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Descent of Man [ 1871 ]

Charles Darwin [ 1809 - 1882 ]

 

Chapter XIV - Birds- Continued


  WHEN the sexes differ in beauty or in the power of singing, or in
producing what I have called instrumental music, it is almost
invariably the male who surpasses the female. These qualities, as we
have just seen, are evidently of high importance to the male. When
they are gained for only a part of the year it is always before the
breeding-season. It is the male alone who elaborately displays his
varied attractions, and often performs strange antics on the ground or
in the air, in the presence of the female. Each male drives away, or
if he can, kills his rivals. Hence we may conclude that it is the
object of the male to induce the female to pair with him, and for this
purpose he tries to excite or charm her in various ways; and this is
the opinion of all those who have carefully studied the habits of
living birds. But there remains a question which has an all
important bearing on sexual selection, namely, does every male of
the same species excite and attract the female equally? Or does she
exert a choice, and prefer certain males? This latter question can
be answered in the affirmative by much direct and indirect evidence.
It is far more difficult to decide what qualities determine the choice
of the females; but here again we have some direct and indirect
evidence that it is to a large extent the external attractions of
the male; though no doubt his vigour, courage, and other mental
qualities come into play. We will begin with the indirect evidence.
  Length of Courtship.- The lengthened period during which both
sexes of certain birds meet day after day at an appointed place
probably depends partly on the courtship being a prolonged affair, and
partly on reiteration in the act of pairing. Thus in Germany and
Scandinavia the balzen or leks of the black-cocks last from the middle
of March, all through April into May. As many as forty or fifty, or
even more birds congregate at the leks; and the same place is often
frequented during successive years. The lek of the capercailzie
lasts from the end of March to the middle or even end of May. In North
America "the partridge dances" of the Tetrao phasianellus "last for
a month or more." Other kinds of grouse, both in North America and
Eastern Siberia,* follow nearly the same habits. The fowlers
discover the hillocks where the ruffs congregate by the grass being
trampled bare, and this shews that the same spot is long frequented.
The Indians of Guiana are well acquainted with the cleared arenas,
where they expect to find the beautiful cocks of the rock; and the
natives of New Guinea know the trees where from ten to twenty male
birds of paradise in full plumage congregate. In this latter case it
is not expressly stated that the females meet on the same trees, but
the hunters, if not specially asked, would probably not mention
their presence, as their skins are valueless. Small parties of an
African weaver (Ploceus) congregate, during the breeding-season, and
perform for hours their graceful evolutions. Large numbers of the
solitary snipe (Scolopax major) assemble during dusk in a morass;
and the same place is frequented for the same purpose during
successive years; here they may be seen running about "like so many
rats," puffing out their feathers, flapping their wings, and
uttering the strangest cries.*(2)

  * Nordman describes (Bull. Soc. Imp. des Nat. Moscou, 1861, tom.
xxxiv., p. 264) the balzen of Tetrao urogalloides in Amur Land. He
estimated the number of birds assembled at above a hundred, not
counting the females, which lie hid in the surrounding bushes. The
noises uttered differ from those of T. urogallus.
  *(2) With respect to the assemblages of the above-named grouse,
see Brehm, Thierleben, B. iv., s. 350; also L. Lloyd, Game Birds of
Sweden, 1867, pp. 19, 78. Richardson, Fauna Bor. Americana: Birds,
p. 362. References in regard to the assemblages of other birds have
already been given. On Paradisea, see Wallace, in Annals and Mag. of
Nat. Hist., vol. xx., 1857, p. 412. On the snipe, Lloyd, ibid., p.
221.

  Some of the above birds,- the black-cock, capercailzie,
pheasant-grouse, ruff, solitary snipe, and perhaps others,- are, as is
believed, polygamists. With such birds it might have been thought that
the stronger males would simply have driven away the weaker, and
then at once have taken possession of as many females as possible; but
if it be indispensable for the male to excite or please the female, we
can understand the length of the courtship and the congregation of
so many individuals of both sexes at the same spot. Certain strictly
monogamous species likewise hold nuptial assemblages; this seems to be
the case in Scandinavia with one of the ptarmigans, and their leks
last from the middle of March to the middle of May. In Australia the
lyre-bird (Menura superba) forms "small round hillocks," and the M.
Alberti scratches for itself shallow holes, or, as they are called
by the natives, corroborying places, where it is believed both sexes
assemble. The meetings of the M. superba are sometimes very large; and
an account has lately been published* by a traveller, who heard in a
valley beneath him, thickly covered with scrub, "a din which
completely astonished" him; on crawling onwards he beheld, to his
amazement, about one hundred and fifty of the magnificent
lyre-cocks, "ranged in order of battle, and fighting with
indescribable fury." The bowers of the bower-birds are the resort of
both sexes during the breeding-season; and "here the males meet and
contend with each other for the favours of the female, and here the
latter assemble and coquet with the males." With two of the genera,
the same bower is resorted to during many years.*(2)

  * Quoted by Mr. T. W. Wood, in The Student, April, 1870, p. 125.
  *(2) Gould, Handbook of the Birds of Australia, vol. i., pp. 300,
308, 448, 451. On the ptarmigan, above alluded to, see Lloyd, ibid.,
p. 129.

  The common magpie (Corvus pica, Linn.), as I have been informed by
the Rev. W. Darwin Fox, used to assemble from all parts of Delamere
Forest, in order to celebrate the great magpie marriage." Some years
ago these birds abounded in extraordinary numbers, so that a
gamekeeper killed in one morning nineteen males, and another killed by
a single shot seven birds at roost together. They then had the habit
of assembling very early in the spring at particular spots, where they
could be seen in flocks, chattering, sometimes fighting, bustling
and flying about the trees. The whole affair was evidently
considered by the birds as one of the highest importance. Shortly
after the meeting they all separated, and were then observed by Mr.
Fox and others to be paired for the season. In any district in which a
species does not exist in large numbers, great assemblages cannot,
of course, be held, and the same species may have different habits
in different countries. For instance, I have heard of only one
instance, from Mr. Wedderburn, of a regular assemblage of black game
in Scotland, yet these assemblages are so well known in Germany and
Scandinavia that they have received special names.
  Unpaired Birds.- From the facts now given, we may conclude that
the courtship of birds belonging to widely different groups, is
often a prolonged, delicate, and troublesome affair. There is even
reason to suspect, improbable as this will at first appear, that
some males and females of the same species, inhabiting the same
district, do not always please each other, and consequently do not
pair. Many accounts have been published of either the male or female
of a pair having been shot, and quickly replaced by another. This
has been observed more frequently with the magpie than with any
other bird, owing perhaps to its conspicuous appearance and nest.
The illustrious Jenner states that in Wiltshire one of a pair was
daily shot no less than seven times successively, "but all to no
purpose, for the remaining magpie soon found another mate"; and the
last pair reared their young. A new partner is generally found on
the succeeding day; but Mr. Thompson gives the case of one being
replaced on the evening of the same day. Even after the eggs are
hatched, if one of the old birds is destroyed a mate will often be
found; this occurred after an interval of two days, in a case recently
observed by one of Sir J. Lubbock's keepers.* The first and most
obvious conjecture is that male magpies must be much more numerous
than females; and that in the above cases, as well as in many others
which could be given, the males alone had been killed. This apparently
holds good in some instances, for the gamekeepers in Delamere Forest
assured Mr. Fox that the magpies and carrion-crows which they formerly
killed in succession in large numbers near their nests, were all
males; and they accounted for this fact by the males being easily
killed whilst bringing food to the sitting females. Macgillivray,
however, gives, on the authority of an excellent observer, an instance
of three magpies successively killed on the same nest, which were
all females; and another case of six magpies successively killed
whilst sitting on the same eggs, which renders it probable that most
of them were females; though, as I hear from Mr. Fox, the male will
sit on the eggs when the female is killed.

  * On magpies, Jenner, in Philosophical Transactions, 1824, p. 21.
Macgillivray, Hist. British Birds, vol. i., p. 570. Thompson, in
Annals and Magazine of Natural History, vol. viii., 1842, p. 494.

  Sir J. Lubbock's gamekeeper has repeatedly shot, but how often he
could not say, one of a pair of jays (Garrulus glandarius), and has
never failed shortly afterwards to find the survivor re-matched. Mr.
Fox, Mr. F. Bond, and others have shot one of a pair of
carrion-crows (Corvus corone), but the nest was soon again tenanted by
a pair. These birds are rather common; but the peregrine-falcon (Falco
peregrinus) is rare, yet Mr. Thompson states that in Ireland "if
either an old male or female be killed in the breeding-season (not
an uncommon circumstance), another mate is found within a very few
days, so that the eyries, notwithstanding such casualties, are sure to
turn out their complement of young." Mr. Jenner Weir has known the
same thing with the peregrine-falcons at Beachy Head. The same
observer informs me that three kestrels (Falco tinnunculus), all
males, were killed one after the other whilst attending the same nest;
two of these were in mature plumage, but the third was in the
plumage of the previous year. Even with the rare golden eagle
(Aquila chrysaetos), Mr. Birkbeck was assured by a trustworthy
gamekeeper in Scotland, that if one is killed, another is soon
found. So with the white owl (Strix flammea), "the survivor readily
found a mate, and the mischief went on."
  White of Selborne, who gives the case of the owl, adds that he
knew a man, who from believing that partridges when paired were
disturbed by the males fighting, used to shoot them; and though he had
widowed the same female several times, she always soon found a fresh
partner. This same naturalist ordered the sparrows, which deprived the
house-martins of their nests, to be shot; but the one which was
left, "be it cock or hen, presently procured a mate, and so for
several times following." I could add analogous cases relating to
the chaffinch, nightingale, and redstart. With respect to the latter
bird (Phoenicura ruticilla), a writer expresses much surprise how
the sitting female could so soon have given effectual notice that
she was a widow, for the species was not common in the
neighbourhood. Mr. Jenner Weir has mentioned to me a nearly similar
case; at Blackheath he never sees or hears the note of the wild
bullfinch, yet when one of his caged males has died, a wild one in the
course of a few days has generally come and perched near the widowed
female, whose call-note is not loud. I will give only one other
fact, on the authority of this same observer; one of a pair of
starlings (Sturnus vulgaris) was shot in the morning; by noon a new
mate was found; this was again shot, but before night the pair was
complete; so that the disconsolate widow or widower was thrice
consoled during the same day. Mr. Engleheart also informs me that he
used during several years to shoot one of a pair of starlings which
built in a hole in a house at Blackheath; but the loss was always
immediately repaired. During one season he kept an account, and
found that he had shot thirty-five birds from the same nest; these
consisted of both males and females, but in what proportion he could
not say: nevertheless, after all this destruction, a brood was
reared.*

  * On the peregrine falcon, see Thompson, Nat. Hist. of Ireland:
Birds, vol. i., 1849, p. 39. On owls, sparrows, and partridges, see
White, Nat. Hist. of Selborne, ed. of 1825, vol. i., p. 139. On the
Phoenicura, see Loudon's Mag. of Nat. Hist., vol. vii., 1834, p.
245. Brehm (Thierleben, B. iv., s. 991) also alludes to cases of birds
thrice mated during the same day.

  These facts well deserve attention. How is it that there are birds
enough ready to replace immediately a lost mate of either sex?
Magpies, jays, carrion-crows, partridges, and some other birds, are
always seen during the spring in pairs, and never by themselves; and
these offer at first sight the most perplexing cases. But birds of the
same sex, although of course not truly paired, sometimes live in pairs
or in small parties, as is known to be the case with pigeons and
partridges. Birds also sometimes live in triplets, as has been
observed with starlings, carrion-crows, parrots, and partridges.
With partridges two females have been known to live with one male, and
two males with one female. In all such cases it is probable that the
union would be easily broken; and one of the three would readily
pair with a widow or widower. The males of certain birds may
occasionally be heard pouring forth their love-song long after the
proper time, shewing that they have either lost or never gained a
mate. Death from accident or disease of one of a pair would leave
the other free and single; and there is reason to believe that
female birds during the breeding-season are especially liable to
premature death. Again, birds which have had their nests destroyed, or
barren pairs, or retarded individuals, would easily be induced to
desert their mates, and would probably be glad to take what share they
could of the pleasures and duties of rearing offspring although not
their own.* Such contingencies as these probably explain most of the
foregoing cases.*(2) Nevertheless, it is a strange fact that within
the same district, during the height of the breeding-season, there
should be so many males and females always ready to repair the loss of
a mated bird. Why do not such spare birds immediately pair together?
Have we not some reason to suspect, and the suspicion has occurred
to Mr. Jenner Weir, that as the courtship of birds appears to be in
many cases prolonged and tedious, so it occasionally happens that
certain males and females do not succeed, during the proper season, in
exciting each other's love, and consequently do not pair? This
suspicion will appear somewhat less improbable after we have seen what
strong antipathies and preferences female birds occasionally evince
towards particular males.

  * See White (Nat. Hist. of Selborne, 1825, vol. i., p. 140) on the
existence, early in the season, of small coveys of male partridges, of
which fact I have heard other instances. See Jenner, on the retarded
state of the generative organs in certain birds, in Phil. Transact.,
1824. In regard to birds living in triplets, I owe to Mr. Jenner
Weir the cases of the starlings and parrots, and to Mr. Fox, of
partridges; on carrion-crows, see the Field, 1868, p. 415. On
various male birds singing after the proper period, see L. Jenyns,
Observations in Natural History, 1846, p. 87.
  *(2) The following case has been given (The Times, Aug. 6, 1868)
by the Rev. F. . Morris, on the authority of the Hon. and Rev. O. W.
Forester. "The gamekeeper here found a hawk's nest this year, with
five young ones on it. He took four and killed them, but left one with
its wings clipped as a decoy to destroy the old ones by. They were
both shot next day, in the act of feeding the young one, and the
keeper thought it was done with. The next day he came again and
found two other charitable hawks, who had come with an adopted feeling
to succour the orphan. These two he killed, and then left the nest. On
returning afterwards he found two more charitable individuals on the
same errand of mercy. One of these he killed; the other he also
shot, but could not find. No more came on the like fruitless errand."

  Mental Qualities of Birds, and their Taste for the Beautiful.-
Before we further discuss the question whether the females select
the more attractive males or accept the first whom they may encounter,
it will be advisable briefly to consider the mental powers of birds.
Their reason is generally, and perhaps justly, ranked as low; yet some
facts could be given* leading to an opposite conclusion. Low powers of
reasoning, however, are compatible, as we see with mankind, with
strong affections, acute perception, and a taste for the beautiful;
and it is with these latter qualities that we are here concerned. It
has often been said that parrots become so deeply attached to each
other that when one dies the other pines for a long time; but Mr.
Jenner Weir thinks that with most birds the strength of their
affection has been much exaggerated. Nevertheless when one of a pair
in a state of nature has been shot, the survivor has been heard for
days afterwards uttering a plaintive call; and Mr. St. John gives
various facts proving the attachment of mated birds.*(2) Mr. Bennett
relates*(3) that in China after a drake of the beautiful mandarin teal
had been stolen, the duck remained disconsolate, though sedulously
courted by another mandarin drake, who displayed before her all his
charms. After an interval of three weeks the stolen drake was
recovered, and instantly the pair recognised each other with extreme
joy. On the other hand, starlings, as we have seen, may be consoled
thrice in the same day for the loss of their mates. Pigeons have
such excellent local memories, that they have been known to return
to their former homes after an interval of nine months, yet, as I hear
from Mr. Harrison Weir, if a pair which naturally would remain mated
for life be separated for a few weeks during the winter, and
afterwards matched with other birds, the two when brought together
again, rarely, if ever, recognise each other.

  * I am indebted to Prof. Newton for the following passage from Mr.
Adam's Travels of a Naturalist, 1870, p. 278. Speaking of Japanese
nut-hatches in confinement, he says: "Instead of the more yielding
fruit of the yew, which is the usual food of the nut-hatch of Japan,
at one time I substituted hard hazel-nuts. As the bird was unable to
crack them, he placed them one by one in his water-glass, evidently
with the notion that they would in time become softer- an
interesting proof of intelligence on the part of these birds."
  *(2) A Tour in Sutherlandshire, vol. i., 1849, p. 185. Dr. Buller
says (Birds of New Zealand, 1872, p. 56) that a male king lory was
killed; and the female "fretted and moped, refused her food, and
died of a broken heart."
  *(3) Wanderings in New South Wales, vol. ii., 1834, p. 62.

  Birds sometimes exhibit benevolent feelings; they will feed the
deserted young ones even of distinct species, but this perhaps ought
to be considered as a mistaken instinct. They will feed, as shewn in
an earlier part of this work, adult birds of their own species which
have become blind. Mr. Buxton gives a curious account of a parrot
which took care of a frost-bitten and crippled bird of a distinct
species, cleansed her feathers, and defended her from the attacks of
the other parrots which roamed freely about his garden. It is a
still more curious fact that these birds apparently evince some
sympathy for the pleasures of their fellows. When a pair of
cockatoos made a nest in an acacia tree, "it was ridiculous to see the
extravagant interest taken in the matter by the others of the same
species." These parrots, also, evinced unbounded curiosity, and
clearly had "the idea of property and possession."* They have good
memories, for in the Zoological Gardens they have plainly recognised
their former masters after an interval of some months.

  * "Acclimatization of Parrots", by C. Buxton, M. P., Annals and Mag.
of Nat. Hist., Nov., 1868, p. 381.

  Birds possess acute powers of observation. Every mated bird, of
course, recognises its fellow. Audubon states that a certain number of
mocking-thrushes (Mimus polyglottus) remain all the year round in
Louisiana, whilst others migrate to the Eastern States; these
latter, on their return, are instantly recognised, and always
attacked, by their southern brethren. Birds under confinement
distinguish different persons, as is proved by the strong and
permanent antipathy or affection which they shew, without any apparent
cause, towards certain individuals. I have heard of numerous instances
with jays, partridges, canaries, and especially bullfinches. Mr.
Hussey has described in how extraordinary a manner a tamed partridge
recognised everybody: and its likes and dislikes were very strong.
This bird seemed "fond of gay colours, and no new gown or cap could be
put on without catching his attention."* Mr. Hewitt has described
the habits of some ducks (recently descended from wild birds),
which, at the approach of a strange dog or cat, would rush headlong
into the water, and exhaust themselves in their attempts to escape;
but they knew Mr. Hewitt's own dogs and cats so well that they would
lie down and bask in the sun close to them. They always moved away
from a strange man, and so they would from the lady who attended
them if she made any great change in her dress. Audubon relates that
he reared and tamed a wild turkey which always ran away from any
strange dog; this bird escaped into the woods, and some days
afterwards Audubon saw, as he thought, a wild turkey, and made his dog
chase it; but, to his astonishment, the bird did not run away, and the
dog, when he came up, did not attack the bird, for they mutually
recognised each other as old friends.*(2)

  * The Zoologist, 1847-48, p. 1602.
  *(2) Hewitt on wild ducks, Journal of Horticulture, Jan. 13, 1863,
p. 39. Audubon on the wild turkey, Ornithological Biography, vol.
i., p. 14. On the mocking-thrush, ibid., vol. i., p. 110.

  Mr. Jenner Weir is convinced that birds pay particular attention
to the colours of other birds, sometimes out of jealousy, and
sometimes as a sign of kinship. Thus he turned a reed-bunting
(Emberiza schaeniculus), which had acquired its black head-dress, into
his aviary, and the newcomer was not noticed by any bird, except by
a bullfinch, which is likewise black-headed. This bullfinch was a very
quiet bird, and had never before quarrelled with any of its
comrades, including another reed-bunting, which had not as yet
become black-headed: but the reed-bunting with a black head was so
unmercifully treated that it had to be removed. Spiza cyanea, during
the breeding-season, is of a bright blue colour; and though
generally peaceable, it attacked S. ciris, which has only the head
blue, and completely scalped the unfortunate bird. Mr. Weir was also
obliged to turn out a robin, as it fiercely attacked all the birds
in his aviary with any red in their plumage, but no other kinds; it
actually killed a red-breasted cross-bill, and nearly killed a
goldfinch. On the other band, he has observed that some birds, when
first introduced, fly towards the species which resemble them most
in colour, and settle by their sides.
   As male birds display their fine plumage and other ornaments with
so much care before the females, it is obviously probable that these
appreciate the beauty of their suitors. It is, however, difficult to
obtain direct evidence of their capacity to appreciate beauty. When
birds gaze at themselves in a looking-glass (of which many instances
have been recorded) we cannot feel sure that it is not from jealousy
of a supposed rival, though this is not the conclusion of some
observers. In other cases it is difficult to distinguish between
mere curiosity and admiration. It is perhaps the former feeling which,
as stated by Lord Lilford,* attracts the ruff towards any bright
object, so that, in the Ionian Islands, "it will dart down to a
bright-coloured handkerchief, regardless of repeated shots." The
common lark is drawn down from the sky, and is caught in large
numbers, by a small mirror made to move and glitter in the sun. Is
it admiration or curiosity which leads the magpie, raven, and some
other birds to steal and secrete bright objects, such as silver
articles or jewels?

  * The Ibis, vol. ii., 1860, p. 344.

  Mr. Gould states that certain humming-birds decorate the outsides of
their nests "with the utmost taste; they instinctively fasten
thereon beautiful pieces of flat lichen, the larger pieces in the
middle, and the smaller on the part attached to the branch. Now and
then a pretty feather is intertwined or fastened to the outer sides,
the stem being always so placed that the feather stands out beyond the
surface." The best evidence, however, of a taste for the beautiful
is afforded by the three genera of Australian bower-birds already
mentioned. Their bowers (see fig. 46), where the sexes congregate
and play strange antics, are variously constructed, but what most
concerns us is, that they are decorated by the several species in a
different manner. The satin bower-bird collects gaily-coloured
articles, such as the blue tail-feathers of parrakeets, bleached bones
and shells, which it sticks between the twigs or arranges at the
entrance. Mr. Gould found in one bower a neatly-worked stone
tomahawk and a slip of blue cotton, evidently procured from a native
encampment. These objects are continually re-arranged, and carried
about by the birds whilst at play. The bower of the spotted bower-bird
"is beautifully lined with tall grasses, so disposed that the heads
nearly meet, and the decorations are very profuse." Round stones are
used to keep the grass-stems in their proper places, and to make
divergent paths leading to the bower. The stones and shells are
often brought from a great distance. The regent bird, as described
by Mr. Ramsay, ornaments its short bower with bleached land-shells
belonging to five or six species, and with "berries of various
colours, blue, red, and black, which give it when fresh a very
pretty appearance. Besides these there were several newly-picked
leaves and young shoots of a pinkish colour, the whole shewing a
decided taste for the beautiful." Well may Mr. Gould say that "these
highly decorated halls of assembly must be regarded as the most
wonderful instances of bird-architecture yet discovered"; and the
taste, as we see, of the several species certainly differs.*

  * On the ornamented nests of humming-birds, Gould, Introduction to
the Trochilidae, 1861, p. 19. On the bower-birds, Gould, Handbook of
the Birds of Australia, 1865, vol. i., pp. 444-461. Ramsay, in the
Ibis, 1867, p. 456.

  Preference for particular Males by the Females.- Having made these
preliminary remarks on the discrimination and taste of birds, I will
give all the facts known to me which bear on the preference shewn by
the female for particular males. It is certain that distinct species
of birds occasionally pair in a state of nature and produce hybrids.
Many instances could be given: thus Macgillivray relates how a male
blackbird and female thrush "fell in love with each other," and
produced offspring.* Several years ago eighteen cases had been
recorded of the occurrence in Great Britain of hybrids between the
black grouse and pheasant;*(2) but most of these cases may perhaps
be accounted for by solitary birds not finding one of their own
species to pair with. With other birds, as Mr. Jenner Weir has
reason to believe, hybrids are sometimes the result of the casual
intercourse of birds building in close proximity. But these remarks do
not apply to the many recorded instances of tamed or domestic birds,
belonging to distinct species, which have become absolutely fascinated
with each other, although living with their own species. Thus
Waterton*(3) states that out of a flock of twenty-three Canada
geese, a female paired with a solitary bernicle gander, although so
different in appearance and size; and they produced hybrid
offspring. A male wigeon (Mareca penelope), living with females of the
same species, has been known to pair with a pintail duck,
Querquedula acuta. Lloyd describes the remarkable attachment between a
shield-drake (Tadorna vulpanser) and a common duck. Many additional
instances could be given; and the Rev. E. S. Dixon remarks that "those
who have kept many different species of geese together well know
what unaccountable attachments they are frequently forming, and that
they are quite as likely to pair and rear young with individuals of
a race (species) apparently the most alien to themselves as with their
own stock."

  * History of Brit. Birds, vol. ii., p. 92.
  *(2) Zoologist, 1853-1854, p. 3940.
  *(3) Waterton, Essays on Nat. Hist., 2nd series, pp. 42 and 117. For
the following statements see on the wigeon, Loudon's Mag. of Nat.
Hist., vol. ix., p. 616; L. Lloyd, Scandinavian Adventures, vol. i.,
1854, p. 452. Dixon, Ornamental and Domestic Poultry p. 137; Hewitt,
in Journal of Horticulture, Jan. 13, 1863, p. 40; Bechstein,
Stubenvogel, 1840, s. 230. Mr. J. Jenner Weir has lately given me an
analogous case with ducks of two species.

  The Rev. W. D. Fox informs me that he possessed at the same time a
pair of Chinese geese (Anser cygnoides), and a common gander with
three geese. The two lots kept quite separate, until the Chinese
gander seduced one of the common geese to live with him. Moreover,
of the young birds hatched from the eggs of the common geese, only
four were pure, the other eighteen proving hybrids; so that the
Chinese gander seems to have had prepotent charms over the common
gander. I will give only one other case; Mr. Hewitt states that a wild
duck, reared in captivity "after breeding a couple of seasons with her
own mallard, at once shook him off on my placing a male pintail on the
water. It was evidently a case of love at first sight, for she swam
about the new-comer caressingly, though he appeared evidently
alarmed and averse to her overtures of affection. From that hour she
forgot her old partner. Winter passed by, and the next spring the
pintail seemed to have become a convert to her blandishments, for they
nested and produced seven or eight young ones."
  What the charm may have been in these several cases, beyond mere
novelty, we cannot even conjecture. Colour, however, sometimes comes
into play; for in order to raise hybrids from the siskin (Fringilla
spinus) and the canary, it is much the best plan, according to
Bechstein, to place birds of the same tint together. Mr. Jenner Weir
turned a female canary into his aviary, where there were male linnets,
goldfinches, siskins, greenfinches, chaffinches, and other birds, in
order to see which she would choose; but there never was any doubt,
and the greenfinch carried the day. They paired and produced hybrid
offspring.
  The fact of the female preferring to pair with one male rather
than with another of the same species is not so likely to excite
attention, as when this occurs, as we have just seen, between distinct
species. The former cases can best be observed with domesticated or
confined birds; but these are often pampered by high feeding, and
sometimes have their instincts vitiated to an extreme degree. Of
this latter fact I could give sufficient proofs with pigeons, and
especially with fowls, but they cannot be here related. Vitiated
instincts may also account for some of the hybrid unions above
mentioned; but in many of these cases the birds were allowed to
range freely over large ponds, and there is no reason to suppose
that they were unnaturally stimulated by high feeding.
  With respect to birds in a state of nature, the first and most
obvious supposition which will occur to every one is that the female
at the proper season accepts the first male whom she may encounter;
but she has at least the opportunity for exerting a choice, as she
is almost invariably pursued by many males. Audubon- and we must
remember that he spent a long life in prowling about the forests of
the United States and observing the birds- does not doubt that the
female deliberately chooses her mate; thus, speaking of a
woodpecker, he says the hen is followed by half-a-dozen gay suitors,
who continue performing strange antics, "until a marked preference
is shewn for one." The female of the red-winged starling (Agelaeus
phaeniceus) is likewise pursued by several males, "until, becoming
fatigued, she alights, receives their addresses, and soon makes a
choice." He describes also how several male night-jars repeatedly
plunge through the air with astonishing rapidity, suddenly turning,
and thus making a singular noise; "but no sooner has the female made
her choice than the other males are driven away." With one of the
vultures (Cathartes aura) of the United States, parties of eight, ten,
or more males and females assemble on fallen logs, "exhibiting the
strongest desire to please mutually," and after many caresses, each
male leads off his partner on the wing. Audubon likewise carefully
observed the wild flocks of Canada geese (Anser canadensis), and gives
a graphic description of their love-anties; he says that the birds
which had been previously mated "renewed their courtship as early as
the month of January, while the others would be contending or
coquetting for hours every day, until all seemed satisfied with the
choice they had made, after which, although they remained together,
any person could easily perceive that they were careful to keep in
pairs. I have observed also that the older the birds the shorter
were the preliminaries of their courtship. The bachelors and old maids
whether in regret, or not caring to be disturbed by the bustle,
quietly moved aside and lay down at some distance from the rest."*
Many similar statements with respect to other birds could be cited
from this same observer.

  * Audubon, Ornithological Biography, vol. i., pp. 191, 349; vol.
ii., pp. 42, 275; vol. iii., p. 2.

  Turning now to domesticated and confined birds, I will commence by
giving what little I have learnt respecting the courtship of fowls.
I have received long letters on this subject from Messrs. Hewitt and
Tegetmeier, and almost an essay from the late Mr. Brent. It will be
admitted by every one that these gentlemen, so well known from their
published works, are careful and experienced observers. They do not
believe that the females prefer certain males on account of the beauty
of their plumage; but some allowance must be made for the artificial
state under which these birds have long been kept. Mr. Tegetmeier is
convinced that a gamecock, though disfigured by being dubbed and
with his hackles trimmed, would be accepted as readily as a male
retaining all his natural ornaments. Mr. Brent, however, admits that
the beauty of the male probably aids in exciting the female; and her
acquiescence is necessary. Mr. Hewitt is convinced that the union is
by no means left to mere chance, for the female almost invariably
prefers the most vigorous, defiant, and mettlesome male; hence it is
almost useless, as he remarks, "to attempt true breeding if a
game-cock in good health and condition runs the locality, for almost
every hen on leaving the roosting-place will resort to the
game-cock, even though that bird may not actually drive away the
male of her own variety." Under ordinary circumstances the males and
females of the fowl seem to come to a mutual understanding by means of
certain gestures, described to me by Mr. Brent. But hens will often
avoid the officious attentions of young males. Old hens, and hens of a
pugnacious disposition, as the same writer informs me, dislike strange
males, and will not yield until well beaten into compliance. Ferguson,
however, describes how a quarrelsome hen was subdued by the gentle
courtship of a Shanghai cock.*

  * Rare and Prize Poultry, 1854, p. 27.

  There is reason to believe that pigeons of both sexes prefer pairing
with birds of the same breed; and dovecot-pigeons dislike all the
highly improved breeds.* Mr. Harrison Weir has lately heard from a
trustworthy observer, who keeps blue pigeons, that these drive away
all other coloured varieties, such as white, red, and yellow; and from
another observer, that a female dun carrier could not, after
repeated trials, be matched with a black male, but immediately
paired with a dun. Again, Mr. Tegetmeier had a female blue turbit that
obstinately refused to pair with two males of the same breed, which
were successively shut up with her for weeks; but on being let out she
would have immediately accepted the first blue dragon that offered. As
she was a valuable bird, she was then shut up for many weeks with a
silver (i. e., very pale blue) male, and at last mated with him.
Nevertheless, as a general rule, colour appears to have little
influence on the pairing of pigeons. Mr. Tegetmeier, at my request,
stained some of his birds with magenta, but they were not much noticed
by the others.

  * Variation of Animals and Plants under Domestication, vol. ii.,
p. 103.

  Female pigeons occasionally feel a strong antipathy towards
certain males, without any assignable cause. Thus M.M. Boitard and
Corbie, whose experience extended over forty-five years, state: "Quand
une femelle eprouve de l'antipathie pour un male avec lequel on veut
l'accoupler, malgre tous les feux de l'amour, malgre l'alpiste et le
chenevis dont on la nourrit pour augmenter son ardeur malgre un
emprisonnement de six mois et meme d'un an, elle refuse constamment
ses caresses; les avances empressees, les agaceries, les tournoiemens,
les tendres roucoulemens, rien ne peut lui plaire ni l'emouvoir;
gonflee, boudeuse, blottie dans un coin de sa prison, elle n'en sort
que pour boire et manger, ou pour repousser avec une espece de rage
des caresses devenues trop pressantes."* On the other hand, Mr.
Harrison Weir has himself observed, and has heard from several
breeders, that a female pigeon will occasionally take a strong fancy
for a particular male, and will desert her own mate for him. Some
females, according to another experienced observer, Riedel,*(2) are of
a profligate disposition. and prefer almost any stranger to their
own mate. Some amorous males, called by our English fanciers "gay
birds," are so successful in their gallantries, that, as Mr. H. Weir
informs me, they must be shut up on account of the mischief which they
cause.

  * Boitard and Corbie, Les Pigeons, &c., 1824, p. 12. Prosper Lucas
(Traite de l'Hered. Nat., tom. ii., 1850, p. 296) has himself observed
nearly similar facts with pigeons.
  *(2) Die Taubenzucht, 1824, s. 86.

  Wild turkeys in the United States, according to Audubon,
"sometimes pay their addresses to the domesticated females, and are
generally received by them with great pleasure." So that these females
apparently prefer the wild to their own males.*

  * Ornithological Biography, vol. i., p. 13. See to the same
effect, Dr. Bryant, in Allen's Mammals and Birds of Florida, p. 344.

  Here is a more curious case. Sir R. Heron during many years kept
an account of the habits of the peafowl, which he bred in large
numbers. He states that "the hens have frequently great preference
to a particular peafowl. They were all so fond of an old pied cock,
that one year, when he was confined, though still in view, they were
constantly assembled close to the trellice-walls of his prison, and
would not suffer a japanned peacock to touch them. On his being let
out in the autumn, the oldest of the hens instantly courted him and
was successful in her courtship. The next year he was shut up in a
stable, and then the hens all courted his rival."* This rival was a
japanned or black-winged peacock, to our eyes a more beautiful bird
than the common kind.

  * Proceedings, Zoological Society, 1835, p. 54. The japanned peacock
is considered by Mr. Sclater as a distinct species, and has been named
Pavo nigri-pennis; but the evidence seems to me to shew that it is
only a variety.

  Lichtenstein, who was a good observer and had excellent
opportunities of observation at the Cape of Good Hope, assured
Rudolphi that the female widow-bird (Chera progne) disowns the male
when robbed of the long tail-feathers with which he is ornamented
during the breeding-season. I presume that this observation must
have been made on birds under confinement.* Here is an analogous case;
Dr. Jaeger,*(2) director of the Zoological Gardens of Vienna, states
that a male silver-pheasant, who had been triumphant over all other
males and was the accepted lover of the females, had his ornamental
plumage spoiled. He was then immediately superseded by a rival, who
got the upper hand and afterwards led the flock.

  * Rudolphi, Beitrage zur Anthropologie, 1812, s. 184.
  *(2) Die Darwin'sche Theorie, und ihre Stellung zu Moral und
Religion, 1869, s. 59.

  It is a remarkable fact, as shewing how important colour is in the
courtship of birds, that Mr. Boardman, a well-known collector and
observer of birds for many years in the Northern United States, has
never in his large experience seen an albino paired with another bird;
yet he has had opportunities of observing many albinos belonging to
several species.* It can hardly be maintained that albinos in a
state of nature are incapable of breeding, as they can be raised
with the greatest facility under confinement. It appears, therefore,
that we must attribute the fact that they do not pair to their
rejection by their normally coloured comrades.

  * This statement is given by Mr. A. Leith Adams, in his Field and
Forest Rambles, 1873, p. 76, and accords with his own experience.

  Female birds not only exert a choice, but in some few cases they
court the male, or even fight together for his possession. Sir R.
Heron states that with peafowl, the first advances are always made
by the female; something of the same kind takes place, according to
Audubon, with the older females of the wild turkey. With the
capercailzie, the females flit round the male whilst he is parading at
one of the places of assemblage, and solicit his attention.* We have
seen that a tame wild-duck seduced an unwilling pintail drake after
a long courtship. Mr. Bartlett believes that the Lophophorus, like
many other gallinaceous birds, is naturally polygamous, but two
females cannot be placed in the same cage with a male, as they fight
so much together. The following instance of rivalry is more surprising
as it relates to bullfinches, which usually pair for life. Mr.
Jenner Weir introduced a dull-coloured and ugly female into his
aviary, and she immediately attacked another mated female so
unmercifully that the latter had to be separated. The new female did
all the courtship, and was at last successful, for she paired with the
male; but after a time she met with a just retribution, for, ceasing
to be pugnacious, she was replaced by the old female, and the male
then deserted his new and returned to his old love.

  * In regard to peafowl, see Sir R. Heron, Proc. Zoolog. Soc.,
1835, p. 54, and the Rev. E. S. Dixon, Ornamental Poultry, 1848, p. 8.
For the turkey, Audubon, ibid., p. 4. For the capercailzie, Lloyd,
Game Birds of Sweden, 1867, p. 23.

  In all ordinary cases the male is so eager that he will accept any
female, and does not, as far as we can judge, prefer one to the other;
but, as we shall hereafter see, exceptions to this rule apparently
occur in some few groups. With domesticated birds, I have heard of
only one case of males shewing any preference for certain females,
namely, that of the domestic cock, who, according to the high
authority of Mr. Hewitt, prefers the younger to the older hens. On the
other hand, in effecting hybrid unions between the male pheasant and
common hens, Mr. Hewitt is convinced that the pheasant invariably
prefers the older birds. He does not appear to be in the least
influenced by their colour; but "is most capricious in his
attachments":* from some inexplicable cause he shews the most
determined aversion to certain hens, which no care on the part of
the breeder can overcome. Mr. Hewitt informs me that some hens are
quite unattractive even to the males of their own species, so that
they may be kept with several cocks during a whole season, and not one
egg out of forty or fifty will prove fertile. On the other hand,
with the long-tailed duck (Harelda glacialis), "it has been remarked,"
says M. Ekstrom, "that certain females are much more courted than
the rest. Frequently, indeed, one sees an individual surrounded by six
or eight amorous males." Whether this statement is credible, I know
not; but the native sportsmen shoot these females in order to stuff
them as decoys.*(2)

  * Mr. Hewitt, quoted in Tegetmeier's Poultry Book, 1866, p. 165.
  *(2) Quoted in Lloyd's Game Birds of Sweden, p. 345.

  With respect to female birds feeling a preference for particular
males, we must bear in mind that we can judge of choice being
exerted only by analogy. If an inhabitant of another planet were to
behold a number of young rustics at a fair courting a pretty girl, and
quarrelling about her like birds at one of their places of assemblage,
he would, by the eagerness of the wooers to please her and to
display their finery, infer that she had the power of choice. Now with
birds the evidence stands thus: they have acute powers of observation,
and they seem to have some taste for the beautiful both in colour
and sound. It is certain that the females occasionally exhibit, from
unknown causes, the strongest antipathies and preferences for
particular males. When the sexes differ in colour or in other
ornaments the males with rare exceptions are the more decorated,
either permanently or temporarily during the breeding-season. They
sedulously display their various ornaments, exert their voices, and
perform strange antics in the presence of the females. Even well-armed
males, who, it might be thought, would altogether depend for success
on the law of battle, are in most cases highly ornamented; and their
ornaments have been acquired at the expense of some loss of power.
In other cases ornaments have been acquired, at the cost of
increased risk from birds and beasts of prey. With various species
many individuals of both sexes congregate at the same spot, and
their courtship is a prolonged affair. There is even reason to suspect
that the males and females within the same district do not always
succeed in pleasing each other and pairing.
  What then are we to conclude from these facts and considerations?
Does the male parade his charms with so much pomp and rivalry for no
purpose? Are we not justified in believing that the female exerts a
choice, and that she receives the addresses of the male who pleases
her most? It is not probable that she consciously deliberates; but she
is most excited or attracted by the most beautiful, or melodious, or
gallant males. Nor need it be supposed that the female studies each
stripe or spot of colour; that the peahen, for instance, admires
each detail in the gorgeous train of the peacock- she is probably
struck only by the general effect. Nevertheless, after hearing how
carefully the male Argus pheasant displays his elegant primary
wing-feathers, and erects his ocellated plumes in the right position
for their full effect; or again, how the male goldfinch alternately
displays his gold-bespangled wings, we ought not to feel too sure that
the female does not attend to each detail of beauty. We can judge,
as already remarked, of choice being exerted, only from analogy; and
the mental powers of birds do not differ fundamentally from ours. From
these various considerations we may conclude that the pairing of birds
is not left to chance; but that those males, which are best able by
their various charms to please or excite the female, are under
ordinary circumstances accepted. If this be admitted, there is not
much difficulty in understanding how male birds have gradually
acquired their ornamental characters. All animals present individual
differences, and as man can modify his domesticated birds by selecting
the individuals which appear to him the most beautiful, so the
habitual or even occasional preference by the female of the more
attractive males would almost certainly lead to their modification;
and such modifications might in the course of time be augmented to
almost any extent, compatible with the existence of the species.
  Variability of Birds, and especially of their Secondary Sexual
Characters.- Variability and inheritance are the foundations for the
work of selection. That domesticated birds have varied greatly,
their variations being inherited, is certain. That birds in a state of
nature have been modified into distinct races is now universally
admitted.* Variations may be divided into two classes; those which
appear to our ignorance to arise spontaneously, and those which are
directly related to the surrounding conditions, so that all or
nearly all the individuals of the same species are similarly modified.
Cases of the latter kind have recently been observed with care by
Mr. J. A. Allen,*(2) who shews that in the United States many
species of birds gradually become more strongly coloured in proceeding
southward, and more lightly coloured in proceeding westward to the
arid plains of the interior. Both sexes seem generally to be
affected in a like manner, but sometimes one sex more than the
other. This result is not incompatible with the belief that the
colours of birds are mainly due to the accumulation of successive
variations through sexual selection; for even after the sexes have
been greatly differentiated, climate might produce an equal effect
on both sexes, or a greater effect on one sex than on the other, owing
to some constitutional difference.

  * According to Dr. Blasius (Ibis, vol. ii., 1860, p. 297), there are
425 indubitable species of birds which breed in Europe, besides
sixty forms, which are frequently regarded as distinct species. Of the
latter, Blasius thinks that only ten are really doubtful, and that the
other fifty ought to be united with their nearest allies; but this
shews that there must be a considerable amount of variation with
some of our European birds. It is also an unsettled point with
naturalists, whether several North American birds ought to be ranked
as specifically distinct from the corresponding European species. So
again many North American forms which until lately were named as
distinct species, are now considered to be local races.
  *(2) Mammals and Birds of East Florida, also an Ornithological
Reconnaissance of Kansas, &c. Notwithstanding the influence of climate
on the colours birds, it is difficult to account for the dull or
dark tints of almost all the species inhabiting certain countries, for
instance, the Galapagos Islands under the equator, the wide
temperate plains of Patagonia, and, as it appears, Egypt (see Mr.
Hartshorne in the American Naturalist, 1873, p. 747). These
countries are open, and afford little shelter to birds; but it seems
doubtful whether the absence of brightly coloured species can be
explained on the principle of protection, for on the Pampas, which are
equally open, though covered by green grass, and where the birds would
be equally exposed to danger, many brilliant and conspicuously
coloured species are common. I have sometimes speculated whether the
prevailing dull tints of the scenery in the above-named countries
may not have affected the appreciation of bright colours by the
birds inhabiting them.

  Individual differences between the members of the same species are
admitted by every one to occur under a state of nature. Sudden and
strongly marked variations are rare; it is also doubtful whether if
beneficial they would often be preserved through selection and
transmitted to succeeding generations.* Nevertheless, it may be
worth while to give the few cases which I have been able to collect,
relating chiefly to colour,- simple albinism and melanism being
excluded. Mr. Gould is well known to admit the existence of few
varieties, for he esteems very slight differences as specific; yet
he states*(2) that near Bogota certain humming-birds belonging to
the genus Cynanthus are divided into two or three races or
varieties, which differ from each other in the colouring of the
tail- "some having the whole of the feathers blue, while others have
the eight central ones tipped with beautiful green." It does not
appear that intermediate gradations have been observed in this or
the following cases. In the males alone of one of the Australian
parrakeets "the thighs in some are scarlet, in others grass-green." In
another parrakeet of the same country "some individuals have the
band across the wing-coverts bright-yellow, while in others the same
part is tinged with red.*(3) In the United States some few of the
males of the scarlet tanager (Tanagra rubra) have "a beautiful
transverse band of glowing red on the smaller wing-coverts";*(4) but
this variation seems to be somewhat rare, so that its preservation
through sexual selection would follow only under usually favourable
circumstances. In Bengal the honey buzzard (Pernis cristata) has
either a small rudimental crest on its head, or none at all: so slight
a difference, however, would not have been worth notice, had not
this same species possessed in southern India a well-marked
occipital crest formed of several graduated feathers."*(5)

  * I had always perceived (Origin of Species) that rare and
strongly-marked deviations of structure, deserving to be called
monstrosities, could seldom be preserved through natural selection,
and that the preservation of even highly-beneficial variations would
depend to a certain extent on chance. I had also fully appreciated the
importance of mere individual differences, and this led me to insist
so strongly on the importance of that unconscious form of selection by
man, which follows from the preservation of the most valued
individuals of each breed, without any intention on his part to modify
the characters of the breed. But until I read an able article in the
North British Review (March 1867, p. 289, et seq.), which has been
of more use to me than any other Review, I did not see how great the
chances were against the preservation of variations, whether slight or
strongly pronounced, occurring only in single individuals.
  *(2) Introduction to the Trochlidae, p. 102.
  *(3) Gould, Handbook of Birds of Australia, vol. ii., pp. 32 and 68.
  *(4) Audubon, Ornithological Biography, 1838, vol. iv., p. 389.
  *(5) Jerdon, Birds of India, vol. i., p. 108; and Mr. Blyth, in Land
and Water, 1868, p. 381.

  The following case is in some respects more interesting. A pied
variety of the raven, with the head, breast, abdomen, and parts of the
wings and tail-feathers white, is confined to the Feroe Islands. It is
not very rare there, for Graba saw during his visit from eight to
ten living specimens. Although the characters of this variety are
not quite constant, yet it has been named by several distinguished
ornithologists as a distinct species. The fact of the pied birds being
pursued and persecuted with much clamour by the other ravens of the
island was the chief cause which led Brunnich to conclude that they
were specifically distinct; but this is now known to be an error.*
This case seems analogous to that lately given of albino birds not
pairing from being rejected by their comrades.

  * Graba, Tagebuch Reise nach Faro, 1830, ss. 51-54. Macgillivray,
History of British Birds, vol. iii., p. 745. Ibis, vol. v., 1863, p.
469.

  In various parts of the northern seas a remarkable variety of the
common guillemot (Uria troile) is found; and in Feroe, one out of
every five birds, according to Graba's estimation, presents this
variation. It is characterised* by a pure white ring round the eye,
with a curved narrow white line, an inch and a half in length,
extending back from the ring. This conspicuous character has caused
the bird to be ranked by several ornithologists as a distinct
species under the name of U. lacrymans, but it is now known to be
merely a variety. It often pairs with the common kind, yet
intermediate gradations have never been seen; nor is this
surprising, for variations which appear suddenly, are often, as I have
elsewhere shewn,*(2) transmitted either unaltered or not at all. We
thus see that two distinct forms of the same species may co-exist in
the same district, and we cannot doubt that if the one had possessed
any advantage over the other, it would soon have been multiplied to
the exclusion of the latter. If, for instance, the male pied ravens,
instead of being persecuted by their comrades, had been highly
attractive (like the above pied peacock) to the black female ravens
their numbers would have rapidly increased. And this would have been a
case of sexual selection.

  * Graba, ibid., s. 54. Macgillivray, ibid., vol. v., p. 327.
  *(2) Variation of Animals and Plants under Domestication, vol.
ii., p. 92.

  With respect to the slight individual differences which are
common, in a greater or less degree, to all the members of the same
species, we have every reason to believe that they are by far the most
important for the work of selection. Secondary sexual characters are
eminently liable to vary, both with animals in a state of nature and
under domestication.* There is also reason to believe, as we have seen
in our eighth chapter, that variations are more apt to occur in the
male than in the female sex. All these contingencies are highly
favourable for sexual selection. Whether characters thus acquired
are transmitted to one sex or to both sexes, depends, as we shall
see in the following chapter, on the form of inheritance which
prevails.

  * On these points see also Variation of Animals and Plants under
Domestication, vol. i., p. 253; vol ii., pp. 73, 75.

  It is sometimes difficult to form an opinion whether certain
slight differences between the sexes of birds are simply the result of
variability with sexually-limited inheritance, without the aid of
sexual selection, or whether they have been augmented through this
latter process. I do not here refer to the many instances where the
male displays splendid colours or other ornaments, of which the female
partakes to a slight degree; for these are almost certainly due to
characters primarily acquired by the male having been more or less
transferred to the female. But what are we to conclude with respect to
certain birds in which, for instance, the eyes differ slightly in
colour in the two sexes?* In some cases the eyes differ conspicuously;
thus with the storks of the genus Xenorhynchus, those of the male
are blackish-hazel, whilst those of the females are gamboge-yellow;
with many hornbills (Buceros), as I hear from Mr. Blyth,*(2) the males
have intense crimson eyes, and those of the females are white. In
the Buceros bicornis, the hind margin of the casque and a stripe on
the crest of the beak are black in the male, but not so in the female.
Are we to suppose that these black marks and the crimson colour of the
eyes have been preserved or augmented through sexual selection in
the males? This is very doubtful; for Mr. Bartlett shewed me in the
Zoological Gardens that the inside of the mouth of this Buceros is
black in the male and flesh-coloured in the female; and their external
appearance or beauty would not be thus affected. I observed in
Chile*(3) that the iris in the condor, when about a year old, is
dark-brown, but changes at maturity into yellowish-brown in the
male, and into bright red in the female. The male has also a small,
longitudinal, leaden-coloured, fleshy crest or comb. The comb of
many gallinaceous birds is highly ornamental, and assumes vivid
colours during the act of courtship; but what are we to think of the
dull-coloured comb of the condor, which does not appear to us in the
least ornamental? The same question may be asked in regard to
various other characters, such as the knob on the base of the beak
of the Chinese goose (Anser cygnoides), which is much larger in the
male than in the female. No certain answer can be given to these
questions; but we ought to be cautious in assuming that knobs and
various fleshy appendages cannot be attractive to the female, when
we remember that with savage races of man various hideous deformities-
deep scars on the face with the flesh raised into protuberances, the
septum of the nose pierced by sticks or bones, holes in the ears and
lips stretched widely open- are all admired as ornamental.

  * See, for instance, on the irides of a Podica and Gallicrex in
Ibis, vol. ii., 1860, p. 206; and vol. V., 1863, p. 426.
  *(2) See also Jerdon, Birds of India, vol. i., pp. 243-245
  *(3) Zoology of the Voyage of H. M. S. Beagle, 1841, p. 6.

  Whether or not unimportant differences between the sexes, such as
those just specified, have been preserved through sexual selection,
these differences, as well as all others, must primarily depend on the
laws of variation. On the principle of correlated development, the
plumage often varies on different parts of the body, or over the whole
body, in the same manner. We see this well illustrated in certain
breeds of the fowl. In all the breeds the feathers on the neck and
loins of the males are elongated, and are called hackles; now when
both sexes acquire a top-knot, which is a new character in the
genus, the feathers on the head of the male become hackle-shaped,
evidently on the principle of correlation; whilst those on the head of
the female are of the ordinary shape. The colour also of the hackles
forming the top-knot of the male, is often correlated with that of the
hackles on the neck and loins, as may be seen by comparing these
feathers in the golden and silver-spangled Polish, the Houdans, and
Creve-coeur breeds. In some natural species we may observe exactly the
same correlation in the colours of these same feathers, as in the
males of the splendid gold and Amherst pheasants.
  The structure of each individual feather, generally causes any
change in its colouring to be symmetrical; we see this in the
various laced, spangled, and pencilled breeds of the fowl; and on
the principle of correlation the feathers over the whole body are
often coloured in the same manner. We are thus enabled without much
trouble to rear breeds with their plumage marked almost as
symmetrically as in natural species. In laced and spangled fowls the
coloured margins of the feathers are abruptly defined; but in a
mongrel raised by me from a black Spanish cock glossed with green, and
a white game-hen, all the feathers were greenish-black, excepting
towards their extremities, which were yellowish-white; but between the
white extremities and the black bases, there was on each feather a
symmetrical, curved zone of dark-brown. In some instances the shaft ofthe feather determines the distribution of the tints; thus with the
body-feathers of a mongrel from the same black Spanish cock and a
silver-spangled Polish hen, the shaft, together with a narrow space on
each side, was greenish-black, and this was surrounded by a regular
zone of dark-brown, edged with brownish-white. In these cases we
have feathers symmetrically shaded, like those which give so much
elegance to the plumage of many natural species. I have also noticed a
variety of the common pigeon with the wing-bars symmetrically zoned
with three bright shades, instead of being simply black on a
slaty-blue ground, as in the parent-species.
  In many groups of birds the plumage is differently coloured in the
several species, yet certain spots, marks, or stripes are retained
by all. Analogous cases occur with the breeds of the pigeon, which
usually retain the two wing-bars, though they may be coloured red,
yellow, white, black, or blue, the rest of the plumage being of some
wholly different tint. Here is a more curious case, in which certain
marks are retained, though coloured in a manner almost exactly the
opposite of what is natural; the aboriginal pigeon has a blue tail,
with the terminal halves of the outer webs of the two outer tail
feathers white; now there is a sub-variety having a white instead of a
blue tail, with precisely that part black which is white in the
parent-species.*

  * Bechstein, Naturgeschichte Deutschlands, B. iv., 1795, s. 31, on a
sub-variety of the monck pigeon.

  Formation and Variability of the Ocelli or eye-like Spots on the
Plumage of Birds.- As no ornaments are more beautiful than the
ocelli on the feathers of various birds, on the hairy coats of some
mammals, on the scales of reptiles and fishes, on the skin of
amphibians, on the wings of many Lepidoptera and other insects, they
deserve to be especially noticed. An ocellus consists of a spot within
a ring of another colour, like the pupil within the iris, but the
central spot is often surrounded by additional concentric zones. The
ocelli on the tail-coverts of the peacock offer a familiar example, as
well as those on the wings of the peacock-butterfly (Vanessa). Mr.
Trimen has given me a description of a S. African moth (Gynanisa
isis), allied to our emperor moth, in which a magnificent ocellus
occupies nearly the whole surface of each hinder wing; it consists
of a black centre, including a semi-transparent crescent-shaped
mark, surrounded by successive, ochre-yellow, black, ochre-yellow,
pink, white, pink, brown, and whitish zones. Although we do not know
the steps by which these wonderfully beautiful and complex ornaments
have been developed, the process has probably been a simple one, at
least with insects; for, as Mr. Trimen writes to me, "no characters of
mere marking or colouration are so unstable in the Lepidoptera as
the ocelli, both in number and size." Mr. Wallace, who first called my
attention to this subject, shewed me a series of specimens of our
common meadow-brown butterfly (Hipparchia janira) exhibiting
numerous gradations from a simple minute black spot to an
elegantly-shaded ocellus. In a S. African butterfly (Cyllo leda,
Linn.), belonging to the same family, the ocelli are even still more
variable. In some specimens (see A, fig. 53) large spaces on the upper
surface of the wings are coloured black, and include irregular white
marks; and from this state a complete gradation can be traced into a
tolerably perfect ocellus (A1), and this results from the
contraction of the irregular blotches of colour. In another series
of specimens a gradation can be followed from excessively minute white
dots, surrounded by a scarcely visible black line (B), into
perfectly symmetrical and large ocelli (B1).* In cases like these, the
development of a perfect ocellus does not require a long course of
variation and selection.

  * This woodcut has been engraved from a beautiful drawing, most
kindly made for me by Mr. Trimen; see also his description of the
wonderful amount of variation in the coloration and shape of the wings
this butterfly, in his Rhopalocera Africae, Australis, p. 186.

  With birds and many other animals, it seems to follow from the
comparison of allied species that circular spots are often generated
by the breaking up and contraction of stripes. In the tragopan
pheasant faint white lines in the female represent the beautiful white
spots in the male;* and something of the same kind may be observed
in the two sexes of the Argus pheasant. However this may be,
appearances strongly favour the belief that on the one hand, a dark
spot is often formed by the colouring matter being drawn towards a
central point from a surrounding zone, which latter is thus rendered
lighter; and, on the other hand, that a white spot is often formed
by the colour being driven away from a central point, so that it
accumulates in a surrounding darker zone. In either case an ocellus is
the result. The colouring matter seems to be a nearly constant
quantity, but is redistributed, either centripetally or centrifugally.
The feathers of the common guinea-fowl offer a good instance of
white spots surrounded by darker zones; and wherever the white spots
are large and stand near each other, the surrounding dark zones become
confluent. In the same wing-feather of the Argus pheasant dark spots
may be seen surrounded by a pale zone, and white spots by a dark zone.
Thus the formation of an ocellus in its most elementary state
appears to be a simple affair. By what further steps the more
complex ocelli, which are surrounded by many successive zones Of
colour, have been generated, I will not pretend to say. But the
zoned feathers of the mongrels from differently coloured fowls, and
the extraordinary variability of the ocelli on many Lepidoptera,
lead us to conclude that their formation is not a complex process, but
depends on some slight and graduated change in the nature of the
adjoining tissues.

  * Jerdon, Birds of India, vol. iii., p. 517.

  Gradation of Secondary Sexual Characters.- Cases of gradation are
important, as shewing us that highly complex ornaments may be acquired
by small successive steps. In order to discover the actual steps by
which the male of any existing bird has acquired his magnificent
colours or other ornaments, we ought to behold the long line of his
extinct progenitors; but this is obviously impossible. We may,
however, generally gain a clue by comparing all the species of the
same group, if it be a large one; for some of them will probably
retain, at least partially, traces of their former characters. Instead
of entering on tedious details respecting various groups, in which
striking instances of gradation could be given, it seems the best plan
to take one or two strongly marked cases, for instance that of the
peacock, in order to see if light can be thrown on the steps by
which this bird bas become so splendidly decorated. The peacock is
chiefly remarkable from the extraordinary length of his
tail-coverts; the tail itself not being much elongated. The barbs
along nearly the whole length of these feathers stand separate or
are decomposed; but this is the case with the feathers of many
species, and with some varieties of the domestic fowl and pigeon.
The barbs coalesce towards the extremity of the shaft forming the oval
disc or ocellus, which is certainly one of the most beautiful
objects in the world. It consists of an iridescent, intensely blue,
indented centre, surrounded by a rich green zone, this by a broad
coppery-brown zone, and this by five other narrow zones of slightly
different iridescent shades. A trifling character in the disc deserves
notice; the barbs, for a space along one of the concentric zones are
more or less destitute of their barbules, so that a part of the disc
is surrounded by an almost transparent zone, which gives it a highly
finished aspect. But I have elsewhere described* an exactly
analogous variation in the hackles of a sub-variety of the
game-cock, in which the tips, having a metallic lustre, "are separated
from the lower part of the feather by a symmetrically shaped
transparent zone, composed of the naked portions of the barbs." The
lower margin or base of the dark-blue centre of the ocellus is
deeply indented on the line of the shaft. The surrounding zones
likewise shew traces, as may be seen in the drawing (see fig. 54),
of indentations, or rather breaks. These indentations are common to
the Indian and Javan peacocks (Pavo cristatus and P. muticus); and
they seem to deserve particular attention, as probably connected
with the development of the ocellus; but for a long time I could not
conjecture their meaning.

  * Variation of Animals and Plants under Domestication, vol. i., p.
254.

  If we admit the principle of gradual evolution, there must
formerly have existed many species which presented every successive
step between the wonderfully elongated tail-coverts of the peacock and
the short tail-coverts of all ordinary birds; and again between the
magnificent ocelli of the former, and the simpler ocelli or mere
coloured spots on other birds; and so with all the other characters of
the peacock. Let us look to the allied Gallinaceae for any
still-existing gradations. The species and sub-species of Polyplectron
inhabit countries adjacent to the native land of the peacock; and they
so far resemble this bird that they are sometimes called
peacock-pheasants. I am also informed by Mr. Bartlett that they
resemble the peacock in their voice and in some of their habits.
During the spring the males, as previously described, strut about
before the comparatively plain-coloured females, expanding and
erecting their tail and wing-feathers, which are ornamented with
numerous ocelli. I request the reader to turn back to the drawing (see
fig. 51) of a Polyplectron; In P. napoleonis the ocelli are confined
to the tail, and the back is of a rich metallic blue; in which
respects this species approaches the Java peacock P. hardwickii
possesses a peculiar topknot, which is also somewhat like that of
the Java peacock. In all species the ocelli on the wings and tail
are either circular or oval, and consist of a beautiful, iridescent,
greenish-blue or greenish-purple disc, with a black border. This
border in P. chinquis shades into brown. edged with cream colour, so
that the ocellus is here surrounded with variously shaded, though
not bright, concentric zones. The unusual length of the tail-coverts
is another remarkable character in Polyplectron; for in some of the
species they are half, and in others two-thirds as long as the true
tail-feathers. The tail-coverts are ocellated as in the peacock.
Thus the several species of Polyplectron manifestly make a graduated
approach to the peacock in the length of their tail-coverts, in the
zoning of the ocelli, and in some other characters.
  Notwithstanding this approach, the first species of Polyplectron
which I examined almost made me give up the search; for I found not
only that the true tail-feathers, which in the peacock are quite
plain, were ornamented with ocelli, but that the ocelli on all the
feathers differed fundamentally from those of the peacock, in there
being two on the same feather (see fig. 55), one on each side of the
shaft.
  Hence I concluded that the early progenitors of the peacock could
not have resembled a Polyplectron. But on continuing my search, I
observed that in some of the species the two ocelli stood very near
each other; that in the tail-feathers of P. hardwickii they touched
each other; and, finally, that on the tail-coverts of this same
species as well as of P. malaccense (see fig. 56) they were actually
confluent. As the central part alone is confluent, an indentation is
left at both the upper and lower ends; and the surrounding coloured
zones are likewise indented. A single ocellus is thus formed on each
tail-covert, though still plainly betraying its double origin. These
confluent ocelli differ from the single ocelli of the peacock in
having an indentation at both ends, instead of only at the lower or
basal end. The explanation, however, of this difference is not
difficult; in some species of Polyplectron the two oval ocelli on
the same feather stand parallel to each other; in other species (as in
P. chinquis) they converge towards one end; now the partial confluence
of two convergent ocelli would manifestly leave a much deeper
indentation at the divergent than at the convergent end. It is also
manifest that if the convergence were strongly pronounced and the
confluence complete, the indentation at the convergent end would
tend to disappear.
  The tail-feathers in both species of the peacock are entirely
destitute of ocelli, and this apparently is related to their being
covered up and concealed by the long tail-coverts. In this respect
they differ remarkably from the tail-feathers of Polyplectron, which
in most of the species are ornamented with larger ocelli than those on
the tail-coverts. Hence I was led carefully to examine the
tail-feathers of the several species, in order to discover whether
their ocelli shewed any tendency to disappear; and to my great
satisfaction, this appeared to be so. The central tail-feathers of
P. napoleonis have the two ocelli on each side of the shaft
perfectly developed; but the inner ocellus becomes less and less
conspicuous on the more exterior tail-feathers, until a mere shadow or
rudiment is left on the inner side of the outermost feather. Again, in
P. malaccense, the ocelli on the tail-coverts are, as we have seen,
confluent; and these feathers are of unusual length, being
two-thirds of the length of the tail-feathers, so that in both these
respects they approach the tail-coverts of the peacock. Now in P.
malaccense, the two central tail-feathers alone are ornamented, each
with two brightly-coloured ocelli, the inner ocellus having completely
disappeared from all the other tail-feathers. Consequently the
tail-coverts and tail-feathers of this species of Polyplectron make
a near approach in structure and ornamentation to the corresponding
feathers of the peacock.
  As far, then, as gradation throws light on the steps by which the
magnificent train of the peacock has been acquired, hardly anything
more is needed. If we picture to ourselves a progenitor of the peacock
in an almost exactly intermediate condition between the existing
peacock, with his enormously elongated tail-coverts, ornamented with
single ocelli, and an ordinary gallinaceous bird with short
tail-coverts, merely spotted with some colour, we shall see a bird
allied to Polyplectron- that is, with tail-coverts, capable of
erection and expansion, ornamented with two partially confluent
ocelli, and long enough almost to conceal the tail-feathers, the
latter having already partially lost their ocelli. The indentation
of the central disc and of the surrounding zones of the ocellus, in
both species of peacock, speaks plainly in favour of this view, and is
otherwise inexplicable. The males of Polyplectron are no doubt
beautiful birds, but their beauty, when viewed from a little distance,
cannot be compared with that of the peacock. Many female progenitors
of the peacock must, during a long line of descent, have appreciated
this superiority; for they have unconsciously, by the continued
preference for the most beautiful males, rendered the peacock the most
splendid of living birds.
  Argus pheasant.- Another excellent case for investigation is offered
by the ocelli on the wing-feathers of the Argus pheasant, which are
shaded in so wonderful a manner as to resemble balls lying loose
within sockets, and consequently differ from ordinary ocelli. No
one, I presume, will attribute the shading, which has excited the
admiration of many experienced artists, to chance- to the fortuitous
concourse of atoms of colouring matter. That these ornaments should
have been formed through the selection of many successive
variations, not one of which was originally intended to produce the
ball-and-socket effect, seems as incredible as that one of Raphael's
Madonnas should have been formed by the selection of chance daubs of
paint made by a long succession of young artists, not one of whom
intended at first to draw the human figure. In order to discover how
the ocelli have been developed, we cannot look to a long line of
progenitors, nor to many closely-allied forms, for such do not now
exist. But fortunately the several feathers on the wing suffice to
give us a clue to the problem, and they prove to demonstration that
a gradation is at least possible from a mere spot to a finished
ball-and-socket ocellus.
  The wing-feathers, bearing the ocelli, are covered with dark stripes
(see fig. 57) or with rows of dark spots (see fig. 59), each stripe or
row of spots running obliquely down the outer side of the shaft to one
of the ocelli. The spots are generally elongated in a line
transverse to the row in which they stand. They often become confluent
either in the line of the row- and then they form a longitudinal
stripe- or transversely, that is, with the spots in the adjoining
rows, and then they form transverse stripes. A spot sometimes breaks
up into smaller spots, which still stand in their proper places.
  It will be convenient first to describe a perfect ball-and-socket
ocellus. This consists of an intensely black circular ring,
surrounding a space shaded so as exactly to resemble a ball. The
figure here given has been admirably drawn by Mr. Ford and well
engraved, but a woodcut cannot exhibit the exquisite shading of the
original. The ring is almost always slightly broken or interrupted
(see fig. 57) at a point in the upper half, a little to the right of
and above the white shade on the enclosed ball; it is also sometimes
broken towards the base on the right hand. These little breaks have an
important meaning. The ring is always much thickened, with the edges
ill-defined towards the left-hand upper corner, the feather being beld
erect, in the position in which it is here drawn. Beneath this
thickened part there is on the surface of the ball an oblique almost
pure-white mark, which shades off downwards into a pale-leaden hue,
and this into yellowish and brown tints, which insensibly become
darker and darker towards the lower part of the ball. It is this
shading which gives so admirably the effect of light shining on a
convex surface. If one of the balls be examined, it will be seen
that the lower part is of a brown tint and is indistinctly separated
by a curved oblique line from the upper part which is yellower and
more leaden; this curved oblique line runs at right angles to the
longer axis of the white patch of light, and indeed of all the
shading; but this difference in colour, which cannot of course be
shewn in the woodcut, does not in the least interfere with the perfect
shading of the ball. It should be particularly observed that each
ocellus stands in obvious connection either with a dark stripe, or
with a longitudinal row of dark spots for both occur indifferently
on the same feather. Thus in fig. 57 (see figure) stripe A runs to
ocellus (a); B runs to ocellus (b); stripe C is broken in the upper
part, and runs down to the next succeeding ocellus, not represented in
the woodcut; D to the next lower one, and so with the stripes E and F.
Lastly, the several ocelli are separated from each other by a pale
surface bearing irregular black marks.
  I will next describe the other extreme of the series, namely, the
first trace of an ocellus. The short secondary wing-feather (see
fig. 58), nearest to the body, is marked like the other feathers, with
oblique, longitudinal, rather irregular, rows of very dark spots.
The basal spot, or that nearest the shaft, in the five lower rows
(excluding the lowest one) is a little larger than the other spots
of the same row, and a little more elongated in a transverse
direction. It differs also from the other spots by being bordered on
its upper side with some dull fulvous shading. But this spot is not in
any way more remarkable than those on the plumage of many birds, and
might easily be overlooked. The next higher spot does not differ atall from the upper ones in the same row. The larger basal spots occupy
exactly the same relative position on these feathers as do the perfect
ocelli on the longer wing-feathers.
  By looking to the next two or three succeeding wing-feathers, an
absolutely insensible gradation can be traced from one of the last
described basal spots, together with the next higher one in the same
row, to a curious ornament, which cannot be called an ocellus, and
which I will name, from the want of a better term, an "elliptic
ornament." These are shewn in the accompanying figure (see fig. 59).
We here see several oblique rows, A, B, C, D, &c. (see the lettered
diagram on the right hand), of dark spots of the usual character. Each
row of spots runs down to and is connected with one of the elliptic
ornaments, in exactly the same manner as each stripe in fig. 57 (see
figure) runs down to, and is connected with, one of the
ball-and-socket ocelli. Looking to any one row, for instance, B, in
fig. 59 (see figure), the lowest mark (b) is thicker and
considerably longer than the upper spots, and has its left extremity
pointed and curved upwards. This black mark is abruptly bordered on
its upper side by a rather broad space of richly shaded tints,
beginning with a narrow brown zone, which passes into orange, and this
into a pale leaden tint, with the end towards the shaft much paler.
These shaded tints together fill up the whole inner space of the
elliptic ornament. The mark (b) corresponds in every respect with
the basal shaded spot of the simple feather described in the last
paragraph (see fig. 58), but is more highly developed and more
brightly coloured. Above and to the right of this spot (see b, fig.
59), with its bright shading, there is a long narrow, black mark
(c), belonging to the same row, and which is arched a little downwards
so as to face (b). This mark is sometimes broken into two portions. It
is also narrowly edged on the lower side with a fulvous tint. To the
left of and above (c), in the same oblique direction, but always
more or less distinct from it, there is another black mark (d). This
mark is generally sub-triangular and irregular in shape, but in the
one lettered in the diagram it is unusually narrow, elongated, and
regular. It apparently consists of a lateral and broken prolongation
of the mark (c), together with its confluence with a broken and
prolonged part of the next spot above; but I do not feel sure of this.
These three marks, b, c, and d, with the intervening bright shades,
form together the so-called elliptic ornament. These ornaments
placed parallel to the shaft, manifestly correspond in position with
the ball-and-socket ocelli. Their extremely elegant appearance
cannot be appreciated in the drawing, as the orange and leaden
tints, contrasting so well with the black marks, cannot be shewn.
  Between one of the elliptic ornaments and a perfect
ball-and-socket ocellus, the gradation is so perfect that it is
scarcely possible to decide when the latter term ought to be used. The
passage from the one into the other is effected by the elongation
and greater curvature in opposite directions of the lower black mark
(see b, fig. 59), and more especially of the upper one (c), together
with the contraction of the elongated sub-triangular or narrow mark
(d), so that at last these three marks become confluent, forming an
irregular elliptic ring. This ring is gradually rendered more and more
circular and regular, increasing at the same time in diameter. I
have here given a drawing (see fig. 60) of the natural size of an
ocellus not as yet quite perfect. The lower part of the black ring
is much more curved than is the lower mark in the elliptic ornament
(see b, fig. 59). The upper part of the ring consists of two or
three separate portions; and there is only a trace of the thickening
of the portion which forms the black mark above the white shade.
This white shade itself is not as yet much concentrated; and beneath
it the surface is brighter coloured than in a perfect
ball-and-socket ocellus. Even in the most perfect ocelli traces of the
junction of three or four elongated black marks, by which the ring has
been formed, may often be detected. The irregular sub-triangular or
narrow mark (see d, fig. 59), manifestly forms, by its contraction and
equalisation, the thickened portion of the ring above the white
shade on a perfect ball-and-socket ocellus. The lower part of the ring
is invariably a little thicker than the other parts (see fig. 57), and
this follows from the lower black mark of the elliptic ornament (see
b, fig. 59) having originally been thicker than the upper mark (c).
Every step can be followed in the process of confluence and
modification; and the black ring which surrounds the ball of the
ocellus is unquestionably formed by the union and modification of
the three black marks, b, c, d, of the elliptic ornament. The
irregular zigzag black marks between the successive ocelli (see
again fig. 57) are plainly due to the breaking up of the somewhat more
regular but similar marks between the elliptic ornaments.
  The successive steps in the shading of the ball-and-socket ocelli
can be followed out with equal clearness. The brown, orange, and
pale-leadened narrow zones, which border the lower black mark of the
elliptic ornament, can be seen gradually to become more and more
softened and shaded into each other, with the upper lighter part
towards the left-hand corner rendered still lighter, so as to become
almost white, and at the same time more contracted. But even in the
most perfect ball-and-socket ocelli a slight difference in the
tints, though not in the shading, between the upper and lower parts of
the ball can be perceived, as before noticed; and the line of
separation is oblique, in the same direction as the bright coloured
shades of the elliptic ornaments. Thus almost every minute detail in
the shape and colouring of the ball-and-socket ocelli can be shewn
to follow from gradual changes in the elliptic ornaments; and the
development of the latter can be traced by equally small steps from
the union of two almost simple spots, the lower one (see fig. 58)
having some dull fulvous shading on its upper side.
  The extremities of the longer secondary feathers which bear the
perfect ball-and-socket ocelli, are peculiarly ornamented (see fig.
61). The oblique longitudinal stripes suddenly cease upwards and
become confused; and above this limit the whole upper end of the
feather (a) is covered with white dots, surrounded by little black
rings, standing on a dark ground. The oblique stripe belonging to
the uppermost ocellus (b) is barely represented by a very short
irregular black mark with the usual, curved, transverse base. As
this stripe is thus abruptly cut off, we can perhaps understand from
what has gone before, how it is that the upper thickened part of the
ring is here absent; for, as before stated, this thickened part
apparently stands in some relation with a broken prolongation from the
next higher spot. From the absence of the upper and thickened part
of the ring, the uppermost ocellus, though perfect in all other
respects, appears as if its top had been obliquely sliced off. It
would, I think, perplex any one, who believes that the plumage of
the Argus pheasant was created as we now see it, to account for the
imperfect condition of the uppermost ocellus. I should add that on the
secondary wing-feather farthest from the body all the ocelli are
smaller and less perfect than on the other feathers, and have the
upper part of the ring deficient, as in the case just mentioned. The
imperfection here seems to be connected with the fact that the spots
on this feather shew less tendency than usual to become confluent into
stripes; they are, on the contrary, often broken up into smaller
spots, so that two or three rows run down to the same ocellus.
  There still remains another very curious point, first observed by
Mr. T. W. Wood,* which deserves attention. In a photograph, given me
by Mr. Ward, of a specimen mounted as in the act of display, it may be
seen that on the feathers which are held perpendicularly, the white
marks on the ocelli, representing light reflected from a convex
surface, are at the upper or further end, that is, are directed
upwards; and the bird whilst displaying himself on the ground would
naturally be illuminated from above. But here comes the curious point;
the outer feathers are held almost horizontally, and their ocelli
ought likewise to appear as if illuminated from above, and
consequently the white marks ought to be placed on the upper sides
of the ocelli; and, wonderful as is the fact, they are thus placed!
Hence the ocelli on the several feathers, though occupying very
different positions with respect to the light, all appear as if
illuminated from above, just as an artist would have shaded them.
Nevertheless they are not illuminated from strictly the same point
as they ought to be; for the white marks on the ocelli of the feathers
which are held almost horizontally, are placed rather too much towards
the further end; that is, they are not sufficiently lateral. We
have, however, no right to expect absolute perfection in a part
rendered ornamental through sexual selection, any more than we have in
a part modified through natural selection for real use; for
instance, in that wondrous organ the human eye. And we know what
Helmholtz, the highest authority in Europe on the subject, has said
about the human eye; that if an optician had sold him an instrument so
carelessly made, he would have thought himself fully justified in
returning it.*(2)

  * The Field, May 28, 1870.
  *(2) Popular Lectures on Scientific Subjects, Eng. trans., 1873, pp.
219, 227, 269, 390.

  We have now seen that a perfect series can be followed, from
simple spots to the wonderful ball-and-socket ornaments. Mr. Gould,
who kindly gave me some of these feathers, fully agrees with me in the
completeness of the gradation. It is obvious that the stages in
development exhibited by the feathers on the same bird do not at all
necessarily shew us the steps passed through by the extinct
progenitors of the species; but they probably give us the clue to
the actual steps, and they at least prove to demonstration that a
gradation is possible. Bearing in mind how carefully the male Argus
pheasant displays his plumes before the female, as well as the many
facts rendering it probable that female birds prefer the more
attractive males, no one who admits the agency of sexual selection
in any case will deny that a simple dark spot with some fulvous
shading might be converted, through the approximation and modification
of two adjoining spots, together with some slight increase of
colour, into one of the so-called elliptic ornaments. These latter
ornaments have been shewn to many persons, and all have admitted
that they are beautiful, some thinking them even more so than the
ball-and-socket ocelli. As the secondary plumes became lengthened
through sexual selection, and as the elliptic ornaments increased in
diameter, their colours apparently became less bright; and then the
ornamentation of the plumes had to be gained by an improvement in
the pattern and shading; and this process was carried on until the
wonderful ball-and-socket ocelli were finally developed. Thus we can
understand- and in no other way as it seems to me- the present
condition and origin of the ornaments on the wing-feathers of the
Argus pheasant.

  From the light afforded by the principle of gradation- from what
we know of the laws of variation- from the changes which have taken
place in many of our domesticated birds- and, lastly, from the
character (as we shall hereafter see more clearly) of the immature
plumage of young birds- we can sometimes indicate, with a certain
amount of confidence, the probable steps by which the males have
acquired their brilliant plumage and various ornaments; yet in many
cases we are involved in complete darkness. Mr. Gould several years
ago pointed out to me a humming-bird, the Urosticte benjamini,
remarkable for the curious differences between the sexes. The male,
besides a splendid gorget, has greenish-black tail-feathers, with
the four central ones tipped with white; in the female, as with most
of the allied species, the three outer tail-feathers on each side
are tipped with white, so that the male has the four central, whilst
the female has the six exterior feathers ornamented with white tips.
What makes the case more curious is that, although the colouring of
the tail differs remarkably in both sexes of many kinds of
humming-birds, Mr. Gould does not know a single species, besides the
Urosticte, in which the male has the four central feathers tipped with
white.
  The Duke of Argyll, in commenting on this case,* passes over
sexual selection, and asks, "What explanation does the law of
natural selection give of such specific varieties as these?" He
answers "none whatever"; and I quite agree with him. But can this be
so confidently said of sexual selection? Seeing in how many ways the
tail-feathers of humming-birds differ, why should not the four central
feathers have varied in this one species alone, so as to have acquired
white tips? The variations may have been gradual, or somewhat abrupt
as in the case recently given of the humming-birds near Bogota, in
which certain individuals alone have the "central tail-feathers tipped
with beautiful green." In the female of the Urosticte I noticed
extremely minute or rudimental white tips to the two outer of the four
central black tail-feathers; so that here we have an indication of
change of some kind in the plumage of this species. If we grant the
possibility of the central tail-feathers of the male varying in
whiteness, there is nothing strange in such variations having been
sexually selected. The white tips, together with the small white
ear-tufts, certainly add, as the Duke of Argyll admits, to the
beauty of the male; and whiteness is apparently appreciated by other
birds, as may be inferred from such cases as the snow-white male of
the bell-bird. The statement made by Sir R. Heron should not be
forgotten, namely, that his peahens, when debarred from access to
the pied peacock, would not unite with any other male, and during that
season produced no offspring. Nor is it strange that variations in the
tail-feathers of the Urosticte should have been specially selected for
the sake of ornament, for the next succeeding genus in the family
takes its name of Metallura from the splendour of these feathers. We
have, moreover, good evidence that humming-birds take especial pains
in displaying their tail-feathers; Mr. Belt,*(2) after describing
the beauty of the Florisuga mellivora, says, "I have seen the female
sitting on a branch, and two males displaying their charms in front of
her. One would shoot up like a rocket, then suddenly expanding the
snow-white tail, like an inverted parachute, slowly descend in front
of her, turning round gradually to shew off back and front.... The
expanded white tail covered more space than all the rest of the
bird, and was evidently the grand feature in the performance. Whilst
one male was descending, the other would shoot up and come slowly down
expanded. The entertainment would end in a fight between the two
performers; but whether the most beautiful or the most pugnacious
was the accepted suitor, I know not." Mr. Gould, after describing
the peculiar plumage of the Urosticte, adds, "that ornament and
variety is the sole object, I have myself but little doubt."*(3) If
this be admitted, we can perceive that the males which during former
times were decked in the most elegant and novel manner would have
gained an advantage, not in the ordinary struggle for life, but in
rivalry with other males, and would have left a larger number of
offspring to inherit their newly-acquired beauty.

  * The Reign of Law, 1867, p. 247.
  *(2) The Naturalist in Nicaragua, 1874, p. 112.
  *(3) Introduction to the Trochilidae, 1861, p. 110.

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