Naturalists commonly know birds and beasts and wild flowers as a surgeon who has dissected the human body, or perhaps sometimes a painter who has made pictures of them knows men and women.

But he knew birds and beasts as one boy knows another--all their delightful little habits and fashions.

He had the most wonderful good fortune.

We used to say that if anything happened in the deep woods which only came about once in a hundred years, Henry Thoreau would be sure to be on the spot at the time and know the whole story.
It seemed that Nature could not raise A plant in any secret place, In quaking bog or snowy hill, Beneath the grass that shades the rill, Under the snow, between the rocks, In damp fields known to bird and fox, But he would come in the very hour It opened in its virgin bower, As if a sunbeam showed the place, And tell its long-descended race.
It seemed as if the breezes brought him; It seemed as if the sparrows taught him; As if by secret sight he knew Where, in the far fields, the orchis grew.
Many haps fall in the field Seldom seen by wishful eyes, But all her shows did Nature yield, To please and win this pilgrim wise.
He saw the partridge drum in the woods; He heard the woodcock's evening hymn; He found the tawny thrushes' broods; And the shy hawk did wait for him; What others did at distance hear, And guessed within the thicket's gloom, Was shown to this philosopher, And at his bidding seemed to come.
These lines fit Henry Thoreau exactly.

Most people think Emerson had him in mind when he wrote them.