The nest was built on a horizontal branch, the smaller twigs of which were so interlaced as to admit of its being built upon them, though their extremities were interwoven into its rim. The nest was small for the bird, being only two inches in depth and four and a half in diameter. The cavity is one and a half inches deep and two and a half wide. Its base and external portions consist of fine, light, dry stalks of wild grasses, and slender twigs and roots. Of the last the firm, strong rim of the nest is exclusively woven. Within, the nest is composed of soft, fine grasses, downy feathers, and the fine hair of the smaller mammals. Mr. Audubon, who observed very closely the habits of these birds during a winter in Florida, describes them as very social among themselves, skipping along the piazza, balancing themselves in the air opposite the sides of the house in search of spiders and insects, diving through the low bushes of the garden after larvæ and worms, and at night roosting among the orange-trees. In his visit to Maine he found them very abundant in early May. The woods seemed alive with them, and wherever he landed, on his way to Labrador, he found them in great numbers. [Illustration: PLATE XIII. 1. Dendroica auduboni, _Towns._ ♂ Rocky Mts., 11965. 2. “ blackburniæ, _Gm._ ♂ Pa., 939. 3. “ “ “ ♀ Pa., 944. 4. Dendroica castanea, _Wils._ ♂ Pa., 2231. 5. “ “ “ ♀ Pa., 949. 6. “ pinus, _Wils._ ♂ Pa., 2942. 7. Dendroica pennsylvanica, _Linn._ ♂ Pa., 2233. 8. “ “ “ ♂ _juv._, Ill., 60883. 9. “ striata, _Forst._ ♂ Pa., 1545. 10. Dendroica cærulea, _Wils._ ♂ Ohio, 7349. 11. “ “ “ ♀ Mo., 6980. 12. “ striata, _Forst._ ♀ Pa., 978.] This Warbler is an expert flycatcher, feeds chiefly on insects, and is a great devourer of small caterpillars; but in the winter its food is largely composed of berries, especially those of the _Myrica cerifera_. It will also feed on grass-seeds. In the warmer wintry days in Florida, when insects are abundant, Mr. Audubon states that these birds are particularly active in their pursuit, and the trees seem full of them. At this time they emit, at each movement, a single note, _twēēt_, so very peculiar that they may be at once recognized by the cry. Wilson states that these Warblers appear in Pennsylvania, from the North, early in October, and stay there several weeks. Some of them remain in the Southern States all winter. They feed with great avidity upon the berries of the red cedar.