The vireos, or greenlets, are a sort of connecting link between the warblers and the true flycatchers, and partake of the characteristics of both.

The red-eyed vireo, whose sweet soliloquy is one of the most constant and cheerful sounds in our woods and groves, is perhaps the most noticeable and abundant species.  The vireos are a little larger than the warblers, and are far less brilliant and variegated in color.

There are five species found in most of our woods, namely the red-eyed vireo, the white-eyed vireo, the warbling vireo, the yellow-throated vireo, and the solitary vireo,—­the red-eyed and warbling being most abundant, and the white-eyed being the most lively and animated songster.  I meet the latter bird only in the thick, bush growths of low, swampy localities, where, eluding the observer, it pours forth its song with a sharpness and a rapidity of articulation that are truly astonishing.  This strain is very marked, and, though inlaid with the notes of several other birds, is entirely unique.  The iris of this bird is white, as that of the red-eyed is red, though in neither case can this mark be distinguished at more than two or three yards.  In most cases the iris of birds is a dark hazel, which passes for black.

The basket-like nest, pendent to the low branches in the woods, which the falling leaves of autumn reveal to all passers, is, in most cases, the nest of the red-eyed, though the solitary constructs a similar tenement, but in much more remote and secluded localities.

Most birds exhibit great alarm and distress, usually with a strong dash of anger, when you approach their nests; but the demeanor of the red-eyed, on such an occasion, is an exception to this rule.  The parent birds move about softly amid the branches above, eying the intruder with a curious, innocent look, uttering, now and then, a subdued note or plaint, solicitous and watchful, but making no demonstration of anger or distress.

The birds, no more than the animals, like to be caught napping; but I remember, one autumn day, coming upon a red-eyed vireo that was clearly oblivious to all that was passing around it.  It was a young bird, though full grown, and it was taking its siesta on a low branch in a remote heathery field.  Its head was snugly stowed away under its wing, and it would have fallen easy prey to the first hawk that came along.  I approached noiselessly, and when within a few feet of it paused to note its breathings, so much more rapid and full than our own.  A bird has greater lung capacity than any other living thing, hence more animal heat, and life at a higher pressure.  When I reached out my hand and carefully closed it around the winged sleeper, its sudden terror and consternation almost paralyzed it.  Then it struggled and cried piteously, and when released hastened and hid itself in some near bushes.  I never expected to surprise it thus a second time.

The flycatchers are a larger group than the vireos, with stronger-marked characteristics.  They are not properly songsters, but are classed by some writers as screechers.  Their pugnacious dispositions are well known, and they not only fight among themselves, but are incessantly quarreling with their neighbors.  The kingbird, or tyrant flycatcher might serve as the type of the order.