CHAPTER XIV.

BIRDS—continued.

Choice exerted by the female—Length of courtship—Unpaired birds—Mental

qualities and taste for the beautiful—Preference or antipathy shewn by

the female for particular males—Variability of birds—Variations

sometimes abrupt—Laws of variation—Formation of ocelli—Gradations of

character—Case of Peacock, Argus pheasant, and Urosticte.

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 (1. 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.), 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 large rats,” puffing out their feathers, flapping

their wings, and uttering the strangest cries. (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 (3. Quoted by Mr. T.W. Wood, in

the ‘Student,’ April 1870, p. 125.) 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. (4. Gould, ‘Handbook to 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. (5. 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.) 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.

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. (6. 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,’

edit. 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. (7. 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 Rev. L. Jenyns, ‘Observations in Natural History,’ 1846, p.

87.) Such contingencies as these probably explain most of the foregoing

cases. (8. The following case has been given (‘The Times,’ Aug. 6,

1868) by the Rev. F.O. 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.”) 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.

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. (9. 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.”) 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. (10. ‘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.”) Mr. Bennett relates

(11. ‘Wanderings in New South Wales,’ vol. ii. 1834, p. 62.) 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.

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.” (12. ‘Acclimatization of Parrots,’ by C. Buxton, M.P.,

‘Annals and Mag. of Nat. Hist.’ Nov. 1868, p. 381.) They have good

memories, for in the Zoological Gardens they have plainly recognised

their former masters after an interval of some months.

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.” (13. The ‘Zoologist,’ 1847-48, p. 1602.) 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. (14. 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 schoeniculus),

which had acquired its black head-dress, into his aviary, and the

new-comer 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 crossbill, and nearly

killed a goldfinch. On the other hand, 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 (15. The ‘Ibis,’ vol. ii. 1860, p. 344.), 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?

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

(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

showing 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. (16. On the

ornamented nests of humming-birds, Gould, ‘Introduction to the

Trochilidae,’ 1861, p. 19. On the bower-birds, Gould, ‘Handbook to the

Birds of Australia,’ 1865, vol. i. pp. 444-461. Ramsay, in the ‘Ibis,’

1867, p. 456.)

PREFERENCE FOR A 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. (17. ‘History of Brit. Birds,’ vol. ii.

p. 92.) Several years ago eighteen cases had been recorded of the

occurrence in Great Britain of hybrids between the black grouse and

pheasant (18. ‘Zoologist,’ 1853-1854, p. 3946.); 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

(19. 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,

‘Stubenvögel,’ 1840, s. 230. Mr. J. Jenner Weir has lately given me an

analogous case with ducks of two species.) 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.”

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 phoeniceus) 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-antics; 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.” (20. Audubon,

‘Ornithological Biography,’ vol. i. pp. 191, 349; vol. ii. pp. 42, 275;

vol. iii. p. 2.) Many similar statements with respect to other birds

could be cited from this same observer.

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. (21. ‘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. (22. ‘Variation of Animals and Plants under

Domestication,’ vol. ii. p. 103.) 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.

Female pigeons occasionally feel a strong antipathy towards certain

males, without any assignable cause. Thus MM. Boitard and Corbie, whose

experience extended over forty-five years, state: “Quand une femelle

éprouve de l’antipathie pour un mâle avec lequel on veut l’accoupler,

malgré tous les feux de l’amour, malgré l’alpiste et le chenevis dont

on la nourrit pour augmenter son ardeur, malgré un emprisonnement de

six mois et même d’un an, elle refuse constamment ses caresses; les

avances empressées, les agaceries, les tournoiemens, les tendres

roucoulemens, rien ne peut lui plaire ni l’émouvoir; gonflée, boudeuse,

blottie dans un coin de sa prison, elle n’en sort que pour boire et

manger, ou pour repousser avec une espèce de rage des caresses devenues

trop pressantes.” (23. Boitard and Corbie, ‘Les Pigeons,’ etc., 1824,

p. 12. Prosper Lucas (‘Traité de l’Héréd. Nat.’ tom. ii. 1850, p. 296)

has himself observed nearly similar facts with pigeons.) 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 (24. Die

Taubenzucht, 1824, s. 86.), 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.

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. (25. ‘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.” (26. ‘Proceedings, Zoological

Society,’ 1835, p. 54. The japanned peacock is considered by Mr.

Sclater as a distinct species, and has been named Pavo nigripennis; but

the evidence seems to me to show that it is only a variety.) This rival

was a japanned or black-winged peacock, to our eyes a more beautiful

bird than the common kind.

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. (27. Rudolphi, ‘Beiträge zur Anthropologie,’

1812, s. 184.) Here is an analogous case; Dr. Jaeger (28. ‘Die

Darwin’sche Theorie, und ihre Stellung zu Moral und Religion,’ 1869, s.

59.), 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.

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. (29. This statement is given by Mr. A. Leith Adams, in

his ‘Field and Forest Rambles,’ 1873, p. 76, and accords with his own

experience.) 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.

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. (30. 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.) 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 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” (31. Mr. Hewitt,

quoted in Tegetmeier’s ‘Poultry Book,’ 1866, p. 165.): 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. (32. 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.

(33. 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.) 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 (34. ‘Mammals and Birds of East

Florida,’ also an ‘Ornithological Reconnaissance of Kansas,’ etc.

Notwithstanding the influence of climate on the colours of 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.), 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.

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. (35. ‘Origin of Species’ fifth

edit. 1869, p.104. I had always perceived, 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.) 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 (36. ‘Introduction to the Trochlidae,’ p. 102.) 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.” (37. Gould, ‘Handbook to

Birds of Australia,’ vol. ii. pp. 32 and 68.) 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”

(38. Audubon, ‘Ornithological Biography,’ 1838, vol. iv. p. 389.); 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.” (39. 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. (40. Graba, ‘Tagebuch

Reise nach Faro,’ 1830, ss. 51-54. Macgillivray, ‘History of British

Birds,’ vol. iii. p. 745, ‘Ibis,’ vol. v. 1863, p. 469.) This case

seems analogous to that lately given of albino birds not pairing from

being rejected by their comrades.

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 (41. Graba, ibid. s. 54. Macgillivray, ibid. vol.

v. p. 327.) 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 (42. ‘Variation of Animals and Plants under

Domestication,’ vol. ii. p. 92.), 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.

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. (43. On these points see also ‘Variation of Animals and

Plants under Domestication,’ vol. i. p. 253; vol ii. pp. 73, 75.) 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.

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? (44. See, for instance, on the irides of a

Podica and Gallicrex in ‘Ibis,’ vol. ii. 1860, p. 206; and vol. v.

1863, p. 426.) 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 (45. See also

Jerdon, ‘Birds of India,’ vol. i. pp. 243-245.), 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 (46. ‘Zoology of the

Voyage of H.M.S. “Beagle,”’ 1841, p. 6.) 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.

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 of the 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. (47.

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.

[Fig. 53. Cyllo leda, Linn., from a drawing by Mr. Trimen, shewing the

extreme range of variation in the ocelli. A. Specimen, from Mauritius,

upper surface of fore-wing. A1. Specimen, from Natal, ditto. B.

Specimen, from Java, upper surface of hind-wing. B1. Specimen, from

Mauritius, ditto.]

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 coloration 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 (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). (48. 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 of this butterfly, in his

‘Rhopalocera Africae Australis,’ p. 186.) In cases like these, the

development of a perfect ocellus does not require a long course of

variation and selection.

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 (49. Jerdon, ‘Birds of India,’ vol. iii. p. 517.); 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.

GRADATION OF SECONDARY SEXUAL CHARACTERS.

[Fig. 54. Feather of Peacock, about two-thirds of natural size, drawn

by Mr. Ford. The transparent zone is represented by the outermost white

zone, confined to the upper end of the disc.]

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 has 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 (50.

‘Variation of Animals and Plants under Domestication,’ vol. i. p. 254.)

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 (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.

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 (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

top-knot, which is also somewhat like that of the Java peacock. In all

the 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.

[Fig. 55. Part of a tail-covert of Polyplectron chinquis, with the two

ocelli of natural size.

Fig. 56. Part of a tail-covert of Polyplectron malaccense, with the two

ocelli, partially confluent, of natural size.]

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 (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 (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.

[Fig. 57. Part of secondary wing-feather of Argus pheasant, shewing two

perfect ocelli, a and b. A, B, C, D, etc., are dark stripes running

obliquely down, each to an ocellus. [Much of the web on both sides,

especially to the left of the shaft, has been cut off.]

Fig.59. Portion of one of the secondary wing-feathers near to the body,

shewing the so-called elliptic ornaments. The right-hand figure is

given merely as a diagram for the sake of the letters of reference. A,

B, C, D, etc. Rows of spots running down to and forming the elliptic

ornaments. b. Lowest spot or mark in row B. c. The next succeeding spot

or mark in the same row. d. Apparently a broken prolongation of the

spot c. in the same row B.]

The wing-feathers, bearing the ocelli, are covered with dark stripes

(Fig. 57) or with rows of dark spots (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 (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 held 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 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.

[Fig. 58. Basal part of the secondary wing feather, nearest to the

body.]

I will next describe the other extreme of the series, namely, the first

trace of an ocellus. The short secondary wing-feather (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 at all 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 (Fig. 59). We

here see several oblique rows, A, B, C, D, etc. (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 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, 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 (Fig. 58), but is more highly developed and more

brightly coloured. Above and to the right of this spot (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.

[Fig. 60. An ocellus in an intermediate condition between the elliptic

ornament and the perfect ball-and-socket ocellus.]

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 (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

(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 (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 (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 (Fig. 57), and this

follows from the lower black mark of the elliptic ornament (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 (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 (Fig. 58) having some dull fulvous

shading on its upper side.

[Fig. 61. Portion near summit of one of the secondary wing-feathers,

bearing perfect ball-and-socket ocelli. a. Ornamented upper part. b.

Uppermost, imperfect ball-and-socket ocellus. (The shading above the

white mark on the summit of the ocellus is here a little too dark.) c.

Perfect ocellus.]

The extremities of the longer secondary feathers which bear the perfect

ball-and-socket ocelli, are peculiarly ornamented (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 (51. The ‘Field,’ May 28, 1870.), 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. (52. ‘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 (53. ‘The Reign of Law,’

1867, p. 247.), 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 (54. ‘The Naturalist in

Nicaragua,’ 1874, p. 112.), 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.” (55. ‘Introduction to the Trochilidae,’ 1861, p. 110.)

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.