Nearly or quite all that has been hitherto written about this Warbler would lead one to infer that its favorite haunts are dense thickets, undergrowth, or low trees, and that it seldom ventures to any considerable height above the ground. Our experience, however, was directly contrary to this. * * * The bird, moreover, not only frequented the tops of the tallest trees, but at all times of the day and under every condition of weather kept at a greater average height than any other Warbler excepting Dendroica dominica. In its marked preference for cypresses it also resembled the species just named, but unlike it was never seen in pines. * * *
At the time of our visit the Suwanee bottoms were alive with small birds many of which were doubtless migrants. They banded together in mixed flocks often of large size and motley composition. * * * Such a gathering was nearly certain to contain from one or two to five or six Bachman’s Warblers.
These with the Parulas were most likely to be feeding in the upper branches of some gigantic cypress, at least one hundred feet above the earth, where they looked scarcely larger than bumble bees. * * *
The habits and movements of Bachman’s Warbler are in some respects peculiar and characteristic. It does not flit from twig to twig nor launch out after flying insects in the manner of most Warblers, and many of its motions are quite as deliberate as those of a Vireo. Alighting near the end of a branch it creeps or sidles outward along a twig, and bending forward until the head points nearly straight down, inserts the bill among the terminal leaflets with a peculiar, slow, listless motion, keeping it there a second or two, and repeating the leisurely thrust many times in succession without changing its foothold. The action is like that of several other members of the genus—notably H. pinus and H. chrysoptera—under similar conditions, and suggests the sucking in of liquid food, perhaps honey or dew. Not infrequently a bird would hang back downwards beneath a twig and feed from the under sides of the leaves in the manner of a Titmouse. * * *
Many of the hackberry trees along the banks of this stream contained compact bunches—nearly as large as a child’s head—of dead leaves blackened by exposure to wind and weather. These bunches probably sheltered insects or their larvae, for they attracted several species of birds, especially the Bachman’s Warblers which would work at them minutes at a time with loud rustling, sometimes burrowing in nearly out of sight and sending the loosened leaves floating down to the ground. Upon exhausting the supply of food or becoming tired of the spot—whether one of the leaf bunches or the extremity of a cypress branch—the bird almost invariably started on a long flight, often going hundreds of yards through the woods or crossing the river, instead of merely passing to the next branch or tree as almost any other Warbler would have done under similar circumstances. This habit seemed to us characteristic of the species.
Atkins wrote from Key West (Scott, 1890):
Bachman’s Warbler in its habits is very much like the Parula Warbler (Compsothlypis americana). The resemblance is more noticeable when feeding and in search of food. The birds will then penetrate a thick bunch of leaves and go through, over and all around in the most thorough manner in their exploration after insects that appeal to their taste. They are very active, and constantly in motion. They are also quarrelsome, and resent the intrusion of other species. Frequently I have noticed them fighting away the White-eyed Vireo, and where two or more Bachman’s Warblers are observed together, one is pretty sure to see them chasing and fighting among themselves. When disturbed or alarmed they are at once alert; a sharp alarm note, something like that of a Yellow-throated Warbler (D. dominica) is uttered, but more forcible and clear cut in its delivery. This is accompanied with a few jerks of the tail, and the bird is off to a neighboring tree. They are found alike in the trees, low bushes, and shrubbery, sometimes on or quite near the ground, and seem to prefer the heavy and more thickly grown woods to trees or bushes more in the open. Young birds are quite tame, but the adults as a rule were very shy and difficult to approach after having been once disturbed.
Voice.—The song of Bachman’s warbler is of a wiry or insect-like character, and has been widely compared by many observers to the music of the worm-eating and parula warblers and the chipping sparrow. It also resembles, according to Aretas A. Saunders (MS.), one of the songs of the blue-winged warbler. Brewster (1891) says:
The song is unlike that of any other species of Helminthophila with which I am acquainted and most resembles the song of the Parula Warbler. It is of the same length and of nearly the same quality or tone, but less guttural and without the upward run at the end, all of its six or eight notes being given in the same key and with equal emphasis. Despite these differences it would be possible to mistake the performance, especially at a distance, for that of a Parula singing listlessly. The voice, although neither loud nor musical, is penetrating and seems to carry as far as most Warblers'. Besides the song the only note which we certainly identified was a low hissing zee-e-eep, very like that of the Black-and-white Creeper.