The function of vocal duets in a New World warbler

Abstract

In many species of birds, mated individuals sing duets. I reviewed avian duet research with a focus on adaptive functions. I also reviewed methods for territory estimation because I needed to calculate territories for my primary study, in which I used acoustic and spatial data to test the function of duetting. My study species, the Adelaide’s warbler (Setophaga Adelaidae), is a Neotropical wood-warbler in which females answer their mates’ songs to form duets. Females answered more of their mates’ songs around the time of aggressive encounters, and when they were close to the territory boundaries or their mate. Females tended to move toward their mate after he sang, but answering did not affect approach behaviour. My findings suggest that female answering functions to defend the female’s territory and partnership, but does not function in mate localization. This is the first evidence of duet function in a New World warbler.