In regard to the song of this species, Dr. Coues states that it appears to have several different notes. One of these is the ordinary _tsip_, given out at all times by both old and young of all kinds of small insectivorous birds. Its true song, heard only in spring, consists of two or three loud sweet whistles, sometimes slurred, followed by several continuous notes, resembling _chir-r-r_, in a wiry but clear tone. Their notes are of great power for the size of the bird. It also has another and quite different song, which Dr. Coues thought greatly resembled the notes of the common American Redstart. As all the birds he noticed had mated by the first of May, he has no doubt that they raise two broods in a season; and the fact that he found newly fledged young as late as the middle of August seems to corroborate the correctness of his supposition. In regard to the eggs, nest, or breeding-habits of this species, we have as yet no information. Dendroica pennsylvanica, BAIRD. CHESTNUT-SIDED WARBLER. _Motacilla pennsylvanica_, LINN. Syst. Nat. I, 1766, 333, no. 19; GMELIN. _Sylvia p._ LATH.; WILSON, I, pl. xiv, fig. 5. _Dendroica p._ BAIRD, Birds N. Am. 1858, 279; Rev. 191.—SCLATER & SALVIN, Ibis, 1859, 11; 1860, 273 (Coban, Guat.; November).—SAMUELS, 231. _Sylvia icterocephala_, LATH. Ind. Orn. II, 1790, 538.—VIEILL.; BON.; AUD. Orn. Biog. I, pl. lix. _Sylvicola ict._ SWAINS.; JARD.; AUD. Birds Am. II, pl. lxxxi. _Dendroica ict._ SCLATER, P. Z. S. 1859, 363 (Xalapa), 373 (Oaxaca). Other localities: _Bahamas_, BRYANT, Pr. Bost. Soc. VII, 1859. _Costa Rica_, CAB. Jour. 1860, 328. _Panama_, winter, LAWR., Ann. N. Y. Lyc. 1861, 322. _Yucatan_, LAWR. _Veragua_, SALV. SP. CHAR. _Male._ Upper parts streaked with black and pale bluish-gray, which becomes nearly white on the forepart of the back; the middle of the back glossed with greenish-yellow. The crown is continuous yellow, bordered by a frontal and superciliary band, and behind by a square spot of white. Loral region black, sending off a line over the eye, and another below it. Ear-coverts and lower eyelid and entire under parts pure white, a purplish-chestnut stripe starting on each side in a line with the black mustache, and extending back to the thighs. Wing and tail-feathers dark brown, edged with bluish-gray, except the secondaries and tertials, which are bordered with light yellowish-green. The shoulders with two greenish-white bands. Three outer tail-feathers with white patches near the end of the inner webs. _Female_ like the male, except that the upper parts are yellowish-green, streaked with black; the black mustache scarcely appreciable. Length, 5.00; wing, 2.50; tail, 2.20. HAB. Eastern Province of the United States; Bahamas; Guatemala to Costa Rica and Panama R. R. Not recorded from Mexico proper or West Indies, except Bahamas.