Comparisons of acoustic structures between sexes in a duetting, montane bird

Female song in birds is more widespread than previously thought, and
studies across different species are critical for better understanding the
entire evolutionary process of bird song. In this study, we recorded the
songs of males and females in a duetting, montane bird species, the
Elliot’s laughingthrush Trochalopteron elliotii, across consecutive
breeding seasons. We specifically focused on identifying the number and
structure of different song types by males and females, and compared these
acoustic structures between the sexes. Our findings revealed that both
males and females sang sex-specific solos. More specifically, females sang
a single type of solo that varied significantly in the number of notes,
whereas males produced three different solos composed of 2, 3, or 4 notes,
respectively. Female solos exhibited significantly more notes and longer
song duration compared to males. Male solos typically had a significantly
higher maximum frequency for the entire song. No significant differences
were observed in the duration of the first note, song rate, and other
frequency characteristics between male and female solos. Furthermore,
paired males and females coordinated their sex-specific solos to form
duets when challenged by conspecific territory intruders, both within and
outside the breeding season. Sex-specific solos suggested that male and
female songs play different roles and may be subject to different
selective pressures. Further research is necessary for elucidating the
functions of male song, female song, and duets in this montane bird
species.