The transition from Thoreau to John Burroughs was through Thomas Wentworth Higginson. Wilson Flagg (1805-1884) had contributed to the early volumes of the _Atlantic_ a series of bird studies Irving-like in atmosphere and sentiment, but he had made little impression. He was too literary, too much the child of the mid century. In his study of the owl, for instance, he could write: "I will not enter into a speculation concerning the nature and origin of those agreeable emotions which are so generally produced by the sight of objects that suggest the ideas of decay and desolation. It is happy for us, that, by the alchemy of poetry, we are able to turn some of our misfortunes into sources of melancholy pleasure, after the poignancy of grief has been assuaged by time," and so on and on till he got to midnight and the owl. It is a literary effort. There is lack of sincerity in it: the author is thinking too exclusively of his reader. The difference between it and a passage from Thoreau is the difference between a reverie in the study and a battle in the woods. Higginson, who followed in the _Atlantic_ with "April Days," "The Life of Birds," and the other studies which he issued as _Out-Door Papers_ in 1863, avoided the over-literary element on one hand and the over-scientific on the other and so became the first of what may be called the modern school of nature writers. As we read Higginson's book to-day we find style and method curiously familiar. For the first time in American literature we have that chatty, anecdotal, half-scientific, half-sentimental treatment of out-door things that soon was to become so common. It is difficult to persuade oneself that a paper like "The Life of Birds," for instance, was not written by the Burroughs of the earlier period. _Out-Door Papers_ and _Wake-Robin_ are pitched in the same key. Who could be positive of the authorship of a fragment like this, were not Higginson's name appended: To a great extent, birds follow the opening foliage northward, and flee from its fading, south; they must keep near the food on which they live, and secure due shelter for their eggs. Our earliest visitors shrink from trusting the bare trees with their nests; the song-sparrow seeks the ground; the blue-bird finds a box or hole somewhere; the red-wing haunts the marshy thickets, safer in the spring than at any other season; and even the sociable robin prefers a pine-tree to an apple-tree, if resolved to begin housekeeping prematurely. The movements of birds are chiefly timed by the advance of vegetation; and the thing most thoroughly surprising about them is not the general fact of the change of latitude, but their accuracy in hitting the precise locality. That the same cat-bird should find its way back, every spring, to almost the same branch of yonder larch-tree--that is the thing astonishing to me.