Some Woodhewers' beaks.

only member known of the genus, with a tail resembling that of the lyre-bird, the extravagantly long feathers being so narrow as to appear almost

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like shafts destitute of webs. This tail appears to be purely ornamental.

This extreme variety in structure indicates a corresponding diversity in habits; and, assuming it to be a true doctrine that habits vary first and structure afterwards, anyone might infer from a study of their forms alone that these birds possess a singular plasticity, or tendency to vary, in their habits--or, in other words, that they are exceptionally intelligent; and that such a conclusion would be right I believe a study of their habits will serve to show.

The same species is often found to differ in its manner of life in different localities. Some species of Xenops and Magarornis, like woodpeckers, climb vertically on tree-trunks in search of insect prey, but also, like tits, explore the smaller twigs and foliage at the extremity of the branches; so that the whole tree, from its root to its topmost foliage, is hunted over by them. The Sclerurus, although an inhabitant of the darkest forest, and provided with sharply-curved claws, never seeks its food on trees, but exclusively on the ground, among the decaying fallen leaves; but, strangely enough, when alarmed it flies to the trunk of the nearest tree, to which it clings in a vertical position, and, remaining silent and motionless, escapes observation by means of its dark protective colour. The Drymornis, a large bird, with feet and tail like a woodpecker, climbs on tree-trunks to seek its food; but also possesses the widely-different habit of resorting to the open plain, especially after a shower, to feed on larvae and earthworms, extracting them from a depth of three

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or four inches beneath the surface with its immense curved probing beak.

Again, when we consider a large number of species of different groups, we find that there is not with the Tree-creepers, as with most families, any special habit or manner of life linking them together; but that, on the contrary, different genera, and, very frequently, different species belonging to one genus, possess habits peculiarly their own. In other families, even where the divergence is greatest, what may be taken as the original or ancestral habit is seldom or never quite obsolete in any of the members. This we see, for instance, in the woodpeckers, some of which have acquired the habit of seeking their food exclusively on the ground in open places, and even of nesting in the banks of streams. Yet all these wanderers, even those which have been structurally modified in accordance with their altered way of life, retain the primitive habit of clinging vertically to the trunks of trees, although the habit has lost its use. With the tyrant birds--a family showing an extraordinary amount of variation--it is the same; for the most divergent kinds are frequently seen reverting to the family habit of perching on an elevation, from which to make forays after passing insects, returning after each capture to the same stand. The thrushes, ranging all over the globe, afford another striking example. Without speaking of their nesting habits, their relationship appears in their love of fruit, in their gait, flight, statuesque attitudes, and abrupt motions.

With the numerous Dendrocolaptine groups, so

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widely separated and apparently unrelated, it would be difficult indeed to say which, of their most striking habits is the ancestral one. Many of the smaller species live in trees or bushes, and in their habits resemble tits, warblers, wrens, and other kinds that subsist on small caterpillars, spiders, &c., gleaned from the leaves and smaller twigs. The Anumbius nests on trees, but feeds exclusively on the ground in open places; while other ground-feeders seek their food among dead leaves in dense gloomy forests. Coryphistera resembles the lark and pipit in its habits; Cinclodes, the wagtail; Geobates a Saxicola; Limnornis lives in reed beds growing in the water; Henicornis in reed beds growing out of the water; and many other ground species exist concealed in the grass on dry plains; Homorus seeks its food by digging in the loose soil and dead leaves about the roots of trees; while Geo-sitta, Furnarius, and Upercerthia obtain a livelihood chiefly by probing in the soil. It would not be possible within the present limits to mention in detail all the different modes of life of those species or groups which do not possess the tree-creeping habit; after them comes a long array of genera in which this habit is ingrained, and in which the greatly modified feet and claws are suited to a climbing existence. As these genera comprise the largest half of the family, also the largest birds in it, we might expect to find in the tree-creeping the parental habit of the Dendrocolaptidae, and that from these tropical forest groups have sprung the widely-diverging thicket, ground, marsh, sea-beach, and rock-frequenting groups. It happens, however,

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that these birds resemble each other only in their climbing feet; in the form of their beaks they are as wide apart as are nuthatches, woodpeckers, crows, and curlews. They also differ markedly in the manner of seeking their food. Some dig like woodpeckers in decayed wood; others probe only in soft rotten wood; while the humming-bird-billed Xiphorhynchus, with a beak too long and slender for probing, explores the interior of deep holes in the trunks to draw out nocturnal insects, spiders, and centipedes from their concealment. Xiphoco-laptes uses its sword-like beak as a lever, thrusting it under and forcing up the loose bark; while Dendrornis, with its stout corvine beak, tears the bark off.

In the nesting habits the diversity is greatest. Some ground species excavate in the earth like kingfishers, only with greater skill, making cylindrical burrows often four to five feet deep, and terminating in a round chamber. Others build a massive oven-shaped structure of clay on a branch or other elevated site. Many of those that creep on trees nest in holes in the wood. The marsh-frequenting kinds attach spherical or oval domed nests to the reeds; and in some cases woven grass and clay are so ingeniously combined that the structure, while light as a basket, is perfectly impervious to the wet and practically indestructible. The most curious nests, however, are the large stick structures on trees and bushes, in the building and repairing of which the birds are in many cases employed more or less constantly all the year round. These stick nests vary greatly in form,

244 The Naturalist in La Plata,

size, and in other respects. Some have a spiral passage-way leading from the entrance to the nest cavity, and the cavity is in many cases only large enough to accommodate the bird; but in the gigantic structure of Homorus gutturalis it is so large that, if the upper half of the nest or dome were removed, a condor could comfortably hatch her eggs and rear her young in it. This nest is spherical. The allied Homorus lophotis builds a nest equally large, but with a small cavity for the eggs inside, and outwardly resembling a gigantic powder-flask, lying horizontally among the lower branches of a spreading tree. Pracellodomtis sibila-trix, a bird in size like the English house sparrow, also makes a huge nest, and places it on the twigs at the terminal end of a horizontal branch from twelve to fifteen feet above the ground; but when finished, the weight of the structure bears down the branch-end to within one or two feet of the surface. Mr. Barrows, who describes this nest, says: "When other branches of the same tree are similarly loaded, and other trees close at hand bear the same kind of fruit, the result is very picturesque." Synallaxis phryganophila makes a stick nest about a foot in depth, and from the top a tubular passage, formed of slender twigs interlaced, runs down the entire length of the nest, like a rain-pipe on the wall of a house, and then becoming external slopes upward, ending at a distance of two to three feet from the nest. Throughout South America there are several varieties of these fruit-and-stem or watering-pot shaped nests; they are not, however, all built by birds of one genus, while in the genus

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Synallaxis many species have no tubular passageways attached to their nests. One species--erythro thorax--in Yucatan, makes so large a nest of sticks, that the natives do not believe that so small a bird can be the builder. They say that when the tzapatan begins to sing, all the birds in the forest repair to it, each one carrying a stick to add to the structure; only one, a tyrant-bird, brings two sticks, one for itself and one for the urubú or vulture, that bird being considered too large, heavy, and ignorant of architecture to assist personally in the work.

In the southern part of South America, where scattered thorn trees grow on a dry soil, these big nests are most abundant. "There are plains," Mr. Barrows writes, "within two miles of the centre of this town (Concepcion, Argentine Republic), where I have stood and counted, from one point within a radius of twenty rods, over two hundred of these curious nests, varying in size from that of a small pumpkin to more than the volume of a barrel. Often a single tree will contain half a dozen nests or more; and, not unfrequently, the nests of several different species are seen crowding each other out of shape on the same bush or tree."

It would be a mistake to think that the widely different nesting habits I have mentioned are found in different genera. I have just spoken of the big stick nests, with or without passage-ways, of the Synallaxes, yet the nest of one member of this group is simply a small straight tube of woven grass, the aperture only large enough to admit the finger, and open at both ends, so that the

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bird can pass in and out without turning round. Another species scoops a circular hollow in the soil, and builds over it a dome of fine woven grass. It should be mentioned that the nesting habits of only about fifteen out of the sixty-five species comprised in this genus are known to us. In the genus Furnarius the oven-shaped clay structure is known to be made by three species; a fourth builds a nest of sticks in a tree; a fifth burrows in the side of a bank, like a kingfisher.

The explanation of the most striking features of the Dendrocolaptidae, their monotonous brown plumage, diversity of structure, versatile habits, and the marvellous development of the nest-making instinct which they exhibit is to be found, it appears to me, in the fact that they are the most defenceless of birds. They are timid, unresisting creatures, without strength or weapons; their movements arc less quick and vigorous than those of other kinds, and their flight is exceedingly feeble. The arboreal species flit at intervals from one tree to another; those that frequent thickets refuse to leave their chosen shelter; while those inhabiting grassy plains or marshes study concealment, and, when forced to rise, flutter away just above the surface, like flying-fish frightened from the water, and, when they have gone thirty or forty yards, dip into the grass or reeds again. Their life is thus one of perpetual danger in a far greater degree than with other passerine families, such as warblers, tyrants, finches, thrushes, &c.; while an exclusively insect diet, laboriously extracted from secret places, and inability to change their climate, contribute to make

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their existence a hard one. It has been with these birds as with human beings, bred in "misfortune's school," and subjected to keen competition. One of their most striking characteristics is a methodical, plodding, almost painful diligence of manner while seeking their food, so that when viewed side by side with other species, rejoicing in a gayer plumage and stronger flight, they seem like sober labourers that never rest among holiday people bent only on enjoyment. That they are able not only to maintain their existence, but to rise to the position of a dominant family, is due to an intelligence and adaptiveness exceeding that of other kinds, and which has been strengthened, and perhaps directly results from the hard conditions of their life.

How great their adaptiveness and variability must be when we find that every portion of the South American continent is occupied by them; for there is really no climate, and no kind of soil or vegetation, which does not possess its appropriate species, modified in colour, form, and habits to suit the surrounding conditions. In the tropical region, so rich in bird life of all kinds, in forest, marsh, and savanna, they are everywhere abundant--food is plentiful there; but when we go to higher elevations avd cold sterile deserts, where their companion families of the tropics dwindle away and disappear, the creepers are still present, for they are evidently able to exist where other kinds would starve. On the stony plateaus of the Andes, and on the most barren spots in Patagonia, where no other bird is seen, there are small species of Synallaxis, which, in their obscure colour and motions

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on the ground, resemble mice rather than birds; indeed, the Quichua name for one of these Synallaxes is ukatchtuka, or mouse-bird. How different is the life habit here from what we see in the tropical groups--the large birds with immense beaks, that run vertically on the trunks of the great forest trees!

At the extreme southern extremity of the South American continent we find several species of Cin-clodes, seeking a subsistence like sandpipers on the beach; they also fly out to sea, and run about on the floating kelp, exploring the fronds for the small marine animals on which they live. In the dreary forests of Tierra del Fuego another creeper, Uxyurus, is by far the commonest bird. "Whether high up or low down, in the most gloomy, wet, and scarcely penetrable ravines," says Darwin, "this little bird is to be met with;" and Dr. Cunningham also relates that in these wintry, savage woods he was always attended in his walks by parties of these little creepers, which assembled to follow him out of curiosity.

To birds placed at so great a disadvantage, by a feeble flight and other adverse circumstances, in the race of life bright colours would certainly prove fatal. It is true that brown is not in itself a protective colour, and the clear, almost silky browns and bright chestnut tints in several species are certainly not protective; but these species are sufficiently protected in other ways, and can afford to be without a strictly adaptive colour, so long as they are not conspicuous. In a majority of cases, however, the colour is undoubtedly protective, the

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brown hue being of a shade that assimilates very closely to the surroundings. There are pale yellowish browns, lined and mottled, in species living amidst a sere, scanty vegetation; earthy browns, in those frequenting open sterile or stony places; while the species that creep on trees in forests are dark brown in colour, and in many cases the feathers are mottled in such a manner as to make them curiously resemble the bark of a tree. The genera Lochmias and Sclerurus are the darkest, the plumage in these birds being nearly or quite black, washed or tinged with rhubarb yellow. Their black plumage would render them conspicuous in the sunshine, but they pass their lives in dense tropical forests, where the sun at noon sheds only a gloomy twilight.

If "colour is ever tending to increase and to appear where it is absent," as Dr. Wallace believes, then we ought to find it varying in the direction of greater brightness in some species in a family so numerous and variable as the Dendrocolaptidae, however feeble and in need of a protective colouring these birds may be in a majority of pases. And this in effect we do find. In many of the dark-plumaged species that live in perpetual shade some parts are a very bright chestnut; while in a few that live in such close concealment as to be almost independent of protective colouring, the lower plumage has become pure white. A large number of species have a bright or nearly bright guiar spot. This is most remarkable in Synallaxis phryganophila, the chin being sulphur-yellow, beneath which is a spot of velvet-black, and on either side a white

2 5O The Naturalist in La Plata.

patch, the throat thus having three strongly contrasted colours, arranged in four divisions. The presence of this bright throat spot in so many species cannot very well be attributed to voluntary sexual selection, although believers in that theory are of course at liberty to imagine that when engaged in courtship, the male bird, or rather male and female both, as both sexes possess the spot, hold up their heads vertically to exhibit it. Perhaps it would be safer to look on it as a mere casual variation, which, like the exquisitely pencilled feathers and delicate tints on the concealed sides and under surfaces of the wings of many species possessing outwardly an obscure protective colouring, is neither injurious nor beneficial in any way, either to the birds or to the theory. It is more than probable, however, that in such small feeble-winged, persecuted birds, this spot of colour would prove highly dangerous on any conspicuous part of the body. In some of the more vigorous, active species, we can see a tendency towards a brighter colouring on large, exposed surfaces. In Auto-malus the tail is bright satiny rufous; in Pseudo-colaptes the entire under surface is rufous of a peculiar vivid tint, verging on orange or red; in Magarornis the bosom is black, and beautifully ornamented with small leaf-shaped spots of a delicate straw-colour. There are several other very pretty birds in this homely family; but the finest of all is Thripodectes flammulatus, the whole body being tortoise-shell colour, the wings and tail bright chesnut. The powerful tanager-like beak of this species seems also to show that it has diverged

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from its timid shade-loving congeners in another direction by becoming a seed and fruit eater.

Probably the sober and generally protective colouring of the tree-creepers, even with the variability and adaptiveness displayed in their habits superadded, would be insufficient to preserve such feeble birds in the struggle of life without the further advantage derived from their wonderful nests. It has been said of domed nests that they are a danger rather than a protection, owing to their large size, which makes it easy for carnivorous species that prey on eggs and young birds to find them; while small open nests are usually well concealed. This may be the case with covered nests made of soft materials, loosely put together; but it cannot be said of the solid structure the tree-creeper bnilds, and which, as often as not, the bird erects in the most conspicuous place it can find, as if, writes Azara, it desired all the world to admire its work. The annual destruction of adult birds is very great--more than double that, I believe, which takes place in other passerine families. Their eggs and young are, however, practically safe in their great elaborate nests or deep burrows, and, as a rule, they lay more eggs than other kinds, the full complement being seldom less than five in the species I am acquainted with, while some lay as many as nine. Their nests are also made so as to keep out a greater pest than their carnivorous or egg-devouring enemies--namely, the parasitical starlings (Molo-thrus), which are found throughout South America, and are excessively abundant and destructive to birds' nests in some districts. In most cases, in the

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big, strong-domed nest or deep burrow, all the eggs are hatched and all the young reared, the thinning, out process commencing only after the brood has been led forth into a world beset with perils. With other families, on the contrary, the greatest amount of destruction falls on the eggs or fledglings. I have frequently kept a dozen or twenty pairs of different species--warblers, finches, tyrants, starlings, &c.--under observation during the breeding season, and have found that in some cases no young-were reared at all; in other cases one or two young; while, as often as not, the young actually reared were only parasitical starlings after all.

I have still to speak of the voice of the tree-creepers, an important point in the study of these birds; for, though not accounted singers, some species emit remarkable sounds; moreover, language in birds is closely related to the social instinct. They seem to be rather solitary than gregarious; and this seems only natural in birds so timid, weak-winged, and hard pressed. It would also be natural to conclude from what has been said concerning their habits that they are comparatively silent; for, as a rule, vigorous social birds are loquacious and loud-voiced, while shy solitary kinds preservo silence, except in the love season. Nevertheless the creepers are loquacious and have loud resonant voices; this fact, however, does not really contradict a well-known principle, for the birds possess the social disposition in an eminent degree, only the social habit is kept down in them by the conditions of a life which makes solitude necessary. Thus, a large proportion of species are found to pair for

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life; and the only reasonable explanation of this habit in birds--one which is not very common in the mammalia--is that such species possess the social temper or feeling, and live in pairs only because they cannot afford to live in flocks. Strictly gregarious species pair only for the breeding season. In the creepers the attachment between the birds thus mated for life is very great, and, as Azara truly says of Anumbiüs, so fond of each other's society are these birds, that when one incubates the other sits at the entrance to the nest, and when one carries food to its young the other accompanies it, even if it has found nothing to cany. In these species that live in pairs, when the two birds are separated they are perpetually calling to each other, showing how impatient of solitude they are; while even from the more solitary kind, a high-pitched call-note is constantly heard in the woods, for these birds, debarred from associating together, satisfy their instinct by conversing with one another over long distances.

The foregoing remarks apply to the Dendrocolap-tidae throughout the temperate countries of South America--the birds inhabiting extensive grassy plains and marshes, and districts with a scanty or scattered tree and bush vegetation. In the forest areas of the hotter regions it is different; there the birds form large gatherings or "wandering bands," composed of all the different species found in each district, associated with birds of other families--wood-peckers, tyrant-birds, bush shrikes, and many others. These miscellaneous gatherings are not of rare occurrence, but out of the breeding season are

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formed daily, the birds beginning to assemble at about nine or ten o'clock in the morning, their number increasing through the day until it reaches its maximum between two and four o'clock in the afternoon, after which it begins to diminish, each bird going off to its customary shelter or dwelling-place. Mr. Bates, who first described these wandering bands, says that he could always find the particular band belonging to a district any day he wished, for when he failed to meet with it in one part of the forest he would try other paths, until he eventually found it. The great Amazonian forests, he tells us, appear strangely silent and devoid of bird life, and it is possible to ramble about for whole days without seeing or hearing birds. But now and then the surrounding trees and bushes appear suddenly swarming with them. "The bustling crowd loses no time, and, always moving in concert, each bird is occupied on its own account in searching bark, or leaf, or twig. In a few moments the host is gone, and the forest path remains deserted and silent as before." Stolzmann, who observed them in Peru, says that the sound caused by the busy crowd searching through the foliage, and the falling of dead leaves and twigs, resembles that produced by a shower of rain. The Indians of the Amazons, Mr. Bates writes, have a curious belief to explain these bird armies; they say that the Papa-uira, supposed to be a small grey bird, fascinates all the others, and leads them on a weary perpetual dance through the forest. It seems very wonderful that birds, at other times solitary, should thus combine daily in large numbers, includ-

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ing in their bands scores of widely different species, and in size ranging from those no larger than a wren to others as big as a magpie. It is certainly very advantageous to them. As Belt remarks, they play into each other's hands; for while the larger creepers explore the trunks of big trees, others run over the branches and cling to the lesser twigs, so that every tree in their route, from its roots to the topmost foliage, is thoroughly examined, and every spider and caterpillar taken, while the winged insects, driven from their lurking-places, are seized where they settle, or caught flying by the tyrant birds.

I have observed the wandering bands only in Patagonia, where they are on a very small scale compared with those of the tropical forests. In the Patagonia thickets the small tit-like creeper, Laptas-thenura, is the prime mover; and after a considerable number of these have gathered, creepers of other species and genera unite with them, and finally the band, as it moves through the thickets, draws to itself other kinds--flycatchers, finches, &c.--many of the birds running or hopping on the ground to search for insects in the loose soil or under dead leaves, while others explore the thorny bushes. My observations of these small bands lead me to believe that everywhere in South America the Dendrocolaptidae are the first in combining to act in concert, and that the birds of other families follow their march and associate with them, knowing from experience that a rich harvest may be thus reaped. In the same way birds of various kinds follow the movements of a column of hunting

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ants, to catch the insects flying up from the earth to escape from their enemies; swallows also learn to keep company with the traveller on horseback, and, crossing and recrossing just before the hoofs, they catch the small twilight moths driven up from the grass.

To return to the subject of voice. The tree-creepers do not possess melodious, or at any rate mellow notes, although in so numerous a family there is great variety of tone, ranging from a small reedy voice like the faint stridulation of a grasshopper, to the resounding, laughter-like, screaming concerts of Homorus, which may be heard distinctly two miles away. As a rule, the notes are loud ringing calls; and in many species the cry, rapidly reiterated, resembles a peal of laughter. With scarcely an exception, they possess no set song; but in most species that live always in pairs there are loud, vehement, gratulatory notes uttered by the two birds in concert when they meet after a brief separation. This habit they possess in common with birds of other families, as, for instance, the tyrants; but, in some creepers, out of this confused outburst of joyous sound has been developed a musical performance very curious, and perhaps unique among birds. On meeting, the male and female, standing close together and facing each other, utter their clear ringing concert, one emitting loud single measured notes, while the notes of its fellow are rapid, rhythmical triplets; their voices have a joyous character, and seem to accord, thus producing a kind of harmony. This manner of singing is perhaps most perfect in the oven-bird,

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Furnarias, and it is very curious that the young birds, when only partially fledged, are constantly heard in the nest or oven apparently practising these duets in the intervals when the parents are absent; single measured notes, triplets, and long concluding trills are all repeated with wonderful fidelity, although these notes are in character utterly unlike the hunger cry, which is like that of other fledglings. I cannot help thinking that this fact of the young birds beginning to sing like the adults, while still confined in their dark cradle, is one of very considerable significance, especially when we consider the singular character of the performance; and that it might even be found to throw some light on the obscure question of the comparative antiquity of the different and widely separated Dendrocolaptine groups. It is a doctrine in evolutionary science that the early maturing of instincts in the young indicates a high antiquity for the species or group; and there is no reason why this principle should not be extended, in the case of birds at any rate, to language. It is true that Daines Barrington's notion that young song-birds learn to sing only by imitating the adults still holds its ground; and Darwin gives it his approval in his Descent of Man. It is perhaps one of those doctrines which are partially true, or which do not contain the whole truth; and it is possible to believe that, while many singing birds do so learn their songs, or acquire a greater proficiency in them from hearing the adults, in other species the song comes instinctively, and is, like other instincts and habits, purely an "inherited memory."

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The case of a species in another order of birds--Crypturi--strikes me as being similar to this of the oven-bird, and seems to lend some force to the suggestion I have made concerning the early development of voice in the young.

Birds peculiar to South America are said by anatomists to be less specialized, lower, more ancient, than the birds of the northern continents, and among those which are considered lowest and most ancient are the Tinamous (rail and partridge like in their habits), birds that lead a solitary, retiring life, and in most cases have sweet melancholy voices. Rhynchotus rufescens, a bird the size of a fowl, inhabiting the pampas, is perhaps the sweetest-voiced, and sings with great frequency. Its song or call is heard oftenest towards the evening, and is composed of five modulated notes, flute-like in character, very expressive, and uttered by many individuals answering each other as they sit far apart concealed in the grass. As we might have expected, the faculties and instincts of the young of this species mature at a very early period; when extremely small, they abandon their parents to shift for themselves in solitude; and when not more than one-fourth the size they eventually attain, they acquire the adult plumage and are able to fly as well as an old bird. I observed a young bird of this species, less than a quail in size, at a house on the pampas, and was told that it had been taken from the nest when just breaking the shell; it had, therefore, never seen or heard the parent birds. Yet this small chick, every day at the approach of evening, would retire to the darkest corner of the

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dining room, and, concealed under a piece of furniture, would continue uttering its evening song for an hour or longer at short intervals, and rendering it so perfectly that I was greatly surprised to hear it; for a thrush or other songster at the same period of life, when attempting to sing, only produces a chirping sound.

The early singing of the oven-bird fledgling is important, owing to the fact that the group it belongs to comprises the least specialized forms in the family. They are strong-legged, square-tailed, terrestrial birds, generally able to perch, have probing beaks, and build the most perfect mud or stick nests, or burrow in the ground. In the numerous tree-creeping groups, which, seem as unrelated to the oven-bird as the woodpecker is to the hoopoe, we find a score of wonderfully different forms of beak; but many of them retain the probing character, and are actually used to probe in rotten wood on trees, and to explore the holes and deep crevices in the trunk. We have also seen that some of these tree-creepers revert to the ancestral habit (if I may so call it) of seeking their food by probing in the soil. In others, like Dendrornis, in which the beak has lost this character, and is used to dig in the wood or to strip off the bark, it has not been highly specialized, and, compared with the woodpecker's beak, is a very imperfect organ, considering the purpose for which it is used. Yet, on the principle that "similar functional requirements frequently lead to the development of similar structures in animals which are otherwise very distinct"--as we see in the tubular tongue in

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honey-eaters and humming birds--we might have expected to find in the Dendrocolaptidae a better imitation of the woodpecker in so variable an organ as the beak, if not in the tongue.

Probably the oven-birds, and their nearest relations--generalized, hardy, builders of strong nests, and prolific--represent the parental form; and when birds of this type had spread over the entire continent they became in different districts frequenters of marshes, forests, thickets and savannas. With altered life-habits the numerous divergent forms originated; some, like Xiphorynchus, retaining a probing beak in a wonderfully modified form, attenuated in an extreme degree, and bent like a sickle; others diverging more in the direction of nuthatches and woodpeckers.

This sketch of the Dendrocolaptidae, necessarily slight and imperfect, is based on a knowledge of the habits of about sixty species, belonging to twenty-eight genera: from personal observation I am acquainted with less than thirty species. It is astonishing to find how little has been written about these most interesting birds in South America. One tree-creeper only, Furnarius rufus, the oven-bird par excellence, has been mentioned, on account of its wonderful architecture, in almost every general work of natural history published during the present century; yet the oven-bird does not surpass, or even equal in interest, many others in this family of nearly three hundred members.

CHAPTER XIX.

MUSIC AND DANCING IN NATURE.

IN reading books of Natural History we meet with numerous instances of birds possessing the habit of assembling together, in many cases always at the same spot, to indulge in antics and dancing performances, with or without the accompaniment of music, vocal or instrumental.; and by instrumental music is here meant all sounds other than vocal made habitually and during the more or less orderly performances; as, for instance, drumming and tapping noises; smiting of wings; and humming, whip-cracking, fan-shutting, grinding, scraping, and horn-blowing sounds, produced as a rule by the quills.

There are human dances, in which only one person performs at a time, the rest of the company looking on; and some birds, in widely separated genera, have dances of this kind. A striking example is the Rupicola, or cock of-the-rock, of tropical South America. A mossy level spot of earth surrounded by bushes is selected for a dancing-place, and kept well cleared of sticks and stones; round this area the birds assemble, when a cock-bird, with vivid orange-scarlet crest and plumage, steps into it, and, with spreading wings and tail,

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begins a series of movements as if dancing a minuet; finally, carried away with excitement, he leaps and gyrates in the most astonishing manner, until, becoming exhausted, he retires, and another bird takes his place.

In other species all the birds in a company unite in the set performances, and seem to obey an impulse which affects them simultaneously and in the same degree; but sometimes one bird prompts the others and takes a principal part. One of the most curious instances I have come across in reading is contained in Mr. Bigg-Wither's Pioneering in South Brazil. He relates that one morning in the dense forest his attention was roused by the unwonted sound of a bird singing--songsters being rare in that district. His men, immediately they caught the sound, invited him to follow them, hinting that he would probably witness a very curious sight. Cautiously making their way through the dense undergrowth, they finally came in sight of a small stony spot of ground, at the end of a tiny glade; and on this spot, some on the stone and some on the shrubs, were assembled a number of little birds, about the size of tom-tits, with lovely blue plumage and red top-knots. One was perched quite still on a twig, singing merrily, while the others were keeping time with wings and feet in a kind of dance, and all twittering an accompaniment. He watched them for some time, and was satisfied that they were having a ball and concert, and thoroughly enjoying themselves; they then became alarmed, and the performance abruptly terminated, the birds all going off in different directions. The natives told

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him that these little creatures were known as the "dancing birds."

This species was probably solitary, except when assembling for the purpose of display; but in a majority of cases, especially in the Passerine order, the solitary species performs its antics alone, or with no witness but its mate. Azara, describing a small finch, which he aptly named Oscilador, says that early and late in the day it mounts up vertically to a moderate height; then, flies off to a distance of twenty yards, describing a perfect curve in its passage; turning, it flies back over the imaginary line it has traced, and so on repeatedly, appearing like a pendulum swung in space by an invisible thread.

Those who seek to know the cause and origin of this kind of display and of song in animals are referred to Darwin's Descent of Man for an explanation. The greater part of that work is occupied with a laborious argument intended to prove that the love-feeling inspires the animals engaged in these exhibitions, and that sexual selection, or the voluntary selection of mates by the females, is the final cause of all set musical and dancing performances, as well as of bright and harmonious colouring, and of ornaments.

The theory, with regard to birds is, that in the love-season, when the males are excited and engage in courtship, the females do not fall to the strongest and most active, nor to those that are first in the field; but that in a large number of species they are endowed with a faculty corresponding to the aesthetic feeling or taste in man, and deliberately

264 The Naturalist in La Plata.

select males for their superiority in some aesthetic quality, such as graceful or fantastic motions, melody of voice, brilliancy of colour, or perfection of ornaments. Doubtless all birds were originally plain-coloured, without ornaments and without melody, and it is assumed that so it would always have been in many cases but for the action of this principle, which, like natural selection, has gone on accumulating countless small variations, tending to give a greater lustre to the species in each case, and resulting in all that we most admire in the animal world--the Rupicola's flame-coloured mantle, the peacock's crest and starry train, the joyous melody of the lark, and the pretty or fantastic dancing performances of birds.

My experience is that mammals and birds, with few exceptions--probably there are really no exceptions--possess the habit of indulging frequently in more or less regular or set performances, with or without sound, or composed of sound exclusively; and that these performances, which in many animals are only discordant cries and choruses, and uncouth, irregular motions, in the more aerial, graceful, and melodious kinds take immeasurably higher, more complex, and more beautiful forms. Among the mammalians the instinct appears almost universal; but their displays are, as a rule, less admirable than those seen in birds. There are some kinds, it is true, like the squirrels and monkeys, of arboreal habits, almost birdlike in their restless energy, and in the swiftness and certitude of their motions, in which the slightest impulse can be instantly expressed in graceful or fantastic action; others, like

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the Chinchillidae family, have greatly developed vocal organs, and resemble birds in loquacity; but mammals generally, compared with birds, are slow and heavy, and not so readily moved to exhibitions of the kind I am discussing.

The terrestrial dances, often very elaborate, of heavy birds, like those of the gallinaceous kind, are represented in the more volatile species by performances in the air, and these are very much more beautiful; while a very large number of birds--hawks, vultures, swifts, swallows, nightjars, storks, ibises, spoonbills, and gulls--circle about in the air, singly or in flocks. Sometimes, in serene weather, they rise to a vast altitude, and float about in one spot for an hour or longer at a stretch, showing a faint bird-cloud in the blue, that does not change its form, nor grow lighter and denser like a flock of starlings; but in the seeming confusion there is perfect order, and amidst many hundreds each swift- or slow-gliding figure keeps its proper distance with such exactitude that no two ever touch, even with the extremity of the long-wings, flapping or motionless:--such a multitude, and such miraculous precision in the endless curving motions of all the members of it, that the spectator can lie for an hour on his back without weariness watching this mystic cloud-dance in the empyrean.

The black-faced ibis of Patagonia, a bird nearly as large as a turkey, indulges in a curious mad performance, usually in the evening when feeding-time is over. The birds of a flock, while winging their way to the roosting-place, all at once seem possessed with frenzy, simultaneously dashing

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downwards with amazing violence, doubling about in the most eccentric manner; and when close to the surface rising again to repeat the action, all the while making the air palpitate for miles around with their hard, metallic cries. Other ibises, also birds of other genera, have similar aerial performances.

The displays of most ducks known to me take the form of mock fights on the water; one exception is the handsome and loquacious whistling widgeon of La Plata, which has a pretty aerial performance. A dozen or twenty birds rise up until they appear like small specks in the sky, and sometimes disappear from sight altogether; and at that great altitude they continue hovering in one spot, often for an hour or longer, alternately closing and separating; the fine, bright, whistling notes and flourishes of the male curiously harmonizing with the grave, measured notes of the female; and every time they close they slap each other on the wings so smartly that the sound can be distinctly heard, like applauding hand-claps, even after the birds have ceased to be visible.

The rails, active, sprightly birds with powerful and varied voices, are great performers; but owing to the nature of the ground they inhabit and to their shy, suspicious character, it is not easy to observe their antics. The finest of the Platan rails is the ypecaha, a beautiful, active bird about the size of the fowl. A number of ypecahas have their assembling place on a small area of smooth, level ground, just above the water, and hemmed in by dense rush beds. First, one bird among the rushes emits a powerful cry, thrice repeated; and this is a

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26?

note of invitation, quickly responded to by other birds from all sides as they hurriedly repair to the usual place. In a few moments they appear, to the number of a dozen or twenty, bursting from the rushes and running into the open space, and instantly beginning the performance. This is a tremendous screaming concert. The screams they utter have a certain resemblance to the human