more exposed situations are,
doubtless, frozen solid. Yet, in time, their blood flows freely once
again and they become as expert on the wing as though the year were
one continual jubilee of insect chasing, and frost and snow were to
them unknown.

All the carnivora, or flesh-eaters, as the mink, skunk, opossum, fox,
and wolf, are in winter active and voracious, needing much food to
supply the necessary animal heat of the body. Hence they are then much
more bold than in summer, and the hen yard or sheep pen of the farmer
is too frequently called upon to supply this extra demand.

[Illustration: A WOLF.]

But of all our animals it seems to me the birds have solved the winter
problem best. Possessing an enduring power of flight and a knowledge
of a southern sunny sky, beneath which food is plentiful, they alone
of all the living forms about us have little fear of the coming of the
frost. True, fifty or more species remain in each of the Northern
States during the cold season, but they are hardy birds which feed
mainly upon seeds, as the snow-bird and song sparrow; on flesh, as the
hawks and crows; or on burrowing insects, as the nut-hatches and
woodpeckers.

Such are some of the solutions to the problem of life in winter which
the plants and animals about us have worked out; such some of the
forms which they undergo; the places which they inhabit.

To the thinking mind a knowledge of these solutions but begets other
and greater problems, such as how can a living thing be frozen solid
for weeks and yet retain vitality enough to fully recover? How can a
warm-blooded animal sleep for months without partaking of food or
drink? And greater than either, what is that which we call life?

I hold in my hand two objects, similar in size, color, organs,
everything--twins from the same mother in all outward respects. One
pulsates and throbs with that which we call "life." It possesses heat,
bodily motion, animal power. The other is cold, motionless, pulseless,
throbless--a thing of clay. What is that "life" which the one
possesses and the other lacks? Ah, there's the rub! With the wisest of
men we can only answer, "_Quien sabe?_" (Who knows?)

[Illustration: WINTER HOUSE OF MUSKRAT.]

BIRDS' NESTS

(FROM WAKE ROBIN.)[3]

BY JOHN BURROUGHS.

[3] Copyright by Houghton, Mifflin & Co.

[Illustration]

How alert and vigilant the birds are, even when absorbed in building
their nests! In an open space in the woods,