Does the male great bowerbird’s (chlamydera nuchalis) bower effect their display sound?

Communication between animals is a crucial aspect to their survival, and many depend on their neighbours to send signals regarding changes in their external environment, so they can respond to threats, find food sources, and locate sexually mature mates more successfully. There are many modes of communication, with one of the most widely used being acoustic signalling. Acoustic signalling is especially important for long distance communication, but it must compete with environmental influences which can alter, change, and/or redirect signals before it reaches the intended receiver. The Great Bowerbird (Chlamydera nuchalis) is a species reliant on acoustic communication and performs vocal displays to attract females. Currently, there is very little research dedicated to the Great Bowerbird’s display sounds, let alone what might influence the sounds the female is able to receive while inside the bower avenue. Hence, this study aimed to determine whether the avenue itself influenced what sounds the female can receive, and whether male displays have evolved to be heard over the external environment. Using sound spectra taken from audio recordings of randomised frequency sweeps and male call clicks, it was discovered that male call clicks can be heard over the external environment at lower frequencies, and when received inside the bower, it was also amplified. Female bowerbirds are therefore receiving the most intensified sounds at lower frequencies, as they are the sound the avenue structure is amplifying. Additionally, snail shells were found to amplify sound frequencies even further. The bower avenue acts in a similar way to the exponential horn constructed by mole crickets, except in reverse. While the mole cricket sings into the bulb of the horn (the point of focus), which amplifies and carries sound outside of the burrow, female bowerbirds are inside the bower avenue (the point of focus), which amplifies and directs the male display sounds at her ear, allowing her to hear more frequency variations. Common decorative materials, like snail shells, also resonate sounds at higher frequencies, amplifying any sounds inside the avenue even further.