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Ch. 18: The Woodhewer Family

_(Dendrocolaptidae.)_


The South American Tree-creepers, or Woodhewers, as they are sometimes
called, although confined exclusively to one continent, their range
extending from Southern Mexico to the Magellanic islands, form one of
the largest families of the order Passeres; no fewer than about two
hundred and ninety species (referable to about forty-six genera) having
been already described. As they are mostly small, inconspicuous,
thicket-frequenting birds, shy and fond of concealment to excess, it is
only reasonable to suppose that our list of this family is more
incomplete than of any other family of birds known. Thus, in the
southern Plata and north Pata-gonian districts, supposed to be
exhausted, where my observations have been made, and where, owing to the
open nature of the country, birds are more easily remarked than in the
forests and marshes of the tropical region, I have made notes on the
habits of five species, of which I did not preserve specimens, and
which, as far as I know, have never been described and named. Probably
long before the whole of South America has been "exhausted," there will
be not less than four to five hundred Dendrocolaptine species known. And
yet with the exception of that dry husk of knowledge, concerning size,
form and colouration, which classifiers and cataloguers obtain from
specimens, very little indeed--scarcely anything, in fact--is known
about the Tree-creepers; and it would not be too much to say that there
are many comparatively obscure and uninteresting species in Europe, any
one of which has a larger literature than the entire Tree-creeper
family. No separate work about these birds has seen the light, even in
these days of monographs; but the reason of this comparative neglect is
not far to seek. In the absence of any knowledge, except of the most
fragmentary kind, of the life-habits of exotic species, the
monograph-makers of the Old World naturally take up only the most
important groups--i.e. the groups which most readily attract the
traveller's eye with their gay conspicuous colouring, and which have
acquired a wide celebrity. We thus have a succession of splendid and
expensive works dealing separately with such groups as woodpeckers,
trogons, humming-birds, tanagers, king-fishers, and birds of paradise;
for with these, even if there be nothing to record beyond the usual
dreary details and technicalities concerning geographical distribution,
variations in size and markings of different species, &c., the little
interest of the letter-press is compensated for in the accompanying
plates, which are now produced on a scale of magnitude, and with so
great a degree of perfection, as regards brilliant colouring, spirited
attitudes and general fidelity to nature, that leaves little further
improvement in this direction to be looked for. The Tree-creepers, being
without the inferior charm of bright colour, offer no attraction to the
bird-painter, whose share in the work of the pictorial monograph is, of
course, all-important. Yet even the very slight knowledge we possess of
this family is enough to show that in many respects it is one richly
endowed, possessing characters of greater interest to the student of the
instincts and mental faculties of birds, than any of |the gaily-tinted
families I have mentioned.

There is, in the Dendrocolaptidae, a splendid harvest for future
observers of the habits of South American birds: some faint idea of its
richness may perhaps be gathered from the small collection of the most
salient facts known to us about them I have brought together and put in
order in this place. And I am here departing a little from the plan
usually observed in this book, which is chiefly occupied with matters of
personal knowledge, seasoned with a little speculation; but in this case
I have thought it best to supplement my own observations with those of
others [Footnote: Azara; D'Orbigny; Darwin; Bridges; Frazer; Leotaud;
Gaumer; Wallace; Bates; Cunningham; Stolzmann; Jelski; Durnford; Gibson;
Burrows; Doering; White, &c.] who have collected and observed birds in
South America, so as to give as comprehensive a survey of the family as
I could.

It is strange to find a Passerine family, numerous as the Tree-creepers,
uniformly of one colour, or nearly so; for, with few exceptions, these
birds have a brown plumage, without a particle of bright colour. But
although they possess no brilliant or metallic tints, in some species,
as we shall see, there are tints approaching to brightness.
Notwithstanding this family likeness in colour, any person, not an
ornithologist, looking at a collection of specimens comprising many
genera, would hear with surprise and almost incredulity that they all
belonged to one family, so great is the diversity exhibited in their
structure. In size they vary from species smaller than the
golden-crested wren to others larger than the woodcock; but the
differences in size are as nothing compared with those shown in the form
of the beak. Between the minute, straight, conical, tit-like beaks of
the Laptasthenura--a tit in appearance and habits--and the extravagantly
long, sword-shaped bill of Nasica, or the excessively attenuated,
sickle-shaped organ in Xiphorynchus, the divergence is amazing, compared
with what is found in other families; while between these two extremes
there is a heterogeneous assemblage of birds with beaks like creepers,
nuthatches, finches, tyrant-birds, woodpeckers, crows, and even curlews
and ibises. In legs, feet and tails, there are corresponding
differences. There are tails of all lengths and all forms; soft and
stiff, square, acuminated, broad and fan-like, narrow and spine-like,
and many as in the woodpeckers, and used as in that bird to support the
body in climbing. An extremely curious modification is found in
Sittosoma: the tail-feathers in this genus are long and graduated, and
the shafts, projecting beyond the webs at the ends, curve downwards and
form stiff hooks. Concerning the habits of these birds, it has only been
reported that they climb on the trunks of trees: probably they are able
to run vertically up or down with equal facility, and even to suspend
themselves by their feather-hooks when engaged in dislodging insects.
Another curious variation is found in Sylviothorhynchus, a small
wren-like bird and the 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 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 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 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, 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, 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 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 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 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 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 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 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 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 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 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 Anumbius, 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 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, including 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 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, 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."

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 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 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.

W. H. Hudson