Studies of the singing behavior of the Swainson?s Warbler were conducted mainly near Macon, Bibb County, Georgia, and in the Dismal Swamp, Nansemond County, Virginia, during the springs of 1965 and 1966. Singing behavior on the ground and in trees is discussed. Swainson?s Warblers sing vigorously from the time they arrive on the breeding ground until the latter part of June, when the singing of most birds becomes more sporadic. At Macon, Georgia, in mid-April, morning song of one bird began about 20 minutes before sunrise; and evening song of the same bird ceased about 15 minutes after sunset. Songs were delivered at the rate of about 8-9 per minute for the first few minutes of morning song, decreasing to 5-6 per minute for most of the morning. Songs are given in courses or series. The rate of singing is usually faster at the beginning of a course. The number of songs sung by a territorial male in 1 day in the Dismal Swamp, Virginia, 2 June, was 1168. It produced 280 songs the first hour, and sang at a fairly constant rate from 5:00 to 8:00 AM, 192, 194, 198 songs per hour.