CHANGES IN RADDE’S WARBER (PHYLLOSCOPUS SCHWARZI) MALE VOCALIZATIONS DURING SEVERAL DAYS
A complex singing behavior has been described in several songbird species, but few studies deal with intra-individual variations in vocalization. In this study, we compared the singing of 19 Radde’s warbler males recorded either on 3 (11 males) or 2 (8 males) different days with a lag of 1–17 days between the successive recorded vocalizations of a male. We used the Jaccard and Simpson indexes to assess the similarity between the song repertoires used by the male in different days. From the Markov transitional matrices, we calculated the sequence linearity score (SLIN) and found that the observed repertoire size and SLIN failed to differ significantly between the recordings. The medians of the Jaccard and Simpson indexes were 0.42 and 0.11, respectively. Therefore, the males could considerably change the repertoire composition within several days. Two types of variation were revealed. The first type was the addition or omission of a song. The second type was the addition or omission of a fixed sequence which included 5–15 song types. The first type was revealed in all males, while the second only in 12 of 19 males. We also found that both Jaccard and Simpson indexes in a given male depended neither on the distance to the nearest male nor on the number of males within 400 m.