The Bird Watcher in the Shetlands/Chapter 30

by Edmund Selous

CHAPTER XXX

INTERSEXUAL SELECTION

IN all the birds which I have enumerated as having a bright or pleasingly coloured mouth cavity, acquired, as I believe, through the agency of sexual selection, the sexes are alike, both in regard to this special feature, and also in their plumage and general appearance. They are alike also in their habit of opening and shutting the bill, as it were, at one another, and in their other nuptial actions or antics. The first of these two identities involves no difficulty. In many birds of bright plumage the female is as gaudy, or almost as gaudy, as the male, and it is then assumed (by those, at least, who follow Darwin) that each successive variation in the hue and markings of the latter has, by the laws of inheritance, been transmitted in an equal or only slightly less degree to the former. As far, therefore, as the particular kind of beauty which I am here considering is, in itself, concerned, the arguments for or against its acquirement by the male, through the choice of the female, are the same as in regard to that of any other kind, nor do they extend any farther; but in the display of it by the female as well as by the male a fresh element enters into the problem, as it does also in the case of any other nuptial display common to the two sexes. The brilliant mouth-cavity can, of course, only be exhibited by the opening of the bill, and in doing this—in the particular way, and with the accompaniments described in each case—both sexes act alike. In other words, if there is really a conscious display in the matter then each sex displays to the other. What conclusion are we to draw from this? Either, as it appears to me, we must assume that both the male and female equally strive to please one another, or that, while the actions of the male mean something, those of the female mean nothing, or nothing in particular, having been transmitted to her, through him, by those same laws of inheritance which have given her, in these and other cases, his own ornamental plumage, and not in accordance with any principle by virtue of which she has been rendered more and more attractive to him. For, except in some special cases where the female is larger and handsomer than the male, the Darwinian theory does not suppose that the hen bird has been modified to please the taste of the cock, whose eagerness, it is assumed, has made this quite unnecessary.

But any uniformly repeated action is a habit, and habits must bear a relation to the psychology of the being practising them, from which it would seem to follow that whatever be the mental state of the male bird through whom any habit has been transmitted to the female, such mental state, being the cause of such habit, must have been transmitted to her along with it. To suppose, however, that the female acts in a certain way in order to please the male, but that since she has not learnt to do so under the true laws of sexual selection, but has acquired her character incidentally, merely, by transmission from the male, and that, therefore, her conduct has no effect upon the male, since it has not been brought about in relation to his disposition, which is so eager as to make it indifferent to him what hen he gets, as long as he gets one—to suppose all this is—well, for me it is very difficult. The plain common sense of the thing seems to be that if the female displays her charms to the male in the same way that he displays his to her, she must do it for the same purpose, and is no more likely to be wasting labour, or expending it unnecessarily, than is he. If we do not give the same value to actions identical in either sex—if we will not allow "sauce for the gander" to be "sauce for the goose"—we become involved, as it appears to me, in inextricable confusion; and, moreover, can it be supposed that a habit which bore no fruit would remain fixed, or be governed by times and seasons, even if it did not cease on account of its inutility? Assuming, then, as I feel bound to assume, that the languishing actions of two fulmar petrels when sitting together on a ledge, or the throwing up of the head and opening the bill at each other of a pair of shags, each during the breeding season, are equally pleasing to one sex as to the other, may we not, or are we not rather compelled to think that such special adornments as we admit in the male to have been acquired through the agency of sexual selection (whether we include amongst these the bright colouring of the mouth or not), have been acquired by the female also in the same way—that there has been, in fact, a double process of sexual selection instead of a single one only; that the male, as well as the female, has been capable of exercising choice?

Great stress has been laid upon the eagerness of the male, as contrasted with the coyness of the female, in courtship, throughout nature; but were the latter to possess some eagerness also, her share of it need not be so great as the male's, so that we should not, by supposing her to, be contravening this principle: she might even fly, or seem to fly, from his pursuit. How, then, might her own ardour become valid to the extent of influencing the choice of the cock? As it appears to me, this might be brought about through the jealousy inspired in one hen bird by the sight of attentions paid to another. She, the jealous one, might have behaved coyly had the same, or another, male wooed her, but her feelings become inflamed and her modesty is lost when she sees that which, for all her seeming, she would have wished for herself, bestowed upon another. She interposes, let us say, at first, by attacking the favoured female, but if this one is as strong and as determined as herself, there will be now a series of indecisive combats, of which the cock will be the spectator; and why should not these combats be varied with displays, or something of that nature, on the part of either combatant, with the view of attracting him? If so, the cock who has previously, we will suppose, been chosen for his good looks, becomes in his turn—for how, under such circumstances, can he help it?—the chooser between those of others; and thus there will be a double process of selection carried on between the two sexes.

But may we not go a step farther in our suppositions?—for which, as I believe, there is a considerable body of evidence, in spite of the frequent great difficulty and consequent absence of proper observation. The theory of sexual selection is based upon the assumption that choice is exercised by the female, and this exercise of choice must go hand-in-hand with a corresponding development of the critical faculty in regard to the comparative merits of different males, which again would involve a power of taking a liking, or a dislike, to any one of them. How are we to reconcile all this with that quiescent, waiting-to-be-spoken-to frame of mind which we assume to be that of the hen bird in regard to the cock, during the season of courtship? A decided preference should show itself in actions. Why should she never exercise her critical faculty except as between such males as are rivals for her favour? If, for instance, she is courted by two or more males, why should she not declare in favour of a third or fourth that is either indifferent or courting another hen, on the ground of his superior beauty alone?

Why, in fact, should it not be with birds as it is with men and women? Women, to casual observation, seem at least as coy and modest as do hen birds, in whom, however, there can be no idea of modesty. They are supposed to be wooed, and not to woo; but they both can, and, to a considerable extent, do exercise the latter power. If they cannot ask, they can demand to be asked; and to think that the latter is a less powerful agency than the former is to think very naively. If women were not often, in reality, very active wooers, such common expressions as "setting her cap at him," "drawing him on," "throwing herself at his head," etc., etc., could hardly have arisen, and it must not be forgotten that the same thing can be done both coarsely and refinedly, visibly and so as to be hardly perceptible. No doubt there is something called modesty amongst civilised women, but there are also jealousy and prudential considerations—very powerful solvents of anything of the sort. Yet with all this we have the prevailing idea that (even in a civilised state of things) it is man who woos and woman who is won; man who advances and woman who retires; man who seeks and woman who shuns. The reason probably is that the actions of man are of a more downright nature, and easier to observe and follow, than those of woman—who, as a clever writer has remarked, approaches her object obliquely—and, secondly, that it is man mostly, and not woman, who has given his opinion on this and other matters through the most authoritative channels—for it is man who, by virtue of his intellect and his selfishness, holds the chief places of authority.

May not these factors have affected in some degree, also, our conclusions in regard to the lower animals? Here, too, the actions of the female may be often more subtle and difficult to follow than those of the male, though in many cases, as I believe, they are seen plainly enough, but, for a reason shortly to be mentioned, attributed to the male. Yet in the case of birds, at any rate, it is very noticeable in some species that the females, after the couples have once paired off, are extremely eager in their enticements of the males to hymeneal pleasures, and it seems difficult to reconcile this eagerness after marriage with any very real coldness before it—especially as the supposed coy sweetheart of one spring has been the forward wife of the spring before. But there is another point, in this connection, which it is of the utmost importance for us to bear in mind. Birds in which, if in any, we might expect to find the courting actions alike or similar in the male and female (and this would imply an active wooing on the part of each) are of two classes—viz. (1) those in which the sexes are alike or nearly so, and (2) those in which, though they may differ conspicuously, the one is as handsome, or nearly as handsome, as the other. In the first case, the colours of the hen must either be due to the selective agency of the cock, or they must have been transmitted to her through the latter (as being prepotent), in which case they can have no significance as far as the theory of sexual selection is concerned—two possibilities which equally require proving. In the second case—but examples of this nature are not, I believe, numerous—a double process of sexual selection seems the only available explanation. Only when the female is plain and unadorned, and the male gaudy, does it seem primâ facie evident that the latter, alone, has been selected for his beauty. But it is just this last class of cases that has attracted the largest amount of notice, for, as might have been expected, it is precisely here that we find the males—often the most ornate of birds—indulging in the most extraordinary antics, which, of course, arrest attention. In observing these birds, however, the sexes are at once, and without difficulty, distinguished, and as the females do not share in such antics, we assume, when we see similar ones on the part of birds, the sexes of which are indistinguishable, that here, also, the same law holds good, though there is by no means the same presumption that this should be the case. Confronted with a certain effect, which implies a corresponding causal process, in one case, we assume this same process in another, though we cannot there see the effect. We see, for instance, one stock-dove manifestly court another, and at once assume that the courting bird is the male. The courtship, as is often the case, ends in a pretty severe battle, where blows with the wing are given and received on either side. We may be surprised to see the female so belligerent, but we do not yet doubt the fact of her being the female. The courting bird is, at last, repelled, and a fight of much the same description takes place between him and another stock-dove. This one might just as well be a female as the first, but in the midst of the strife both birds bow, several times, according to their custom, and we then feel sure that both are males. Meanwhile, however, our assured female, who has been left where she was, is seen to bow to another bird who has alighted near her, upon which we change our minds, conclude that she is a male after all, and that what we, at first, thought to be courtship, was only a fight between two cocks. And thus we go on, correcting and correcting our opinion—until in a gathering of perhaps a dozen or more stock-doves there would seem to be no female at all—because if they were pheasants or blackcocks the hens would not behave in this way. Again, when one first sees a shag throw itself down before another one, and go through a variety of strange gestures to which the latter makes no response—if not by a caress of the bill—it is impossible not to feel sure that the bird thus acting is the male shag, and the other the female. But when one afterwards sees two birds at the nest—male and female beyond a doubt—mutually or alternately performing some portion of these antics, though without the primary prostration,^[1] what is one to think then? In such cases as these, where the sexes are not to be distinguished except by dissection, or having the bird in one's hands, we cannot be sure that it is always the male we see displaying to the female, and never the female to the male. I believe, however, that we have tacitly assumed this to be the case.

An incident which I have recorded elsewhere seems to me to bear upon the foregoing remarks.^[2] Here a stone-curlew that had been sitting quietly for some time rose and uttered some shrill cries, in obedience to which another came running up, and after the two, standing close together, had each assumed a remarkable and precisely similar posture, the nuptial rite was performed. Were it not that, even by the witnessing of this last, it is not always possible to differentiate the sexes of birds, I could say with certainty that it was the female stone-curlew, in this instance, that called up the male; but the very striking attitude which the birds assumed, and which, if it was not a sexual display, it is difficult to know what to call it, was identical in both. Again, in the case of a pair of crested grebes that I watched during two successive springs everything (and there was once something very striking) in the nature of an antic or display was indulged in equally by the male and female. Peewits, also, behave during the nuptial season in a very marked manner, both whilst flying and upon the ground, and as far as I can make out—though I will not here speak with certainty—the conduct of both sexes is the same throughout.

The nuptial cries or notes of birds are a chief way in which the one sex, on the theory of sexual selection, endeavours to render itself pleasing to the other. When these charm our own ears to an extent which we think deserving of the name of song, it is usually the male alone that utters them, those uttered by the female not rising to the height of such a definition. To how great an extent this law prevails I have not the knowledge to say, but it is not universal. The female canary, robin, lark, and bullfinch all sing, especially when widowed, though their song is not equal to that of the male, whilst in the red oven-bird of Argentina both sexes frequently join one another for the express purpose of singing a duet. Surely in this last case, especially, if it be assumed that the song of the male is uttered with the purpose of pleasing the female, or has that effect, the converse ought also to be assumed: and if so, why should not the hens, as well as the cocks, be sometimes chosen for their song?

But all nuptial notes of birds are equally song, in the sense that they are uttered under the impulse of sexual passion, and many of these are the same in both the sexes. Here, again, there is a danger of assuming, without sufficient evidence, that the characteristic courting or love-note is uttered only by the male. A mistake of this kind has been made in the case of the nightjar—both sexes of which I have heard "churr" together on the nest—and no doubt in many other instances, including, very possibly, the cuckoo. In a vast number of cases, however, the cries of the two sexes during the love-season are known to be the same. They may not always, when this is the case, be either very wonderful or very beautiful, but to suppose that the nuptial actions and notes of male birds are intended to attract and charm the female only when they are of a very pronounced and extraordinary character, or very musical, would not be logical. They must be always directed to this end, if at all, and if the females indulge in the same gestures and utter the same sounds, their motive in doing so, and the effect produced by their doing it, should be the same, but directed towards, and acting upon, the male.

Why, then, should the male not exercise some choice, especially should there be, in addition, jealousy and competition amongst the females? As to this, it is not easy to imagine a desire on the part of one sex to please the other, unattended with jealousy, nor can jealousy exist without competition. We are not, however, confined to likelihood, for it is certain that the hen bird does sometimes court the cock and fight for him with rival hens, even in those cases where the cock alone is beautiful. In support of this I will quote some cases long ago brought forward by Darwin, though not as pointing in the direction in which they seem to me to point. Darwin, then, in his magnificent work, The Descent of Man—now, as it appears to me, little read and much required to be—writes as follows: "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" (p. 415). (Here, then, we have a male as coy as a female, who is wooed and ultimately won.) Again: "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" (p. 418). (Audubon, I think, is here quoted.) Again: "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, are of a profligate disposition, and prefer almost any stranger to their own mate" (pp. 418-419). I myself had once a pigeon of this feather, and so marked was her personality, and really and strangely profligate her acts, that I have never forgotten her. Again we have: "'Sir R. Heron states that the hens have frequently great preference to a particular peacock. 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 trellis-walls of his prison, and would not suffer a japaned 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.' Female birds not only exert a choice, but in some few cases they court the male and even fight together for his possession. (I, however, would demur to the word "few" and ask how much we really know about it.) Sir R. Heron states that with pea-fowl 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" (pp. 418-419). What is this if not a double courtship? And the male capercailzie, if I remember rightly, is capricious in his selection of the hens. Again: "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" (p. 420). Finally we have this: "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" (p. 420).

How ill do such facts as the above accord with the theory that the male bird is too eager to exercise choice in regard to the female. Darwin also (p. 420) adduces evidence to show that the domestic cock prefers the younger to the older hens; that the male pheasant, when hybridised with the fowl, has the opposite taste, "is most capricious in his attachments, and, from some inexplicable cause, shows the most determined aversion to certain hens"; that some hens are quite unattractive, even to the males of their own species; and that, with the long-tailed duck, certain females are much more courted than the rest, of which last state of things I have, if I mistake not, seen a hint with the eider-duck. Again, then, what becomes of the supposed indiscriminate eagerness of the male? Has not this theory been accepted too unreservedly, and on a too slender foundation of evidence?

It is significant that most of the above-quoted observations were made on birds in confinement, or under domestication, in which states, of course, they are very much easier to watch. Of the intimate domestic habits of birds—that is to say, of most birds—in a wild state, we know, I believe, very little, and have assumed very much. I might give here two cases—I have elsewhere given some instances—of what appeared to me to be violent rivalry on the part of hen blackbirds; but I refer again to what I have noticed in regard to the nuptial habits of those seabirds, the bright interior colouring of whose mouths I have drawn attention to, and endeavoured to account for.

To recapitulate. As the theory of sexual selection supposes that the one sex has been adorned and made beautiful in accordance with the taste and choice of the opposite one during the love season, we might expect that amongst those birds where the males are beautiful and the females plain, the more active part in courtship would be taken by the former; for this is the very road along which such beauty must have been gained. On the other hand, if the females had been equally ardent they would have arrived, by the same road, at the same, or a similar, goal. Therefore, in the above cases we ought to be prepared to find what we do find. But when the sexes, whether beautiful or not, resemble one another, there is not the same reason for supposing that the male alone actively courts, and since, in such cases, it is very difficult to tell by actual observation whether this is so, or not, we really know very little about the matter. Instead of knowing, we assume, and of two birds, either of which may be, as far as outward appearance goes, either the male or the female, that one which we see pursuing or paying court to the other is always the male in our eyes. Yet even amongst those species where the male alone is adorned, courting on the part of the female is by no means unknown, and rival hens sometimes fight for the cock. How much more, therefore, is this likely to be the case where the sexes are alike, and where, consequently, as already explained, there is not the same primâ facie probability of one only (the male) having been selected!

The fact that both the male and female of various birds of this class utter the same cries, and indulge in the same antics, during the nuptial season, is some evidence that either sex tries to please—i.e. courts—the other; for similar actions and utterances must be taken as implying a similar psychology—they are not like colours or markings—and we cannot, therefore, conceive of them as being merely transmitted, by the laws of inheritance, through the male to the female, and having a mental significance only in the case of the former, or conversely. A bad constitution—the result of intemperance—might descend through the father to the temperate daughter; but if the habit of drinking be also inherited, so must the flaw in the character, of which it is the outcome.

If we admit that certain antics (or cries) common to both sexes of certain birds, have had a like origin in the case of either, then, if by such common actions some common beauty is displayed, it is unreasonable to think that this has been acquired through the action of sexual selection in the case of the one sex (the male) and not in the case of the other (the female), for where the psychology and actions are the same, the laws governing them must be the same, and their effects the same.

The above considerations, enforced as they have been by much that I have myself observed, make me doubt whether the view that where any species of bird has come under the influence of sexual selection, it is the one sex only—almost always the male—that has been modified by its action, is a correct one. It seems to me more probable that where the sexes are alike, or where they differ markedly, and are both handsome, each of them has acquired such beauty as it possesses in accordance with the taste and choice of the opposite one. Darwin, though he did not consider this probable, yet recognised its possibility, as the following passage will show: "It may be suggested that in some cases a double process of selection has been carried on: that the males have selected the more attractive females, and the latter the more attractive males. This process, however, though it might lead to the modification of both sexes, would not make the one sex different from the other, unless, indeed, their tastes for the beautiful differed; but this is a supposition too improbable to be worth considering in the case of any animal excepting man. There are, however, many animals in which the sexes resemble each other, both being furnished with the same ornaments, which analogy would lead us to attribute to the agency of sexual selection. In such cases it may be suggested with more plausibility that there has been a double or mutual process of sexual selection, the more vigorous and precocious females selecting the more attractive and vigorous males, the latter rejecting all except the more attractive females. But from what we know of the habits of animals this view is hardly probable, for the male is generally eager to pair with any female. It is more probable that the ornaments common to both sexes were acquired by one sex, generally the male, and then transmitted to the offspring of both sexes."^[3]

I have given my reasons for doubting whether this last hypothesis really is more probable than the other one of a double process of sexual selection—at any rate as far as birds are concerned: and I suggest that, in their case, the whole question of the relations of the sexes to one another should be reconsidered after much more careful observation, especially in regard to those species where the male and female are alike, or where they differ markedly, and are both handsome. As to the possibility of the taste for the beautiful differing in the two sexes of any bird or animal, I cannot see why this should not sometimes be the case. One sex is attracted only by the beauty of the opposite one, so that if, owing to slight constitutional differences between them, the variations which occurred in the one were somewhat different to those which occurred in the other (which hardly seems very unlikely), these might be selected and "added up"—to use Darwin's expression—along two gradually diverging lines, and this would lead, insensibly and necessarily, to divergence of taste as between the male and the female. The law is for the one sex to admire what it gets in the other. Therefore, supposing individual differences in both, and a choice in regard to them on the opposite side, taste, in each case, must be guided by the variations offered for it to work upon; and though the final result of this, if such variations were affected by sex, might appear very surprising, there would be nothing remarkable in the process by which it had been arrived at. Must not, in fact, a difference of taste as between the two sexes—and that often a very decided one—in any case exist? For the male bird of paradise, let us say, is attracted by the dull hen, whilst she, presumably, admires only the resplendent cock. Beauty is only a relative term, and even the plainest bird possesses a good deal of it. We may, of course, say that it is only the hen bird, in such cases, which can be said to admire, but it would be difficult, I think, to defend this view. Both are sexually excited, and the eye is a channel for both.

These, then, are my arguments in favour of a process of intersexual selection in nature, and I think that those men, at any rate, who grant taste and choice to female animals, should be prepared to grant it, also, to their own sex, though the thinking woman, perhaps, may be expected to take another view. But, of course, I know that there are still numbers of people who do not accept the theory—or, as I would prefer to call it, the fact—of sexual selection at all, even in its narrower scope. I believe, however, that the chariness and hesitation which has been shown in adopting the latter of Darwin's two great principles, is a survival of that attitude of mind which caused such opposition to his whole teaching. Man's body is one thing, but his mind—especially all those supposed high things in it which we call, together, spirituality—is quite another. It offends our human pride to think that animals should woo and marry very much as we—when the better part of our nature is not in a strait-jacket—do ourselves. Therefore, there must be no preferences, no love-matches here, all must be in obedience to a blind sexual instinct—something very animal—about which we, of course, with our rings and our ceremonies, our novels, sonnets, spiritual affinities, and prudential considerations, know nothing. Unlike ourselves, the female brute must be ready to mate with any male brute that chance may throw in her way, and if it throw several, she must be absolutely impartial between them, there being neither looks, soul, nor money for her to found a choice on. Therefore she will go to the strongest, and ask no better, for love she knows not, nor can parental authority and filial obedience combine here to give the preference to riches or title, coupled with age or disease. Only by her complete passivity could the female brute be properly differentiated from the human female, and this she must be, or man (the worst brute that the world has yet seen or is ever likely to see) would lose his pre-eminence.

But do no difficulties attend this theory of entire impartiality on the part of the hen bird (for we will keep now to birds) in respect to the cock, during the pairing season? That she is sexually excited by him—as a male, at least, if not as an individual male—we would surely have to conclude, even in the absence of direct evidence, for how otherwise could the breeding be accomplished? Then what a most extraordinary thing it would be if she were excited in precisely the same degree—not one jot or tittle more or less—by any one male as by any other! Whatever the nature of that sexual appeal may be which every cock makes to every hen, and by virtue of which she feels that he is a cock, and not a hen like herself, why should we suppose that any two individuals should be more exactly alike in it than they are in anything else? But if there is not this absolute unity, then there is difference, and such difference in the degree of the sexual charm flung out by each male, must produce preference and choice in the female. The whole theory of evolution is based upon the undisputed and indisputable fact of individual variability; nor is there any one thing or quality, bodily or mental—amongst the higher animals at least—that does not vary largely in the different individuals possessing it. As it appears to me, therefore, choice in the one sex with regard to the other is what might have been, on a priori considerations, expected; though I can well understand that, as amongst ourselves, it would often be held in abeyance, or nullified, by the operation of higher—that is to say, more inexorable—laws, and also that its manifestations would often be too subtle and hidden for us to follow them. But we first, in deference to our human prejudices, assume something which is improbable in itself, and then obstinately resist a mass of the most striking evidence which shows our assumption to be wrong. In all intellectual and spiritual qualities, man, by the laws of evolution, may have greatly outdistanced his fellow animals; but it should never be forgotten that in judging of how far this has been the case, we—and there is no other court—are the most partial and prejudiced judges—dishonest, blinded, full of assumptions, delighting to deceive ourselves, and miserably vain.

If female birds are really so apathetic and male ones so equally satisfied with any partner they can get, it seems difficult to see on what principle the two, when paired, remain constant to one another during the nesting season, and still more, perhaps, why numbers of birds pair for life. Such a state of things ought, one would think, to lead to promiscuous intercourse. But if birds mate by preference and elective affinity, such constancy is what one might expect. What we want, however, to settle this and all other questions relating to the habits of animals is long, close, hard, exhaustive observation—real observation as distinct from mere writing, and even from good literature. There is wofully little of this, in my opinion, and none the less so because an impression exists that there is a great deal.

1. I instance only what I have actually seen, and go no farther.
2. Bird Watching, pp. 18-19.
3. Descent of Man, pp. 225-226.