In the elms on Boston Common, and in all the lofty trees in the suburbs as well as in the country villages, are two little birds whose songs are heard daily and hourly, from the middle of May until the latter part of summer.  These are the Warbling Fly-catchers (Vireo gilvus and V. olivaceus).  The first is commonly designated as the Warbling Vireo, the second as the Red-eyed Vireo.  The former arrives about a week or ten days earlier than the other, and becomes silent likewise at a somewhat earlier period.  Both species are very similar in their habits, frequenting the villages in preference to the woods, singing at all hours of the day, particularly at noon, taking all their insect prey from the leaves and branches of trees, or seizing it as it flits by their perch, and amusing themselves, while thus employed, with oft-repeated fragments of song.  Each builds a pensile nest, or places it in the fork of the slender branches of a tree.  I have seen a nest of the Warbling Vireo placed less than fifteen feet from the ground, on a pear-tree, directly opposite the window of a chamber that was constantly occupied; but the nests of both species are usually suspended at a considerable height from the ground.

The notes of the Warbling Vireo have been described by the words, “Brigadier, Brigadier, Bridget.”  They are few, simple, and melodious, and being often repeated, they form a very important part of the sylvan music of cultivated and thickly-settled places.  It is difficult to obtain sight of this little warbler while he is singing, on account of his small size, the olive color of his plumage, and his habit of perching among the dense foliage of the trees.

The Red-eyed Vireo is more generally known by his note, because he is particularly vocal during the heat of the long summer-days, when other birds are comparatively silent.  The modulation of his notes is similar to that of the common Robin, but his tones are sharper, and he sings in a very desultory manner, leaving off very frequently in the middle of a strain to seize a moth or a beetle.  Singing, while he is engaged in song, never seems to be his sole employment.  This is the little bird that warbles for us late in the summer, after almost all other birds have become silent, uttering his moderate notes, as if for his own amusement, during all the heat of the day, from the trees by the roadsides and in our inclosures.  We might then suppose him to be repeating very moderately the words, “Do you hear me?  Do you see me?” with the rising inflection of the voice, and with a pause after each sentence, as if he waited for an answer.