of these ornamental
appendages. Elongated feathers or plumes spring from almost every part
of the body. The feathers on the throat and breast are sometimes
developed into beautiful ruffs and collars. The tail-feathers are
frequently increased in length; as we see in the tail-coverts of the
peacock, and in the tail itself of the Argus pheasant. With the
peacock even the bones of the tail have been modified to support the
heavy tail-coverts.*(2) The body of the Argus is not larger than
that of a fowl; yet the length from the end of the beak to the
extremity of the tail is no less than five feet three inches,*(3)
and that of the beautifully ocellated secondary wing-feathers nearly
three feet. In a small African night-jar (Cosmetornis vexillarius) one
of the primary wing-feathers, during the breeding-season, attains a
length of twenty-six inches, whilst the bird itself is only ten inches
in length. In another closely-allied genus of night-jars, the shafts
of the elongated wing-feathers are naked, except at the extremity,
where there is a disc.*(4) Again, in another genus of night-jars,
the tail-feathers are even still more prodigiously developed. In
general the feathers of the tail are more often elongated than those
of the wings, as any great elongation of the latter impedes flight. We
thus see that in closely-allied birds ornaments of the same kind
have been gained by the males through the development of widely
different feathers.

  * "Uber die Schadelhocker," Niederland. Archiv. fur Zoologie, B. i.,
Heft 2, 1872.
  *(2) Dr. W. Marshall, "Uber den Vogelschwanz," ibid., B. i., Heft 2,
1872.
  *(3) Jardine's Naturalist Library: Birds, vol. xiv., p. 166.
  *(4) Sclater, in the Ibis, vol. vi., 1864, p. 114; Livingstone,
Expedition to the Zambesi, 1865, p. 66.

  It is a curious fact that the feathers of species belonging to
very distinct groups have been modified in almost exactly the same
peculiar manner. Thus the wing-feathers in one of the
above-mentioned night-jars are bare along the shaft, and terminate
in a disc; or are, as they are sometimes called, spoon or
racket-shaped. Feathers of this kind occur in the tail of a motmot
(Eumomota superciliaris), of a king-fisher, finch, humming-bird,
parrot, several Indian drongos (Dicrurus and Edolius, in one of
which the disc stands vertically), and in the tail of certain birds of
paradise. In these latter birds, similar feathers, beautifully
ocellated, ornament the head, as is likewise the case with some
gallinaceous birds. In an Indian bustard (Sypheotides auritus) the
feathers forming the ear-tufts, which are about four inches in length,
also terminate in discs.* It is a most singular fact that the motmots,
as Mr. Salvin has clearly shown,*(2) give to their tail feathers the
racket-shape by biting off the barbs, and, further, that this
continued mutilation has produced a certain amount of inherited
effect.

  * Jerdon, Birds of India, vol. iii., p. 620.
  *(2) Proceedings, Zoological Society, 1873, p. 429.

  Again, the barbs of the feathers in various widely-distinct birds
are filamentous or plumose, as with some herons, ibises, birds of
paradise, and Gallinaceae. In other cases the barbs disappear, leaving
the shafts bare from end to end; and these in the tail of the
Paradisea apoda attain a length of thirty-four inches:* in P.
Papuana (see fig. 47) they are much shorter and thin. Smaller feathers
when thus denuded appear like bristles, as on the breast of the
turkey-cock. As any fleeting fashion in dress comes to be admired by
man, so with birds a change of almost any kind in the structure or
colouring of the feathers in the male appears to have been admired
by the female. The fact of the feathers in widely distinct groups
having been modified in an analogous manner no doubt depends primarily
on all the feathers having nearly the same structure and manner of
development, and consequently tending to vary in the same manner. We
often see a tendency to analogous variability in the plumage of our
domestic breeds belonging to distinct species. Thus top-knots have
appeared in several species. In an extinct variety of the turkey,
the top-knot consisted of bare quills surmounted with plumes of
down, so that they somewhat resembled the racket-shaped feathers above
described. In certain breeds of the pigeon and fowl the feathers are
plumose, with some tendency in the shafts to be naked. In the
Sebastopol goose the scapular feathers are greatly elongated,
curled, or even spirally twisted, with the margins plumose.*(2)

  * Wallace, in Annals and Magazine of Natural History, vol. xx.,
1857, p. 416, and in his Malay Archipelago, vol. ii., 1869, p. 390.
  *(2) See my work on The Variation of Animals and Plants under
Domestication, vol. i., pp. 289, 293.

  In regard to colour, hardly anything need here be said, for every
one knows how splendid are the tints of many birds, and how
harmoniously they are combined. The colours are often metallic and
iridescent. Circular spots are sometimes surrounded by one or more
differently shaded zones, and are thus converted into ocelli. Nor need
much be said on the wonderful difference between the sexes of many
birds. The common peacock offers a striking instance. Female birds
of paradise are obscurely coloured and destitute of all ornaments,
whilst the males are probably the most highly decorated of all
birds, and in so many different ways that they must be seen to be
appreciated. The elongated and golden-orange plumes which spring
from beneath the wings of the Paradisea apoda, when vertically erected
and made to vibrate, are described as forming a sort of halo, in the
centre of which the head "looks like a little emerald sun with its
rays formed by the two plumes."* In another most beautiful species the
head is bald, "and of a rich cobalt blue, crossed by several lines
of black velvety feathers."*(2)
  * Quoted from M. de Lafresnaye in Annals and Mag. of Natural
History, vol. xiii., 1854, p. 157: see also Mr. Wallace's much
fuller account in vol. xx., 1857, p. 412, and in his The Malay
Archipelago.
  *(2) Wallace, The Malay Archipelago, vol. ii., 1869, p. 405.

  Male humming-birds (see figs. 48 and 49) almost vie with birds of
paradise in their beauty, as every one will admit who has seen Mr.
Gould's splendid volumes, or his rich collection. It is very
remarkable in how many different ways these birds are ornamented.
Almost every part of their plumage has been taken advantage of, and
modified; and the modifications have been carried, as Mr. Gould shewed
me, to a wonderful extreme in some species belonging to nearly every
sub-group. Such cases are curiously like those which we see in our
fancy breeds, reared by man for the sake of ornament; certain
individuals originally varied in one character, and other
individuals of the same species in other characters; and these have
been seized on by man and much augmented- as shewn by the tail of
the fantail-pigeon, the hood of the jacobin, the beak and wattle of
the carrier, and so forth. The sole difference between these cases
is that in the one, the result is due to man's selection, whilst in
the other, as with humming-birds, birds of paradise, &c., it is due to
the selection by the females of the more beautiful males.
  I will mention only one other bird, remarkable from the extreme
contrast in colour between the sexes, namely the famous bell-bird
(Chasmorhynchus niveus) of S. America, the note of which can be
distinguished at the distance of nearly three miles, and astonishes
every one when first hearing it. The male is pure white, whilst the
female is dusky-green; and white is a very rare colour in
terrestrial species of moderate size and inoffensive habits. The male,
also, as described by Waterton, has a spiral tube, nearly three inches
in length, which rises from the base of the beak. It is jet-black,
dotted over with minute downy feathers. This tube can be inflated with
air, through a communication with the palate; and when not inflated
hangs down on one side. The genus consists of four species, the
males of which are very distinct, whilst the females, as described
by Mr. Sclater in a very interesting paper, closely resemble each
other, thus offering an excellent instance of the common rule that
within the same group the males differ much more from each other
than do the females. In a second species (C. nudicollis) the male is
likewise snow-white, with the exception of a large space of naked skin
on the throat and round the eyes, which during the breeding-season
is of a fine green colour. In a third species (C. tricarunculatus) the
head and neck alone of the male are white, the rest of the body
being chestnut-brown, and the male of this species is provided with
three filamentous projections half as long as the body- one rising
from the base of the beak, and the two others from the corners of
the mouth.*

  * Mr. Sclater, Intellectual Observer, Jan., 1867. Waterton's
Wanderings, p. 118. See also Mr. Salvin's interesting paper, with a
plate, in the Ibis, 1865, p. 90.

  The coloured plumage and certain other ornaments of the adult
males are either retained for life, or are periodically renewed during
the summer and breeding-season. At this same season the beak and naked
skin about the head frequently change colour, as with some herons,
ibises, gulls, one of the bell-birds just noticed, &c. In the white
ibis, the cheeks, the inflatable skin of the throat, and the basal
portion of the beak then become crimson.* In one of the rails,
Gallicrex cristatus, a large red caruncle is developed during this
period on the head of the male. So it is with a thin horny crest on
the beak of one of the pelicans, P. erythrorhynchus; for, after the
breeding-season, these horny crests are shed, like horns from the
heads of stags, and the shore of an island in a lake in Nevada was
found covered with these curious exuviae.*(2)

  * Land and Water, 1867, p. 394.
  *(2) Mr. D. G. Elliot, in Proc. Zool. Soc., 1869, p. 589.

  Changes of colour in the plumage according to the season depend,
firstly on a double annual moult, secondly on an actual change of
colour in the feathers themselves, and thirdly on their
dull-coloured margins being periodically shed, or on these three
processes more or less combined. The shedding of the deciduary margins
may be compared with the shedding of their down by very young birds;
for the down in most cases arises from the summits of the first true
feathers.*

  * Nitzsch's "Pterylography," edited by P. L. Sclater, Ray Society,
1867, p. 14.

  With respect to the birds which annually undergo a double moult,
there are, firstly, some kinds, for instance snipes, swallow-plovers
(Glareolae), and curlews, in which the two sexes resemble each
other, and do not change colour at any season. I do not know whether
the winter plumage is thicker and warmer than the summer plumage,
but warmth seems the most probable end attained of a double moult,
where there is no change of colour. Secondly, there are birds, for
instance, certain species of Totanus and other Grallatores, the
sexes of which resemble each other, but in which the summer and winter
plumage differ slightly in colour. The difference, however, in these
cases is so small that it can hardly be an advantage to them; and it
may, perhaps, be attributed to the direct action of the different
conditions to which the birds are exposed during the two seasons.
Thirdly, there are many other birds the sexes of which are alike,
but which are widely different in their summer and winter plumage.
Fourthly, there are birds the sexes of which differ from each other in
colour; but the females, though moulting twice, retain the same
colours throughout the year, whilst the males undergo a change of
colour, sometimes a great one, as with certain bustards. Fifthly and
lastly, there are birds the sexes of which differ from each other each
other in both their summer and winter plumage; but the male
undergoes a greater amount of change at each recurrent season than the
female of which the ruff (Machetes pugnax) offers a good instance.
  With respect to the cause or purpose of the differences in colour
between the summer and winter plumage, this may in some instances,
as with the ptarmigan,* serve during both seasons as a protection.
When the difference between the two plumages is slight it may
perhaps be attributed, as already remarked, to the direct action of
the conditions of life. But with many birds there can hardly be a
doubt that the summer plumage is ornamental, even when both sexes
are alike. We may conclude that this is the case with many herons,
egrets, &c., for they acquire their beautiful plumes only during the
breeding-season. Moreover, such plumes, top-knots, &c., though
possessed by both sexes, are occasionally a little more developed in
the male than in the female; and they resemble the plumes and
ornaments possessed by the males alone of other birds. It is also
known that confinement, by affecting the reproductive system of male
birds, frequently checks the development of their secondary sexual
characters, but has no immediate influence on any other characters;
and I am informed by Mr. Bartlett that eight or nine specimens of
the knot (Tringa canutus) retained their unadorned winter plumage in
the Zoological Gardens throughout the year, from which fact we may
infer that the summer plumage, though common to both sexes, partakes
of the nature of the exclusively masculine plumage of many other
birds.*(2)

  * The brown mottled summer plumage of the ptarmigan is of as much
importance to it, as a protection, as the white winter plumage; for in
Scandinavia during the spring, when the snow has disappeared, this
bird is known to suffer greatly from birds of prey, before it has
acquired its summer dress: see Wilhelm von Wright, in Lloyd, Game
Birds of Sweden, 1867, p. 125.
  *(2) In regard to the previous statements on moulting, see, on
snipes, &c., Macgillivray, Hist. Brit. Birds, vol. iv., p. 371; on
Glareolae, curlews, and bustards, Jerdon, Birds of India, vol. iii.,
pp. 615, 630, 683; on Totanus, ibid., p. 700; on the plumes of herons,
ibid., p. 738, and Macgillivray, vol. iv., pp. 435 and 444, and Mr.
Stafford Allen, in the Ibis, vol. v., 1863, p. 33.

  From the foregoing facts, more especially from neither sex of
certain birds changing colour during either annual moult, or
changing so slightly that the change can hardly be of any service to
them, and from the females of other species moulting twice yet
retaining the same colours throughout the year, we may conclude that
the habit of annually moulting twice has not been acquired in order
that the male should assume an ornamental character during the
breeding-season; but that the double moult, having been originally
acquired for some distinct purpose, has subsequently been taken
advantage of in certain cases for gaining a nuptial plumage.
  It appears at first sight a surprising circumstance that some
closely-allied species should regularly undergo a double annual moult,
and others only a single one. The ptarmigan, for instance, moults
twice or even thrice in the year, and the blackcock only once: some of
the splendidly coloured honey-suckers (Nectariniae) of India and
some sub-genera of obscurely coloured pipits (Anthus) have a double,
whilst others have only a single annual moult.* But the gradations
in the manner of moulting, which are known to occur with various
birds, shew us how species, or whole groups, might have originally
acquired their double annual moult, or having once gained the habit,
have again lost it. With certain bustards and plovers the vernal moult
is far from complete, some feathers being renewed, and some changed in
colour. There is also reason to believe that with certain bustards and
rail-like birds, which properly undergo a double moult, some of the
older males retain their nuptial plumage throughout the year. A few
highly modified feathers may merely be added during the spring to
the plumage, as occurs with the disc-formed tail-feathers of certain
drongos (Bhringa) in India, and with the elongated feathers on the
back, neck, and crest of certain herons. By such steps as these, the
vernal moult might be rendered more and more complete, until a perfect
double moult was acquired. Some of the birds of paradise retain
their nuptial feathers throughout the year, and thus have only a
single moult; others cast them directly after the breeding-season, and
thus have a double moult; and others again cast them at this season
during the first year, but not afterwards; so that these latter
species are intermediate in their manner of moulting. There is also
a great difference with many birds in the length of time during
which the two annual plumages are retained; so that the one might come
to be retained for the whole year, and the other completely lost. Thus
in the spring Machetes pugnax retains his ruff for barely two
months. In Natal the male widow-bird (Chera progne) acquires his
fine plumage and long tail-feathers in December or January, and
loses them in March; so that they are retained only for about three
months. Most species, which undergo a double moult, keep their
ornamental feathers for about six months. The male, however, of the
wild Gallus bankiva retains his neck-hackles for nine or ten months;
and when these are cast off, the underlying black feathers on the neck
are fully exposed to view. But with the domesticated descendant of
this species, the neck-hackles of the male are immediately replaced by
new ones; so that we here see, as to part of the plumage, a double
moult changed under domestication into a single moult.*(2)

  * On the moulting of the ptarmigan, see Gould's Birds of Great
Britain. On the honey-suckers, Jerdon, Birds of India, vol. i., pp.
359, 365, 369. On the moulting of Anthus, see Blyth, in Ibis, 1867, p.
32.
  *(2) For the foregoing statements in regard to partial moults, and
on old males retaining their nuptial plumage, see Jerdon, on
bustards and plovers, in Birds of India, vol. iii., pp. 617, 637, 709,
711. Also Blyth in Land and Water, 1867, p. 84. On the moulting of
Paradisea, see an interesting article by Dr. W. Marshall, Archives
Neerlandaises, tom. vi., 1871. On the Vidua, Ibis, vol. iii., 1861, p.
133. On the Drongoshrikes, Perdon, ibid., vol. i., p. 435. On the
vernal moult of the Herodias bubulcus, Mr. S. S. Allen, in Ibis, 1863,
p. 33. On Gallus bankiva, Blyth, in Annals and Mag. of Natural
History, vol. i., 1848, p. 455; see, also, on this subject, my
Variation of Animals under Domestication, vol. i., p. 236.

  The common drake (Anas boschas), after the breeding-season, is
well known to lose his male plumage for a period of three months,
during which time he assumes that of the female. The male pin-tail
duck (Anas acuta) loses his plumage for the shorter period of six
weeks or two months; and Montagu remarks that "this double moult
within so short a time is a most extraordinary circumstance, that
seems to bid defiance to all human reasoning." But the believer in the
gradual modification of species will be far from feeling surprise at
finding gradations of all kinds. If the male pin-tail were to
acquire his new plumage within a still shorter period, the new male
feathers would almost necessarily be mingled with the old, and both
with some proper to the female; and this apparently is the case with
the male of a not distantly-allied bird, namely the Merganser
serrator, for the males are said to "undergo a change of plumage,
which assimilates them in some measure to the female." By a little
further acceleration in the process, the double moult would be
completely lost.*

  * See Macgillivray, Hist. British Birds (vol. v., pp. 34, 70, and
223), on the moulting of the Anatidae, with quotations from Waterton
and Montagu. Also Yarrell, History of British Birds, vol. iii., p.
243.

  Some male birds, as before stated, become more brightly coloured
in the spring, not by a vernal moult, but either by an actual change
of colour in the feathers, or by their obscurely-coloured deciduary
margins being shed. Changes of colour thus caused may last for a
longer or shorter time. In the Pelecanus onocrotalus a beautiful
rosy tint, with lemon-coloured marks on the breast, overspreads the
whole plumage in the spring; but these tints, as Mr. Sclater states,
"do not last long, disappearing generally in about six weeks or two
months after they have been attained." Certain finches shed the
margins of their feathers in the spring, and then become brighter
coloured, while other finches undergo no such change. Thus the
Fringilla tristis of the United States (as well as many other American
species) exhibits its bright colours only when the winter is past,
whilst our goldfinch, which exactly represents this bird in habits,
and our siskin, which represents it still more closely in structure,
undergo no such annual change. But a difference of this kind in the
plumage of allied species is not surprising, for with the common
linnet, which belongs to the same family, the crimson forehead and
breast are displayed only during the summer in England, whilst in
Madeira these colours are retained throughout the year.*

  * On the pelican, see Sclater, in Proc. Zool. Soc., 1868, p. 265. On
the American finches, see Audubon, Ornithological Biography, vol.
i., pp. 174, 221, and Jerdon, Birds of India, vol. ii., p. 383. On the
Fringilla cannabina of Madeira, Mr. E. Vernon Harcourt, Ibis, vol. v.,
1863, p. 230.

  Display by Male Birds of their Plumage.- Ornaments of all kinds,
whether permanently or temporarily gained, are sedulously displayed by
the males, and apparently serve to excite, attract, or fascinate the
females. But the males will sometimes display their ornaments, when
not in the presence of the females, as occasionally occurs with grouse
at their balz-places, and as may be noticed with the peacock; this
latter bird, however, evidently wishes for a spectator of some kind,
and, as I have often seen, will show off his finery before poultry, or
even pigs.* All naturalists who have closely attended to the habits of
birds, whether in a state of nature or under confinement, are
unanimously of opinion that the males take delight in displaying their
beauty. Audubon frequently speaks of the male as endeavouring in
various ways to charm the female. Mr. Gould, after describing some
peculiarities in a male humming-bird, says he has no doubt that it has
the power of displaying them to the greatest advantage before the
female. Dr. Jerdon*(2) insists that the beautiful plumage of the
male serves "to fascinate and attract the female." Mr. Bartlett, at
the Zoological Gardens, expressed himself to me in the strongest terms
to the same effect.

  * See also Ornamental Poultry, by Rev. E. S. Dixon, 1848, p. 8.
  *(2) Birds of India, introduct., vol. i., p. xxiv.; on the
peacock, vol. iii., p. 507. See Gould's Introduction to Trochilidae,
1861, pp. 15 and 111.

  It must be a grand sight in the forests of India "to come suddenly
on twenty or thirty pea-fowl, the males displaying their gorgeous
trains, and strutting about in all the pomp of pride before the
gratified females." The wild turkey-cock erects his glittering
plumage, expands his finely-zoned tail and barred wing-feather, and
altogether, with his crimson and blue wattles, makes a superb, though,
to our eye, grotesque appearance. Similar facts have already been
given with respect to grouse of various kinds. Turning to another
Order: The male Rupicola crocea (see fig. 50) is one of the most
beautiful birds in the world, being of a splendid orange, with some of
the feathers curiously truncated and plumose. The female is
brownish-green, shaded with red, and has a much smaller crest. Sir
R. Schomburgk has described their courtship; he found one of their
meeting-places where ten males and two females were present. The space
was from four to five feet in diameter, and appeared to have been
cleared of every blade of grass and smoothed as if by human hands. A
male "was capering, to the apparent delight of several others. Now
spreading its wings, throwing up its head, or opening its tail like
a fan; now strutting about with a hopping gait until tired, when it
gabbled some kind of note, and was relieved by another. Thus three
of them successively took the field, and then, with
self-approbation, withdrew to rest." The Indians, in order to obtain
their skins, wait at one of the meeting-places till the birds are
eagerly engaged in dancing, and then are able to kill with their
poisoned arrows four or five males, one after the other.* With birds
of paradise a dozen or more full-plumaged males congregate in a tree
to hold a dancing-party, as it is called by the natives: and here they
fly about, raise their wings, elevate their exquisite plumes, and make
them vibrate, and the whole tree seems, as Mr. Wallace remarks, to
be filled with waving plumes. When thus engaged, they become so
absorbed that a skilful archer may shoot nearly the whole party. These
birds, when kept in confinement in the Malay Archipelago, are said
to take much care in keeping their feathers clean; often spreading
them out, examining them, and removing every speck of dirt. One
observer, who kept several pairs alive, did not doubt that the display
of the male was intended to please the female.*(2)

  * Journal of R. Geograph. Soc., vol. x., 1840, p. 236.
  *(2) Annals and Mag. of Nat. Hist., vol. xiii., 1854, p. 157; also
Wallace, ibid., vol. xx., 1857, p. 412, and The Malay Archipelago,
vol. ii., 1869, p. 252. Also Dr. Bennett, as quoted by Brehm,
Illustriertes Thierleben, B. iii., s. 326.

  The gold and Amherst pheasants during their courtship not only
expand and raise their splendid frills, but twist them, as I have
myself seen, obliquely towards the female on whichever side she may be
standing, obviously in order that a large surface may be displayed
before her.* They likewise turn their beautiful tails and tail-coverts
a little towards the same side. Mr. Bartlett has observed a male
Polyplectron (see fig. 51) in the act of courtship, and has shown me a
specimen stuffed in the attitude then assumed. The tail and
wing-feathers of this bird are ornamented with beautiful ocelli,
like those on the peacock's train. Now when the peacock displays
himself, he expands and erects his tail transversely to his body,
for he stands in front of the female, and has to shew off, at the same
time, his rich blue throat and breast. But the breast of the
Polyplectron is obscurely coloured, and the ocelli are not confined to
the tail-feathers. Consequently the Polyplectron does not stand in
front of the female; but he erects and expands his tail-feathers a
little obliquely, lowering the expanded wing on the same side, and
raising that on the opposite side. In this attitude the ocelli over
the whole body are exposed at the same time before the eyes of the
admiring female in one grand bespangled expanse. To whichever side she
may turn, the expanded wings and the obliquely-held tail are turned
towards her. The male tragopan pheasant acts in nearly the same
manner, for he raises the feathers of the body, though not the wing
itself, on the side which is opposite to the female, and which would
otherwise be concealed, so that nearly all the beautifully spotted
feathers are exhibited at the same time.

  * Mr. T. W. Wood has given (The Student, April, 1870, p. 115) a full
account of this manner of display, by the gold pheasant and by the
Japanese pheasant, Ph. versicolor; and he calls it the lateral or
one-sided display.

  The Argus pheasant affords a much more remarkable case. The
immensely developed secondary wing-feathers are confined to the
male; and each is ornamented with a row of from twenty to twenty-three
ocelli, above an inch in diameter. These feathers are also elegantly
marked with oblique stripes and rows of spots of a dark colour, like
those on the skin of a tiger and leopard combined. These beautiful
ornaments are hidden until the male shows himself off before the
female. He then erects his tail, and expands his wing-feathers into
a great, almost upright, circular fan or shield, which is carried in
front of the body. The neck and head are held on one side, so that
they are concealed by the fan; but the bird in order to see the
female, before whom he is displaying himself, sometimes pushes his
head between two of the long wing-feathers (as Mr. Bartlett has seen),
and then presents a grotesque appearance. This must be a frequent
habit with the bird in a state of nature, for Mr. Bartlett and his son
on examining some perfect skins sent from the East, found a place
between two of the feathers which was much frayed, as if the head
had here frequently been pushed through. Mr. Wood thinks that the male
can also peep at the female on one side, beyond the margin of the fan.
  The ocelli on the wing-feathers are wonderful objects; for they
are so shaded that, as the Duke of Argyll remarks,* they stand out
like balls lying loosely within sockets. When I looked at the specimen
in the British Museum, which is mounted with the wings expanded and
trailing downwards, I was however greatly disappointed, for the ocelli
appeared flat, or even concave. But Mr. Gould soon made the case clear
to me, for he held the feathers erect. in the position in which they
would naturally be displayed, and now from the light shining on them
from above each ocellus at once resembled the ornament called a ball
and socket. These feathers have been shewn to several artists, and all
have expressed their admiration at the perfect shading. It may well be
asked, could such artistically shaded ornaments have been formed by
means of sexual selection? But it will be convenient to defer giving
an answer to this question until we treat in the next chapter of the
principle of gradation.

  * The Reign of Law, 1867, p. 203.

  The foregoing remarks relate to the secondary wing-feathers, but the
primary wing-feathers, which in most gallinaceous birds are
uniformly coloured, are in the Argus pheasant equally wonderful.
They are of a soft brown tint with numerous dark spots, each of
which consists of two or three black dots with a surrounding dark
zone. But the chief ornament is a space parallel to the dark-blue
shaft, which in outline forms a perfect second feather lying within
the true feather. This inner part is coloured of a lighter chestnut,
and is thickly dotted with minute white points. I have shewn this
feather to several persons, and many have admired it even more than
the ball and socket feathers, and have declared that it was more
like a work of art than of nature. Now these feathers are quite hidden
on all ordinary occasions, but are fully displayed, together with
the long secondary feathers, when they are all expanded together so as
to form the great fan or shield.
  The case of the male Argus pheasant is eminently interesting,
because it affords good evidence that the most refined beauty may
serve as a sexual charm, and for no other purpose. We must conclude
that this is the case, as the secondary and primary wing-feathers
are not at all displayed, and the ball and socket ornaments are not
exhibited in full perfection until the male assumes the attitude of
courtship. The Argus pheasant does not possess brilliant colours, so
that his success in love appears to depend on the great size of his
plumes, and on the elaboration of the most elegant patterns. Many will
declare that it is utterly incredible that a female bird should be
able to appreciate fine shading and exquisite patterns, It is
undoubtedly a marvellous fact that she should possess this almost
human degree of taste. He who thinks that he can safely gauge the
discrimination and taste of the lower animals may deny that the female
Argus pheasant can appreciate such refined beauty; but he will then be
compelled to admit that the extraordinary attitudes assumed by the
male during the act of courtship, by which the wonderful beauty of his
plumage is fully displayed, are purposeless; and this is a
conclusion which I for one will never admit.
  Although so many pheasants and allied gallinaceous birds carefully
display their plumage before the females, it is remarkable, as Mr.
Bartlett informs me, that this is not the case with the
dull-coloured Eared and Cheer pheasants (Crossoptilon auritum and
Phasianus wallichii); so that these birds seem conscious that they
have little beauty to display. Mr. Bartlett has never seen the males
of either of these species fighting together, though he has not had
such good opportunities for observing the Cheer or the Eared pheasant.
Mr. Jenner Weir, also, finds that all male birds with rich or
strongly-characterised plumage are more quarrelsome than the
dull-coloured species belonging to the same groups. The goldfinch, for
instance, is far more pugnacious than the linnet, and the blackbird
than the thrush. Those birds which undergo a seasonal change of
plumage likewise become much more pugnacious at the period when they
are most gaily ornamented. No doubt the males of some
obscurely-coloured birds fight desperately together, but it appears
that when sexual selection has been highly influential, and has
given bright colours to the males of any species, it has also very
often given a strong tendency to pugnacity. We shall meet with
nearly analogous cases when we treat of mammals. On the other hand,
with birds the power of song and brilliant colours have rarely been
both acquired by the males of the same species; but in this case the
advantage gained would have been the same, namely, success in charming
the female. Nevertheless it must be owned that the males of several
brilliantly coloured birds have had their feathers specially
modified for the sake of producing instrumental music, though the
beauty of this cannot be compared, at least according to our taste,
with that of the vocal music of many songsters.
  We will now turn to male birds which are not ornamented in any
high degree, but which nevertheless display during their courtship
whatever attractions they may possess. These cases are in some
respects more curious than the foregoing, and have been but little
noticed. I owe the following facts to Mr. Weir, who has long kept
confined birds of many kinds, including all the British Fringillidae
and Emberizidae. The facts have been selected from a large body of
valuable notes kindly sent me by him. The bullfinch makes his advances
in front of the female, and then puffs out his breast, so that many
more of the crimson feathers are seen at once than otherwise would
be the case. At the same time he twists and bows his black tail from
side to side in a ludicrous manner. The male chaffinch also stands
in front of the female, thus showing his red breast and "blue bell,"
as the fanciers call his head; the wings at the same time being
slightly expanded, with the pure white bands on the shoulders thus
rendered conspicuous. The common linnet distends his rosy breast,
slightly expands his brown wings and tail, so as to make the best of
them by exhibiting their white edgings. We must, however, be
cautious in concluding that the wings are spread out solely for
display, as some birds do so whose wings are not beautiful. This is
the case with the domestic cock, but it is always the wing on the side
opposite to the female which is expanded, and at the same time scraped
on the ground. The male gold-finch behaves differently from all
other finches: his wings are beautiful, the shoulders being black,
with the dark-tipped wing-feathers spotted with white and edged with
golden yellow. When he courts the female, he sways his body from
side to side, and quickly turns his slightly expanded wings first to
one side, then to the other, with a golden flashing effect. Mr. Weir
informs me that no other British finch turns thus from side to side
during his courtship, not even the closely-allied male siskin, for
he would not thus add to his beauty.
  Most of the British buntings are plain coloured birds; but in the
spring the feathers on the head of the male reed-bunting (Emberiza
schaeniculus) acquire a fine black colour by the abrasion of the dusky
tips; and these are erected during the act of courtship. Mr. Weir
has kept two species of Amadina from Australia: the A. castanotis is a
very small and chastely coloured finch, with a dark tail, white
rump, and jet-black upper tail-coverts, each of the latter being
marked with three large conspicuous oval spots of white.* This
species, when courting the female, slightly spreads out and vibrates
these parti-coloured tail-coverts in a very peculiar manner. The
male Amadina lathami behaves very differently, exhibiting before the
female his brilliantly spotted breast, scarlet rump, and scarlet upper
tail-coverts. I may here add from Dr. Jerdon that the Indian bulbul
(Pycnonotus hoemorrhous) has its under tail-coverts of a crimson
colour, and these, it might be thought could never be well
exhibited; but the bird "when excited often spreads them out laterally
so that they can be seen even from above."*(2) The crimson under
tail-coverts of some other birds as with one of the woodpeckers, Picus
major, can be seen without any such display. The common pigeon has
iridescent feathers on the breast, and every one must have seen how
the male inflates his breast whilst courting the female, thus
shewing them off to the best advantage. One of the beautiful
bronze-winged pigeons of Australia (Ocyphaps lophotes) behaves, as
described to me by Mr. Weir, very differently: the male, whilst
standing before the female, lowers his head almost to the ground,
spreads out and raises his tail, and half expands his wings. He then
alternately and slowly raises and depresses his body, so that the
iridescent metallic feathers are all seen at once, and glitter in
the sun.

  * For the description of these birds, see Gould's Handbook of the
Birds of Australia, vol. i., 1865, p. 417.
  *(2) Birds of India, vol. ii., p. 96.

  Sufficient facts have now been given to shew with what care male
birds display their various charms, and this they do with the utmost
skill. Whilst preening their feathers, they have frequent
opportunities for admiring themselves, and of studying how best to
exhibit their beauty. But as all the males of the same species display
themselves in exactly the same manner, it appears that actions, at
first perhaps intentional, have become instinctive. If so, we ought
not to accuse birds of conscious vanity; yet when we see a peacock
strutting about, with expanded and quivering tail-feathers, he seems
the very emblem of pride and vanity.
  The various ornaments possessed by the males are certainly of the
highest importance to them, for in some cases they have been
acquired at the expense of greatly impeded powers of flight or of
running. The African night-jar (Cosmetornis), which during the
pairing-season has one of its primary wing-feathers developed into a
streamer of very great length, is thereby much retarded in its flight,
although at other times remarkable for its swiftness. The "unwieldy
size" of the secondary wing-feather of the male Argus pheasant is said
"almost entirely to deprive the bird of flight." The fine plumes of
male birds of paradise trouble them during a high wind. The
extremely long tail-feathers of the male widow-birds (Vidua) of
Southern Africa render "their flight heavy;" but as soon as these
are cast off they fly as well as the females. As birds always breed
when food is abundant, the males probably do not suffer much
inconvenience in searching for food from their impeded powers of
movement; but there can hardly be a doubt that they must be much
more liable to be struck down by birds of prey. Nor can we doubt
that the long train of the peacock and the long tail and wing-feathers
of the Argus pheasant must render them an easier prey to any
prowling tiger-cat than would otherwise be the case. Even the bright
colours of many male birds cannot fail to make them conspicuous to
their enemies of all kinds. Hence, as Mr. Gould has remarked, it
probably is that such birds are generally of a shy disposition, as
if conscious that their beauty was a source of danger, and are much
more difficult to discover or approach, than the sombre coloured and
comparatively tame females or than the young and as yet unadorned
males.*

  * On the Cosmetornis, see Livingstone's Expedition to the Zambesi,
1865, p. 66. On the Argus pheasant, Jardine's Nat. Hist. Lib.:
Birds, vol. xiv., p. 167. On birds of paradise, Lesson, quoted by
Brehm, Thierleben, B. iii., s. 325. On the widow-bird, Barrow's
Travels in Africa, vol. i., p. 243, and Ibis. vol., iii., 1861 p. 133.
Mr. Gould, on the shyness of male birds, Handbook to Birds of
Australia, vol. i., 1865, pp. 210, 457

  It is a more curious fact that the males of some birds which are
provided with special weapons for battle, and which in a state of
nature are so pugnacious that they often kill each other, suffer
from possessing certain ornaments. Cock-fighters trim the hackles
and cut off the combs and gills of their cocks; and the birds are then
said to be dubbed. An undubbed bird, as Mr. Tegetmeier insists, "is at
a fearful disadvantage; the comb and gills offer an easy hold to his
adversary's beak, and as a cock always strikes where he holds, when
once he has seized his foe, he has him entirely in his power. Even
supposing that the bird is not killed, the loss of blood suffered by
an undubbed cock is much greater than that sustained by one that has
been trimmed."* Young turkey-cocks in fighting always seize hold of
each other's wattles; and I presume that the old birds fight in the
same manner. It may perhaps be objected that the comb and wattles
are not ornamental, and cannot be of service to the birds in this way;
but even to our eyes, the beauty of the glossy black Spanish cock is
much enhanced by his white face and crimson comb; and no one who has
ever seen the splendid blue wattles of the male tragopan pheasant
distended in courtship can for a moment doubt that beauty is the
object gained. From the foregoing facts we clearly see that the plumes
and other ornaments of the males must be of the highest importance
to them; and we further see that beauty is even sometimes more
important than success in battle.

  * Tegetmeier, The Poultry Book, 1866, p. 139.

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