A young duck of the year, whose wings are at last strong and fit, waves them in ecstasy, vibrating from side to side and end to end of his natal pond. Then one day we follow his upward glances to where a thin, black arrow is throbbing southward, so high in the blue sky that the individual ducks are merged into a single long thread. The young bird, calling again and again, spurns the water with feet and wings, finally rising in a slowly ascending arc. Somewhere, miles to the southward, another segment approaches--touches--merges.
But what of our smaller birds? When the gray days begin to chill we may watch them hopping among the branches all day in their search for insects--a keener search now that so many of the more delicate flies and bugs have fallen chilled to the earth. Toward night the birds become more restless, feed less, wander aimlessly about, but, as we can tell by their chirps, remain near us until night has settled down. Then the irresistible maelstrom of migration instinct draws them upward,--upward,--climbing on fluttering wings, a mile or even higher into the thin air, and in company with thousands and tens of thousands they drift southward, sending vague notes down, but themselves invisible to us, save when now and then a tiny black mote floats across the face of the moon--an army of feathered mites, passing from tundra and spruce to bayou and palm.
In the morning, instead of the half-hearted warble of an insect eater, there sounds in our ears, like the ring of skates on ice, the metallic, whip-like chirp of a snowbird, confident of his winter's seed feast.
To all wild creatures fire is an unknown and hated thing, although it is often so fascinating to them that they will stand transfixed gazing at its mysterious light, while a hunter, unnoticed, creeps up behind and shoots them.
In the depth of the sea, where the sun is powerless to send a single ray of light and warmth, there live many strange beings, fish and worms, which, by means of phosphorescent spots and patches, may light their own way. Of these strange sea folk we know nothing except from the fragments which are brought to the surface by the dredge; but over our fields and hedges, throughout the summer nights, we may see and study most interesting examples of creatures which produce their own light. Heedless of whether the moon shines brightly, or whether an overcast sky cloaks the blackest of nights, the fireflies blaze their sinuous path through life. These little yellow and black beetles, which illumine our way like a cloud of tiny meteors, have indeed a wonderful power, for the light which they produce within their own bodies is a cold glow, totally different from any fire of human agency.