Responses of Four Warbler Species to Playback of Their Two Song Types

Abstract

RECENTLY renewed attention has been focused on the communicatory function of avian vocalizations (e.g. Marler, 1967; Smith, 1966). One problem in avian communication studies is determining what the message of a vocalization is for the recipient. The purpose of this study was to use song playback experiments to determine if intraspecific song variants have different messages. Few studies of the role of song have been made in species where each individual has more than one song type, although Hinde (1958) studied vocal responses of Chaffinches (Fringilla coelebs) to their two song types in captivity. Many species of warblers have two song types that apparently differ in motivation and function (Ficken and Ficken, 1962, 1965; Morse, 1966, 1967). The American Redstart (Setophaga ruticilla), Chestnutsided Warbler (Dendroica pensylvanica), and Yellow Warbler (D. petechia) possess an accented ending song (AE) and an unaccented ending song (UE). The Yellow Warbler also sings intermediate songs (IE) (Morse, 1966). In all three species song type AE is given more commonly by undisturbed, unmated males, while type UE songs are more common after pairing and during territorial encounters (Ficken and Ficken, 1965). The Black-throated Green Warbler (D. virens) has two song types, referred to as A and B by Morse (1967).