Biological and Cultural Success of Song Memes in Indigo Buntings

Song behavior, breeding success, and survival of individuals and the survival of their local song traditions or memes were compared in two populations of Indigo Buntings (Passerina cyanea) in southern Michigan. First—year males were less successful than older males. First—year males with the song of a neighbouring adult tended to be more successful in mating and in fledging young than were 1st—yr males that retained an individualistic song. Adults that were members of a local song neighourhood tended to be more successful than adults that were not. Reproductive and survival success of individual birds did not vary with the number of males in the meme. The different song traditions (memes) are equivalent in biological terms to mating success, breeding success, and survival of their bearers. Memes are successful in a cultural sense if they survive from year to year. Meme survival is determined largely by the number of individual birds in the song group; chances are high that at least one male with the song will return in the larger groups. Songs are learned outside the family context, kin usually do not have the same song, and a female selects a mate independently of whether his song is the same as her father's. The change over time in the local meme pool is independent of any obviously associated genetic traits, and cultural extinction of song memes is described in probabilistic terms of meme size.