Microgeographic Variation in the Song of the Scarlet Rosefinch Carpodacus erythrinus

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Abstract
The song of the Scarlet Rosefinch was studied during a 3-year period. The song was short (about 1 s) consisting of 4-7 syllables and could easily be categorized into song types. Each song type was distinct and a male with a particular song type did not generally change song type during a season, but occasionally between seasons. Each song type was sung by one or several males. Males singing the same song type differed only in small details (e.g. length of strophe or mean frequency), but not in number or order of syllables. Males sharing song types clustered microgeographically, thus producing song-neighbourhoods. Males not present in previous years were found singing song types sung in earlier years by other males, which suggests that at least some males exhibit between-year copying. The fact that males can shift song types at adult age both between seasons and within a season suggests that song learning is open-ended and is involved in a social strategy. I suggest that song neighbourhoods and dialects are best interpreted in terms of ecology and social environment, rather than in terms of timing of song learning. The similar ecology and recent geographical expansion of the Scarlet Rosefinch and the congeneric Housefinch Carpodacus mexicanus have apparently not resulted in similar singing behaviour in the two species.