_The Birds and Their Families._
The next step to be taken was the study of the birds. Everywhere could
be seen father and mother birds busy making their house for the babes,
which were soon to come to live with them.
Great fun it was to hunt for nests and count the number each one
discovered. First, right in Bobby’s yard was a young horse chestnut
tree, and here in this tree Mr. and Mrs. Thrush had already built their
nest, or house, and were even now waiting for the first egg to come.
Again the children were told that Mrs. Bird was more active and more
intelligent than Mrs. Frog or Toad; that altogether she was a _higher_
creature than either the flower, the fish or the frog; that all father
birds and all father creatures on up the scale of development use
greater care to fertilize the egg than either Mr. Buttercup, Mr. Fish,
Mr. Toad or Mr. Frog. For, instead of fertilizing it in the water, or
with the help of the insects or wind, the egg of the higher creatures is
fertilized while still in the mother’s body.
Just like the flowers, Mrs. Bird has an ovary, where the little seeds or
eggs are kept. This ovary is attached to a tiny tube, and this tube has
no separate opening directly out of the body, but runs into the
intestine very close to the outer opening of the body, where the
intestines throw off the waste food.
Now, these little eggs have been within the Mother Bird’s body _always_,
ever since she herself came out of the egg, and they have been growing
slowly all the time until a time comes when, like the stigma of the
pistil (which at a certain time is ripe for fertilization and becomes
moist and sticky), they, too, are ripe for fertilization.
That this time has arrived is shown by many outward signs—such as
beautiful plumage and charming songs. Especially in the male bird does
this show itself. His whole nature seems bubbling over with the desire
to mate and the knowledge that at last he, too, has developed. For
though there are no eggs within his body, there is something else there
just as important to the creating of new little birds, and he feels the
time has come when this fertilizing substance is ready to do its work.
His color becomes bright, even brilliant, and his voice becomes
enchanting. Thus he tells the world of this glorious happiness.
This period is called the mating season—the time when both father and
mother birds awaken to the desire of building their nest and creating
offspring.
The egg has become as developed as Mrs. Bird alone can make it. For,
like the flower seed, the fish and frog egg, it needs the fertilizing
substance from the father bird to complete its development.
As has been said before, the father bird knows that there are so few
eggs that he and Mrs. Bird cannot afford to lose even one, so _great,
very great_ care must be taken to fertilize every egg.
There is an instinct in all creatures implanted there for millions of
years to preserve or perpetuate their species, and this instinct shows
itself when the father creature, like the father bird, places himself in
such a position that the fertilizing fluid can get into the mother’s
body as near as possible to the undeveloped eggs. And as every atom of
this substance is alive, it moves on, on and on, until it reaches the
egg, where it mingles with it and the two different substances have
become one. Now after the two substances have mingled, the egg passes
down the little tube on through the opening out of the body into the
nest. While it is passing through the tube, however, it accumulates a
food substance called the “white” of the egg. This is not the _living_
part of the egg, but simply food just as the frog eggs were incased in a
soft substance, which served as food for the tadpole—so in the yolk, is
the new baby bird, incased within the “white” of the egg.
At the bottom of the tube, through which the egg passes to its opening,
is a fluid which also incases the whole egg and hardens into a shell,
and it is then ready to go into the little nest.
After the fertilization takes place the egg is soon ready to be laid,
and so the nest must be ready, soft and cozy. And this is what Mrs.
Thrush was now waiting for in the nest she and Mr. Thrush had built in
the horse chestnut tree.
But even this was not all. For, though the eggs were here, the new
little birds were not yet here. And again it was shown that while the
frogs and toads left the eggs in the water to care for themselves, Mr.
and Mrs. Bird do not and can not do this. The eggs must be kept warm
almost constantly, and so Mrs. Bird gathers them close to her warm body
and sits on them day after day, until they are ready to burst the shell
open, and come out—the real new birds.