LAUSR

Recent studies have shown that birdsong is not exclusively a male trait. However, despite increasing research intensity, female singing is still rarely reported in temperate migratory species. Here, we report the observation and description of female vocalization in the great reed warbler, Acrocephalus arundinaceus . We analysed vocal expression of individually marked great reed warbler females in two central European populations in Slovakia and the Czech Republic and show that these vocalizations meet criteria for song. We found that 39.5% of nesting females sang from the nest during early incubation within two hours of video recording. Female mating status, locality, day of the season, and male singing activity did not predict song use in this species, but song rates decreased over the breeding period. Based on current and previous observations, we hypothesize that female great reed warblers use song to signal their territorial presence and reproductive status, potentially deterring conspecific female competitors. However, given that this study was done only in one context and moment in the breeding cycle (early incubation), we encourage further investigation of the functions of female song in this and other temperate migratory species whose female song was overlooked in the past.