The unusual mixed song of a River Warbler (Locustella fluviatilis) was recorded in eastern Poland. The identified male used 2 types of songs recalling the River Warbler and the Grasshopper Warbler (Locustella naevia) alternately, which was confirmed by the interpretation of the sonograms. The most likely explanation of this unusual song is vocal mimicry, caused by the exposure of the recorded individual to the song of the Grasshopper Warbler in its acoustic environment at an early stage of its life.
POLAKOWSKI, MICHAL; BRONISZEWSKA, MONIKA; JANKOWIAK, LUKASZ; and COFTA, TOMASZ
"Hybridisation or vocal mimicry? A case of a mixed singing River Warbler Locustella fluviatilis in eastern Poland,"
Turkish Journal of Zoology: Vol. 37:
2, Article 18.
Available at: https://journals.tubitak.gov.tr/zoology/vol37/iss2/18