_Food._--Nothing seems to have been published on the food of the blue-winged warbler beyond that mentioned above as food given to the young, which is doubtless eaten by the adults as well. It is apparently wholly insectivorous, seeking its food near the ground in the weed patches and underbrush where it lives and among the lower branches of the trees in its haunts. Probably any small insects that it can find in such places, as well as their larvae and eggs, including many small caterpillars, are eaten. Small grasshoppers and spiders are probably included. Prof. Aughey (1878) observed it catching small locusts in Nebraska. It is evidently a harmless and a very useful bird in destroying insects that are injurious to foliage. _Behavior._--Dr. Chapman (1907) writes: "It is rather deliberate in movements for a Warbler, and is less of a flutterer than the average member of the genus _Dendroica_. Some of its motions suggest those of the tree-inhabiting Vireos, while at times, as the bird hangs downward from some cocoon it is investigating, one is reminded of a Chickadee." And he quotes Burns as follows: Perched inconspicuously near the top and well out on the branchlets of a tree or sapling, preferably facing an opening, if in a thicket; it is in itself so minute an object as to be passed unseen by many, more especially as it is much less active than most of our Warblers. With body feathers puffed out to a delightful plumpness, except for the backward sweep of the head while in the act of singing, it remains motionless for quite a while. When it moves it is with a combination of nervous haste and deliberation, and its song may be heard from quite another part of the landscape with no apparent reason for the change. While it has its favorite song perches, it is quite a wanderer and not infrequently sings beyond possible hearing of its brooding mate, but oftener within fifty to two hundred feet of the nest. _Voice._--Aretas A. Saunders contributes the following study of the songs of this warbler: "The territory song of the blue-winged warbler consists of two long, buzz-like notes, the second usually lower in pitch than the first and rougher in sound, _bzzzzzzz-brrrrrrrr_. The pitch interval between the two notes varies from one tone to four and a half tones, but the smaller intervals, one tone and one and a half tones, are much commoner. The second note is lower in pitch than the first in about 75 percent of my records, and higher in most of the others. In a few songs the second buzz is a double note, and one may hear both lower and higher notes from a medium distance, only the lower from a greater distance, and only the higher when very near the bird.