The First Bird.
"And let Fowl fly above the earth; with wings
Displayed in the open firmanent of heaven."--_Milton._
The ancestors of birds--The first known bird and its many remarkable
features--The gradual evolution of the birds of to-day.
Sooner or later all bird-lovers find
themselves pondering over the problem of the origin of birds: how they
evolved their peculiar covering of feathers: what was the fashion of
the original arm and hand out of which the wing was fashioned: and
finally, whence have the birds been derived?
Since these pages are avowedly devoted to the subject of Flight, any
attempt to summarize the state of our knowledge on these aspects of the
history of birds would be in the nature of a trespass on the space, of
necessity limited, which even a cursory survey of flight demands.
Let it suffice, then, to say, that birds are descended from reptiles.
The skeleton of modern birds bears undubitable testimony of this. For
we have the evidence furnished us by the remains of two remarkable
skeletons, belonging to that very wonderful reptile-like bird,
Archæopteryx.
Only two skeletons of this wonderful bird are known, and they were
obtained, many years ago, from the Solenhofen, or Lithographic slates
of Bavaria. The wing and tail-feathers are as perfectly developed as
in modern birds. But these precious fossils present two characters
which have long since been lost by birds. The first of these is the
presence of well developed teeth in the jaws. The birds of to-day have
horny beaks. The teeth bespeak the reptile. The second is the long,
tapering tail, which is composed of a series of cylindrical bones,
forming a lizard-like appendage. But each bone, be it noted, supported
a pair of stiff, tail-quills, so that the tail of this ancient bird,
in its general appearance, differs in a very striking way from that of
a modern bird, wherein these feathers seem all to spring from a common
base, fan-wise. But as a matter of fact this appearance is deceptive,
for the large bone, or "pygostyle" which supports the tail feathers
of the adult, is found, in the embryo, to be made up of a series of
separate pieces, agreeing in number with those of the tail of the
fossil ancestor, Archæopteryx. Each of these separate bones has, in
fact, in the course of the ages, been shortened up to the condition of
mere discs; and this "telescoping" of the vertebræ has brought the once
separated feathers close up, so that their bases lie packed in like the
spokes of a fan. As a result, a much more efficient tail for the needs
of flight has come into being. And the tail, it must be remembered,
plays, especially in some birds, an important part. But this is not
all. We have now to consider the wing. In all essentials this agrees
with that of living birds. And this agreement is strikingly close when
it is compared with the embryonic and early nestling stages. A detailed
account of these resemblances, and differences, would be out of place
here. Suffice it to say that its closest modern counterparts are to
be found in the wing of the nestling of that strange South American
bird, the Hoatzin, and the "Game-birds," such as of a young pheasant,
or a young fowl. The evidence these can furnish in this matter of the
evolution of the birds wing will be found in Chapter VI. For the moment
it will be more profitable to discuss the broad outlines of the origin
of flight, so far as this is possible.
On this theme there are, as might be supposed, many opinions--some of
them bearing little relation to fact.
The feet of Archæopteryx, it is important to remember, bear a very
extraordinary likeness to the feet of a "perching" bird, say that of a
crow. They are without any semblance of doubt, the feet of a bird which
lived in trees. Archæopteryx, then, was an arboreal bird. And this
being so, the most reasonable hypothesis of the origin of flight is
that it developed out of "gliding" movements, made for the purpose of
passing from the topmost branches of one tree to the lower branches of
another, after the mode of the "flying-squirrels," and "flying-lemur"
of to-day. The wing, at this primitive stage of its evolution, was
even then, probably, a three-fingered limb, provided with a broad
fringe of incipient feathers along its hinder border. At this stage
the body would have been less bird-like than that of Archæopteryx, and
have been still more like that of the ancestral reptilian stock from
which the birds have sprung. That feathers are, so to speak, glorified
reptilian scales cannot be certainly demonstrated, but men of Science
are generally agreed that this was their origin.
By the time that Archæopteryx had come into being, true flight had been
arrived at, though probably it could not have been long sustained.
As these primitive birds increased in numbers, and spread from the
woodlands to the open country, life became more strenuous. New
enemies had to be evaded, longer journeys had to be made for food.
Only the very best performers on the wing could survive, and thus,
in each generation, the failures would be speedily weeded out, while
competition among the survivors would raise the standard. We see the
result of this "struggle for existence" in the many and varied types of
wings, and of flight, which are presented in this book.
[Illustration: Archæopteryx.
Pterodactyles.]