Age-related song repertoire changes in a songbird: the black redstart

Songbirds learn their songs but their sensitive periods vary: some species end their learning period when several months-old while others learn throughout their lives. We investigated the turnover of song repertoires in a migratory population of a territorial songbird, the black redstart (Phoenicurus ochruros), following colour-ringed individuals during seven breeding seasons (2007-2008 and 2015-2019). Birds have an uneven spatial distribution resulting in groups of 2-8 territorial males sharing most of their songs (microdialects). We recorded 17 one-year-old males on the day of their arrival from migration (March) and again one month later. Most birds (15/17) sang the local dialect when they arrived but two males sang different song types. We did not observe modifications during their first breeding season but one year later these latter two individuals added some songs from the local dialect to their repertoire and one of them progressively dropped all of his non-shared songs. Eighteen additional males aged at least two years old were recorded over two consecutive breeding seasons. None of them added or dropped any songs from one year to the next. These results suggest that male black redstarts learn their songs during their first autumn, prior to migration. If they return to the exact hamlet where they learned their songs they do not modify their repertoires, but if they return to a neighbouring hamlet they are able to learn the specific dialect of that hamlet; however, they do not express it immediately, suggesting the existence of a delayed vocal imitation