SECONDARY SEXUAL CHARACTERS OF BIRDS.
Sexual differences—Law of battle—Special weapons—Vocal
organs—Instrumental music—Love-antics and dances—Decorations, permanent
and seasonal—Double and single annual moults—Display of ornaments by
the males.
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 (1. ‘Ibis,’ vol. iii. (new series), 1867, p.
414.), 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. Gould, ‘Handbook
of the Birds of Australia,’ 1865, vol. ii. p. 383.) 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 shewn 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.
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 (3. Quoted by
Mr. Gould, ‘Introduction to the Trochilidae,’ 1861, page 29.) 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.” (4.
Gould, ibid. p. 52.) 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. (5. W. Thompson, ‘Natural History of Ireland: Birds,’ vol.
ii. 1850, p. 327.) 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.” (6. Jerdon,
‘Birds of India,’ 1863, vol. ii. p. 96.)
[Fig. 37. The Ruff or Machetes pugnax (from Brehm’s ‘Thierleben’).]
The polygamous ruff (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. (7. Macgillivray, ‘History of British Birds,’ vol. iv.
1852, pp. 177-181.) 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.” (8. Sir R. Schomburgk, in ‘Journal of Royal Geographic
Society,’ vol. xiii. 1843, p. 31.) 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.” (9. ‘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. (10. Gould,
‘Handbook of Birds of Australia,’ vol. i. p. 395; vol. ii. p. 383.)
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.
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 (11. Mr. Hewitt, in the ‘Poultry
Book’ by Tegetmeier, 1866, p. 137.) 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. (12. Layard,
‘Annals and Magazine of Natural History,’ vol. xiv. 1854, p. 63.) 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.” (13.
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. (14. Brehm,
‘Thierleben,’ 1867, B. iv. s. 351. Some of the foregoing statements are
taken from L. Lloyd, ‘The Game Birds of Sweden,’ etc., 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 (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 erythrophthalmus) 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. (15. Jerdon, ‘Birds of
India’: on Ithaginis, vol. iii. p. 523; on Galloperdix, p. 541.) 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.
[Fig.38. Palamedea cornuta (from Brehm), shewing the double wing-spurs,
and the filament on the head.]
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 (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. (16. For the Egyptian goose, see
Macgillivray, ‘British Birds,’ vol. iv. p. 639. For Plectropterus,
Livingstone’s ‘Travels,’ p. 254. For Palamedea, Brehm’s ‘Thierleben,’
B. iv. s. 740. See also on this bird Azara, ‘Voyages dans l’Amerique
merid.’ tom. iv. 1809, pp. 179, 253.) 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. (17. See, on our peewit, Mr.
R. Carr in ‘Land and Water,’ Aug. 8th, 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 (18. Audubon, ‘Ornithological Biography,’ vol. ii. p. 492;
vol. i. pp. 4-13.), 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. (19. Mr. Blyth, ‘Land and Water,’ 1867, p.
212.) 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 (20. 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
gray-hens in Scandinavia, and with other species in N. America.), which
afterwards pair with the victorious combatants. But in some cases the
pairing precedes instead of succeeding the combat: thus according to
Audubon (21. ‘Ornithological Biography,’ vol. ii. p. 275.), 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. (22. Brehm, ‘Thierleben,’ etc., 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 (23. ‘Land and Water,’ July 25, 1868, p. 14.) 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.” (24. 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 (25. ‘Ornithological Biography,’
vol. v. p. 601.), 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”
(26. The Hon. Daines Barrington, ‘Philosophical Transactions,’ 1773, p.
252.); 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.
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 song-birds 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 amorous notes, which, by instinct, the female knows, and
repairs to the spot to choose her mate.” (27. ‘Ornithological
Dictionary,’ 1833, p. 475.) 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. (28.
‘Naturgeschichte der Stubenvögel,’ 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.”)
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. (29.
‘Philosophical Transactions,’ 1773, p. 263. White’s ‘Natural History of
Selborne,’ 1825, vol. i. p. 246.) Barrington, however, admits that
“superiority in song gives to birds an amazing ascendancy over others,
as is well known to bird-catchers.”
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 (30. ‘Naturgesch. der Stubenvögel,’ 1840, s. 252.), 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 (31. Mr. Bold, ‘Zoologist,’ 1843-44, p. 659.) 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.
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
(32. D. Barrington, ‘Philosophical Transactions,’ 1773, p. 262.
Bechstein, ‘Stubenvögel,’ 1840, s. 4.), 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. (33. This is likewise the case with the
water-ouzel; see Mr. Hepburn in the ‘Zoologist,’ 1845-46, p. 1068.) 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. (34. L. Lloyd, ‘Game Birds
of Sweden,’ 1867, p. 25.) Hence it is not at all surprising that male
birds should continue singing for their own amusement after the season
for courtship is over.
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 (35. Barrington, ibid. p. 264,
Bechstein, ibid. s. 5.), and sometimes that of their neighbours. (36.
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.)
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 (37. Bishop, in
‘Todd’s Cyclopaedia of Anatomy and Physiology,’ vol. iv. p. 1496.),
though they never sing, and do not naturally modulate their voices to
any great extent. Hunter asserts (38. As stated by Barrington in
‘Philosophical Transactions,’ 1773, p. 262.) 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.
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. (39.
Gould, ‘Handbook to the Birds of Australia,’ vol. i. 1865, pp. 308-310.
See also Mr. T.W. Wood in the ‘Student,’ April 1870, p. 125.) 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, woodpeckers, etc., utter harsh
cries; and the brilliant birds of the tropics are hardly ever
songsters. (40. See remarks to this effect in Gould’s ‘Introduction to
the Trochilidae,’ 1861, p. 22.) 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.
[Fig. 39. Tetrao cupido: male. (T.W. Wood.)]
In some birds the vocal organs differ greatly in the two sexes. In the
Tetrao cupido (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.” (41. ‘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.)
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. (42.
Richardson, ‘Fauna Bor. Americana: Birds,’ 1831, p. 359. Audubon, ibid.
vol. iv. p. 507.)
[Fig. 40. The Umbrella-bird or Cephalopterus ornatus, male (from
Brehm).]
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.” (43. 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.) 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. (44.
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. (45. Bishop, in Todd’s
‘Cyclopaedia of Anatomy and Physiology,’ vol. iv. p. 1499.) 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. (46. Prof.
Newton, ‘Proc. Zoolog. Soc.’ 1871, p. 651.) 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. (47. 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.) 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. (48. ‘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.) Highly important
structures have, therefore, in these cases been modified according to
sex.
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 gobbling noise made, when with
erected feathers, rustling wings and distended wattles, he puffs and
struts before her. (49. C.L. Bonaparte, quoted in the ‘Naturalist
Library: Birds,’ vol. xiv. p. 126.) 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. (50. L. Lloyd, ‘The Game Birds of Sweden,’ etc., 1867, pp. 22,
81.) The voice of the common rook is known to alter during the
breeding-season, and is therefore in some way sexual. (51. Jenner,
‘Philosophical Transactions,’ 1824, p. 20.) 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.
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.
(52. For the foregoing facts see, on Birds of Paradise, Brehm,
‘Thierleben,’ Band 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.)
[Fig. 41. Outer tail-feather of Scolopax gallinago (from ‘Proc. Zool.
Soc.’ 1858).
Fig. 42. Outer tail-feather of Scolopax frenata.
Fig. 43. Outer tail-feather of Scolopax javensis.]
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
(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 (Fig.
42), four feathers, and in S. javensis (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. (53. 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.)
[Fig. 44. Primary wing-feather of a Humming-bird, the Selasphorus
platycercus (from a sketch by Mr. Salvin). Upper figure, that of male;
lower figure, corresponding feather of female.]
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. (54. 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.) 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. (55. Jerdon, ‘Birds of
India,’ vol. iii. pp. 618, 621.) 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
(Fig. 44), thus excised. Whilst flying from flower to flower he makes
“a shrill, almost whistling noise” (56. Gould, ‘Introduction to the
Trochilidae,’ 1861, p. 49. Salvin, ‘Proceedings, Zoological Society,’
1867, p. 160.); but it did not appear to Mr. Salvin that the noise was
intentionally made.
[Fig. 45. Secondary wing-feathers of Pipra deliciosa (from Mr. Sclater,
in ‘Proc. Zool. Soc.’ 1860). The three upper feathers, a, b, c, from
the male; the three lower corresponding feathers, d, e, f, from the
female. a and d, fifth secondary wing-feather of male and female, upper
surface. b and e, sixth secondary, upper surface. c and f, seventh
secondary, lower surface.]
Lastly, in several species of a sub-genus of Pipra 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 (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.” (57. 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 (58. ‘The Nile Tributaries of Abyssinia,’ 1867, p.
203.), 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.”
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. (59. For Tetrao phasianellus, see Richardson, ‘Fauna, Bor.
America,’ 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.)
[Fig. 46. Bower-bird, Chlamydera maculata, with bower (from Brehm).]
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 (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 (60. 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.) 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 head; 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
structures, formed solely as halls of assemblage, where both sexes
amuse themselves and pay their court, must cost the birds much labour.
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.
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. (61. See remarks to this
effect, on the ‘Feeling of Beauty among Animals,’ by Mr. J. Shaw, in
the ‘Athenaeum,’ Nov. 24th, 1866, p. 681.) 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 (Fig. 39) 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 top-knot; and these are then coloured of the most
intense blue which I have ever beheld. (62. See Dr. Murie’s account
with coloured figures in ‘Proceedings, Zoological Society,’ 1872, p.
730.) 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.” (63. Mr. Monteiro, ‘Ibis,’
vol. iv. 1862, p. 339.) 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.” (64. ‘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 (65. ‘Ueber die Schädelhöcker,’ etc., ‘Niederland.
Archiv. fur Zoologie,’ B. I. Heft 2, 1872.), 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. (66. Dr.
W. Marshall, ‘Über den Vogelschwanz,’ ibid. B. I. Heft 2, 1872.) 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 (67. Jardine’s ‘Naturalist Library: Birds,’ vol.
xiv. p. 166.), 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. (68. Sclater, in the ‘Ibis,’
vol. vi. 1864, p. 114; Livingstone, ‘Expedition to the Zambesi,’ 1865,
p. 66.) 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.
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. (69. Jerdon, ‘Birds of India,’ vol. iii. p.
620.) It is a most singular fact that the motmots, as Mr. Salvin has
clearly shewn (70. ‘Proceedings, Zoological Society,’ 1873, p. 429.),
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.
[Fig. 47. Paradisea Papuana (T.W. Wood).]
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 (71. Wallace, in ‘Annals and
Magazine of Natural History,’ vol. xx. 1857, p. 416, and in his ‘Malay
Archipelago,’ vol. ii. 1869, p. 390.): in P. Papuana (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. (72. 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.” (73. 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 ‘Malay
Archipelago.’) In another most beautiful species the head is bald, “and
of a rich cobalt blue, crossed by several lines of black velvety
feathers.” (74. Wallace, ‘The Malay Archipelago,’ vol. ii. 1869, p.
405.)
[Fig. 48. Lophornis ornatus, male and female (from Brehm).
Fig. 49. Spathura underwoodi, male and female (from Brehm).]
Male humming-birds (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, etc., 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. (75. 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, etc. In the white ibis, the cheeks,
the inflatable skin of the throat, and the basal portion of the beak
then become crimson. (76. ‘Land and Water,’ 1867, p. 394.) 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. (77. 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. (78.
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 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 (79. 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.), 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, etc., for they acquire their beautiful plumes only
during the breeding-season. Moreover, such plumes, top-knots, etc.,
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. (80.
In regard to the previous statements on moulting, see, on snipes, etc.,
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. (81. 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.) 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. (82. 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 Drongo-shrikes, Jerdon, 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. (83. 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. (84. 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 shew off
his finery before poultry, or even pigs. (85. See also ‘Ornamental
Poultry,’ by Rev. E.S. Dixon, 1848, p. 8.) 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 (86. ‘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.) 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.
[Fig. 50. Rupicola crocea, male (T.W. Wood).]
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-feathers, and altogether, with
his crimson and blue wattles, makes a superb, though, to our eyes,
grotesque appearance. Similar facts have already been given with
respect to grouse of various kinds. Turning to another Order: The male
Rupicola crocea (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. (87. ‘Journal
of R. Geograph. Soc.’ vol. x. 1840, p. 236.) 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. (88. ‘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, ‘Thierleben,’ B. iii. s. 326.)
[Fig. 51. Polyplectron chinquis, male (T.W. Wood).]
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.
(89. 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.) They likewise turn their beautiful tails and
tail-coverts a little towards the same side. Mr. Bartlett has observed
a male Polyplectron (Fig. 51) in the act of courtship, and has shewn 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.
[Fig. 52. Side view of male Argus pheasant, whilst displaying before
the female. Observed and sketched from nature by T.W. Wood.]
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 (90. ‘The Reign of Law,’
1867, p. 203.), 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 shown 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 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 as 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
shewing 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 goldfinch 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
schoeniculus) 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. (91. For the description
of these birds, see Gould’s ‘Handbook to the Birds of Australia,’ vol.
i. 1865, p. 417.) 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.” (92. ‘Birds
of India,’ vol. ii. p. 96.) 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.
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-feathers 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. (93. 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.” (94. Tegetmeier, ‘The Poultry Book,’ 1866, p. 139.) 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.