Sutirtha Lahiri, Bablu Sonowal

A diverse array of animals use a multidimensional acoustic space as a primary source of communication, especially in habitats where other signals are limited. However, in complex habitats, species must contend with other co-occurring species to send their message in a backdrop of ambient noise. This is exacerbated in closely related species that occur in sympatry, and we do not know how species that learn their vocalization and have diverse repertoires partition their acoustic space. In this study, we studied four species of closely related group of birds, the drongos, in a tropical evergreen forest in South Asia. We made field vocal recordings as well as estimated song perch heights in the four species from December 2018-April 2019. Using ordination methods like PCA and LDA, we find wide overlap in the acoustic space in the four sympatric drongos. We, however, find that drongos segregate vertically. We hypothesize that drongos overlap in acoustic space owing to their ability to mimic other species, which increases their acoustic signal breadth. To partition their acoustic space, drongos potentially vocalize from different perch heights. Our study broadens our understanding of how a vocally diverse group of birds may partition in the acoustic signal space.