Complex song has been described in several songbird species, but few studies have dealt with intra-individual variability in song bout organization. In this study, we compared the song bouts of 19 Radde's warbler males recorded either on three (11 males) or two (eight males) different days with a lag of 1-17 days between the successive recordings of a male. We used the Jaccard and Simpson indexes to assess the similarity between the song repertoires used by the male on different days. From the Markov transitional matrices, we calculated the sequence linearity index (S-LIN). We found that the observed repertoire size and S-LIN did not differ between the recordings of a male. However, the medians of the Jaccard and Simpson coefficients between different recordings of a male were 0.42 and 0.11, respectively. Therefore, the males can vary their repertoire considerably over several days. Two patterns of such variability were identified. First, male can add or omit a single song type. Secondly, male can add or omit a fixed sequence that included 5-15 song types. The first pattern was revealed in all males, while the second was found only in 12 out of 19 males. We also found that the Jaccard and Simpson indexes in a given male did not depend either on the distance to the nearest male or on the number of males within 400 m.
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