Abstract
African Penguins Spheniscus demersus are endangered and declining seabirds which make extensive use of vocal signals for intra‐specific vocal communication. Accordingly, passive acoustic monitoring tools could be developed as robust population monitoring methods that cause minimal disturbance to the birds. In this study, we collected soundscape recordings at the Stony Point penguin colony (Betty’s Bay, South Africa) during the breeding season in 2019 to document the circadian rhythms of vocal activity of this species and to investigate whether the magnitude of variation of three different ecoacoustic indices correlates with the number of ecstatic and mutual display songs counted in recordings, which might inform on the breeding activity of the colony. Indeed, whereas ecstatic display songs are produced by males during intersexual competition and territorial defence, mutual display songs are given by parents returning to the nest after foraging trips. We found that the vast majority of the display songs (> 80%) occurred between 04:00–08:00 and 17:30–21:30 h. We also found that the Acoustic Entropy Index was a good predictor of the number of penguins’ songs within a recording. Overall, our study shows that African Penguins vocalizations have the potential to assist the monitoring of this species while minimizing disturbance.
Highlights
African Penguins Spheniscus demersus are endangered and declining seabirds which make extensive use of vocal signals for intra-specific vocal communication
We collected soundscape recordings at the Stony Point penguin colony (Betty’s Bay, South Africa) during the breeding season in 2019 to document the circadian rhythms of vocal activity of this species and to investigate whether the magnitude of variation of three different ecoacoustic indices correlates with the number of ecstatic and mutual display songs counted in recordings, which might inform on the breeding activity of the colony
We investigated whether the variation of the indices could be a useful predictor of the number of ecstatic display songs, which are an indicator of the number of active breeding males or the number of mutual display songs, and peak as the birds return to the colony after foraging trips
Summary
African Penguins Spheniscus demersus are endangered and declining seabirds which make extensive use of vocal signals for intra-specific vocal communication. The ACI measures the average absolute fractional change in signal amplitude from one frame to the through a recording This index characterizes the acoustic environments dominated by bird songs. The species has been recently identified as one of the most critical in need of conservation among penguins (Boersma et al 2019), as the global population is nowadays estimated at under 21 000 breeding pairs, down from over 1.5 million pairs in the early 1900s (Crawford et al 2011) In this context, monitoring of population trends and activity is crucial to, inter alia, measure the success of management actions and keep track of the species population dynamics overall. The African Penguin Management Plan (DEA 2013) recommends that strict minimal disturbance must be ensured to limit the impacts of monitoring methods and researchers on this threatened species
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