Songs of the Eastern Phoebe, a suboscine songbird, are individually distinctive but do not vary geographically

Abstract

Animal displays may vary both within and among individuals and also within and among populations. This variation may contain important information used by animals for individual recognition. Suboscine birds are thought to develop song by fully innate mechanisms and are poorly studied relative to oscine birds, where song learning results in significant variation in song structure among individuals and the development of dialects. Recent research, however, demonstrates that suboscine song is often individually distinctive and in some cases shows signs of regional variation. We used spectrogram cross-correlation and canonical discriminant function analysis to examine individual and geographic variations in songs of Eastern Phoebes (Sayornis phoebe), suboscine birds with two song types. Both song types were individually distinctive and showed significantly higher cross-correlations within than among individuals. Discriminant function analysis correctly assigned 85.3% of “phee-bee” and 90.0% of “phee-b-be-bee” songs to the correct male, levels that are significantly higher than expected by chance. The individually distinctive characters of songs were also significantly repeatable among recording sessions. Eastern Phoebe song did not vary geographically between two populations separated by 640 km; permuted discriminant function analysis assigned 65% of “phee-bee” and 70% of “phee-b-be-bee” songs to the correct population, which did not differ significantly from chance expectations. Variation among males in song characteristics could be used by both males and females to discriminate among individuals. These detailed bioacoustic analyses support the idea that individual distinctive acoustic signals are widespread across suboscine birds.