within the tropics than in any other part of the globe, and a great
number of peculiar groups are found there which never extend into
temperate regions. Endless eccentricities of form, and extreme
richness of colour are its most prominent features; and these
are manifested in the highest degree in those equatorial lands
where the vegetation acquires its greatest beauty and its fullest
development. The causes of these essentially tropical features are
not to be found in the comparatively simple influence of solar light
and heat, but rather in the uniformity and permanence with which
these and all other terrestrial conditions have acted; neither
varying prejudicially throughout the year, nor having undergone any
important change for countless past ages. While successive glacial
periods have devastated the temperate zones, and destroyed most of
the larger and more specialized forms which during more favourable
epochs had been developed, the equatorial lands must always have
remained thronged with life; and have been unintermittingly subject
to those complex influences of organism upon organism, which seem the
main agents in developing the greatest variety of forms and filling
up every vacant place in nature. A constant struggle against the
vicissitudes and recurring severities of climate must always have
restricted the range of effective animal variation in the temperate
and frigid zones, and have checked all such developments of form
and colour as were in the least degree injurious in themselves,
or which co-existed with any constitutional incapacity to resist
great changes of temperature or other unfavourable conditions. Such
disadvantages were not experienced in the equatorial zone. The
struggle for existence as against the forces of nature was there
always less severe,--food was there more abundant and more regularly
supplied,--shelter and concealment were at all times more easily
obtained; and almost the only physical changes experienced, being
dependent on cosmical or geological changes, were so slow, that
variation and natural selection were always able to keep the teeming
mass of organisms in nicely balanced harmony with the changing
physical conditions. The equatorial zone, in short, exhibits to us
the result of a comparatively continuous and unchecked development
of organic forms; while in the temperate regions, there have been
a series of periodical checks and extinctions of a more or less
disastrous nature, necessitating the commencement of the work of
development in certain lines over and over again. In the one,
evolution has had a fair chance; in the other it has had countless
difficulties thrown in its way. The equatorial regions are then,
as regards their past and present life history, a more ancient
world than that represented by the temperate zones, a world in
which the laws which have governed the progressive development of
life have operated with comparatively little check for countless
ages, and have resulted in those infinitely varied and beautiful
forms--those wonderful eccentricities of structure, of function, and
of instinct--that rich variety of colour, and that nicely balanced
harmony of relations--which delight and astonish us in the animal
productions of all tropical countries.
IV.
HUMMING-BIRDS:
AS ILLUSTRATING THE LUXURIANCE OF TROPICAL NATURE.
Structure--Colours and Ornaments--Display of Ornaments by
the Male--Descriptive Names--The Motions and Habits of
Humming-birds--Food--Nests--Geographical Distribution and
Variation--Humming-birds of Juan Fernandez as illustrating
Variation and Natural Selection--The relations and affinities of
Humming-birds--How to determine doubtful affinities--Resemblances
of Swifts and Humming-birds--Differences between Sun-birds and
Humming-birds--Conclusion.
There are now about ten thousand different kinds of birds known to
naturalists, and these are classed in one hundred and thirty families
which vary greatly in extent, some containing a single species only,
while others comprise many hundreds. The two largest families are
those of the warblers, with more than six hundred, and the finches
with more than five hundred species, spread over the whole globe;
the hawks and the pigeons, also spread over the whole globe, number
about three hundred and thirty, and three hundred and sixty species
respectively; while the diminutive humming-birds, confined to one
hemisphere, consist of about four hundred different species. They
are thus, as regards the number of distinct kinds collected in a
limited area, the most remarkable of all the families of birds. It
may, however, very reasonably be asked, whether the four hundred
species of humming-birds above alluded to are really all distinct--as
distinct on the average as the ten thousand species of birds are
from each other. We reply that they certainly are perfectly distinct
species which never intermingle; and their differences do not consist
in colour only, but in peculiarities of form, of structure, and
of habits; so that they have to be classed in more than a hundred
distinct genera or systematic groups of species, these genera being
really as unlike each other as stonechats and nightingales, or as
partridges and blackcocks. The figures we have quoted, as showing
the proportion of birds in general to humming-birds, thus represent
real facts; and they teach us that these small and in some respects
insignificant birds, constitute an important item in the animal
life of the globe.
Humming-birds are, in many respects, unusually interesting and
instructive. They are highly peculiar in form, in structure, and
in habits, and are quite unrivalled as regards variety and beauty.
Though the name is familiar to every one, few but naturalists
are acquainted with the many curious facts in their history, or
know how much material they afford for admiration and study. It
is proposed, therefore, to give a brief and popular account of
the form, structure, habits, distribution, and affinities, of
this remarkable family of birds, as illustrative of the teeming
luxuriance of tropical nature, and as throwing light on some of
the most interesting problems of natural history.
_Structure._--The humming-birds form one compact family named
Trochilidæ. They are all small birds, the largest known being about
the size of a swallow, while the smallest are minute creatures whose
bodies are hardly larger than a humble-bee. Their distinguishing
features are excessively short legs and feet, very long and pointed
wings, a long and slender bill, and a long extensible tubular
tongue: and these characters are found combined in no other birds.
The feet are exceedingly small and delicate, often beautifully
tufted with down, and so short as to be hardly visible beyond the
plumage. The toes are placed as in most birds, three in front and
one behind, and have very strong and sharply curved claws; and the
feet serve probably to cling to a perch rather than to give any
movement to the body. The wings are long and narrow, but strongly
formed; and the first quill is the longest, a peculiarity found in
hardly any other birds but a few of the swifts. The bill varies
greatly in length, but is always long, slender, and pointed, the
upper mandible being the widest and lapping over the lower at each
side, thus affording complete protection to the delicate tongue the
perfect action of which is essential to the bird’s existence. The
humming-bird’s tongue is very long, and is capable of being greatly
extended beyond the beak and rapidly drawn back, by means of muscles
which are attached to the hyoid or tongue-bones, and bend round
over the back and top of the head to the very forehead, just as in
the woodpeckers. The two blades or laminæ, of which the tongues
of birds usually seem to be formed, are here greatly lengthened,
broadened out, and each rolled up; so as to form a complete double
tube connected down the middle, and with the outer edges in contact
but not united. The extremities of the tubes are, however, flat
and fibrous. This tubular and retractile tongue enables the bird to
suck up honey from the nectaries of flowers, and also to capture
small insects; but whether the latter pass down the tubes, or are
entangled in the fibrous tips and thus draw back into the gullet,
is not known. The only other birds with a similar tubular tongue
are the sun-birds of the East, which however, as we shall presently
explain, have no affinity whatever with the humming-birds.
_Colours and Ornaments._--The colours of these small birds are
exceedingly varied and exquisitely beautiful. The basis of the
colouring may be said to be green, as in parrots; but whereas in
the latter it is a silky green, in humming-birds it is always
metallic. The majority of the species have some green about them,
especially on the back; but in a considerable number rich blues,
purples, and various shades of red are the prevailing tints. The
greater part of the plumage has more or less of a metallic gloss,
but there is almost always some part which has an intense lustre, as
if actually formed of scales of burnished metal. A gorget, covering
the greater part of the neck and breast, most commonly displays
this vivid colour; but it also frequently occurs on the head, on
the back, on the tail-coverts above or below, on the upper surface
of the tail, on the shoulders or even the quills. The hue of every
precious stone and the lustre of every metal is here represented;
and such terms as topaz, amethyst, beryl, emerald, garnet, ruby,
sapphire; golden, golden-green, coppery, fiery, glowing, iridescent,
refulgent, celestial, glittering, shining, are constantly used to
name or describe the different species.
No less remarkable than the colours are the varied developments
of plumage with which these birds are adorned. The head is often
crested in a variety of ways; either a simple flat crest, or with
radiating feathers, or diverging into two horns, or spreading
laterally like wings, or erect and bushy, or recurved and pointed
like that of a plover. The throat and breast are usually adorned
with broad scale-like feathers, or these diverge into a tippet,
or send out pointed collars, or elegant frills of long and narrow
plumes tipped with metallic spots of various colours. But the tail
is even a more varied and beautiful ornament, either short and
rounded, but pure white or some other strongly contrasted tint; or
with short pointed feathers forming a star; or with the three outer
feathers on each side long and tapering to a point; or larger, and
either square, or round, or deeply forked, or acutely pointed; or
with the two middle feathers excessively long and narrow; or with
the tail very long and deeply forked, with broad and richly-coloured
feathers; or with the two outer feathers wire-like and having
broad spoon-shaped tips. All these ornaments, whether of the head,
neck, breast or tail, are invariably coloured in some effective or
brilliant manner, and often contrast strikingly with the rest of
the plumage. Again, these colours often vary in tint according to
the direction in which they are seen. In some species they must
be looked at from above, in others from below; in some from the
front, in others from behind, in order to catch the full glow of
the metallic lustre; hence, when the birds are seen in their native
haunts, the colours come and go and change with their motions, so
as to produce a startling and beautiful effect.
The bill differs greatly in length and shape, being either straight
or gently curved, in some species bent like a sickle, in others
turned up like the bill of the avoset. It is usually long and
slender, but in one group is so enormously developed that it is
nearly the same length as the rest of the bird. The legs, usually
little seen, are in some groups adorned with globular tufts of white,
brown, or black down, a peculiarity possessed by no other birds. The
reader will now be in a position to understand how the four hundred
species of humming-birds may be easily distinguished, by the varied
combinations of the characters here briefly enumerated, together
with many others of less importance. One group of birds will have a
short round tail, with crest and long neck-frill; another group a
deeply-forked broad tail, combined with glowing crown and gorget;
one is both bearded and crested; others have a luminous back and
pendent neck-plumes; and in each of these groups the species will
vary in combinations of colour, in size, and in the proportions of
the ornamental plumes, so as to produce an unmistakable distinctness;
while, without any new developments of form or structure, there
is room for the discovery of hundreds more of distinct kinds of
humming-birds.
_Descriptive Names._--The name we usually give to the birds of this
family is derived from the sound of their rapidly-moving wings, a
sound which is produced by the largest as well as by the smallest
member of the group. The Creoles of Guiana similarly call them
Bourdons or hummers. The French term, Oiseau-mouche, refers to their
small size; while Colibri is a native name which has come down
from the Carib inhabitants of the West Indies. The Spaniards and
Portuguese call them by more poetical names, such as Flower-peckers,
Flower-kissers, Myrtle-suckers--while the Mexican and Peruvian
names show a still higher appreciation of their beauties, their
meaning being rays of the sun, tresses of the day-star, and other
such appellations. Even our modern naturalists, while studying
the structure and noting the peculiarities of these living gems,
have been so struck by their inimitable beauties that they have
endeavoured to invent appropriate English names for the more
beautiful and remarkable genera. Hence we find in common use such
terms as Sun-gems, Sun-stars, Hill-stars, Wood-stars, Sun-angels,
Star-throats, Comets, Coquettes, Flame-bearers, Sylphs, and Fairies;
together with many others derived from the character of the tail
or the crests.
_The Motions and Habits of Humming-birds._--Let us now consider
briefly, the peculiarities of flight, the motions, the food,
the nests, and general habits of the humming-birds, quoting the
descriptions of those modern naturalists who have personally
observed them. Their appearance, remarks Professor Alfred Newton,
is entirely unlike that of any other bird:--“One is admiring some
brilliant and beautiful flower, when between the blossom and one’s
eye suddenly appears a small dark object, suspended as it were
between four short black threads meeting each other in a cross. For
an instant it shows in front of the flower; again another instant,
and emitting a momentary flash of emerald and sapphire light, it
is vanishing, lessening in the distance, as it shoots away, to a
speck that the eye cannot take note of.” Audubon observes that the
Ruby Humming-birds pass through the air in long undulations, but
the smallness of their size precludes the possibility of following
them with the eye further than fifty or sixty yards, without great
difficulty. A person standing in a garden by the side of a common
althæa in bloom, will hear the humming of their wings and see the
little birds themselves within a few feet of him one moment, while
the next they will be out of sight and hearing. Mr. Gould, who
visited North America in order to see living humming-birds while
preparing his great work on the family, remarks, that the action
of the wings reminded him of a piece of machinery acted upon by a
powerful spring. When poised before a flower, the motion is so rapid
that a hazy semicircle of indistinctness on each side of the bird
is all that is perceptible. Although many short intermissions of
rest are taken, the bird may be said to live in the air--an element
in which it performs every kind of evolution with the utmost ease,
frequently rising perpendicularly, flying backward, pirouetting
or dancing off, as it were, from place to place, or from one part
of a tree to another, sometimes descending, at others ascending.
It often mounts up above the towering trees, and then shoots off
like a little meteor at a right angle. At other times it gently
buzzes away among the little flowers near the ground; at one moment
it is poised over a diminutive weed, at the next it is seen at a
distance of forty yards, whither it has vanished with the quickness
of thought.
The Rufous Flame-bearer, an exquisite species found on the west
coast of North America, is thus described by Mr. Nuttall:--“When
engaged in collecting its accustomed sweets, in all the energy of
life, it seemed like a breathing gem, a magic carbuncle of flaming
fire, stretching out its glorious ruff as if to emulate the sun
itself in splendour.” The Sappho Comet, whose long forked tail
barred with crimson and black renders it one of the most imposing
of humming-birds, is abundant in many parts of the Andes; and Mr.
Bonelli tells us that the difficulty of shooting them is very great
from the extraordinary turns and evolutions they make when on the
wing; at one instant darting headlong into a flower, at the next
describing a circle in the air with such rapidity that the eye,
unable to follow the movement, loses sight of the bird until it again
returns to the flower which at first attracted its attention. Of
the little Vervain humming-bird of Jamaica, Mr. Gosse writes:--“I
have sometimes watched with much delight the evolutions of this
little species at the Moringa-tree.[13] When only one is present,
he pursues the round of the blossoms soberly enough. But if two
are at the tree, one will fly off, and suspend himself in the air
a few yards distant; the other presently starts off to him, and
then, without touching each other, they mount upwards with strong
rushing wings, perhaps for five hundred feet. They then separate,
and each starts diagonally towards the ground like a ball from a
rifle, and wheeling round comes up to the blossoms again as if it
had not moved away at all. The figure of the smaller humming-birds
on the wing, their rapidity, their wavering course, and their
whole manner of flight are entirely those of an insect.” Mr. Bates
remarks, that on the Amazons during the cooler hours of the morning
and from four to six in the afternoon humming-birds are to be seen
whirring about the trees by scores; their motions being unlike
those of any other birds. They dart to and fro so swiftly that the
eye can scarcely follow them, and when they stop before a flower
it is only for a few moments. They poise themselves in an unsteady
manner, their wings moving with inconceivable rapidity, probe the
flower, and then shoot off to another part of the tree. They do
not proceed in that methodical manner which bees follow, taking
the flowers seriatim, but skip about from one part of the tree to
another in the most capricious way. Mr. Belt remarks on the excessive
rapidity of the flight of the humming-bird giving it a sense of
security from danger, so that it will approach a person nearer than
any other bird, often hovering within two or three yards (or even
one or two feet) of one’s face. He watched them bathing in a small
pool in the forest, hovering over the water, turning from side to
side by quick jerks of the tail; now showing a throat of gleaming
emerald, now shoulders of glistening amethyst; then darting beneath
the water, and rising instantly, throw off a shower of spray from
their quivering wings, and again fly up to an overhanging bough
and commence to preen their feathers. All humming-birds bathe on
the wing, and generally take three or four dips, hovering between
times about three or four inches above the surface. Mr. Belt also
remarks on the immense numbers of humming-birds in the forests, and
the great difficulty of seeing them; and his conclusion is, that in
the part of Nicaragua where he was living they equalled in number
all the rest of the birds together, if they did not greatly exceed
them.
[13] Sometimes called the horse-radish tree. It is the _Moringa
pterygosperma_, a native of the East Indies, but commonly cultivated
in Jamaica. It has yellow flowers.
The extreme pugnacity of humming-birds has been noticed by all
observers. Mr. Gosse describes two meeting and chasing each other
through the labyrinths of twigs and flowers till, an opportunity
occurring, the one would dart with seeming fury upon the other,
and then, with a loud rustling of their wings, they would twirl
together, round and round, till they nearly came to the earth.
Then they parted, and after a time another tussle took place. Two
of the same species can hardly meet without an encounter, while in
many cases distinct species attack each other with equal fury. Mr.
Salvin describes the splendid Eugenes fulgens attacking two other
species with as much ferocity as its own fellows. One will knock
another off its perch, and the two will go fighting and screaming
away at a pace hardly to be followed by the eye. Audubon says they
attack any other birds that approach them, and think nothing of
assaulting tyrant-shrikes and even birds of prey that come too near
their home.
_Display of Ornaments by the Male._--It is a well-known fact, that
when male birds possess any unusual ornaments, they take such
positions or perform such evolutions as to exhibit them to the
best advantage while endeavouring to attract or charm the females
or in rivalry with other males. It is therefore probable that the
wonderfully varied decorations of humming-birds, whether burnished
breast-shields, resplendent tail, crested head, or glittering
back, are thus exhibited; but almost the only actual observation
of this kind is that of Mr. Belt, who describes how two males of
the Florisuga mellivora displayed their ornaments before a female
bird. One would shoot up like a rocket, then, suddenly expanding
the snow-white tail like an inverted parachute, slowly descend in
front of her, turning round gradually to show off both back and
front. The expanded white tail covered more space than all the rest
of the bird, and was evidently the grand feature of the performance.
Whilst one was descending the other would shoot up and come slowly
down expanded.[14]
[14] _The Naturalist in Nicaragua_, p. 112.
_Food._--The food of humming-birds has been a matter of much
controversy. All the early writers down to Buffon believed that they
lived solely on the nectar of flowers; but since that time every
close observer of their habits maintains that they feed largely,
and in some cases wholly, on insects. Azara observed them on the
La Plata in winter taking insects out of the webs of spiders at a
time and place where there were no flowers. Bullock, in Mexico,
declares that he saw them catch small butterflies, and that he found
many kinds of insects in their stomachs. Waterton made a similar
statement. Hundreds and perhaps thousands of specimens have since
been dissected by collecting naturalists, and in almost every
instance their stomachs have been found full of insects, sometimes,
but not generally, mixed with a proportion of honey. Many of them in
fact may be seen catching gnats and other small insects just like
flycatchers, sitting on a dead twig over water, darting off for a
time in the air, and then returning to the twig. Others come out
just at dusk, and remain on the wing, now stationary, now darting
about with the greatest rapidity, imitating in a limited space the
evolutions of the goatsuckers, and evidently for the same end and
purpose. Mr. Gosse also remarks:--“All the humming-birds have
more or less the habit, when in flight, of pausing in the air and
throwing the body and tail into rapid and odd contortions. This is
most observable in the Polytmus, from the effect that such motions
have on the long feathers of the tail. That the object of these
quick turns is the capture of insects, I am sure, having watched
one thus engaged pretty close to me. I observed it carefully, and
distinctly saw the minute flies in the air which it pursued and
caught, and heard repeatedly the snapping of the beak. My presence
scarcely disturbed it, if at all.”
There is also an extensive group of small brown humming-birds,
forming the subfamily Phaëthornithinæ, which rarely or never visit
flowers, but frequent the shady recesses of the forest, where
they hunt for minute insects. They dart about among the foliage,
and visit in rapid succession every leaf upon a branch, balancing
themselves vertically in the air, passing their beaks closely over
the under-surface of each leaf, and thus capturing, no doubt, any
small insects that may lurk there. While doing this, the two long
feathers of the tail have a vibrating motion, serving apparently
as a rudder, to assist them in performing the delicate operation.
Others search up and down stems and dead sticks in the same manner,
every now and then picking off something, exactly as a bush-shrike
or a tree-creeper does, with the difference that the humming-bird
is constantly on the wing; while the remarkable Sickle-bill is said
to probe the scale-covered stems of palms and tree-ferns to obtain
its insect food.