Vocalization of the Black-Hooded Oriole (Oriolus xanthornus, Oriolidae, Passeriformes, Aves): Female Singing and Duetting

Singing is known to play significant roles in songbird communication. For a long time, singing was believed to be a male attribute, whereas rare episodes of female singing were seen as deviations. However, there has been more and more research on female vocals in recent times, suggesting this in no way to be a rare event. In this study, we investigated the vocalization of the black-hooded oriole (Oriolus xanthornus) in Nam Cat Tien National Park, southern Vietnam. We identified two singing variants significantly differing in both maximum frequency and frequency range, these parameters being higher in variant 2. Variant 1 appeared to be more often, being performed in various situations: spontaneous singing, territorial interactions, and duets. Variant 2 occurred only in duets or in territorial interactions where the bird focal pair also performed in duets. No syntax variation was found between the different singing variants. In addition, no variation was revealed in the syntax of variant 1 in the different situations (spontaneous singing and duets). In one observation, we reliably discovered that the male used variant 1, while the female used variant 2. Variant 1 is likely usually to be used by males, while variant 2 is typically used by females. We also identified two types of calls for this species.