Sunda Scops-Owl Density Estimation via Distance Sampling and Call  Playback

Pilla, Phillcaine; Chong, Leong Puan; Lim, Voon-Ching; Mohamed, Badrul Azhar; Mohamed, Zainalabidin

doi:10.17576/jsm-2018-4703-03

Cited by 7 publications

(1 citation statement)

References 28 publications

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“…Eight of these were placed within the estimated area of distribution of the owl, whereas two transects were placed in its vicinity, in areas of native forest, with occupancy potential (Freitas et al 2023). Point counts within the transects were considered independent and used as sampling units as they were spaced 150 m apart in order to prevent double counting, similarly to what has been used for other owl species in similar environments (Borges et al 2004;Pilla et al 2018). This distance also takes into account the inability of AudioMoths to capture owl calls at 96 m of distance (BF pers.…”

Section: Survey Designmentioning

confidence: 99%

Passive acoustic monitoring in difficult terrains: the case of the Principe Scops-Owl

et al. 2023

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Many species are difficult to study either due to their rarity, elusiveness, difficult access to their area of occurrence, or any combination of these. This can be particularly problematic for threatened species. Passive acoustic monitoring (PAM) is a recently developed survey technique that has shown great potential in addressing this problem for species that communicate through vocalizations. However, the large amount of data it generates can be difficult to process manually. Here, we present an entirely automatic workflow to record and detect the vocalizations of a bird species that is both elusive (nocturnal) and restricted to difficult terrain in the most remote rainforests of an oceanic island: the recently discovered Principe Scops-Owl. Specifically, we evaluated (i) the performance of the workflow to monitor the presence of the owl, (ii) we assessed the most suitable time for monitoring it; and (iii) we examined the potential of this species to present detectable vocal individual signatures. For 12 days, we deployed omnidirectional recording stations (AudioMoth devices) in 72 points along 10 transects that were surveyed during one night at the same time by observers in the field. We trained TADARIDA, a machine learning software toolbox, to automatically detect owl calls. Results on the presence of the owl per site were similar for both methods. The automatic workflow showed that the owl is active during the whole night and the PAM recording setting should encompass at least the 21-23 h interval. Possibly, vocalizations had individual signatures-but the small sample size and temporal window prevented a definite conclusion. The automatic workflow developed here is an efficient method to monitor the Principe Scops-Owl and can be easily adapted for other elusive vocal species.

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Section: Survey Designmentioning

confidence: 99%

Passive acoustic monitoring in difficult terrains: the case of the Principe Scops-Owl

et al. 2023

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The first comprehensive survey of habitat suitability and population size for the endangered Grande Comoro Scops Owl (Otus pauliani): implications for its conservation

et al. 2019

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The recently discovered Principe Scops-owl is highly threatened: distribution, habitat associations, and population estimates

Freitas

Melo

Jesus

et al. 2022

Bird Conservation International

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Summary Species baseline information is required for effective biodiversity conservation. Here we provide sound ecological data to support effective conservation of the Principe Scops-owl, Otusbikegila Melo, Freitas, Verbelen, Costa, Pereira, Fuchs, Sangster, Correia, de Lima & Crottini 2022, discovered in 2016. We mapped the observed and potential distribution, inferred habitat associations, estimated population size, and assessed the International Union for Conservation of Nature (IUCN) Red List category for this species. Surveys were carried out across Príncipe Island during the long and short dry seasons, recording owl presence in sampling points along transects. These data were used to model distribution, revealing that the Principe Scops-owl is restricted to 34.4 km2 in the south of the island, inside the Príncipe Obô Natural Park. Most records were in lower altitude native forest. Remoteness was the most important variable to explain presence at island level, followed by land use, which showed that the species is restricted to forest, clearly depending on native forest. Distance sampling using different models suggested a population density ranging between 33.4 individuals/km2 (95% CI: 23.6–47.2) and 46.4 individuals/km2 (95% CI: 29.3–73.6), which extrapolates to an estimated population size ranging from 1,149 individuals (95% CI: 813–1,623) to 1,597 individuals (95% CI: 1,007–2,533). We propose that the species is classified as “Critically Endangered” due to the small extent of occurrence, coupled with occurrence in a single location and inferred continuing declines in the extent of occurrence, area of occupancy, number of mature individuals and area, extent, and quality of habitat. Effective conservation of the Principe Scops-owl requires regular monitoring and further studies focusing on reproduction and potential nest predation by introduced mammals. Widespread support for the conservation of the Natural Park is vital to ensure the protection of this species and the endemic-rich native forests of Príncipe on which it depends.

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Sunda Scops-Owl Density Estimation via Distance Sampling and Call Playback

Abstract: Nocturnal birds in the tropics

Cited by 7 publications

References 28 publications

Passive acoustic monitoring in difficult terrains: the case of the Principe Scops-Owl

Passive acoustic monitoring in difficult terrains: the case of the Principe Scops-Owl

The first comprehensive survey of habitat suitability and population size for the endangered Grande Comoro Scops Owl (Otus pauliani): implications for its conservation

The recently discovered Principe Scops-owl is highly threatened: distribution, habitat associations, and population estimates

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