Most songbirds exhibit a song repertoire of variable size and composition which plays an important role in mate attraction and territorial defence. Individual repertoire composition and its potential for modification depends on when songs can be memorized in life. Songbirds are broadly classified as open-ended learners if they learn throughout life or as age-limited learners when the learning is limited to the early life. Although great tits have been classified as age-limited learners, several studies have suggested that they can add new songs as adults and may even have a very flexible repertoire. We studied the flexibility of the song type repertoire of adult territorial great tits using two approaches. Firstly, in a longitudinal field study we recorded complete dawn choruses of males in two consecutive years and we compared repertoire size and composition. Secondly, we explored the effects of playbacks on repertoire size and composition. The playback experiment was performed in three phases: 1) birds were recorded during dawn chorus before the playback; 2) a 12 minutes playback consisting of 3 loops of 2 minutes song - 3 minutes silence was carried out during two consecutive days in the early morning; and 3) a second complete dawn chorus was recorded after the playback. Two groups of 9 individuals each, were tested with an unfamiliar song or with their own song. Our results show that repertoire size and composition are highly repeatable between years and within the breeding season after confrontation with a novel song. Our study suggests a very limited repertoire flexibility in our great tit population, which contrasts with previous studies, and we suggest that an adequate assessment of the repertoire is important when studying age- or playback-induced changes in repertoire size and composition.
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