The first nuptial plumage is acquired by a partial prenuptial molt in early spring, "which involves most of the body plumage, the wing coverts and the tertiaries, but not the primaries, their coverts, the secondaries, nor the tail. The whole plumage becomes golden lemon-yellow, greener above and [in the male] brightly streaked on the throat, breast and sides with pale chestnut, somewhat veiled by the feather edgings. The forehead and crown are yellower than the back and usually chestnut tinged. The tertiaries and wing coverts are broadly edged with bright lemon yellow." The female in this plumage is yellower than in the fall and has a few obscure chestnut streaks below. Old and young birds are now very much alike, often practically indistinguishable, except for the worn juvenal wings and tail. Adults have a complete postnuptial molt in July before or while they migrate and a partial prenuptial molt, as in the young bird, before they arrive in the spring. In El Salvador, according to Dickey and van Rossem (1938), "both adults and young of the year were in complete fall (postnuptial) plumage by the time they arrived. * * * An adult male taken April 10 is in the midst of the spring (prenuptial) molt and presents an extremely ragged appearance. Another, collected on April 24, has entirely finished this molt." In both adult male and female plumages the colors are richer and the streakings below heavier than in the young bird, but the female is always duller in color and the streaking is less prominent or entirely missing. _Food._--Edward H. Forbush (1907) writes of the food of the eastern yellow warbler in Massachusetts: It would be hard to find a summer bird more useful among the shade trees or in the orchard and small-fruit garden than this species. Almost entirely insectivorous, it feeds on many of the greatest pests that attack our fruit trees, vines and berry bushes. Whenever the caterpillars of which it is fond are plentiful, they form about two-thirds of its food. It is destructive to the small caterpillars of the gipsy moth and the brown-tail moth, and is ordinately fond of canker-worms and other measuring worms. Tent caterpillars are commonly eaten. Small bark beetles and boring beetle are eaten, among them the imago of the currant borer. Weevils are greedily taken. A few useful beetles are sacrificed; among them ground beetles, soldier beetles, and small scavenger beetles. The Yellow Warbler has some expertness as a flycatcher among the branches, and seizes small moths, like the coddling moth, with ease, but apparently does not take many parasitic hymenoptera, although some flies are taken. Plant lice sometimes form a considerable portion of its food. No part of the tree where it can find insect food is exempt from its visits, and it even takes grasshoppers, spiders, and myriapods from the ground, grass, or low-growing herbage.