A Previously Undescribed Method of Song Matching in a Species with a Single Song “Type”, the Kentucky Warbler (Oporornis formosus)

Abstract

AbstractThe song of male Kentucky warblers consists of several repetitions of syllables containing 2 to 7 elements within a frequency range from 1.8 to 6.0 kHz. Each male has a single, individually distinctive song type that spans part or all of this frequency range. Song responses to playbacks of songs artificially elevated or lowered in frequency by 200 Hz show that a bird is able to alter its song in two ways. It may lower or raise the frequency range of the song or put more energy into the lower or higher frequencies within the song's elements to more closely match the energy distribution of the playback song. The syllable or element structure of the song is kept constant with only the song's energy distribution among frequencies changing. Thus, Kentucky warblers are able to alter their single song type to “match countersing” in a way similar to that of species with song repertoires who switch song types to match those of rivals. The Kentucky warbler may have a single songtype because of its ability to change its song's energy distribution. This ability may perform the same functions as song matching does in species with larger repertoires. This finding is discussed in relation to ideas on the evolution of song repertoires in intrasexual competition.