DOI: 10.5061/dryad.tqjq2bvtd
title: Singing behind the stage: thrush nightingales produce more variable songs on their wintering grounds

description: The songs of migratory passerine birds have a key role in mate attraction
 and territory defence during the breeding season. Many species also sing
 on their wintering grounds, but the function of this behaviour remains
 unclear. One possible explanation, proposed by the song improvement
 hypothesis, is that the birds take advantage of this period to develop
 their singing skills for the next breeding season. If so, non-breeding
 songs should reflect features of an early phase in song development,
 characterized by high vocal plasticity. In our study, we tested this
 prediction by comparing songs of thrush nightingales (Luscinia luscinia)
 recorded at two different breeding areas in Europe and one wintering area
 in Africa. While all songs from European localities had a typical
 structure characteristic of the study species, 89% of the songs recorded
 from Africa were highly variable, lacking such typical structure. We
 conducted further detailed analysis of breeding and winter songs that
 exhibited species-specific structure. First, we explored plasticity at the
 syllable level using a cross-correlation analysis, to obtain similarity
 scores as a measure of consistency. Second, we asked multiple human
 observers to quantify element variability. Our results showed significant
 differences in syllable consistency between breeding and wintering
 grounds, with more consistent delivery of syllables in the breeding areas.
 Likewise, element variability was substantially lower in the breeding
 populations. While both results fit the predictions of the song
 improvement hypothesis, more research is needed to elucidate the roles of
 singing on the wintering grounds.
description: Data files including information about experiments:
 -
 Souriau_et_al_2019_BEAS_Source_data_Syl_Correlation.xls: 
 A XLS spreadsheet containing information on the cross-correlation
 analysis comparing the syllable consistency in thrush nightingale
 (Luscinia luscinia) songs from breeding and wintering grounds, as well as
 additional information on the recordings. -
 Souriau_et_al_2019_BEAS_Source_data_Syl_Correlation.txt: 
 A tab-delimited TXT file containing information on the
 cross-correlation analysis comparing the syllable consistency in thrush
 nightingale (Luscinia luscinia) songs from breeding and wintering
 grounds. -
 Souriau_et_al_2019_BEAS_Source_data_Elt_Variability.xls: 
 A XLS spreadsheet containing information on the element
 variability analysis comparing songs of the thrush nightingale (Luscinia
 luscinia) from breeding and wintering grounds. -
 Souriau_et_al_2019_BEAS_Source_data_Elt_Variability.xls: 
 A tab-delimited TXT file containing information on the element
 variability analysis comparing songs of the thrush nightingale (Luscinia
 luscinia) from breeding and wintering grounds.
 - Souriau_et_al_2019_BEAS_Spectrograms_Elt_Variability_analysis.pdf: A PDF file displaying the spectrograms used for the element variability visual assessment of thrush nightingale (Luscinia luscinia) songs from breeding and wintering grounds (see Methods).<br>