02504nas a2200253   4500008004100000245010500041210006900146520167700215653002401892653002501916653002101941653001801962653002001980653002302000100001802023700002202041700002902063700002202092700002102114700002002135700001602155700002402171856005502195       2019                        eng d00aSinging behind the stage: thrush nightingales produce more variable songs on their wintering grounds0 aSinging behind the stage thrush nightingales produce more variab3 a<p>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.</p>
10aElement variability10aNon-breeding singing10aSong consistency10aSong function10aSong plasticity10aThrush nightingale1 aSouriau, Abel1 aGeberzahn, Nicole1 aIvanitskii, Vladimir, V.1 aMarova, Irina, M.1 aVokurková, Jana1 aReifová, Radka1 aReif, Jiři1 aPetrusková, Tereza  uhttp://link.springer.com/10.1007/s00265-019-2765-x