Acoustic Partitioning of Insect-Bird Vocalisation During Dawn and Dusk at Limbang Mangrove National Park, Sarawak

Nur Amirah Husna, Che Anwar (2022) Acoustic Partitioning of Insect-Bird Vocalisation During Dawn and Dusk at Limbang Mangrove National Park, Sarawak. [Final Year Project Report] (Unpublished)

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Abstract

Many animals communicate by using acoustic signals, and acoustic space may be viewed as a limited resource that organisms compete for. Due to lack of understanding on how animals can partition the acoustic space in acoustically diverse environments particularly tropical forests, hence a research study was conducted at Limbang Mangrove National Park, Sarawak with three different points which are i) Patiambun Jetty, ii) Limbang Airport, and iii) Coastal area of mangrove forest during dawn and dusk time interval. The objective of this study is to assess the acoustic partitioning of birds during dawn and dusk period and to determine the influence of insect vocalisations specifically cicada towards frequency and timing for bird vocalisation at Limbang Mangrove National Park. This study began from February 2022 by using secondary data where the audio recordings were obtained using passive automatic recording system (Song Meter 4). A total of five parameters were analysed in this study which are i) minimum frequency (kHz) (s), ii) maximum frequency (kHz), iii) amplitude (kU), iv) call duration (s), v) total number of bird species vocalised before and after cicada vocalisation. All the raw audio files were trimmed through Audacity Version 3.1.2 and filtered with RavenPro 1.6.1 software. The annotations of birds and cicada signals were visualised by spectrogram. Based on findings, it was discovered that cicadas vary the timing of their signals throughout the day, and that the frequency range and timing of bird vocalisations are closely related to cicada signals. Birds have performed their acoustic strategy in avoiding temporal overlap with cicadas by reducing and frequently stopping vocalisations at the onset of cicada signals in the same frequency range. It provides a deeper understanding of the community dynamics of acoustic signalling and reveal how biotic noise patterns shape the frequency and timing of bird vocalisations in tropical forests

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