Dr. Roberts (1936) lists "ants, and other insects and their larvae," as its food. Some of the food of the young is mentioned above, most of which is doubtless included in the food of the adults. Spiders, beetles, may-flies, and other insects should be included, as well as many caterpillars and the larvae of water insects. Audubon (1841) says: "It often perches upon the rank grasses and water plants, in quest of minute molluscous animals which creep upon them, and which, together with small land snails, I have found in its stomach." _Behavior._--Brewster (1878a) observes: When seen among the upper branches, where it often goes to plume its feathers and sing in the warm sunshine, it almost invariably sits nearly motionless. Its flight is much like that of the Water-Thrush (either species), and is remarkably swift, firm, and decided. When crossing a broad stream it is slightly undulating, though always direct. * * * In general activity and restlessness few birds equal the species under consideration. Not a nook or corner of his domain but is repeatedly visited through the day. Now he sings a few times from the top of some tall willow that leans out over the stream, sitting motionless among the yellowish foliage, fully aware, perhaps, of the protection afforded by its harmonizing tints. The next moment he descends to the cool shades beneath, where dark, coffee-colored water, the overflow of the pond or river, stretches back among the trees. Here he loves to hop about on floating drift-wood, wet by the lapping of pulsating wavelets; now following up some long, inclining, half-submerged log, peeping into every crevice and occasionally dragging forth from its concealment a spider or small beetle, turning alternately his bright yellow breast and olive back towards the light; now jetting his beautiful tail or quivering his wings tremulously, he darts off into some thicket in response to a call from his mate; or, flying to a neighboring tree-trunk, clings for a moment against the mossy bole to pipe his little strain or look up the exact whereabouts of some suspected insect prize. _Voice._--The same gifted writer and careful observer (Brewster, 1878) gives the following good account of the distinctive song of this warbler: