A Catalog of Song Syllables of Indigo and Lazuli Buntings

Abstract

Tape recording of singing male Indigo Buntings (Passerina cyanea) and Lazuli Buntings (P. amoena) from allopatric populations produced catalogs of 127 indigo and 122 lazuli syllable types. These totals result from adding newly-described syllable types (29 indigo, 42 lazuli) to previous descriptions (Thompson 1970, 1976). While some syllable types are more variable than others, the overall variation is remarkably discontinuous and syllable types are usually easily recognized. The same syllable types occur and at similar frequencies of abundance in different populations and at different times. The patterns of commoness and rarity of syllable types fit a "broken-stick" distribution, a model developed to explain relative abundance of species in communities. Some syllable types are specialized in their position within songs, some are used virtually anywhere in the song, but many are intermediate in degree of specialization of position. Together with results from other studies of bunting songs, our data suggest that the individual syllables in bunting songs can be considered memes, the cultural equivalent of genes. These syllable memes constitute the units of recombination from which whole-song variation is generated. A minor amount of variation is introduced by mutation of syllables. The syllable types are geographically widely distributed and may be considered species universal song elements, similar to findings in the songs in populations of Swamp Sparrows (Melospiza georgiana, Marler and Pickert 1984). The stability of syllables over space and time raises the possibility of a canalizing factor that guides the learning process in young buntings even during cross-species syllable acquisition.