The song of the Kentucky Warbler is a familiar sound of rich, moist, deciduous forests in the southeastern United States. A skulking, ground-nesting bird, this warbler is heard more often than seen. In early spring, the male sings incessantly, sometimes partly concealed and almost motionless except for his vibrating throat, in bouts from the same perch for 5–15 minutes, typically at heights of 5–15 meters. Although his song may be confused with that of the Carolina Wren (Thryothorus ludovicianus), or even the Ovenbird (Seiurus aurocapilla), a flash of yellow and black when he changes perches confirms the Kentucky Warbler.
Reference: Birds of the World - Cornell Lab of Ornithology