The small number of birds yet present in early April gives a better opportunity for careful study,—­more especially if one goes armed with that best of fowling-pieces, a small spy-glass:  the best,—­since how valueless for purposes of observation is the bleeding, gasping, dying body, compared with the fresh and living creature, as it tilts, trembles, and warbles on the bough before you!  Observe that robin in the oak-tree’s top:  as he sits and sings, every one of the dozen different notes which he flings down to you is accompanied by a separate flirt and flutter of his whole body, and, as Thoreau says of the squirrel, “each movement seems to imply a spectator,” and to imply, further, that the spectator is looking through a spy-glass.  Study that song-sparrow:  why is it that he always goes so ragged in spring, and the bluebird so neat? is it that the song-sparrow is a wild artist, absorbed in the composition of his lay, and oblivious of ordinary proprieties, while the smooth bluebird and his ash-colored mate cultivate their delicate warble only as a domestic accomplishment, and are always nicely dressed before sitting down to the piano?  Then how exciting is the gradual arrival of the birds in their summer-plumage! to watch it is as good as sitting at the window on Easter Sunday to observe the new bonnets.  Yonder, in that clump of alders by the brook, is the delicious jargoning of the first flock of yellow-birds; there are the little gentlemen in black and yellow, and the little ladies in olive-brown; “sweet, sweet, sweet” is the only word they say, and often they will so lower their ceaseless warble, that, though almost within reach, the little minstrels seem far away.  There is the very earliest cat-bird, mimicking the bobolink before the bobolink has come:  what is the history of his song, then? is it a reminiscence of last year? or has the little coquette been practising it all winter, in some gay Southern society, where cat-birds and bobolinks grow intimate, just as Southern fashionables from different States may meet and sing duets at Saratoga?  There sounds the sweet, low, long-continued trill of the little hair-bird, or chipping-sparrow, a suggestion of insect sounds in sultry summer, and produced, like them, by a slight fluttering of the wings against the sides:  by-and-by we shall sometimes hear that same delicate rhythm burst the silence of the June midnights, and then, ceasing, make stillness more still.  Now watch that woodpecker, roving in ceaseless search, travelling over fifty trees in an hour, running from top to bottom of some small sycamore, pecking at every crevice, pausing to dot a dozen inexplicable holes in a row upon an apple-tree, but never once intermitting the low, querulous murmur of housekeeping anxiety:  now she stops to hammer with all her little life at some tough piece of bark, strikes harder and harder blows, throws herself back at last, flapping her wings furiously as she brings down her whole strength again upon it; finally it yields, and grub after grub goes down her throat, till she whets her beak after the meal as a wild beast licks its claws, and off on her pressing business once more.