Acoustic Sound Space Competition in the Neotropics Between Bird and Cicada Communities

Acoustic signaling is the primary form of communication for many terrestrial organisms, especially birds, mammals, frogs, and insects. Acoustic space is shared by all animals in a community but can only be partitioned in two primary dimensions (spectral and temporal). It has been hypothesized that because acoustic communication consumes energy, animals should maximize the efficiency of signal transmission to receivers by reducing interference and masking by other signals. The extent to which animals are able to partition acoustic space, and thus avoid signal interference in diverse and noisy habitats such as tropical rainforests is poorly known. Here we demonstrate that a community of birds in a Costa Rican rainforest actively avoids spectral and temporal overlap with signals produced by insects.  Using automated acoustic monitors, we found that several species of cicadas and Orthopterans dominate a variety of bandwidths throughout the day and night, and that the frequency range of bird songs closely track, but rarely overlap with the temporally dynamic insect song. In addition, insect signaling is rare only during a relatively short time window beginning at sunrise, during which birds dominate bandwidths that are otherwise used by insects. Bandwidths used by two species of cicadas during portions of the day are so broad that most bird communication is effectively shut down except in very narrow, unused bandwidths. Our results provide evidence for community-level competition for acoustic space and greatly improve our understanding of the community dynamics of acoustic signaling in a diverse tropical rainforest.