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The Descent of Man and Selection in Relation to Sex by Charles Darwin

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males suffer from their small size, for according to M. Carbonnier, they
are liable to be devoured by the females of their own species when
carnivorous, and no doubt by other species. Increased size must be in some
manner of more importance to the females, than strength and size are to the
males for fighting with other males; and this perhaps is to allow of the
production of a vast number of ova.

[Fig. 29. Callionymus lyra.
Upper figure, male;
lower figure, female.
N.B. The lower figure is more reduced than the upper.]

In many species the male alone is ornamented with bright colours; or these
are much brighter in the male than the female. The male, also, is
sometimes provided with appendages which appear to be of no more use to him
for the ordinary purposes of life, than are the tail feathers to the
peacock. I am indebted for most of the following facts to the kindness of
Dr. Gunther. There is reason to suspect that many tropical fishes differ
sexually in colour and structure; and there are some striking cases with
our British fishes. The male Callionymus lyra has been called the gemmeous
dragonet "from its brilliant gem-like colours." When fresh caught from the
sea the body is yellow of various shades, striped and spotted with vivid
blue on the head; the dorsal fins are pale brown with dark longitudinal
bands; the ventral, caudal, and anal fins being bluish-black. The female,
or sordid dragonet, was considered by Linnaeus, and by many subsequent
naturalists, as a distinct species; it is of a dingy reddish-brown, with
the dorsal fin brown and the other fins white. The sexes differ also in
the proportional size of the head and mouth, and in the position of the
eyes (12. I have drawn up this description from Yarrell's 'British
Fishes,' vol. i. 1836, pp. 261 and 266.); but the most striking difference
is the extraordinary elongation in the male (Fig. 29) of the dorsal fin.
Mr. W. Saville Kent remarks that this "singular appendage appears from my
observations of the species in confinement, to be subservient to the same
end as the wattles, crests, and other abnormal adjuncts of the male in
gallinaceous birds, for the purpose of fascinating their mates." (13.
'Nature,' July 1873, p. 264.) The young males resemble the adult females
in structure and colour. Throughout the genus Callionymus (14. 'Catalogue
of Acanth. Fishes in the British Museum,' by Dr. Gunther, 1861, pp. 138-
151.), the male is generally much more brightly spotted than the female,
and in several species, not only the dorsal, but the anal fin is much
elongated in the males.

The male of the Cottus scorpius, or sea-scorpion, is slenderer and smaller
than the female. There is also a great difference in colour between them.
It is difficult, as Mr. Lloyd (15. 'Game Birds of Sweden,' etc., 1867, p.
466.) remarks, "for any one, who has not seen this fish during the
spawning-season, when its hues are brightest, to conceive the admixture of
brilliant colours with which it, in other respects so ill-favoured, is at
that time adorned." Both sexes of the Labrus mixtus, although very
different in colour, are beautiful; the male being orange with bright blue
stripes, and the female bright red with some black spots on the back.

[Fig. 30. Xiphophorus Hellerii.
Upper figure, male;
lower figure, female.]

In the very distinct family of the Cyprinodontidae--inhabitants of the
fresh waters of foreign lands--the sexes sometimes differ much in various
characters. In the male of the Mollienesia petenensis (16. With respect
to this and the following species I am indebted to Dr. Gunther for
information: see also his paper on the 'Fishes of Central America,' in
'Transact. Zoological Soc.' vol. vi. 1868, p. 485.), the dorsal fin is
greatly developed and is marked with a row of large, round, ocellated,
bright-coloured spots; whilst the same fin in the female is smaller, of a
different shape, and marked only with irregularly curved brown spots. In
the male the basal margin of the anal fin is also a little produced and
dark coloured. In the male of an allied form, the Xiphophorus Hellerii
(Fig. 30), the inferior margin of the caudal fin is developed into a long
filament, which, as I hear from Dr. Gunther, is striped with bright
colours. This filament does not contain any muscles, and apparently cannot
be of any direct use to the fish. As in the case of the Callionymus, the
males whilst young resemble the adult females in colour and structure.
Sexual differences such as these may be strictly compared with those which
are so frequent with gallinaceous birds. (17. Dr. Gunther makes this
remark; 'Catalogue of Fishes in the British Museum,' vol. iii. 1861, p.

[Fig.31. Plecostomus barbatus.
Upper figure, head of male;
lower figure, female.]

In a siluroid fish, inhabiting the fresh waters of South America, the
Plecostomus barbatus (18. See Dr. Gunther on this genus, in 'Proceedings
of the Zoological Society,' 1868, p. 232.) (Fig. 31), the male has its
mouth and inter-operculum fringed with a beard of stiff hairs, of which the
female shows hardly a trace. These hairs are of the nature of scales. In
another species of the same genus, soft flexible tentacles project from the
front part of the head of the male, which are absent in the female. These
tentacles are prolongations of the true skin, and therefore are not
homologous with the stiff hairs of the former species; but it can hardly be
doubted that both serve the same purpose. What this purpose may be, it is
difficult to conjecture; ornament does not here seem probable, but we can
hardly suppose that stiff hairs and flexible filaments can be useful in any
ordinary way to the males alone. In that strange monster, the Chimaera
monstrosa, the male has a hook-shaped bone on the top of the head, directed
forwards, with its end rounded and covered with sharp spines; in the female
"this crown is altogether absent," but what its use may be to the male is
utterly unknown. (19. F. Buckland, in 'Land and Water,' July 1868, p.
377, with a figure. Many other cases could be added of structures peculiar
to the male, of which the uses are not known.)

The structures as yet referred to are permanent in the male after he has
arrived at maturity; but with some Blennies, and in another allied genus
(20. Dr. Gunther, 'Catalogue of Fishes,' vol. iii. pp. 221 and 240.), a
crest is developed on the head of the male only during the breeding-season,
and the body at the same time becomes more brightly-coloured. There can be
little doubt that this crest serves as a temporary sexual ornament, for the
female does not exhibit a trace of it. In other species of the same genus
both sexes possess a crest, and in at least one species neither sex is thus
provided. In many of the Chromidae, for instance in Geophagus and
especially in Cichla, the males, as I hear from Professor Agassiz (21. See
also 'A Journey in Brazil,' by Prof. and Mrs. Agassiz, 1868, p. 220.), have
a conspicuous protuberance on the forehead, which is wholly wanting in the
females and in the young males. Professor Agassiz adds, "I have often
observed these fishes at the time of spawning when the protuberance is
largest, and at other seasons when it is totally wanting, and the two sexes
shew no difference whatever in the outline of the profile of the head. I
never could ascertain that it subserves any special function, and the
Indians on the Amazon know nothing about its use." These protuberances
resemble, in their periodical appearance, the fleshy carbuncles on the
heads of certain birds; but whether they serve as ornaments must remain at
present doubtful.

I hear from Professor Agassiz and Dr. Gunther, that the males of those
fishes, which differ permanently in colour from the females, often become
more brilliant during the breeding-season. This is likewise the case with
a multitude of fishes, the sexes of which are identical in colour at all
other seasons of the year. The tench, roach, and perch may be given as
instances. The male salmon at this season is "marked on the cheeks with
orange-coloured stripes, which give it the appearance of a Labrus, and the
body partakes of a golden orange tinge. The females are dark in colour,
and are commonly called black-fish." (22. Yarrell, 'History of British
Fishes,' vol. ii. 1836, pp. 10, 12, 35.) An analogous and even greater
change takes place with the Salmo eriox or bull trout; the males of the
char (S. umbla) are likewise at this season rather brighter in colour than
the females. (23. W. Thompson, in 'Annals and Magazine of Natural
History,' vol. vi. 1841, p. 440.) The colours of the pike (Esox
reticulatus) of the United States, especially of the male, become, during
the breeding-season, exceedingly intense, brilliant, and iridescent. (24.
'The American Agriculturalist,' 1868, p. 100.) Another striking instance
out of many is afforded by the male stickleback (Gasterosteus leiurus),
which is described by Mr. Warington (25. 'Annals and Mag. of Nat. Hist.'
Oct. 1852.), as being then "beautiful beyond description." The back and
eyes of the female are simply brown, and the belly white. The eyes of the
male, on the other hand, are "of the most splendid green, having a metallic
lustre like the green feathers of some humming-birds. The throat and belly
are of a bright crimson, the back of an ashy-green, and the whole fish
appears as though it were somewhat translucent and glowed with an internal
incandescence." After the breeding season these colours all change, the
throat and belly become of a paler red, the back more green, and the
glowing tints subside.

With respect to the courtship of fishes, other cases have been observed
since the first edition of this book appeared, besides that already given
of the stickleback. Mr. W.S. Kent says that the male of the Labrus mixtus,
which, as we have seen, differs in colour from the female, makes "a deep
hollow in the sand of the tank, and then endeavours in the most persuasive
manner to induce a female of the same species to share it with him,
swimming backwards and forwards between her and the completed nest, and
plainly exhibiting the greatest anxiety for her to follow." The males of
Cantharus lineatus become, during the breeding-season, of deep leaden-
black; they then retire from the shoal, and excavate a hollow as a nest.
"Each male now mounts vigilant guard over his respective hollow, and
vigorously attacks and drives away any other fish of the same sex. Towards
his companions of the opposite sex his conduct is far different; many of
the latter are now distended with spawn, and these he endeavours by all the
means in his power to lure singly to his prepared hollow, and there to
deposit the myriad ova with which they are laden, which he then protects
and guards with the greatest care." (26. 'Nature,' May 1873, p. 25.)

A more striking case of courtship, as well as of display, by the males of a
Chinese Macropus has been given by M. Carbonnier, who carefully observed
these fishes under confinement. (27. 'Bulletin de la Societe d'Acclimat.'
Paris, July 1869, and Jan. 1870.) The males are most beautifully coloured,
more so than the females. During the breeding-season they contend for the
possession of the females; and, in the act of courtship, expand their fins,
which are spotted and ornamented with brightly coloured rays, in the same
manner, according to M. Carbonnier, as the peacock. They then also bound
about the females with much vivacity, and appear by "l'etalage de leurs
vives couleurs chercher a attirer l'attention des femelles, lesquelles ne
paraissaient indifferentes a ce manege, elles nageaient avec une molle
lenteur vers les males et semblaient se complaire dans leur voisinage."
After the male has won his bride, he makes a little disc of froth by
blowing air and mucus out of his mouth. He then collects the fertilised
ova, dropped by the female, in his mouth; and this caused M. Carbonnier
much alarm, as he thought that they were going to be devoured. But the
male soon deposits them in the disc of froth, afterwards guarding them,
repairing the froth, and taking care of the young when hatched. I mention
these particulars because, as we shall presently see, there are fishes, the
males of which hatch their eggs in their mouths; and those who do not
believe in the principle of gradual evolution might ask how could such a
habit have originated; but the difficulty is much diminished when we know
that there are fishes which thus collect and carry the eggs; for if delayed
by any cause in depositing them, the habit of hatching them in their mouths
might have been acquired.

To return to our more immediate subject. The case stands thus: female
fishes, as far as I can learn, never willingly spawn except in the presence
of the males; and the males never fertilise the ova except in the presence
of the females. The males fight for the possession of the females. In
many species, the males whilst young resemble the females in colour; but
when adult become much more brilliant, and retain their colours throughout
life. In other species the males become brighter than the females and
otherwise more highly ornamented, only during the season of love. The
males sedulously court the females, and in one case, as we have seen, take
pains in displaying their beauty before them. Can it be believed that they
would thus act to no purpose during their courtship? And this would be the
case, unless the females exert some choice and select those males which
please or excite them most. If the female exerts such choice, all the
above facts on the ornamentation of the males become at once intelligible
by the aid of sexual selection.

We have next to inquire whether this view of the bright colours of certain
male fishes having been acquired through sexual selection can, through the
law of the equal transmission of characters to both sexes, be extended to
those groups in which the males and females are brilliant in the same, or
nearly the same degree and manner. In such a genus as Labrus, which
includes some of the most splendid fishes in the world--for instance, the
Peacock Labrus (L. pavo), described (28. Bory Saint Vincent, in 'Dict.
Class. d'Hist. Nat.' tom. ix. 1826, p. 151.), with pardonable exaggeration,
as formed of polished scales of gold, encrusting lapis-lazuli, rubies,
sapphires, emeralds, and amethysts--we may, with much probability, accept
this belief; for we have seen that the sexes in at least one species of the
genus differ greatly in colour. With some fishes, as with many of the
lowest animals, splendid colours may be the direct result of the nature of
their tissues and of the surrounding conditions, without the aid of
selection of any kind. The gold-fish (Cyprinus auratus), judging from the
analogy of the golden variety of the common carp, is perhaps a case in
point, as it may owe its splendid colours to a single abrupt variation, due
to the conditions to which this fish has been subjected under confinement.
It is, however, more probable that these colours have been intensified
through artificial selection, as this species has been carefully bred in
China from a remote period. (29. Owing to some remarks on this subject,
made in my work 'On the Variation of Animals under Domestication,' Mr. W.F.
Mayers ('Chinese Notes and Queries,' Aug. 1868, p. 123) has searched the
ancient Chinese encyclopedias. He finds that gold-fish were first reared
in confinement during the Sung Dynasty, which commenced A.D. 960. In the
year 1129 these fishes abounded. In another place it is said that since
the year 1548 there has been "produced at Hangchow a variety called the
fire-fish, from its intensely red colour. It is universally admired, and
there is not a household where it is not cultivated, IN RIVALRY AS TO ITS
COLOUR, and as a source of profit.") Under natural conditions it does not
seem probable that beings so highly organised as fishes, and which live
under such complex relations, should become brilliantly coloured without
suffering some evil or receiving some benefit from so great a change, and
consequently without the intervention of natural selection.

What, then, are we to conclude in regard to the many fishes, both sexes of
which are splendidly coloured? Mr. Wallace (30. 'Westminster Review,'
July 1867, p. 7.) believes that the species which frequent reefs, where
corals and other brightly-coloured organisms abound, are brightly coloured
in order to escape detection by their enemies; but according to my
recollection they were thus rendered highly conspicuous. In the fresh-
waters of the tropics there are no brilliantly-coloured corals or other
organisms for the fishes to resemble; yet many species in the Amazons are
beautifully coloured, and many of the carnivorous Cyprinidae in India are
ornamented with "bright longitudinal lines of various tints." (31.
'Indian Cyprinidae,' by Mr. M'Clelland, 'Asiatic Researches,' vol. xix.
part ii. 1839, p. 230.) Mr. M'Clelland, in describing these fishes, goes
so far as to suppose that "the peculiar brilliancy of their colours" serves
as "a better mark for king-fishers, terns, and other birds which are
destined to keep the number of these fishes in check"; but at the present
day few naturalists will admit that any animal has been made conspicuous as
an aid to its own destruction. It is possible that certain fishes may have
been rendered conspicuous in order to warn birds and beasts of prey that
they were unpalatable, as explained when treating of caterpillars; but it
is not, I believe, known that any fish, at least any fresh-water fish, is
rejected from being distasteful to fish-devouring animals. On the whole,
the most probable view in regard to the fishes, of which both sexes are
brilliantly coloured, is that their colours were acquired by the males as a
sexual ornament, and were transferred equally, or nearly so, to the other

We have now to consider whether, when the male differs in a marked manner
from the female in colour or in other ornaments, he alone has been
modified, the variations being inherited by his male offspring alone; or
whether the female has been specially modified and rendered inconspicuous
for the sake of protection, such modifications being inherited only by the
females. It is impossible to doubt that colour has been gained by many
fishes as a protection: no one can examine the speckled upper surface of a
flounder, and overlook its resemblance to the sandy bed of the sea on which
it lives. Certain fishes, moreover, can through the action of the nervous
system change their colours in adaptation to surrounding objects, and that
within a short time. (32. G. Pouchet, 'L'Institut.' Nov. 1, 1871, p.
134.) One of the most striking instances ever recorded of an animal being
protected by its colour (as far as it can be judged of in preserved
specimens), as well as by its form, is that given by Dr. Gunther (33.
'Proc. Zoolog. Soc.' 1865, p. 327, pl. xiv. and xv.) of a pipe-fish, which,
with its reddish streaming filaments, is hardly distinguishable from the
sea-weed to which it clings with its prehensile tail. But the question now
under consideration is whether the females alone have been modified for
this object. We can see that one sex will not be modified through natural
selection for the sake of protection more than the other, supposing both to
vary, unless one sex is exposed for a longer period to danger, or has less
power of escaping from such danger than the other; and it does not appear
that with fishes the sexes differ in these respects. As far as there is
any difference, the males, from being generally smaller and from wandering
more about, are exposed to greater danger than the females; and yet, when
the sexes differ, the males are almost always the more conspicuously
coloured. The ova are fertilised immediately after being deposited; and
when this process lasts for several days, as in the case of the salmon (34.
Yarrell, 'British Fishes,' vol. ii. p. 11.), the female, during the whole
time, is attended by the male. After the ova are fertilised they are, in
most cases, left unprotected by both parents, so that the males and
females, as far as oviposition is concerned, are equally exposed to danger,
and both are equally important for the production of fertile ova;
consequently the more or less brightly-coloured individuals of either sex
would be equally liable to be destroyed or preserved, and both would have
an equal influence on the colours of their offspring.

Certain fishes, belonging to several families, make nests, and some of them
take care of their young when hatched. Both sexes of the bright coloured
Crenilabrus massa and melops work together in building their nests with
sea-weed, shells, etc. (35. According to the observations of M. Gerbe;
see Gunther's 'Record of Zoolog. Literature,' 1865, p. 194.) But the males
of certain fishes do all the work, and afterwards take exclusive charge of
the young. This is the case with the dull-coloured gobies (36. Cuvier,
'Regne Animal,' vol. ii. 1829, p. 242.), in which the sexes are not known
to differ in colour, and likewise with the sticklebacks (Gasterosteus), in
which the males become brilliantly coloured during the spawning season.
The male of the smooth-tailed stickleback (G. leiurus) performs the duties
of a nurse with exemplary care and vigilance during a long time, and is
continually employed in gently leading back the young to the nest, when
they stray too far. He courageously drives away all enemies including the
females of his own species. It would indeed be no small relief to the
male, if the female, after depositing her eggs, were immediately devoured
by some enemy, for he is forced incessantly to drive her from the nest.
(37. See Mr. Warington's most interesting description of the habits of the
Gasterosteus leiurus in 'Annals and Magazine of Nat. History,' November

The males of certain other fishes inhabiting South America and Ceylon,
belonging to two distinct Orders, have the extraordinary habit of hatching
within their mouths, or branchial cavities, the eggs laid by the females.
(38. Prof. Wyman, in 'Proc. Boston Soc. of Nat. Hist.' Sept. 15, 1857.
Also Prof. Turner, in 'Journal of Anatomy and Physiology,' Nov. 1, 1866, p.
78. Dr. Gunther has likewise described other cases.) I am informed by
Professor Agassiz that the males of the Amazonian species which follow this
habit, "not only are generally brighter than the females, but the
difference is greater at the spawning-season than at any other time." The
species of Geophagus act in the same manner; and in this genus, a
conspicuous protuberance becomes developed on the forehead of the males
during the breeding-season. With the various species of Chromids, as
Professor Agassiz likewise informs me, sexual differences in colour may be
observed, "whether they lay their eggs in the water among aquatic plants,
or deposit them in holes, leaving them to come out without further care, or
build shallow nests in the river mud, over which they sit, as our Pomotis
does. It ought also to be observed that these sitters are among the
brightest species in their respective families; for instance, Hygrogonus is
bright green, with large black ocelli, encircled with the most brilliant
red." Whether with all the species of Chromids it is the male alone which
sits on the eggs is not known. It is, however, manifest that the fact of
the eggs being protected or unprotected by the parents, has had little or
no influence on the differences in colour between the sexes. It is further
manifest, in all the cases in which the males take exclusive charge of the
nests and young, that the destruction of the brighter-coloured males would
be far more influential on the character of the race, than the destruction
of the brighter-coloured females; for the death of the male during the
period of incubation or nursing would entail the death of the young, so
that they could not inherit his peculiarities; yet, in many of these very
cases the males are more conspicuously coloured than the females.

In most of the Lophobranchii (Pipe-fish, Hippocampi, etc.) the males have
either marsupial sacks or hemispherical depressions on the abdomen, in
which the ova laid by the female are hatched. The males also shew great
attachment to their young. (39. Yarrell, 'History of British Fishes,'
vol. ii. 1836, pp. 329, 338.) The sexes do not commonly differ much in
colour; but Dr. Gunther believes that the male Hippocampi are rather
brighter than the females. The genus Solenostoma, however, offers a
curious exceptional case (40. Dr. Gunther, since publishing an account of
this species in 'The Fishes of Zanzibar,' by Col. Playfair, 1866, p. 137,
has re-examined the specimens, and has given me the above information.),
for the female is much more vividly-coloured and spotted than the male, and
she alone has a marsupial sack and hatches the eggs; so that the female of
Solenostoma differs from all the other Lophobranchii in this latter
respect, and from almost all other fishes, in being more brightly-coloured
than the male. It is improbable that this remarkable double inversion of
character in the female should be an accidental coincidence. As the males
of several fishes, which take exclusive charge of the eggs and young, are
more brightly coloured than the females, and as here the female Solenostoma
takes the same charge and is brighter than the male, it might be argued
that the conspicuous colours of that sex which is the more important of the
two for the welfare of the offspring, must be in some manner protective.
But from the large number of fishes, of which the males are either
permanently or periodically brighter than the females, but whose life is
not at all more important for the welfare of the species than that of the
female, this view can hardly be maintained. When we treat of birds we
shall meet with analogous cases, where there has been a complete inversion
of the usual attributes of the two sexes, and we shall then give what
appears to be the probable explanation, namely, that the males have
selected the more attractive females, instead of the latter having
selected, in accordance with the usual rule throughout the animal kingdom,
the more attractive males.

On the whole we may conclude, that with most fishes, in which the sexes
differ in colour or in other ornamental characters, the males originally
varied, with their variations transmitted to the same sex, and accumulated
through sexual selection by attracting or exciting the females. In many
cases, however, such characters have been transferred, either partially or
completely, to the females. In other cases, again, both sexes have been
coloured alike for the sake of protection; but in no instance does it
appear that the female alone has had her colours or other characters
specially modified for this latter purpose.

The last point which need be noticed is that fishes are known to make
various noises, some of which are described as being musical. Dr. Dufosse,
who has especially attended to this subject, says that the sounds are
voluntarily produced in several ways by different fishes: by the friction
of the pharyngeal bones--by the vibration of certain muscles attached to
the swim bladder, which serves as a resounding board--and by the vibration
of the intrinsic muscles of the swim bladder. By this latter means the
Trigla produces pure and long-drawn sounds which range over nearly an
octave. But the most interesting case for us is that of two species of
Ophidium, in which the males alone are provided with a sound-producing
apparatus, consisting of small movable bones, with proper muscles, in
connection with the swim bladder. (41. 'Comptes-Rendus,' tom. xlvi. 1858,
p. 353; tom. xlvii. 1858, p. 916; tom. liv. 1862, p. 393. The noise made
by the Umbrinas (Sciaena aquila), is said by some authors to be more like
that of a flute or organ, than drumming: Dr. Zouteveen, in the Dutch
translation of this work (vol. ii. p. 36), gives some further particulars
on the sounds made by fishes.) The drumming of the Umbrinas in the
European seas is said to be audible from a depth of twenty fathoms; and the
fishermen of Rochelle assert "that the males alone make the noise during
the spawning-time; and that it is possible by imitating it, to take them
without bait." (42. The Rev. C. Kingsley, in 'Nature,' May 1870, p. 40.)
From this statement, and more especially from the case of Ophidium, it is
almost certain that in this, the lowest class of the Vertebrata, as with so
many insects and spiders, sound-producing instruments have, at least in
some cases, been developed through sexual selection, as a means for
bringing the sexes together.



[Fig. 32. Triton cristatus (half natural size, from Bell's 'British
Upper figure, male during the breeding season;
lower figure, female.]

I will begin with the tailed amphibians. The sexes of salamanders or newts
often differ much both in colour and structure. In some species prehensile
claws are developed on the fore-legs of the males during the breeding-
season: and at this season in the male Triton palmipes the hind-feet are
provided with a swimming-web, which is almost completely absorbed during
the winter; so that their feet then resemble those of the female. (43.
Bell, 'History of British Reptiles,' 2nd ed., 1849, pp. 156-159.) This
structure no doubt aids the male in his eager search and pursuit of the
female. Whilst courting her he rapidly vibrates the end of his tail. With
our common newts (Triton punctatus and cristatus) a deep, much indented
crest is developed along the back and tail of the male during the breeding-
season, which disappears during the winter. Mr. St. George Mivart informs
me that it is not furnished with muscles, and therefore cannot be used for
locomotion. As during the season of courtship it becomes edged with bright
colours, there can hardly be a doubt that it is a masculine ornament. In
many species the body presents strongly contrasted, though lurid tints, and
these become more vivid during the breeding-season. The male, for
instance, of our common little newt (Triton punctatus) is "brownish-grey
above, passing into yellow beneath, which in the spring becomes a rich
bright orange, marked everywhere with round dark spots." The edge of the
crest also is then tipped with bright red or violet. The female is usually
of a yellowish-brown colour with scattered brown dots, and the lower
surface is often quite plain. (44. Bell, 'History of British Reptiles,'
2nd ed., 1849, pp. 146, 151.) The young are obscurely tinted. The ova are
fertilised during the act of deposition, and are not subsequently tended by
either parent. We may therefore conclude that the males have acquired
their strongly-marked colours and ornamental appendages through sexual
selection; these being transmitted either to the male offspring alone, or
to both sexes.


With many frogs and toads the colours evidently serve as a protection, such
as the bright green tints of tree frogs and the obscure mottled shades of
many terrestrial species. The most conspicuously-coloured toad which I
ever saw, the Phryniscus nigricans (45. 'Zoology of the Voyage of the
"Beagle,"' 1843. Bell, ibid. p. 49.), had the whole upper surface of the
body as black as ink, with the soles of the feet and parts of the abdomen
spotted with the brightest vermilion. It crawled about the bare sandy or
open grassy plains of La Plata under a scorching sun, and could not fail to
catch the eye of every passing creature. These colours are probably
beneficial by making this animal known to all birds of prey as a nauseous

In Nicaragua there is a little frog "dressed in a bright livery of red and
blue" which does not conceal itself like most other species, but hops about
during the daytime, and Mr. Belt says (46. 'The Naturalist in Nicaragua,'
1874, p. 321.) that as soon as he saw its happy sense of security, he felt
sure that it was uneatable. After several trials he succeeded in tempting
a young duck to snatch up a young one, but it was instantly rejected; and
the duck "went about jerking its head, as if trying to throw off some
unpleasant taste."

With respect to sexual differences of colour, Dr. Gunther does not know of
any striking instance either with frogs or toads; yet he can often
distinguish the male from the female by the tints of the former being a
little more intense. Nor does he know of any striking difference in
external structure between the sexes, excepting the prominences which
become developed during the breeding-season on the front legs of the male,
by which he is enabled to hold the female. (47. The male alone of the
Bufo sikimmensis (Dr. Anderson, 'Proc. Zoolog. Soc.' 1871, p. 204) has two
plate-like callosities on the thorax and certain rugosities on the fingers,
which perhaps subserve the same end as the above-mentioned prominences.)
It is surprising that these animals have not acquired more strongly-marked
sexual characters; for though cold-blooded their passions are strong. Dr.
Gunther informs me that he has several times found an unfortunate female
toad dead and smothered from having been so closely embraced by three or
four males. Frogs have been observed by Professor Hoffman in Giessen
fighting all day long during the breeding-season, and with so much violence
that one had its body ripped open.

Frogs and toads offer one interesting sexual difference, namely, in the
musical powers possessed by the males; but to speak of music, when applied
to the discordant and overwhelming sounds emitted by male bull-frogs and
some other species, seems, according to our taste, a singularly
inappropriate expression. Nevertheless, certain frogs sing in a decidedly
pleasing manner. Near Rio Janeiro I used often to sit in the evening to
listen to a number of little Hylae, perched on blades of grass close to the
water, which sent forth sweet chirping notes in harmony. The various
sounds are emitted chiefly by the males during the breeding-season, as in
the case of the croaking of our common frog. (48. Bell, 'History British
Reptiles,' 1849, p. 93.) In accordance with this fact the vocal organs of
the males are more highly-developed than those of the females. In some
genera the males alone are provided with sacs which open into the larynx.
(49. J. Bishop, in 'Todd's Cyclopaedia of Anatomy and Physiology,' vol.
iv. p. 1503.) For instance, in the edible frog (Rana esculenta) "the sacs
are peculiar to the males, and become, when filled with air in the act of
croaking, large globular bladders, standing out one on each side of the
head, near the corners of the mouth." The croak of the male is thus
rendered exceedingly powerful; whilst that of the female is only a slight
groaning noise. (50. Bell, ibid. pp. 112-114.) In the several genera of
the family the vocal organs differ considerably in structure, and their
development in all cases may be attributed to sexual selection.



Tortoises and turtles do not offer well-marked sexual differences. In some
species, the tail of the male is longer than that of the female. In some,
the plastron or lower surface of the shell of the male is slightly concave
in relation to the back of the female. The male of the mud-turtle of the
United States (Chrysemys picta) has claws on its front feet twice as long
as those of the female; and these are used when the sexes unite. (51. Mr.
C.J. Maynard, 'The American Naturalist,' Dec. 1869, p. 555.) With the huge
tortoise of the Galapagos Islands (Testudo nigra) the males are said to
grow to a larger size than the females: during the pairing-season, and at
no other time, the male utters a hoarse bellowing noise, which can be heard
at the distance of more than a hundred yards; the female, on the other
hand, never uses her voice. (52. See my 'Journal of Researches during the
Voyage of the "Beagle,"' 1845, p. 384.)

With the Testudo elegans of India, it is said "that the combats of the
males may be heard at some distance, from the noise they produce in butting
against each other." (53. Dr. Gunther, 'Reptiles of British India,' 1864,
p. 7.)


The sexes apparently do not differ in colour; nor do I know that the males
fight together, though this is probable, for some kinds make a prodigious
display before the females. Bartram (54. 'Travels through Carolina,'
etc., 1791, p. 128.) describes the male alligator as striving to win the
female by splashing and roaring in the midst of a lagoon, "swollen to an
extent ready to burst, with its head and tail lifted up, he springs or
twirls round on the surface of the water, like an Indian chief rehearsing
his feats of war." During the season of love, a musky odour is emitted by
the submaxiliary glands of the crocodile, and pervades their haunts. (55.
Owen, 'Anatomy of Vertebrates,' vol. i. 1866, p. 615.)


Dr. Gunther informs me that the males are always smaller than the females,
and generally have longer and slenderer tails; but he knows of no other
difference in external structure. In regard to colour, be can almost
always distinguish the male from the female, by his more strongly-
pronounced tints; thus the black zigzag band on the back of the male
English viper is more distinctly defined than in the female. The
difference is much plainer in the rattle-snakes of N. America, the male of
which, as the keeper in the Zoological Gardens shewed me, can at once be
distinguished from the female by having more lurid yellow about its whole
body. In S. Africa the Bucephalus capensis presents an analogous
difference, for the female "is never so fully variegated with yellow on the
sides as the male." (56. Sir Andrew Smith, 'Zoology of S. Africa:
Reptilia,' 1849, pl. x.) The male of the Indian Dipsas cynodon, on the
other hand, is blackish-brown, with the belly partly black, whilst the
female is reddish or yellowish-olive, with the belly either uniform
yellowish or marbled with black. In the Tragops dispar of the same country
the male is bright green, and the female bronze-coloured. (57. Dr. A.
Gunther, 'Reptiles of British India,' Ray Soc., 1864, pp. 304, 308.) No
doubt the colours of some snakes are protective, as shewn by the green
tints of tree-snakes, and the various mottled shades of the species which
live in sandy places; but it is doubtful whether the colours of many kinds,
for instance of the common English snake and viper, serve to conceal them;
and this is still more doubtful with the many foreign species which are
coloured with extreme elegance. The colours of certain species are very
different in the adult and young states. (58. Dr. Stoliczka, 'Journal of
Asiatic Society of Bengal,' vol. xxxix, 1870, pp. 205, 211.)

During the breeding-season the anal scent-glands of snakes are in active
function (59. Owen, 'Anatomy of Vertebrates,' vol. i. 1866, p. 615.); and
so it is with the same glands in lizards, and as we have seen with the
submaxiliary glands of crocodiles. As the males of most animals search for
the females, these odoriferous glands probably serve to excite or charm the
female, rather than to guide her to the spot where the male may be found.
Male snakes, though appearing so sluggish, are amorous; for many have been
observed crowding round the same female, and even round her dead body.
They are not known to fight together from rivalry. Their intellectual
powers are higher than might have been anticipated. In the Zoological
Gardens they soon learn not to strike at the iron bar with which their
cages are cleaned; and Dr. Keen of Philadelphia informs me that some snakes
which he kept learned after four or five times to avoid a noose, with which
they were at first easily caught. An excellent observer in Ceylon, Mr. E.
Layard, saw (60. 'Rambles in Ceylon,' in 'Annals and Magazine of Natural
History,' 2nd series, vol. ix. 1852, p. 333.) a cobra thrust its head
through a narrow hole and swallow a toad. "With this encumbrance he could
not withdraw himself; finding this, he reluctantly disgorged the precious
morsel, which began to move off; this was too much for snake philosophy to
bear, and the toad was again seized, and again was the snake, after violent
efforts to escape, compelled to part with its prey. This time, however, a
lesson had been learnt, and the toad was seized by one leg, withdrawn, and
then swallowed in triumph."

The keeper in the Zoological Gardens is positive that certain snakes, for
instance Crotalus and Python, distinguish him from all other persons.
Cobras kept together in the same cage apparently feel some attachment
towards each other. (61. Dr. Gunther, 'Reptiles of British India,' 1864,
p. 340.)

It does not, however, follow because snakes have some reasoning power,
strong passions and mutual affection, that they should likewise be endowed
with sufficient taste to admire brilliant colours in their partners, so as
to lead to the adornment of the species through sexual selection.
Nevertheless, it is difficult to account in any other manner for the
extreme beauty of certain species; for instance, of the coral-snakes of S.
America, which are of a rich red with black and yellow transverse bands. I
well remember how much surprise I felt at the beauty of the first coral-
snake which I saw gliding across a path in Brazil. Snakes coloured in this
peculiar manner, as Mr. Wallace states on the authority of Dr. Gunther (62.
'Westminster Review,' July 1st, 1867, p. 32.), are found nowhere else in
the world except in S. America, and here no less than four genera occur.
One of these, Elaps, is venomous; a second and widely-distinct genus is
doubtfully venomous, and the two others are quite harmless. The species
belonging to these distinct genera inhabit the same districts, and are so
like each other that no one "but a naturalist would distinguish the
harmless from the poisonous kinds." Hence, as Mr. Wallace believes, the
innocuous kinds have probably acquired their colours as a protection, on
the principle of imitation; for they would naturally be thought dangerous
by their enemies. The cause, however, of the bright colours of the
venomous Elaps remains to be explained, and this may perhaps be sexual

Snakes produce other sounds besides hissing. The deadly Echis carinata has
on its sides some oblique rows of scales of a peculiar structure with
serrated edges; and when this snake is excited these scales are rubbed
against each other, which produces "a curious prolonged, almost hissing
sound." (63. Dr. Anderson, 'Proc. Zoolog. Soc.' 1871, p. 196.) With
respect to the rattling of the rattle-snake, we have at last some definite
information: for Professor Aughey states (64. The 'American Naturalist,'
1873, p. 85.), that on two occasions, being himself unseen, he watched from
a little distance a rattle-snake coiled up with head erect, which continued
to rattle at short intervals for half an hour: and at last he saw another
snake approach, and when they met they paired. Hence he is satisfied that
one of the uses of the rattle is to bring the sexes together.
Unfortunately he did not ascertain whether it was the male or the female
which remained stationary and called for the other. But it by no means
follows from the above fact that the rattle may not be of use to these
snakes in other ways, as a warning to animals which would otherwise attack
them. Nor can I quite disbelieve the several accounts which have appeared
of their thus paralysing their prey with fear. Some other snakes also make
a distinct noise by rapidly vibrating their tails against the surrounding
stalks of plants; and I have myself heard this in the case of a
Trigonocephalus in S. America.


The males of some, probably of many kinds of lizards, fight together from
rivalry. Thus the arboreal Anolis cristatellus of S. America is extremely
pugnacious: "During the spring and early part of the summer, two adult
males rarely meet without a contest. On first seeing one another, they nod
their heads up and down three or four times, and at the same time expanding
the frill or pouch beneath the throat; their eyes glisten with rage, and
after waving their tails from side to side for a few seconds, as if to
gather energy, they dart at each other furiously, rolling over and over,
and holding firmly with their teeth. The conflict generally ends in one of
the combatants losing his tail, which is often devoured by the victor."
The male of this species is considerably larger than the female (65. Mr.
N.L. Austen kept these animals alive for a considerable time; see 'Land and
Water,' July 1867, p. 9.); and this, as far as Dr. Gunther has been able to
ascertain, is the general rule with lizards of all kinds. The male alone
of the Cyrtodactylus rubidus of the Andaman Islands possesses pre-anal
pores; and these pores, judging from analogy, probably serve to emit an
odour. (66. Stoliczka, 'Journal of the Asiatic Society of Bengal,' vol.
xxxiv. 1870, p. 166.)

[Fig.33. Sitana minor.
Male with the gular pouch expanded (from Gunther's 'Reptiles of India')']

The sexes often differ greatly in various external characters. The male of
the above-mentioned Anolis is furnished with a crest which runs along the
back and tail, and can be erected at pleasure; but of this crest the female
does not exhibit a trace. In the Indian Cophotis ceylanica, the female has
a dorsal crest, though much less developed than in the male; and so it is,
as Dr. Gunther informs me, with the females of many Iguanas, Chameleons,
and other lizards. In some species, however, the crest is equally
developed in both sexes, as in the Iguana tuberculata. In the genus
Sitana, the males alone are furnished with a large throat pouch (Fig. 33),
which can be folded up like a fan, and is coloured blue, black, and red;
but these splendid colours are exhibited only during the pairing-season.
The female does not possess even a rudiment of this appendage. In the
Anolis cristatellus, according to Mr. Austen, the throat pouch, which is
bright red marbled with yellow, is present in the female, though in a
rudimental condition. Again, in certain other lizards, both sexes are
equally well provided with throat pouches. Here we see with species
belonging to the same group, as in so many previous cases, the same
character either confined to the males, or more largely developed in them
than in the females, or again equally developed in both sexes. The little
lizards of the genus Draco, which glide through the air on their rib-
supported parachutes, and which in the beauty of their colours baffle
description, are furnished with skinny appendages to the throat "like the
wattles of gallinaceous birds." These become erected when the animal is
excited. They occur in both sexes, but are best developed when the male
arrives at maturity, at which age the middle appendage is sometimes twice
as long as the head. Most of the species likewise have a low crest running
along the neck; and this is much more developed in the full-grown males
than in the females or young males. (67. All the foregoing statements and
quotations, in regard to Cophotis, Sitana and Draco, as well as the
following facts in regard to Ceratophora and Chamaeleon, are from Dr.
Gunther himself, or from his magnificent work on the 'Reptiles of British
India,' Ray Soc., 1864, pp. 122, 130, 135.)

A Chinese species is said to live in pairs during the spring; "and if one
is caught, the other falls from the tree to the ground, and allows itself
to be captured with impunity"--I presume from despair. (68. Mr. Swinhoe,
'Proc. Zoolog. Soc.' 1870, p. 240.)

[Fig. 34. Ceratophora Stoddartii.
Upper figure;
lower figure, female.]

There are other and much more remarkable differences between the sexes of
certain lizards. The male of Ceratophora aspera bears on the extremity of
his snout an appendage half as long as the head. It is cylindrical,
covered with scales, flexible, and apparently capable of erection: in the
female it is quite rudimental. In a second species of the same genus a
terminal scale forms a minute horn on the summit of the flexible appendage;
and in a third species (C. Stoddartii, fig. 34) the whole appendage is
converted into a horn, which is usually of a white colour, but assumes a
purplish tint when the animal is excited. In the adult male of this latter
species the horn is half an inch in length, but it is of quite minute size
in the female and in the young. These appendages, as Dr. Gunther has
remarked to me, may be compared with the combs of gallinaceous birds, and
apparently serve as ornaments.

[Fig. 35. Chamaeleo bifurcus.
Upper figure, male;
lower figure, female.

Fig. 36. Chamaeleo Owenii.
Upper figure, male;
lower figure, female.]

In the genus Chamaeleon we come to the acme of difference between the
sexes. The upper part of the skull of the male C. bifurcus (Fig. 35), an
inhabitant of Madagascar, is produced into two great, solid, bony
projections, covered with scales like the rest of the head; and of this
wonderful modification of structure the female exhibits only a rudiment.
Again, in Chamaeleo Owenii (Fig. 36), from the West Coast of Africa, the
male bears on his snout and forehead three curious horns, of which the
female has not a trace. These horns consist of an excrescence of bone
covered with a smooth sheath, forming part of the general integuments of
the body, so that they are identical in structure with those of a bull,
goat, or other sheath-horned ruminant. Although the three horns differ so
much in appearance from the two great prolongations of the skull in C.
bifurcus, we can hardly doubt that they serve the same general purpose in
the economy of these two animals. The first conjecture, which will occur
to every one, is that they are used by the males for fighting together; and
as these animals are very quarrelsome (69. Dr. Buchholz, 'Monatsbericht K.
Preuss. Akad.' Jan. 1874, p. 78.), this is probably a correct view. Mr.
T.W. Wood also informs me that he once watched two individuals of C.
pumilus fighting violently on the branch of a tree; they flung their heads
about and tried to bite each other; they then rested for a time and
afterwards continued their battle.

With many lizards the sexes differ slightly in colour, the tints and
stripes of the males being brighter and more distinctly defined than in the
females. This, for instance, is the case with the above Cophotis and with
the Acanthodactylus capensis of S. Africa. In a Cordylus of the latter
country, the male is either much redder or greener than the female. In the
Indian Calotes nigrilabris there is a still greater difference; the lips
also of the male are black, whilst those of the female are green. In our
common little viviparous lizard (Zootoca vivipara) "the under side of the
body and base of the tail in the male are bright orange, spotted with
black; in the female these parts are pale-greyish-green without spots."
(70. Bell, 'History of British Reptiles,' 2nd ed., 1849, p. 40.) We have
seen that the males alone of Sitana possess a throat-pouch; and this is
splendidly tinted with blue, black, and red. In the Proctotretus tenuis of
Chile the male alone is marked with spots of blue, green, and coppery-red.
(71. For Proctotretus, see 'Zoology of the Voyage of the "Beagle";
Reptiles,' by Mr. Bell, p. 8. For the Lizards of S. Africa, see 'Zoology
of S. Africa: Reptiles,' by Sir Andrew Smith, pl. 25 and 39. For the
Indian Calotes, see 'Reptiles of British India,' by Dr. Gunther, p. 143.)
In many cases the males retain the same colours throughout the year, but in
others they become much brighter during the breeding-season; I may give as
an additional instance the Calotes maria, which at this season has a bright
red head, the rest of the body being green. (72. Gunther in 'Proceedings,
Zoological Society,' 1870, p. 778, with a coloured figure.)

Both sexes of many species are beautifully coloured exactly alike; and
there is no reason to suppose that such colours are protective. No doubt
with the bright green kinds which live in the midst of vegetation, this
colour serves to conceal them; and in N. Patagonia I saw a lizard
(Proctotretus multimaculatus) which, when frightened, flattened its body,
closed its eyes, and then from its mottled tints was hardly distinguishable
from the surrounding sand. But the bright colours with which so many
lizards are ornamented, as well as their various curious appendages, were
probably acquired by the males as an attraction, and then transmitted
either to their male offspring alone, or to both sexes. Sexual selection,
indeed, seems to have played almost as important a part with reptiles as
with birds; and the less conspicuous colours of the females in comparison
with the males cannot be accounted for, as Mr. Wallace believes to be the
case with birds, by the greater exposure of the females to danger during



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

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

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.


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.)


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
armorous 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 Stubenvogel,' 1840, s. 4.
Mr. Harrison Weir likewise writes to me:--"I am informed that the best
singing males generally get a mate first, when they are bred in the same
room.") 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-

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 Stubenvogel,' 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, 'Stubenvogel,'
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

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. American: 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

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.

[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."


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 bead; he continues opening first one wing then the other, uttering a
low, whistling note, and, like the domestic cock, seems to be picking up
something from the ground, until at last the female goes gently towards
him." Captain Stokes has described the habits and "play-houses" of another
species, the Great Bower-bird, which was seen "amusing itself by flying
backwards and forwards, taking a shell alternately from each side, and
carrying it through the archway in its mouth." These curious 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.


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 Schadelhocker,' 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, 'Uber 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,

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.'S) 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.

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.)


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,

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