Cultural conformity generates extremely stable traditions in bird song

A large recorded corpus of wild swamp sparrow song was analysed by fitting competing models of cultural transmission — unbiased copying, copying with error, and conformist copying in which common variants are preferentially learned — and comparing how well each reproduced the observed distribution of song types.

Studied in

Melospiza georgiana

Sample size

large corpus of wild swamp sparrow songs fitted to cultural transmission models

The observed pattern was best explained by conformist learning, and the fitted models implied that some song types have persisted essentially unchanged for many hundreds of years.

• The centuries-long persistence is a model output, not an observation; it inherits every assumption in the transmission model.
• One species with a small, discrete repertoire, which is the easiest case for this kind of inference.
• Conformist copying is inferred from the distribution of variants rather than from watching individual birds choose.

• Birdsong dialects

  Song culture can also do the opposite of changing. Where young birds preferentially copy the commonest version they hear, a song type can persist essentially unchanged for centuries.