A spatiotemporal analysis of acoustic interactions between great reed warblers (Acrocephalus arundinaceus) using microphone arrays and robot audition software HARK

Abstract

Acoustic interactions are important for understanding intra‐ and interspecific communication in songbird communities from the viewpoint of soundscape ecology. It has been suggested that birds may divide up sound space to increase communication efficiency in such a manner that they tend to avoid overlap with other birds when they sing. We are interested in clarifying the dynamics underlying the process as an example of complex systems based on short‐term behavioral plasticity. However, it is very problematic to manually collect spatiotemporal patterns of acoustic events in natural habitats using data derived from a standard single‐channel recording of several species singing simultaneously. Our purpose here was to investigate fine‐scale spatiotemporal acoustic interactions of the great reed warbler. We surveyed spatial and temporal patterns of several vocalizing color‐banded great reed warblers (Acrocephalus arundinaceus) using an open‐source software for robot audition HARK (Honda Research Institute Japan Audition for Robots with Kyoto University) and three new 16‐channel, stand‐alone, and water‐resistant microphone arrays, named DACHO spread out in the bird's habitat. We first show that our system estimated the location of two color‐banded individuals’ song posts with mean error distance of 5.5 ± 4.5 m from the location of observed song posts. We then evaluated the temporal localization accuracy of the songs by comparing the duration of localized songs around the song posts with those annotated by human observers, with an accuracy score of average 0.89 for one bird that stayed at one song post. We further found significant temporal overlap avoidance and an asymmetric relationship between songs of the two singing individuals, using transfer entropy. We believe that our system and analytical approach contribute to a better understanding of fine‐scale acoustic interactions in time and space in bird communities.

Acoustic localization of terrestrial wildlife: Current practices and future opportunities

“…Of the 95 studies, 33 localized multiple species (e.g., Campbell & Francis, 2012; Kojima et al, 2017; Surlykke & Kalko, 2008). Thirty studies performed simultaneous localization of multiple individuals across a large spatial extent (e.g., Araya‐Salas, Wojczulanis‐Jakubas, Phillips, Mennill, & Wright, 2017; Campbell & Francis, 2012; Foote, Ratcliffe, Mennill, & Fitzsimmons, 2010; Lapierre, Mennill, & MacDougall‐Shackleton, 2011; Patricelli & Krakauer, 2010; Suzuki et al, 2018).…”

“…Commercial sources include both wildlife recording ARUs and general purpose ARUs. Wildlife recorders, commercially available ARUs built specifically for deployment in the field to record wildlife, were used in 15 studies (e.g., Kershenbaum et al, 2019; Spillmann et al, 2017; Suzuki et al, 2018). The most notable manufacturer of these ARUs is Wildlife Acoustics (Maynard, MA, USA), which sells ARUs that are ready to be deployed “out of the box” and include features such as programmable recording schedules, built‐in data storage and batteries, and waterproofing, making them ideal for long‐term autonomous deployment.…”

“…Both Wildlife Acoustics and Frontier Laboratories (Brisbane, Australia), currently, sell wildlife recorders which synchronize automatically using GPS. Another wildlife recording system, the DACHO 16‐channel array used by Suzuki et al (2018) and sold by System in Frontier (Tokyo, Japan), is apparently no longer available. Five studies performed DOA localization using general purpose, commercially available ARUs that were not originally designed for wildlife recording.…”

“…Certain noise reduction techniques require that the number of microphone elements is greater than the number of active sound sources (e.g., Suzuki et al, 2017). Several applications used ARUs containing more than the minimum number of microphones (e.g., a 16‐microphone setup, Suzuki et al, 2018). Although both hyperbolic and DOA localization employ multimicrophone ARUs, microphone placement and spacing differ between these two applications (see Section “Placement”).…”

“…Synchronization methods include cable synchronization, acoustic synchronization, GPS synchronization, or network communication between recorders. In one case, ARUs were not synchronized (Suzuki et al, 2018).…”