THE UNDERLYING IDEA
We have seen in the preceding chapters how the idea of evolution
worked its way through the minds of men. Man after man got a glimpse
of the idea, even among the ancient philosophers. But no one could
speak convincingly on the subject before modern times, when a wider
acquaintance with the animal world gave a body of facts on which it
was safe to base conclusions. Even then the idea eluded men, until
there came a worker trained by a long voyage around the world in which
he had nothing to do except to study nature. He finally gathered in
his mind material sufficient to convince himself not only of the truth
of evolution but of the process by which this evolution was brought
about. Every scientific principle is simple in its basal idea. In
actual life the action of the principle may be so bound up with others
as to need a skillful mind for its detection. But under all the
complexities and modifications, like a silver thread woven into a
cloth, runs the basal idea. Until a master has detected it the
presence of it may be unsuspected. But once discovered and expounded,
thereafter anyone may follow out its workings. So it is with the
Darwinian idea of selection. It waited long for a discoverer, but,
once found, we cannot but wonder why men did not see it earlier, it is
so simple.
Mr. Darwin's mind, while slow and cautious, had a wonderful
perseverance. When he had finished his work he had not only given a
clear account of the process of evolution, but he had foreseen almost
all the valid objections that were afterward to be brought against his
theory. Some of them he had explained quite fully; of others he
indicated a possible explanation; of still other questions he
confessed that as yet they were not plain. But the whole theory is so
simple in its fundamental ideas that it has completely revolutionized
the whole aspect of modern biology and, indeed, of modern thinking in
many lines.
There are four underlying conceptions, each simple in itself, which
must be clearly perceived before one can understand Mr. Darwin's
theory of "Natural Selection." The first of these is known under the
name of Heredity. It is a matter of common observation that every
animal or plant produces offspring after its own kind. Under no
conditions would we expect a duck to lay an egg from which could hatch
anything but a duck. No Plymouth Rock chicken mated with another of
her own kind will ever lay an egg that will produce a Rhode Island
Red. We may believe that the dog has descended from some form of wolf,
but it is not meant that at any particular time in the past any wolf
mated with a wolf ever produced pups that were anything but wolves.
Why this should be so is one of the most profound problems of biology.
Nothing but the fact that the process has gone on under our eyes for
so long a time could blind us to its marvelous character. To open the
egg of a chicken and examine it by the most refined methods known to
science is to find in it absolutely nothing that could be by the
widest stretch of the imagination considered anything like a chicken.
The biologist who has examined such eggs before and knows them in all
stages of the process may recognize in an egg which had been incubated
for a short time something which his previous experience tells him
will become a chicken. But it has not the faintest resemblance to a
chicken until later in its development. In early spring one may gather
pond snails from any country stream and place them in an aquarium. The
change from the cold water on the outside to the warmer water of the
aquarium and the temperate climate of the room hastens the process
which in the stream would not take place until later. In a short time
one may find fastened to the glass side of the aquarium the little
mass of transparent jelly which surrounds and protects the delicate
eggs of these creatures. Fastened as they are it is easy to direct a
magnifying glass so as to observe the change which goes on within
these transparent eggs. It is even possible to apply a microscope in
such a way as to watch the transformation under the low power of the
glass. At first the eggs are as clear as water, having at the center a
slightly yellowish spot. This central mass divides and subdivides
until the separated sections grow so small and numerous as to lose
individuality. Then the mass begins to press out here and dent in
there. After a little while a double line of fine, hairlike
projections runs around the creature. These hairs wave in such fashion
as to make the embryo snail revolve slowly in its egg. A little later
and swellings become more pronounced over the surface. One side
flattens; the rotary motion stops; eyes appear at the front of the
animal; a hump on the back begins to be covered with a shell, and the
little creatures, pushing from the jelly, start their life journey on
the side of the aquarium. Why did it happen? How did it happen? Here
we have seen creation at work. Here surely the hand of the Creator is
working in the only sense in which the Creator may be properly said to
have a hand. How the history of the substance out of which the egg was
produced provides for the future development of that egg no man has
yet clearly said. This is not to say that we shall never know, still
less is it to say that this can never be known. Ralph Waldo Emerson
has said that there is no question propounded by the order of nature
which the order of nature will not at some time solve. If he is right,
and I believe he is, we shall at some time know how it is that this
egg produces this snail. But, as I said before, nothing but the
frequency with which the process goes on under our eyes could possibly
blind us to the marvel of it.
The regularity with which each animal reproduces its kind is no more
surprising than the faithfulness of that reproduction. Some of our
birds have wonderful markings on their plumage. It is astonishing to
see with what fidelity the feather of a bird may reproduce the
corresponding feather of its parent. It will occur to everyone how, in
the human family to which he belongs, there is some little peculiarity
which, while not appearing in every member of the family, when it does
appear is remarkably uniform. It may be only the droop of an eyelid,
it may be a tendency to lift one side of the lip more than the other,
it may be the peculiar shape of a certain tooth in the set, and yet
when it appears it comes with astonishing similarity in all who
possess it. So much for the principle of Heredity.
The second great underlying idea is known by the name of Variation. We
have just been dwelling on the regularity with which parents produce
offspring like themselves. We must now draw attention to the fact
that, while it is true animals must absolutely belong to the same
genus or species, even to the same variety, none the less no animal is
exactly like his parents. Furthermore, in a group of animals produced
at the same time from the same parent each one will have at least some
small point in which he differs from every other one in the group. Two
animals may look alike at first to the undiscerning eye, but a keen
analysis of the measurements of the various parts of their bodies will
show distinct differences. This is quite as true among lower animals.
A toad may lay a double string of four hundred eggs which may be
fertilized by the same male at the same time. These eggs may develop
into tadpoles in the same pool not over a foot square. Within a few
weeks these little toads may have gained their legs, lost their tails,
and all may have left the water and taken to the ground upon the same
day. Already the careful observer will notice differences among them.
Some are larger than others, having grown more rapidly even though
their surroundings were exactly the same; others are more skillful in
their peculiar method of throwing the tongue at an insect they wish to
catch. Still others will be differently colored. They might be
arranged to show a considerable gradation between the lightest and the
darkest of the group, though there may not be anywhere in the row a
considerable gap. It is variation in animals of the same parentage and
same surroundings which in the mind of Mr. Darwin made evolution
possible. He always favored the idea that it was the continuous
accumulation of these small variations that finally produced the
profound changes which mark the new species. He admitted the
possibility of the occasional appearance of those more distinct leaps
in variation on which the present school of mutationists so strongly
insists; but he believed them to be less influential, in the general
trend of evolution, than the slower but much more frequent variations.
One of the most complicated and perplexing problems in the biology of
to-day is the question of the origin of these variations. It is quite
as hard to understand as is the method by which animals produce their
own kind. No problem is being more earnestly studied. Suppositions we
have in considerable number, and two of these at least may reasonably
be mentioned. We will consider first the less certain theory. There is
nothing in the egg that in the remotest degree resembles its parent.
The old idea that every acorn had in it a miniature oak which only
needed to unfold itself, or that the hen's egg had within it a
miniature chick which only needed the warming process in order to make
it evident, could not possibly survive the invention of the
microscope. We may not, and we certainly do not, know everything that
is in one of these eggs, but we do know most certainly that what is
there has no resemblance to what it will be in time. The biologist
finds in the nucleus or central core of every growing and reproducing
cell certain minute bodies which Weissmann believes do much to
determine the growth of the rest of the cell. He believes also that
there are many more such "determinants" than are necessary for the
reproduction of the cell. Each of these determinants may be fitted to
produce slightly different results, but what decides which of them
shall have its own way is quite uncertain. It may be that one
determinant happens to be more favorably placed than others in the
cell and that it has consequently secured more of the nourishment that
comes to the cell in the blood of its parent. If this is true it would
certainly be favored in the competition. We are becoming quite certain
that whatever variations arise really start in the egg. The simplest
conception as to the cause of variation would seem to be varied
experience. One man trains his brain, another his hand; and in each
case the organ so trained develops. But science is strongly of the
mind that such influence does not reach the next generation.
A musician may have taught his fingers to be nimble; may have given
them speed of motion and precision in their action. No child of his
born after he acquired this wonderful facility of execution is any
more likely to be a skilled musician than a child born before he had
ever practiced enough to be anything more than a crude performer.
Science is nearly certain that his children are just as likely to be
talented along musical lines if he himself never had become a
musician, simply because he had it in him to be a musician. In other
words, they may inherit the talent which he developed, but they
inherited it not because he developed it, but because it was in him to
be developed. This is in accordance with the famous principle that
there is no inheritance of acquired characters. We shall touch this
question a little more fully in a later chapter, in speaking of the
development of the evolution theory since Darwin's time.
If we are right in this matter, and we certainly are nearly right,
variation must take place for the most part in the germ. These
variations may not show until the animal has grown up, but they must
have taken place among the determinants in the germ cell or they would
not reappear in subsequent generations.
There is another process by which new variations may arise and which
is more easily understood. It is the method of double parentage. The
Barred Plymouth Rock chicken had its origin in such a double ancestry.
The one parent was a Black Java whose color has disappeared entirely
in the cross, but whose single comb with its few large points comes
out clearly in the newly produced fowl. The other parent was a Barred
Dominique. It is to this parent that the Plymouth Rock owes the
interesting cross markings on its feathers. The comb on the head of
the Barred Dominique is of the type known as the rose-comb, having
many rows of slight projections. This has completely disappeared from
the Plymouth Rock fowls. I am told that the skilled chicken fancier
can tell, concerning many points in this fowl, to which of the crossed
ancestors each quality is due. To a certain extent it is undoubtedly
true that here we have the secret of the origin of many of those
interesting people whom we are pleased to call geniuses. They may not
possess any qualities not clearly discernible in various of their near
ancestors, but in them we find what we, for the lack of a better
understanding, call chance combination in one individual of the finer
qualities of many ancestors, and this individual is so placed in life
as to have these qualities developed and strengthened.
Charles Darwin, humanly speaking, may be accounted for as the happy
combination of a double heredity and a favorable environment. He
inherited the scientific inclinations of his grandfather, Erasmus
Darwin, and the patient, sturdy honesty of his other grandfather,
Josiah Wedgwood. These developed under the stimulus of the long
five-year voyage, face to face with the world of nature. This happy
complex produced the master biologist. To believe that he came about
purely by chance requires a great stretch of the imagination. "There's
a divinity that shapes our ends."
We have endeavored to make clear two of the basal ideas underlying
evolution. One of these is responsible for the continued production of
animals or plants of the same kind, preventing the world from becoming
a wild kaleidoscopic and fantastic dream. Heredity is the conservative
force of nature. The other idea underlies the development of new
departures which keep the world from being a dull, dead, unending
repetition of the same monotonous material. Variation is the
progressive tendency in nature.
The third basal idea is that of Multiplication. Animals and plants
multiply; they do not simply increase, they increase in a geometrical
ratio. Anyone who has worked out one of these geometrical ratios knows
how wondrously they mount up. There is an old familiar story of the
blacksmith who asked the price at which the stranger would sell the
horse he was shoeing. The owner of the horse replied that, if the
blacksmith would give him one penny for the first nail he drove into
the shoe, two for the second, four for the third, and so on, he might
have the horse. No hundred horses in the world taken together have
ever brought such a price as the blacksmith would have had to pay for
the animal on which he was working. This is no circumstance to the
awful story of what would happen to the earth if any animal could
multiply unrestricted. The usual number of eggs laid by a mother robin
for a single brood is four, and she may produce two broods in one
season. This would mean that the original pair had produced eight
offspring, four times their own number. If we can imagine these mating
the next year and producing their kind in the same proportion; and, if
we further suppose that each robin needs a space one hundred feet
square from which to gather his food, we realize the astonishing fact
that in fifteen years every patch one hundred feet square in
Pennsylvania and New York would each have its resident robin, while
the following season would find a robin on every similar patch from
Maine to the Carolinas. Of course this could never happen, this is
simply what would happen if all the robins could grow to maturity and
reproduce at the normal ratio. But the robin is a comparatively slow
producer.
Our turtles are more prolific. Twenty eggs would probably not be an
unusual number. If we could imagine a turtle to live in the sea and to
produce at this rate; and, if each turtle should need as much room
each way as the robin, and a depth of water equal to its width, before
the robins had spread over New York and Pennsylvania the turtles would
have filled all the seas of the globe. Frogs are even more remarkable
in this respect. Two hundred eggs is not an uncommon number. If each
frog required a space twenty-five feet square on which to subsist, the
entire earth would be more than covered with them within six years. It
is ludicrous to think of such numbers, especially when we realize the
hundreds of thousands of kinds of animals there are in the world, each
of which is also multiplying, and it becomes evident at once that only
an infinitely small proportion of all these creatures can possibly
survive. This, then, is multiplication.
Here comes into play the fourth basal idea in Mr. Darwin's
explanation. This is the part of Selection. When man produces new
varieties of animals he does it by picking out from his flocks or his
herds such as conform most nearly to his idea of what is desirable.
These he mates, and from their progeny he selects the ones that suit
him best. Generation by generation he gets his domesticated animals to
conform more nearly to the standard of his desires. Natural selection
works in exactly similar fashion. Of all the eggs that are produced by
the animals at large in nature an overwhelming proportion never
develop at all. They dry up, are eaten by their enemies, find no
suitable place or time for development and decay, or are overtaken by
some other calamity. Of the animals which emerge from the remainder an
overwhelming majority come to an untimely end within the first few
days of life. Each has countless enemies which prey upon him, and
these have scarcely devoured him before they themselves become the
prey of some stronger creature. Until Mr. Darwin gave us his elemental
idea it was taken for granted that it was a matter of pure accident
which survived and which yielded in the struggle and cares of life. It
was Darwin who showed us that in this tremendous struggle against
those of his own kind in the search for the same food, against the
elements, in securing a mate, any animals possessing a superiority,
however slight, must have some little advantage in the battle.
Certainly, where so many must utterly fail, only those could possibly
succeed who were well fitted to the circumstances in which they must
live. We used to think animals were destroyed by the "accidents" of
life and no one could foretell accidents. Mr. Darwin made clear that
it was not a question of chance. That which might happen to any
individual animal might be what we, not knowing the process, called
accident, and yet there could be no possible doubt that those who
succeeded were better fitted to battle with life than those who
failed, and that their success was due primarily to their being thus
advantaged. Consequently, if generation by generation the so-called
accidents of life are constantly eliminating the unfit in overwhelming
proportions, not only must the positively unfit disappear, but even
the less fit. The more keen the struggle, the fewer could survive and
the fitter they must be to survive at all. This is Selection. These,
then, are Darwin's four great factors of evolution: Heredity,
Variation, Multiplication, Selection.
From these it results that the animals and plants naturally become
better adapted to the situation in which they are placed. When, as is
constantly happening through the history of the earth, a change occurs
in the physical geography of any region, when a plain is lifted to be
a plateau, or a mountain chain is submerged until it becomes a row of
small islands, this alteration will produce uncommon hardships among
animals, even though they were well fitted to the old conditions. Any
animal or any species of animals which meets such a calamity has
before it only three possible outcomes of the struggle. First it may
be plastic enough and it may vary enough in the right direction to
adjust itself to the changed conditions. In this case it and a favored
few like it will occupy the altered territory. The second possibility
is that it may migrate while the actual change is going on, thus
remaining in the sort of situation suited to it and its kind. The
third possibility is the one which overtakes a great majority of
animals--they die. Even the entire line dies out, and the strata of
the rocks are filled with the bones, shells, and teeth of such as have
met this fate. They have become extinct.
Thus far in this chapter we have been considering the influences under
which it is conceivable that animals should advance. There is no
question whatever that there are too many animals born, nor is there
any possible question that a very large proportion of them must
certainly die. There is equally no doubt that every animal produces
after its own kind, and that its offspring, while they resemble it
closely, still vary a little from it and from each other. This fact is
perfectly plain to the most superficial observer who thinks on the
matter at all. It is not so plain, nor is it easily demonstrated, that
all of these acting together do surely, even if slowly, alter the form
and behavior of the animal world. It is difficult to prove that there
is going on under our eyes a steady and real improvement in the
adaptation of the animals and plants around us to the situation in
which they are placed. As far back as man's memory runs they seem to
have been about what they now are; as far even as man's historical
record runs they seem to have suffered no great alteration. The
Egyptian of the old tombs is much like the Egyptian of the same rank
to-day. The African of the tombs has the African features of to-day.
Under such circumstances it is hard to prove that there is a steady
and undoubted advance. For the most part the balance of the animal
world is fairly even, and any species does not ordinarily change
rapidly enough or migrate widely enough to show us its new features.
It is difficult to see the struggle which we are so sure is going on.
The life of animals is so hidden in many of its details that their
joys and sorrows, if such we may call them, scarcely fall under our
observation. Now and then an opportunity comes to see the process of
adaptation work itself out. The struggle for existence begins anew and
is carried on with special vigor, with victory, temporary or
permanent, to one of the participants in the struggle.
The opportunity to observe such a change is presented in the United
States by the introduction of the so-called English sparrow. This
little creature, received at first with such joy, soon became the
object of an almost bitter hatred on the part of very many people.
This is really due to the fact that this bird is one of nature's
darlings and thoroughly succeeds where it has an even chance.
The number of birds of any particular species which a region will
support seems to be fairly definite. If a species is especially
protected until it becomes unusually abundant, the removal of the
protection commonly brings it down promptly to its original numbers.
On the other hand, an accident of severe character or a special
persecution may much diminish the number of the species, and still it
will, within a comparatively few years, return to its previous
abundance.
The inhabitants of Florida who own orange groves will never forget the
winter of '94-5. A bitter cold wave swept along the coast and killed
such large numbers of orange trees as almost to cut Florida out of the
orange market and to open the gate to California, who was eagerly
offering her fruit. This same frost caught the migrating blue birds
and killed them by the thousands. When spring came bird-lovers
throughout the eastern United States found an astonishing scarcity of
these favorites. It was feared that with numbers so small they could
not possibly compete with their enemies and with whatever untoward
circumstances should be their lot. But there is room in this
environment for a definite number of bluebirds. When this number was
suddenly reduced the chances to make a bluebird's living were so
wondrously multiplied that young bluebirds had such an opportunity in
life as their fellows had not had for many long years. Accordingly
they thrived as never before, and, of their progeny, a larger
proportion lived to the following year. It was only a few years before
the number of bluebirds had risen. Now we probably have as many as we
have had for a long time past. I cite this simply to show that a
region can support a certain number of animals of any one particular
kind, and that the animal is likely to multiply, if given a fair
chance, until it has reached such proportions. Now to my story of the
rapid development of a newcomer.
In the year 1850 a resident of Brooklyn came home from a trip to
Europe. He was a lover of birds, and while in Europe had been
particularly attracted, no one now knows quite why, to the common
House Sparrow, as it should be called. It is no more abundant in
England than in many parts of the continent of Europe. A name that has
been used for a long time is very hard to cast aside, and we shall
probably continue to mistakenly call him the English Sparrow to the
end. Our Brooklyn traveler brought home with him from Europe eight of
these interesting little birds and succeeded in inducing his
colleagues in a scientific society to share his interest in them. Not
wishing to commit the newcomers suddenly to the rigors of the American
winter, these men built a large cage for the sparrows, meaning to set
them free in the spring. For some reason or other when the winter was
over the birds were all dead, and this first attempt to introduce the
sparrow into America failed entirely. The little bird had won so many
friends that his success was now sure. Finding a favorable
opportunity, these Brooklyn men dispatched an order to a man in
Europe, asking him to supply them with one hundred English sparrows.
The consignment came in good shape and the birds were liberated on the
edge of Brooklyn. This was the first of a number of introductions. A
little later New York City sent for two hundred and twenty of these
interesting creatures and turned them loose in her parks, while
Rochester, with what was then considered great public spirit,
purchased one hundred for herself. But the most progressive city in
this respect was Philadelphia. She had long been troubled with the
spanworm on her trees. This detestable larva had the unpleasant
fashion of lowering itself by a long silken thread from the shade
trees then so abundant in that beautiful city. The spanworms traveling
around over the clothing of the passersby were so objectionable to
everybody that it was with greatest delight that Philadelphia heard
of the new birds which ate the pest. One wonders why some
ornithologist did not look at the bird long enough to see that it had
the sort of a bill characteristic of birds that eat seeds. It is true
that most birds feed their young on insects, hence there is a time
when any bird is apt to be insectivorous. But the structure of the
sparrow's bill, like that of all finches, should have warned these
bird-lovers that the sparrow was not to be depended upon to earn his
living by catching worms. It is easy, however, to be wise after the
event. Philadelphia believed she was engaging in a particularly
advanced movement when she imported from England one thousand English
sparrows, nearly as many as were liberated by all other cities
together. These birds were turned loose among the shady streets and
wide spreading parks of the City of Brotherly Love.
It is a serious matter lightly to disturb the balance of nature by the
introduction of a new species. It is true that the sparrow did eat
some spanworms and for a while enthusiastic bird-lovers hoped that
here was the solution of the difficulty. Philadelphians will also
remember that, with the spanworm removed from competition, the tussock
moth, whose caterpillar carries on his back a series of yellow, red,
and black paint brushes, at once become the permanent parasite of the
long-suffering shade trees. This caterpillar is covered with bristling
hairs, very closely set. Almost any bird objects to hair in his
victuals; and this particular larva has hair more than ordinarily
objectionable, for it irritates wherever it pricks the sensitive skin.
This coating seems to protect the caterpillar from the sparrow, with
the result that Philadelphia's trees were soon nearly defoliated by
this comparatively new pest, worse than the spanworm. With the paving
of the city's highways and the consequent shutting off of the air from
the roots, the trees have largely disappeared from the streets of
Philadelphia. With them have gone a fair portion of the tussock worms,
but the sparrow holds his own. Here is a new bird in the field, and
the struggle for existence on the part of every other kind of bird is
now more complicated and severe. The sparrow can live where the rest
of the birds have no possible chance. He throve so well in this
country that by 1875 he had spread over five hundred square miles in
the neighborhood of our larger Eastern cities. Thus far almost
everybody was pleased with the new introduction. Within the next five
years he had spread over more than fifteen thousand square miles, and
wise men were beginning to feel doubtful of the virtues of their
aforetime friend. When by 1885 more than five hundred thousand square
miles had been occupied by the enterprising little fellow, there
remained no longer a doubt in the minds of most people that the
sparrow was an unmitigated nuisance and great fears were entertained
that he had multiplied to such an extent as to be a serious menace.
Here, then, is a modern instance under our own eyes of a victory in
the struggle. If the sparrow has multiplied rapidly, while all the
other birds have either only held their own or even have diminished in
numbers, it is quite evident he must be better fitted to the
conditions than they are. What are his fit points? Why does he succeed
while others fail? The thoughtful bird-lover will have little trouble
in understanding at least some of his victory-winning characteristics.
How did he come to be almost the only bird who can live in large
numbers in our great cities, without losing his ability to get along
in less crowded situations?
In the first place this interesting bird is a clannish fellow. He has
lost the ordinary sparrow habit and has come to like to live in
crowded groups. Seclusion is not at all to his taste, and if there are
only a few sparrows in the neighborhood those few will most certainly
be found living near each other. One of the early adaptations of the
sparrow to his city surroundings was the ability to find for himself a
considerable proportion of his food in the undigested seed that could
be picked up from the droppings of the horses. This naturally led the
surplus sparrows out through the many thoroughfares leading from any
large city. Where horses went sparrows could follow. Accordingly along
the great lines of travel this bird found the simple path by which he
could enter new territory. Meanwhile box-cars came into our large
cities with freight. Sometimes they had carried grain, sometimes
cattle. In either case it was not unlikely that a certain amount of
grain should be found scattered over the floor of such cars. The
sparrow visited these cars for the grain, and it must have been no
infrequent accident that a door should be shut upon a group of
sparrows, especially in inclement weather, when they were apt to be
huddled in a dark corner of the car. These prisoners would be carried
to the destination of the car and there liberated, thus producing a
new center of what we are now inclined to call infestation. By such
means the English sparrow has spread over much the larger portion of
the American continent. Few birds are bold enough to visit a railroad
car. Of the few who might be tempted, most are timid enough to fly on
the first approach of man. Hence they fail to gain this chance of
spreading. They must remain in the old crowded home. Meanwhile the
sparrow, thus transported, finds a new home with fewer or no sparrows.
The struggle is less keen. More of his kind can live. His boldness
has been here a fit quality and has helped him in the race.
Man is only slowly coming to be a city-dwelling animal. Although it is
a voluntary process with him, he still usually visits the country with
much enjoyment. He has not as yet learned to adapt himself thoroughly
to the city, for somehow city life kills him. Families that move into
the city gradually have a smaller number of children in each
generation until shortly the family is wiped out. The population of
the city must constantly be replenished from the country. But the
English sparrow is more adaptable than are the people. He has made
himself at home in the heart of the biggest city. The Wall Street
canyon is not deep enough, nor contracted enough, nor free enough of
food to blot out the life of the English sparrow. At the heart of the
deepest gully among the skyscrapers of our biggest cities we find this
little bird hopping between the horses' feet, darting out from under
the wheel of the push-cart, fluttering only a few yards to a place of
safety, to return at once to his scanty meal upon the pavement as soon
as opportunity offers. He is a typical city dweller and has learned to
thrive there. Again in this matter he has distanced other birds to
whom the city is more deadly than it is to people.
Another very important element in his fitness for the struggle of
life lies in the fact that he is unafraid of man. He is wary of man;
by which I mean he will quickly fly up from in front of man's feet. It
is exceedingly difficult to catch a sparrow in one's hand. It is far
easier to lure a pigeon within reach. But the sparrow, when escaping
your hands, comes to rest but a slight distance away, only to elude
you quite as successfully if you try again. If the sparrow is let
severely alone he becomes more and more familiar with men, flies less
promptly, and goes a shorter distance, but any attempt to trap him
renders him shy more quickly than almost any other bird we have. He
soon learns to avoid a trap in which his companions have come to
grief. Those who would poison or trap sparrows must change constantly
the base of their operations. This fearlessness of man is a valuable
asset to the bird, for it is an important defense against other foes.
The most serious enemy the birds at large have, after man himself, is
the bird of prey. Hawks and owls capture a large quantity of our
smaller birds. Now the hawks and owls are for the most part shy of
man. They have gotten a bad reputation, especially if they are of any
size, because of their more or less pronounced proclivities for
seizing our domestic poultry, and consequently many people will fire
upon a hawk or an owl who would probably fire upon no other bird. By
living close to man the sparrow is largely saved from the danger of
capture by these carnivorous creatures, and this is the first and a
very important element of the advantage to the sparrow of living near
man. But there is the additional advantage that man scatters about
him, in one way or another, a very considerable amount of waste food.
I have suggested that the seeds in the droppings of the horse form a
large proportion of the sparrow's food, and horses are to be found
only with men. In the neighborhood of man's home, unless he has become
sanitary to a degree which has only been attained in recent years,
there is usually more or less garbage, kitchen offal of one sort or
another. To this the sparrow has easy access and from it he makes many
a meal. But this fearlessness of man gives him still another advantage
which his competitors fear to use, it provides him with nesting sites.
Man has the faculty of putting up ornamental trimmings on his house,
and there is no spot the sparrow chooses more willingly in which to
build his nest than the ornamental quirks and cornices of man's
architecture. A Corinthian column with comely leaves in its capital
seems especially designed for the comfort of the sparrow, and his
distinctly untidy nest is the familiar disfigurement of almost every
ornate public building. These are the advantages which come to the
sparrow from his willingness to associate with man, and there are
comparatively few birds with whom he must share them. Few birds select
the immediate neighborhood of man's home for their nests. They may
live in the neighboring trees, they may haunt his orchard, but his
house, for the most part, they decline to frequent.
Still another quality which makes for success in this buccaneer is the
willingness with which he will vary his food as occasion requires. It
is a not infrequent characteristic of the bird family that each
species should have its own rather restricted diet. Birds are quite
particular eaters, and many of them will come well nigh to starvation
before they will use unaccustomed food. The sparrow, on the contrary,
like man, eats almost anything he comes across that could reasonably
be considered edible. He belongs to a group of birds which are
structurally adapted to cracking the hard coats of seeds. This group
of birds known as the finches is provided with the sort of bill
familiar in the ordinary canary bird. It is short, heavy at the base,
comes quickly to a point, and is firm and strong. With it the bird
readily breaks through the hard outer coat of most seeds and feeds
upon the rich cotyledons that are enclosed within. Nowhere in its
entire structure does the plant crowd so much nourishment in so little
space as it does in the seeds. It is not by chance that the great
human food is grain. The sparrow belongs to the one bird group that
makes a specialty of such seeds.
Most of the English sparrow's cousins in this finch group confine
themselves rather rigidly to this diet. Here the variability of the
sparrow again gives him the advantage. He may have the family fondness
for seeds, but in their absence he can be content with almost anything
edible. In the early springtime, when the seeds of last year are gone
and those of the new year have not yet been produced, the sparrow is
not averse to eating young buds from the trees. At this time he is not
unlikely to eat our sprouting lettuce and peas. It is easy to be
severe on him in this matter; but for a creature like man, who has the
same tastes, who eats the enormous buds of the cabbage, the
cauliflower, and the brussels sprouts, or the more tender buds which
he calls heads of lettuce, it seems particularly inappropriate that he
should throw stones at this little creature whose tastes are so
similar to his own.
While seeds are more suitable for an elder bird they are altogether
too indigestible to be the food of nestlings. So when the sparrow
finds its nest full we know he must sally forth in search of
nourishment more simple of digestion. Now for a few weeks he searches
assiduously, catching insects and caterpillars of various kinds, and
feeds them to his young. This taste passes as his children grow older,
especially as shortly the seeds begin to ripen. Now is the time for
the sparrow to fatten. Now he is eating the food for which he was
really built. By the time the wheat is ripe there are sparrows enough
about to form quite a flock, and when these settle down in a wheat,
rye, or oats field and feed upon the grain, meanwhile shaking out upon
the ground perhaps as much as they eat, the farmer begins to realize
that the sparrow is not his friend.
When winter comes the struggle for existence among the birds is
intensified, and comparatively few of them dare face it. Most of our
birds betake themselves to less rigorous quarters, leaving to the
sparrow a comparatively small number of competitors for the diminished
supply of food. As long as the snow is off the ground the sparrows can
find sufficient sustenance. They gather themselves into groups and
sally out from the city into the open country. The immediate result is
that great quantities of weed seeds are seized upon by the English
sparrow, as, indeed, by every other finch which is with us in winter.
Perhaps we have not given the little fellow credit for the good he
does at this particular time, for the rest of the account truly does
not help him in our esteem.
There is a further direct advantage in the sparrow's sociability. One
robin may nest in the vines about your porch. If there were room for a
dozen, scarcely more than one would be likely to use it, because he
would drive away any other robin who attempted to share the
neighborhood with him. To the sparrow company is always in order.
While he may quarrel from morning until night with his fellow, it is a
sociable quarrel and neither would willingly forgo it. This union is
strength among birds, as with man. Every animal is safer from his
enemies when he can have the constant presence of others of his own
kind. The deer that stays in the herd is safer from the wolves. It is
only when the latter succeed in cutting out some weaker or less
sagacious animal that these carnivorous creatures succeed in tearing
down their prey. I think the superiority of the sparrow over most of
our common birds, when considered as a city dweller, is scarcely
understood. Because he had won in the race with other birds is no
necessary indication that he warred directly against them. Bird-men
often attribute to him a quarrelsome disposition, as if he actually
drove other birds away. It almost seems like animosity against the
sparrow to speak of him as attacking blackbirds and crows. It is a
cowardly crow who can be driven away by a sparrow, and if the two
cannot live together it seems to me certainly to the discredit of the
crow and not of the sparrow. I believe the truth to be that, while
the sparrow is undoubtedly a quarrelsome fellow, his bickerings are
his form of social converse with those of his own kind. A quarrel
among themselves seems not to indicate animosity, but would appear to
be the sparrow's idea of conviviality. It rarely leads to serious
results. I have never seen a male sparrow trounce any other bird with
half the vigor that I have occasionally seen the mother sparrow evince
when she caught her male companion by the feathers of his head, hung
him over the side of the limb, and vigorously and thoroughly shook him
until he desisted from his annoying and possibly insulting attentions.
The truth of the matter is that a colony of these little birds, with
their continual social chatter, including their quarrels, makes such a
continuous noise that the ordinary bird, which is generally of rather
quiet disposition, is too much annoyed by the unending nuisance to
find the neighborhood at all to his taste. Where a large number of
sparrows have gathered together the conditions are such as would give
a robin or a bluebird nervous prostration, and his only recourse is to
depart to a neighborhood where there is more peace and quiet. But our
English sparrow is not only better fitted for the struggle than the
robins and bluebirds, the orioles and the wrens. He has one important
advantage over even his own sparrow cousins. The males are
handsome--much more so than the females or than their sparrow cousins
in general.
In the song sparrow, field sparrow, chipping sparrow, and the fox
sparrow the male and female are very nearly alike in color. It often
becomes necessary for the bird-man to examine the internal organs of
the bird he is stuffing before he can certainly decide its sex. But
there is no difficulty whatever in telling the male from the female of
the English sparrow. The male is far the more ornate bird. His back is
striped with a richer brown; his head has two splendid dashes of
chestnut over the eyes; his throat and breast are splashed with red
and lustrous black; his bill is a clear fine black. Altogether the
bird is strikingly colored for a sparrow, and this characteristic is
the more remarkable when we see how quiet and somber is his more
modest mate. This brilliancy of male plumage in the presence of the
somber color of his mate would seem to indicate that the English
sparrow is eye-minded rather than ear-minded. It is true among human
beings that most of them are eye-minded. That is to say, they notice
things with their eyes chiefly. Memories they have are memories of
things seen; recollections of their friends bring up the appearance of
their friends. Their language is full of metaphors which imply form
and shape. But occasionally we come across an ear-minded person. He
remembers voices quite as well as he remembers faces. To him music is
an unending delight, and painting and sculpture fall into a distinctly
secondary place. This is ear-mindedness. Now, most of the sparrows
seem to be ear-minded, at least as far as their recognition of their
mates are concerned. In this group beauty of song is developed many
times oftener than is especial ornateness of plumage. The bird-lover
who is himself keen of ear is never tired of listening, when in the
field, for the two low notes with which the vesper sparrow introduces
a song, the rest of which is not at all unlike the one of his
song-sparrow cousin. The field sparrow begins more like the song
sparrow, but ends with an often repeated note, which not a little
resembles in general character the somewhat more monotonous song of
the grasshopper sparrow or of the chippy. In comparison with these
melodious birds the English sparrow makes no showing whatever. His
voice is harsh and querulous, although very occasionally it is
possible for the bird-lover to detect a note or two which would
indicate that, if he were properly educated, his voice might amount to
something. He wins his wife not by his pleasant voice, but by his
attractive appearance and his winning ways. We have every right to
infer from the character of its fellow birds of the sparrow family
that once the female and male sparrow were colored about alike. But
Madam English Sparrow was apparently eye-minded rather than
ear-minded. Whatever pleasant voice a suitor might have seems to have
been to her without attraction, and there was nothing to encourage him
in developing it, nor was she likely to mate with him for it and
transmit it to her male children. On the other hand, let a suitor
appear in whom a more brilliant coloring proclaimed his superior
vigor, and this seems to catch her eye at once. The less accomplished
rival in the tournament of love seems to have been already forgotten.
To their children these successful characteristics were naturally
handed on and led to equal success on their part. If any of these
children possessed this badge of honor in a more than ordinary degree,
he was the more likely to win a mate and thus again the opportunity of
passing on to his offspring his own distinct advantage. Generation by
generation the males have become more beautiful and the females more
discriminating. That the bird is either instinctively or actually
conscious of this advantage would appear from the constant fluffing of
his feathers and spreading of his highly colored wings with which he
evinces his admiration for his ladylove. Even the most hardened
dweller in the city can scarcely have failed to see the sparrow spread
his wings, fluff his feathers, and sink close to the ground, twirling
and gyrating about the object of his affection. It must give him a
shock to see how often she proves temporarily or hypocritically
indifferent to the demonstrative proceedings. Indeed they may
terminate in a thorough trouncing of the male on the part of the lady
of his affections. Now this preference for color over song must have
evidently evolved in connection with the development of social habits
in the English sparrows. His cousins of the fields, our native
sparrows, are much less social, much less likely to be met with in
flocks. To birds who scatter more, beautiful song is a great
advantage. It can be heard at a long distance. But when birds flock
together a much better advantage is that of beautiful clothing, added
to alluring ways.
But we have not nearly exhausted the catalogue of the traits belonging
to our little friend which give him the advantage over other birds in
the struggle for life. His ability to remain with us in winter when
most birds are gone stands him in good stead.
It is readily observed by one who pays the least attention to outdoor
life that winter finds us with comparatively few birds. North of
Maryland and the Ohio River the robin is practically absent in the
winter, except in much diminished numbers close to the border. The
bluebird is similarly absent; the great flocks of blackbirds are gone;
the bobolink is missing entirely; the thrush and the catbird have all
left; the flicker and red-headed woodpecker are also spending their
winter in the South. The great mass of our bird population has left us
until warmer weather shall bring back to us once more our feathered
friends. It is true that we are south to the snowbirds or juncos, and
their little slate-colored bodies, with their light breasts and their
white on each side of the tail, make our bare hedge rows brighter by
their presence. A few of our birds like the song sparrow and the
cardinal are hidden away in the thicket, and have not all joined their
comrades in the south.
The English sparrow was once probably quite as migratory as any of the
rest of these, but a great change has come over his habits. With his
newly acquired fondness for the haunts of men he has suffered a change
in this respect also. Whatever may have been his reason for migrating,
it no longer holds. He now finds himself quite able to stand the cold
of winter. Accordingly he never leaves us, except very temporarily.
When the migrating season comes the sparrows of the neighborhood are
very likely to gather themselves together in a single group and take
to the neighboring country. I believe this flocking on their part at
this time of the year is a remnant of the old migratory habit. Until
snow covers the ground the sparrow is not likely to be seen again in
such numbers in the city. The advantage the sparrow gains over his
competitors by not going south does not appear during winter. When
spring comes, however, his gain is evident. He has his choice of all
the nesting sites in the region. When the migratory birds return every
first-class place is filled by a sparrow's nest. Nothing but second
choice situations remain, and with these the late comers must be
content. When we consider how much the safety of the next generation
depends upon the security of the young while helpless in the nest, we
appreciate what the English sparrow has gained by staying throughout
the year. Often while the season is so inclement that it would seem
there is still danger of frost, the sparrow builds her nest. All sorts
of places are open to her choice. She will find a protected corner
under a roof, above a spout, in the corner of the porch, behind an
open shutter, in the vines against the side of the house, on top of an
old robin's nest in the tree, in the bird boxes which have been put up
for more desirable creatures; anywhere and everywhere this industrious
little mother is liable to build her nest. Her husband will help her
more or less in the task, often bringing material and helping to place
it in the negligent pile of which their nest is composed. But he does
a good deal more fussing and cheering up than he does actual work, and
she seems to depend much upon his cheerful presence for her happiness.
It is hard to discourage Madam Sparrow when once she has set her mind
on home-making. A bird-lover, some time since, reported how a pair of
sparrows had started to build a nest upon his lawn. He, wishing to
interfere with the process, took a small rifle and shot the male bird.
Within twenty minutes the female, who had scouted round the
neighborhood, returned with another mate and resumed her nest-building
process. Again he interjected the tragic note into her life by
shooting her second husband, only to find her start out in pursuit of
a third, with whom she returned in the course of an hour. He felt that
by this time he had interfered with her domestic happiness as much as
he had any right to do, and suffered her to continue her housekeeping
with her third husband without further molestation. I imagine it would
have puzzled both birds to tell who was the father of the nestlings
who appeared two weeks later.
Not only do sparrows nest early, they nest often. I suggested to one
of my students that she locate as early in the season as she could the
nest of a pair of English sparrows, which was sufficiently accessible,
and that she keep it under observation at intervals of a few days
throughout the summer. In the fall she came to me with glowing eyes
and gave me her report. "It is simply great," she said. "I never went
to that nest a single time this summer to find it empty. When I first
got there I found four eggs; after a while these hatched out, and the
young were on the nest until they were old enough to fly; but before
they had left she had slipped a fresh egg among them, ready to start a
new batch. Whenever I saw the nest throughout the entire summer, I
found in it either eggs, or young, or both." Such reproductive energy
as this is hard to beat; compared with this rate of increase, the
ordinary bird is the exponent of race suicide. How can a robin hope to
compete with this family industry? What can a bluebird offer that will
approach such chances of a worthy successor when his work shall be
finished?
These, then, are the most important points in which the English
sparrow has varied from his sparrow cousins and made of himself the
most successful town dweller in the bird world. He has become clannish
and gained the advantages of cooeperation. He has used man's highways
and cars by means of which to expand his area. He has cultivated the
presence of man and thus gained protection from his enemies, food from
man's waste, and nesting sites on man's house. He has assumed a varied
diet. The male has become handsome. He has given up migrating, and
thus secured the best nesting sites. He has learned to produce many
offspring. With all his versatility, why should he not succeed?
Thrown into competition with our native birds, he easily beats them
on their own ground. He survives against the competition of birds
which seem to us more estimable in every way. The very fact that he
survives proclaims his superiority over them, and shows that our
criterion is not the one by which nature judges. We like the birds
which serve our purpose. We admire the brilliant plumage of the jay,
cardinal and goldfinch. We love the mellow notes of the woodthrush,
and of the veery, the clear, rollicking outpourings of the bobolink,
the musical love song of the brown thrasher, the cheerful scolding of
the wren. We are fond of the birds who busy themselves taking the
insects out from among our grain and from off our fruit trees. We can
only understand the value of the bird to nature when he is valuable to
us. So, because the English sparrow does little that is to our
advantage and much that is to our annoyance, he is in our estimation a
reprobate and an unending nuisance.
All sensible bird-men must clearly acknowledge that he is a very
undesirable citizen. I write the above sentence to show that I realize
the whole duty of the bird-lover in the matter of the sparrow. This
pestiferous creature should be exterminated by traps, by grain soaked
in alcohol, or strychnia, by fair means or foul. But personally, I am
taking no share in his destruction. Any bird-lover, after reading the
foregoing account, can scarcely have missed the undercurrent of my
affection for the little rascal. He is a thorough optimist; he is
absolutely persistent; no hardship seems to dampen his ardor. His
heart is valiant above that of most birds so that he has dared to make
of man his near neighbor when other birds consider him their worst
enemy. I love him for it. When I am in the midst of a big city with
its cliffs of offices and its gorges of paved streets, it is to me a
cheer and a delight to see this happy little fellow who has adapted
himself to circumstances against which no other bird, excepting the
pigeon, can cope. I confess that it would be with regret that I should
see him disappear from the landscape. I have missed a long line of
spring peas through his ravages, and he has objectionably decorated
many places about my own home. But I have yet the first violent hand
to lay upon the sparrow, and I doubt whether my hand is ever to be
reddened with his blood.
I am going to ask bird-men to forgive me if I say that I believe,
although I speak only from general impression, and not from careful
research, that the sparrow within the past eight years has reached his
equilibrium in the neighborhood of Philadelphia and is growing no more
abundant. Meanwhile another and very desirable state of affairs is
arising. Bird love and bird protection are so active in this
neighborhood that there is growing to be a new race of birds who lack
the fear of man their ancestors justly had. Under these conditions the
wild birds, which for a while we believed to have been completely
driven out by the sparrow, are rapidly returning to our villages and
towns, and we have many more robins and catbirds, wrens and flickers
than we had ten years ago. We have seen the worst of the English
sparrow; he has now found his equilibrium.