Tape recording of singing male Indigo Buntings (Passerina cyanea) and
Lazuli Buntings (P. amoena) from allopatric populations produced catal
ogs of 127 indigo and 122 lazuli syllable types. These totals result f
rom adding newly-described syllable types (29 indigo, 42 lazuli) to pr
evious descriptions (Thompson 1970, 1976). While some syllable types a
re more variable than others, the overall variation is remarkably disc
ontinuous and syllable types are usually easily recognized. The same s
yllable types occur and at similar frequencies of abundance in differe
nt populations and at different times. The patterns of commoness and r
arity of syllable types fit a ''broken-stick'' distribution, a model d
eveloped to explain relative abundance of species in communities. Some
syllable types are specialized in their position within songs, some a
re used virtually anywhere in the song, but many are intermediate in d
egree of specialization of position. Together with results from other
studies of bunting songs, our data suggest that the individual syllabl
es in bunting songs can be considered memes, the cultural equivalent o
f genes. These syllable memes constitute the units of recombination fr
om which whole-song variation is generated. A minor amount of variatio
n is introduced by mutation of syllables. The syllable types are geogr
aphically widely distributed and may be considered species universal s
ong elements, similar to findings in the songs in populations of Swamp
Sparrows (Melospiza georgiana, Marler and Pickert 1984). The stabilit
y of syllables over space and time raises the possibility of a canaliz
ing factor that guides the learning process in young buntings even dur
ing cross-species syllable acquisition.