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.

Nocturnal songs in a diurnal passerine: attracting mates or repelling intruders?

“…The correlation analysis was based on spectrograms (DFT size: 512; hop size: 13; overlap: 94.9), using a band-pass filter from 2 to 6 kHz, and linear power values from the spectrograms. We reduced effects of background noise, such as low-level wind and other nonfocal sounds, by setting the power level to 0 dB of any signal with an amplitude below À70 dB using the clipping function (Foote et al, 2012). Correlation values were standardized, resulting in values between 0 and 1 (with values of 1 indicating that two samples are identical).…”

“…To assess whether multiple songs came from the same individual, we compared variation within and between songs of focal field sparrows (Foote, Palazzi, & Mennill, 2012). We randomly selected up to 10 songs per individual from a large set of focal recordings collected in the study site.…”

Comparison of autonomous and manual recording methods for discrimination of individually distinctive Ovenbird songs

“…We selected a higher sampling rate because the recordings were of lower duration and a higher sampling rate is typical of directional recording datasets (e.g. Wilson and Mennill 2010;Foote et al 2013). Each male was recorded as often as required to achieve at least 10 high quality songs free of background noise.…”

“…For individual recognition, individual variation must be low relative to between individual variation in the signal (Falls 1982). Indeed in most examples studied to date, within individual variation is low relative to between individual variation (Wilson and Mennill 2010;Charlton et al 2011;Kirschel et al 2011;Foote et al 2013). Experiments have established that birds do recognize and discriminate among individuals by their songs (Falls 1982).…”

“…This technique has been used to distinguish among individuals in many taxa based on their distinct vocal features including birds (Foote et al 2013), mammals (Charlton et al 2011) and anurans (Pettitt et al, 2013). While directional microphones produce high-quality recordings for bioacoustics analyses, this task must be accomplished manually and subjects must be available to be recorded.…”