s, the mosquitoes! Think, too, of the frogs and the hylas! If
these cold-blooded, low-lived creatures, after sleeping all winter in
the mud,[3] are free to make so much use of their voices, surely a bird
of the air may sing his unobtrusive song without being cross-examined
concerning the purpose of it. Why do the mice sing, and the monkeys, and
the woodchucks? Indeed, sir,--if one may be so bold,--why do you sing,
yourself?"

This matter-of-fact Darwinism need not frighten us. It will do us no
harm to remember, now and then, "the hole of the pit whence we were
digged;" and besides, as far as any relationship between us and the
birds is concerned, it is doubtful whether we are the party to complain.

But avoiding "genealogies and contentions," and taking up the question
with which we began, we may safely say that birds sing, sometimes to
gratify an innate love for sweet sounds; sometimes to win a mate, or to
tell their love to a mate already won; sometimes as practice, with a
view to self-improvement; and sometimes for no better reason than the
poet's,--"I do but sing because I must." In general, they sing for joy;
and their joy, of course, has various causes.

For one thing, they are very sensitive to the weather. With them, as
with us, sunlight and a genial warmth go to produce serenity. A bright
summer-like day, late in October, or even in November, will set the
smaller birds to singing, and the grouse to drumming. I heard a robin
venturing a little song on the 25th of last December; but that, for
aught I know, was a Christmas carol. No matter what the season, you will
not hear a great deal of bird music during a high wind; and if you are
caught in the woods by a sudden shower in May or June, and are not too
much taken up with thoughts of your own condition, you will hardly fail
to notice the instant silence which falls upon the woods with the rain.
Birds, however, are more or less inconsistent (that is, a part of their
likeness to us), and sometimes sing most freely when the sky is
overcast.

But their highest joys are by no means dependent upon the moods of the
weather. A comfortable state of mind is not to be contemned, but beings
who are capable of deep and passionate affection recognize a difference
between comfort and ecstasy. And the peculiar glory of birds is just
here, in the all-consuming fervor of their love. It would be commonplace
to call them models of conjugal and parental faithfulness. With a few
e