_Plumages._--The young black-throated gray warbler in juvenal plumage shows the characters of the species more than do the young of other wood warblers; the black and white areas about the head and throat are strongly indicated in a duller pattern and there are two broad white bars tipping the median and greater wing coverts (see pl. 35); these markings are more subdued in the female than in the male, thus making a slight sexual difference. The back is brownish gray and the underparts grayish white, faintly streaked with black. I have not been able to trace the postjuvenal molt, but it is perhaps less extensive than in most other warblers. In first winter plumage the young male is much like the adult male at that season, but it is more strongly washed with brown above and with yellowish beneath, the chin is white, the black throat is mottled with white, and the streaking above and below is duller and more obscured. The young female differs from the adult female in about the same way. Apparently, the nuptial plumage is produced mainly by wear, or by a limited prenuptial molt. The postnuptial molt is evidently complete in late summer. The adult winter plumages of both sexes differ but little from the spring plumages; in the male, the feathers of the upper parts and cheeks are margined with brownish gray and the throat with white, the sides are washed with brown and the black streaks are obscured; in the female, the plumage is tinged with brownish in the same way and the black streaks are obscured. _Food._--No extensive study of the food of the black-throated gray warbler seems to have been made. It is evidently mainly, if not wholly, insectivorous, for several observers have mentioned its zeal in foraging among the foliage of trees and bushes for insects, with a special fondness shown for oak worms and other green caterpillars. Bowles (1902) says that "it seems to prefer oak trees in the spring because of the small green caterpillars that are very numerous on them and which are devoured on all occasions. One female must have eaten nearly half its weight of them (from three-fourths to one and one-half inches long) while its nest was being taken." Mrs. Wheelock (1904) writes in the same vein: "In the spring these oaks are particularly infested with the green caterpillars, and the Warblers never seem to tire of devouring the pests. They lean way over to peer under every leaf, or reach up to the twigs overhead, never missing one. Twenty of these worms is an average meal for a Black-throated Gray Warbler, and the total for a day must reach into the hundreds."