ИСТИНА

Song of Blyth's reed warbler consists of series of more or less complex acoustic constructions, many of them are based on imitations of other birds' voices. Singing males usually repeat series of rather simple elements that they have heard from the neighbour male. In 2009, in Kostroma region (Russia) we demonstrated to birds records of natural and artificial songs (the latter included fragments of some allopatric birds' voices). We found that males were not actually copying other birds' songs, but used resembling constructions from their own repertoires. Such songs produced by males in conflict situations usually lacked the most complex elements. Nevertheless, some bachelors in the end of breeding season gave inadequate reactions by producing more complex songs. Our results show that song of Blyth's reed warbler includes two sorts of elements that are usually based on imitations, mixed with each other and do not form a strict sequence: (1) rather common (shared by many individuals) and less complex addressed presumably to males, and (2) quite unique and more complex addressed to females. Blyth's reed warbler is socially monogamous bird, although extra-pair copulations are common, and several (rare) cases of polygyny were recorded. We suppose that differences in functional and structural song organization between existing Acrocephalinae species indicate that the complex song in this group was evolved quite recently in its evolutionary history after the loss of short and stereotypic babbler-like song.