Outwardly composed of the broad blades of a coarse grass, the dead leaves of the maple, beech, chestnut, cherry and oak trees; the leaf points curving upward and inward forming a deep cuplike nest in which the bird's head and tail seem almost to meet over her back. Occasionally grass stems, coarse strips or wild grapevine bark, shreds of corn fodder, and fragments of beech and wild cherry bark appear in the make-up. Lined most frequently with wild grapevine bark laid across, instead of bent around in a circle, shredded finest on top, to which is added an occasional long black horse-hair or split grass stem, with now and then a final lining of split grass stems in place of fine bark. The shape varies in accordance to situation, outwardly a short cornucopia, a round basket, and once a wall-pocket affair, would best describe the shapes I have noticed. _Eggs._--From 4 to 7 eggs may be found in the nest of the blue-winged warbler; 5 seems to be the commonest number, and sets of 6 are not very rare. The eggs are ovate, with a tendency to short ovate, and they have only a slight gloss. The white ground color is finely speckled or sparingly spotted with "chestnut brown," "mummy brown," and "sayal brown," with under markings in shades of "drab-gray." Some sets have three or four eggs that are almost immaculate, with one egg sparingly spotted; other sets occasionally are prominently spotted with "drab-gray," "light Quaker drab," and "dark vinaceous-drab," or, less often, with spots of dark "mummy brown." Usually the majority of the markings are confined to the large end. The measurements of 50 eggs average 15.7 by 12.5 millimeters; the eggs showing the four extremes measure =16.8= by =13.0= and =14.2= by =11.6= millimeters (Harris). _Young._--An egg is laid each day until the set is complete, and incubation generally begins when the last egg is laid. The period of incubation is 10 or 11 days, and the young remain in the nest from 8 to 10 days. Mr. Burns gave Dr. Chapman (1907) the following full account of the nest life: The task of incubation falls on the female alone. It appears that an airing is taken in the early morning or a little before midday, and again in the early evening, though perhaps not regularly every day. I have not seen the male about the nest with food at this period. The female will allow a close approach, looking into one's eyes with that hunted look so common in wild animals, and often flushing without a protesting note. The period of incubation in the one instance was exactly ten days. On June 13, at 6.30 p. m., five young just hatched were blind, naked and prostrate from chin to sternum. The shells were disposed of immediately, in what manner I am unable to state; the female was reluctant to vacate.