Song Variation in a Population of Indigo Buntings

Abstract

IN a previous paper (Thompson, 1968) I described the general characteristics of the songs of several species of the genus Passerina. For a fuller understanding of a behavioral characteristic, just as in the case of a morphological feature, it is important to study the kind and amount of variation within a single population and, especially for behavior, within a single individual. This paper describes the song characteristics of the members of a single population of Indigo Buntings, Passerina cyanea. A paper now in preparation will describe song variation in individual Indigo Buntings. Male Indigo Buntings sing three rather distinct types of song: advertising song (in the sense of Borror, 1961), a squeaky song in intensive territorial defense, and flight song. This paper deals only with advertising song. A typical Indigo Bunting advertising song is composed of a series of sounds, or song figures. The song in Figure 5A, for example, includes eight song figures of five different types. I define the term song figure (Thompson, 1968) as a sound or sounds that produce a single, complete, and distinct impression to the human ear and form a distinct unit of a song. A song figure may be composed of one or more continuous sounds or syllables. Each male Indigo Bunting usually sings a regular sequence of several different figures. Figures may occur singly in the song, or they may be repeated. In a typical advertising song repeated figures occur together. The fixed sequence of figures sung by each male is called a song pattern.