The influence of the acoustic community on songs of birds in a neotropical rain forest

The efficacy of communication depends on the detection of species-specific signals in background noise that includes other species’ signals. To avoid confusion with each others’ signals, species should partition communication space. I investigated this possibility for the dawn chorus of birds in an Amazonian rain forest. Acoustic censuses at a location in Matto Grosso, Brazil, detected 82 sedentary species of birds that sang frequently during dawn choruses. Eleven features of these species’ songs were analyzed to characterize the acoustic space of this community. The Euclidean distances between species’ songs in this acoustic space were then used to investigate spatial, temporal, and phylogenetic influences on the divergence of songs. Songs of species in the same stratum of the forest and during the same 30-min interval had the most dispersed songs. Songs of congeners and family members were more dispersed than songs of random species. These results indicate that in this complex acoustic environment, species singing at the same place and time partition signal space. These species either choose times and places for singing to minimize acoustic interference from other species or they have evolved different songs to reduce this interference.